Unitt d States
Environmental Protection
Agency
Toxic Substances
Washington DC 20460
ePA-560/2-79-003
March 1979
Toxic Substances
Proceedings of the
Workshop On Alternatives
For Cadmium Electroplating
In Metal Finishing
October 4-6, 1977
Sponsored by:
Consumer Product Safety Commission
U.S. Department of Commerce
U.S. Department of Defense
U.S. Department of Health, Education, and Welfare
U.S. Department of the Interior
U.S. Department of Labor
Environmental Protection Agency
General Services Administration
at the
National Bureau of Standards
Gaithersburg, Maryland
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EPA-560/2-79-003
PROCEEDINGS OF THE
WORKSHOP ON ALTERNATIVES FOR CADMIUM ELECTROPLATING
IN METAL FINISHING,
October 4-6, 1977
Sponsored by:
U.S.
Consumer Product Safety Commission
U.S. Department of Commerce
U.S. Department of Defense
Department of Health, Education, and
U.S. Department of the Interior
U.S. Department of Labor
Environmental Protection Agency
General Services Administration
Welfare
at the
National Bureau of Standards
Gaithersburg, Maryland
Elbert Dage
Edward Dyckman
William Isler
Fielding Ogburn
Editors
March 1979
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DISCLAIMER NOTICE
Convention of this Workshop on Alternatives for Cadmium
Electroplating in Metal Finishing and publication of this
document do not signify that the contents necessarily reflect
the joint or separate views and policies of each sponsoring
Agency. Mention of trade names or commercial products does
not constitute endorsement or recommendation for use.
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ACKNOWLEDGEMENT
This document was reproduced by the Environmental Protection Agency.
Transcription services for the Workshop were provided by the Occupa-
tional Safety and Health Administration. Transcripts of the dialogue
taking place during the workshop were edited by Fielding Ogburn, National
Bureau of Standards; William Isler, Harry Diamond Laboratories; Elbert
Dage, Environmental Protection Agency; and Edward Dyckman, Defense
Industrial Resources Support Office.
Additional Copies Of This Report May Be Ordered From The
National Technical Information Service
U.S. Department of Commerce
5185 Port Royal Road
Springfield, Virginia 22151
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FOREWARD
Forty two representatives of government and one hundred
eighteen representatives of industry participated in this
Government organized workshop, "Alternatives for Cadmium
Electroplating in Metal Finishing" held 4-6 October 1977 at
the National Bureau of Standards, Gaithersburg, Maryland.
The workshop was sponsored and organized by a steering
committee composed of representatives from the Consumer
Products Safety Commission, Department of Commerce, Depart-
ment of Defense, Department of Health, Education and Wel-
fare, Department of the Interior, Department of Labor,
Environmental Protection Agency, and the General Services
Administration.
The workshop was prompted by the concern of government
agencies over environmental damage resulting from present
day cadmium electroplating processes. Cadmium electroplat-
ing and stripping operations are responsible for as much as
fifty percent of the industrial discharges of cadmium to
water in the United States. Cadmium that reaches drinking
water supplies, navigable waters, and food chains is hazard-
ous to humans.
The purpose of the workshop was to examine techniques and
alternatives to minimize the loss of cadmium into the
environment by (a) applying cadmium by mechanisms that
reduce -the loss of cadmium during plating and (b) developing
suitable and cost-effective alternative materials, methods,
and coatings that can be utilized where possible in the
design and manufacture of items that are now characteris-
tically electroplated with cadmium.
A secondary purpose of the workshop was to develop a model
of a technical forum in which government and industry
representatives could discuss a wide spectrum of issues
concerning the use of and alternatives for industrial
materials suspected of being hazardous to health and the
environment. Similar workshops concerning other materials
might be organized in the future by agencies responsible for
regulating the use of toxic substances.
The concept adopted by the steering committee was to divide
the workshop into two sessions. The first session concen-
trated on presentations reporting the efficacy of individual
alternative materials and processes for electrodeposited
cadmium. The second session dealt with the presentation of
laboratory and field trials comparing a number of the alter-
natives described during the first session. Interspersed
throughout these presentations were a number of papers on
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closely related areas, including the development of environ-
mentally compatible processes for electroplating cadmium,
the importance of electrodeposited cadmium coatings, and the
environmental and health effects of cadmium.
In addition to presentations, two panel sessions were held.
The first panel addressed the question, "Are specifications
and standards barriers to change?" Panelistlwere individuals
with current responsibilities or backgrounds in the prepara-
tion and use of government and industry specifications and
standards. They extemporaneously discussed probleDs and
issues related to the identification, testing, qualification,
documentation, and application of alternative materials and
processes for electrodeposited cadmium. The second panel
addressed the question, "How essential is electrodeposited
cadmium?" Panelists included platers, cadmium suppliers and
cadmium users. They discussed technical, economic, environ-
mental, and health issues germane to the production and use
of electrodeposited cadmium.
This document presents the proceedings of the workshop,
including an edited transcript of the dialogue from question
and answer periods following each presentation and from each
discussion panel. The workshop proceedings will be used by
participating agencies in their efforts to assess the
various approaches to minimizing loss of cadmium to the en-
vironment.
The information presented during this workshop is of timely
importance, not only to the government, but to the indus-
trial community as well. To avoid delays in the dissemina-
tion of this information, this report has been produced
directly from statements submitted by the participants for
publication.
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CONTENTS
WORKSHOP ON ALTERNATIVES FOR CADMIUM ELECTROPLATING
IN METAL FINISHING
National Bureau of Standards
Gaithersburg, Maryland
October 4-6, 1977
PAPERS
Introductory Remarks
Emanuel Horowitz, Deputy Director, Institute for
Materials Research, National Bureau of Standards
Introductory Remarks
George Marienthal, Deputy Assistant Secretary of
Defense for Energy, Environment and Safety
A New Strategy for Controlling Priority Water Pollutants
*
.Ernst Hall and Dev Barnes, Effluent Guidelines Division,
Office of Water Planning and Standards, Environmental
Protection Agency
Cost Effectiveness for Cadmium Waste Treatment in the Electroplating
Industry
Kenneth J. Yost, Institute for Environmental Health,
Purdue University
* Presented Paper
PAGE
1
5
9
15
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PAPERS
~
Surface Alloying by Ion Implantation:
Cadmium Electroplating
An Alternative to
41
B. D. Sartwell and F. X. McCawley, College Park Metallurgy
Research Center, U.S. Bureau of Mines
Ion Vapor Deposited Aluminum Coatings
67
E. R. Fannin, McDonnell Aircraft Company
Cadmium in Food and Drinking Water - FDA Considerations
87
George L. Braude and Samuel Shibko, Public Health
Service, Food and Drug Administration
Cadmium Plating with Environmental Restrictions
103
L.E. Vaaler and J. Gurklis, Battelle-Columbus
Laboratories
Outstanding Corrosion Protection Provided with Zinc Flake in a
Water-Based Coating
113
J. A. deRidder and J. R. Kovelan, Diamond Shamrock
Corporation
A Practical Wet Impact Alternative to Cadmium Electroplating
135
Lester Coch, Waldes Kohinoor, Inc.
Electrodeposition of Zinc-Nickel Alloy Coatings
171
J. W. Dini and H. R. Johnson, Sandia Laboratories
(Presented by Donald J. Levy, Lockheed Research Laboratory)
Corrosion Resistant Coatings Containing Lubricating Solids As an 207
A;L,ternative to .Cadrnitnn Electroplating on Fasteners & other Hardware
G. R. Kliemann and D. J. Sargent, ElM Lubricants, Inc.
Artificial Shellfish for Monitoring Ambient Cadmium
Levels in Seawater
215
William B. Kerfoot, Environmental Devices Corporation
Unique Characteristics of Cadmium Electroplating
241
Albert R. Cook, International Lead Zinc Research
Organization, Inc.
The Properties of Cadmium and Tin-Zinc Electrodeposits
259
John M. Bihl, Tin Research Institute
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PAPERS
The Advantages of Chloride Zinc Plating
Edward R. Jorczyk, 3M Company
Manganese Pressure Phosphate Coatings as a Substitute
for Cadmium Coatings
Henry Crain, Rock Island Arsenal, Department of the Army
Effects of Cadmium in the Environment
Calvin Menzie, U.S. Fish and Wildlife Service
A New Non-Cyanide Cadmiwn Electroplating Bath
Edward R.Jorczyk, 3M Company
Bonded Solid Dry Film Lubricants as an Alternative
to Cadmium Electroplating
Theodore M. Pochily, Watervleit Arsenal, Department
of the Army
Alternatives for Cadmium Metal Deposition in the
Field of Mechanical Plating
Edward A. Davis, 3M Company
State of the Art for High Rate Sputter Deposition
E. D. McClanahan, R. W. Moss, N. Laegreid, J. W. Patten,
R. A. Busch, M. A. Bayne, and E. N. Greenwell
Cadmium as a Commodity
John M. Lucas and John M. Hague, U. S. Bureau of Mines
Replacement of Cadmium Electroplating on IBM Hardware
Allen W. Grobin, Jr., IBM Corporation
Evaluation of Coated Fasteners:
Alternatives To Cadmium Plating
H. J. Dolejs and R. E. Geisert, Gould, Inc.
Evaluation of Protective Coatings for Army
Ordnance Items
A. Edwards and W. E. Isler, Harry Diamond Laboratories,
Department of the Army
PAGE
289
307
325
365
381
409
423
465
479
495
519
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PAPERS
~
Corrosion Performance of New Fastener Coatings
on Operational Military Aircraft
541
Fred H. Meyer,Jr., Air Force Materials Laboratory and
Edward Jankowsky, Naval Air Development Center
The Ideal Aerospace Fastener Coatin~
555
E. Taylor and J. Laurilliard, Standard Pressed
Steel Company
Appendix I -
571
Panel Discussion:
"Are Specifications and Standards
Barriers to Change?"
Appendix II -
585
Panel Discussion:
"How Essential is Electrodeposited
Cadmium?"
Appendix III -
607
Attendance List
Appendix IV -
617
Sponsoring Agencies and Representatives
Appendix V -
621
Aerospace Industries Association
Surveys on Alternatives to Cadmium Plating
Appendix VI -
637
Results of Workshop Questionnaires
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INTRODUCTORY RE}~S
DR. El~UEL HOROWITZ, DEPUTY DIRECTOR
INSTITUTE FOR MATERIALS RESEARCH
NATIONAL BUREAU OF STANDARDS
I want to welcome you to the National Bureau of Standards on behalf of
the Institute for ~~terials Research.
Some of
be very
to take
you may be visiting the Bureau for the first time, and may not
familiar with what we do here. I thought it would be worthwhile
a few minutes to tell you something about the Bureau.
The Bureau was established in 1901 and it was meant to function as the
National Measurement Laboratory with responsibilities for developing
national standards, improved and new methods of measurement in the field
in engineering and science, and to provide a focal point in the United
States Government for standardization activities.
In 1965 the Bureau of Standards was reorganized into its current structure.
It consists of four major organizational units, or institutes. The
largest one is the Institute for Basic Standards which provides the
central basis within the United States of a complete and consistent
system of physical measurement; coordinates that system with the measure-
ment systems of other nations; and furnishes essential services leading
to accurate and uniform physical measurements throughout the Nation's
scientific community, industry, and commerce.
There is also an Institute for Applied Technology which provides technical
services to promote the use of available technology and to facilitate
technological innovation in industry and government; cooperates with
public and private organizations leading to the development of technological
standards (including safety standards) and codes and methods of test;
provides technical advice and services to government agencies upon
request; monitors NBS engineering standards activities, and provides
liaison between NBS and national and international engineering standards
bodies; and carries out programs falling into three broad categories:
(1) those which are safety related, (2) those which relate to improvin8
the industrial economy and to facilitating domestic and international
commerce, and (3) those which relate to improving the efficiency of
governmental operations.
The Institute for Computer Science and Technology has the responsibility
for the standardization of hardware and software in the computer field,
particularly with respect to purchases by the Federal Government.
The Institute for Materials Research, which is a co-sponsor of this
meeting, has as its mission the assistance and stimulation of industry
in the development of new and improved products and the full utilization
of existing products through increased understanding of basic properties
of materials. The Institute (a) develops, produces, and distributes
standard reference materials for the calibration of instruments and
equipment, the comparison of measurements on materials, and for assistance
in the control of production processes in industry and in Laboratories
1
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that are of direct benefit to the general public, e.g., clinical
laboratories and air pollution laboratories; (b) conducts research on
the properties and performance of materials which are of importance to
industry, commerce, science, and the general public, as well as the
collection and dissemination of data on these properties; (c) develops
techniques for the preparation of special research materials and for the
measurement of their properties; (d) develops criteria and tests,
including nondestructive tests, by which the performance characteristics
of materials may be evaluated; (e) provides advisory and research
services for other agencies; and (f) assists national and international
standardization organizations in developing methods of measurement and
establishing standards for materials.
In recent years, we in IMR have focussed on a number of national
one of which is the general problem that you are here to discuss
morning. I will touch on that briefly in a moment.
problems,
this
Some of our major programs at the present time concern the utilization
and the conservation of materials in society. We have a major program
in failure analysis (how and why do things fail) trying to predict the
performance of materials so that materials can be properly used in design
and then maintained properly.
We are concerned with clinical chemistry measurements, and measurement
and standards matters related to health. For example, we have a major
program in developing referee or definitive tests to make the clinical
analyses that are performed by approximately 15,000 clinical laboratories
in this country more accurate and meaningful. Last year there were
about 5 billion clinical measurements made in the United States. We
are also providing standard reference materials for calibrating instruments
and measurement methods so that analytical results can be compared from
one laboratory to another.
We are concerned with accurate measurements for air and water pollution.
While we are not responsible for the regulatory aspects of the environment,
we are concerned with providing accurate methodology and standards for
the analysis of particulates, trace metals, organics, and some of the
gases which are found in the environment. These methods, can then, be
adapted by the Environmental Protection Agency for some of their monitoring
activities and are available for industry use.
One of the problems that we have been concerned with over the last three
years in this latter program has been the analysis of toxic metals in
the environment. We have been particularly concerned with the chemistry
of heavy metals in the Chesapeake Bay. We have published a number of
papers describing the chemical transformations involving mercury and
other heavy metals that occur in the sediment of Chesapeake Bay;
specifically, those reactions involving strains of pseudomonas bacteria
and traces of tin which result in the transformation of non-toxic inorganic
mercury to methylated (organic) mercury.
2
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That brings me to the question of other heavy metals, including cadmium
which is under consideration at this workshop. We share your concern about
heavy metals finding their way into the environment. It is an important
health effects problem, and we need to understand the reaction mechanisms
involving heavy metals which lead to toxic compounds. There is also a
question of the conservation of cadmium as a strategic and critical
material.
To conclude with a brief comment on e1ectrodeposition efforts, NBS has
been active in this field since 1913. As many of you may know, NBS
scientists invented several forms of electrodeposition, including
electro1ess nickel. The staff concerned with e1ectrodeposition at NES
over the years has published more than 300 technical reports, including
the mechanical properties and the corrosion characteristics of some of
the e1ectrodeposited materials. We have a strong interest in the subject
that you are due to discuss here and we will be following the discussions
with keen interest.
3
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INTRODUCTORY REMARKS
MR. GEORGE MARIENTHAL,
DEPUTY ASSISTANT SECRETARY OF DEFENSE
FOR ENERGY, ENVIRONMENT, AND SAFETY
I appreciate the opportunity to be here with you this morning. I want to
thank those of you from industry, from the academic world,and from Federal
agencies for being here this morning and for your thoughtful papers. With-
out that support, this workshop would not be possible.
I represent the Department of Defense in the areas of energy, environment
and safety. The Department of Defense is vitally concerned with each of
those issues. In the energy area, we are working with the newly formed
Department of Energy, which was created last Saturday. The Defense Depart-
ment is a large consumer of our nation's energy and, as a result, we have
petroleum logistics problems. We must, for example, ask the question of
'~here do we place our petroleum in order to make sure that our fleet
and other mobile forces are run properly during times of emergency?" Our
more mundane activities involve the operation of thousands of installations
in an energy-conservation manner.
Hopefully, one issue during this conference will be the recognition that
energy is a problem and, as we are looking at alternative processes and
substitutes, the question of energy should be considered.
I also represent the Department in areas of occupational safety and health.
We are a very large employer, employing about 3 million people. These em-
ployees deserve a healthful working place, and my responsibility is to try
to provide that under such laws as the Occupational Safety and Health
Act.
Without going into occupational safety and health
say that all employers today have a major problem
work place.
further, suffice it to
in providing that safe
You may have seen in the media today that the National Institute of Occu-
pational Safety and Health has recently completed a major report. Dr.
Finklea of NIOSH announced that they had surveyed a large population of
employers, including a high percentage of those who employed more than
500 people, and had found that one out of every four employees was sub-
jected to hazardous materials and other hazards which would be injurious
to their health.
Our mutual concerns with safety and occupational health are among the
reasons we are here today. This issue will relate to the output of
this workshop.
I am concerned with and represent DoD in the area of environmental pro-
tection. We are,of course,doing the best we can in air pollution, water
pollution, safe drinking water, radiation, solid waste management and the
myriad of suth laws that affect our day-to-day operations in the Depart-
ment of Defense.
5
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Paramount in this workshop is the question of environmental protection.
It is not unusual at all, therefore, for the Department of Defense to be
a co-sponsor of this workshop. We became interested in cadmium more than
two years ago, and this workshop is a direct result of our interest.
The bulk of the credit for bringing this about belongs to Mr. Ed Dyckman,
who works for the Department of Defense.
In any event, the Department of Defense has addressed cadmium uses, alterna-
tive processes, and possible substitutes for several years. I would
like to say that the Defense Department does not have any preconceived
notions as to the future of cadmium.
There may be many of you here today who will say: "Cadmium is the greatest
thing. It is absolutely essential, and all we have to do is improve plat-
ing processes from an environmental protection point of view."
There are others who are saying, "Cadmium is bad,and it must be banned."
I suppose that there are a lot of you who have an opinion someplace between
these two.
I am not standing up here taking any side,and I am hopefully exploring al-
ternatives and all aspects of this issue. The DoD placed special interest
on our cadmium uses in early 1975, primarily due to some outside pressure from an
environmental group. The environmental group became concerned with heavy
metals from the Philadelphia sludge that was being ocean-dumped, which you
still can read about today. The Philadelphia EPA office in Region III
has recently extended the permit for ocean dumping.
The environmental group knew that there was a high concentration of heavy
metals in the sludge and selected cadmium as an example. They started
asking questions such as "How did cadmium get there to begin with?" In
response, the electroplaters of the area indicated that Department of De-
fense contracts caused the cadmium to be in the sludge, and the Department
of Defense is predominantly the number one user of cadmium and, therefore,
it is their fault. This brought me into the problem in a hurry.
This pressure was most helpful. It caused us to study cadmium comprehen-
sively, and it caused us to look at our use of it in the Department of
Defense, specification by specification.
The truth is that we consume, or cause industry to consume, about 5.2
percent of the U.S. annual consumption of cadmium. The bulk of cadmium
is used, as you know, in electroplating, and of that, the DoD is respon-
sible for consuming less than seven percent of the total. Therefore, we
do not wish to continue to carry the total burden on us from the environ-
mental groups.
That is why we are thankful for you being here today, to help us carry that
burden.
As we began to study our usage of cadmium from several points of view, che
primary concern was to protect public health and welfare, as dictated by the
6
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laws concerning safety, occupational health, and
such as the Federal Water Pollution Control Act,
304-B, and the Toxic Substances Control Act.
environmental protection,
Section 307 and Section
Our second concern was to develop a sound working relationship with the U.S.
Environmental Protection Agency in the area of cadmium.
We carried out that cooperative effort over the past two and a half years,
and this workshop is evidence that it is going well.
Thirdly, we are always interested in improving our materials processes and,
therefore, we initiated our own study to identify alternatives for cadmium.
Our study did idpntify options and many of those are, of course, described
in your papers. *
We are very interested in continuing our cooperative efforts with
and with other Federal agencies to minimize environmental insults
could occur from cadmium. Similarly, we are anxious to identify,
perfect, and test alternative materials and processes for defense
cations.
industry
which
appli-
The purpose of this conference, therefore, is to try to provide consumers with a
suitable selection of options to electrodeposited cadmium. This workshop
could also provide the regulatory agencies, such as the U.S. Environmental
Protection Agency, with an overview of the essentiality of camaium to U.S.
consumers.
Electrodeposited Cadmium may be absolutely essential in many applications
and EPA and other regulatory bodies should recognize that possibility.
I expect that this workshop will provide us with an understanding of the
currently available technology and hopefully provide the basis for estimat-
ing the best available technology in the 1980's and beyond. You have been
reading more and more about the amendments to the Federal Water Pollution
Control Act and the role that BAT will provide in the 1983 and 1985 time
frame.
If,during the next few years,it becomes evident that the usage of elec-
troplated cadmium decreases or changes on a national scale, a result that
may, in part, be attributable to this workshop, then regulatory agencies
responsible for restricting or changing the usage of other toxic sub-
stances may wish to sponsor similar workshops on these materials. As
such, a workshop that brings together scientists and engineers to thorough-
ly discuss alternatives, who then proceed to adopt those alternatives,
may be a promising mechanism for voluntary compliance as opposed to
mandatory compliance. For example~ we currently find ourselves in a mode
of mandatory compliance with a Phase II type change to the Federal Water
Pollution Control Act. Here we are going away from a guidelines type act
to a "how to do it" type act on a much more voluminous scale.
*
"Cadmium - Utilization, Environmental Impact, Materials and Processes
Specifications, and Substitutes", Ed,.;r-"rd J. Dyckman, Defense Industrial
Resources Support Office (DIRSO), June 1975.
7
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The proceedings of this workshop, which will include not only the papers
presented, but transcripts of all discussions held during the workshop,
will be used by all elements of the Department of Defense in our effort to
assess the various approaches to minimize the loss of cadmium to the environ-
ment.
Four of the 17 papers here this week are from the Department of Defense, and
we are proud of that achievement.
Once again, we are very proud to be a part of these proceedings, and we are
most sincere in our efforts to protect the environment and to protect our
workers. We trust and pray that the week's outcome will be a series of
positive approaches to meet both of those goals and, of course, your own
individual goals.
8
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Alternative Materials and Processes
Session I
Tuesday Morning 9:35
A NEW STRATEGY FOR CONTROLLING PRIORITY WATER POLLUTANTS
Dev Barnes
Ernst p. Hall
Effluent Guidelines Division
Office of Water Planning and Standards
Environmental Protection Agency
Washington, D.C. 20460
In June of 1976 the Environmental Protection Agency (EPA) entered into
a consent agreement settling outstanding litigation by NRDC and others. This
settlement can be characterized as having five major parts, one of which re-
moved cadmium as well as lead and cyanide from the 307(a) toxics list as it
then existed. This change allows us to approach the cadmium plating waste
problem by considering not only toxicity but also balancing technology, ec-
onomics, exposures and other factors as may be pertinent against the needs of
the enviroTh~ent and society.
This consent agreement requires EPA, inter alia, to reevaluate and
revise effluent limitations for 21 categories based on the best available
technology economically achievable (BAT) considering the need to regulate 65
listed pollutants (priority pollutants) ~s well as conventional pollutants.
One of these categories is electroplating and cadmium is one the 65 priority
pollutants. Therefore we are committed to revising the cadmium discharge
allowance for electroplating. Electroplating applies as a manufacturing unit
process anywhere it is practiced and is not limited to independent or job
shop platers.
The program of BAT
the technical and economic
Revised regulations are to
revision for electroplating
studies are to be completed
be promulgated by 1-1-80.
has only now begun and
by January 1, 1979.
Because we are at such a preliminary stage of this study it is haz-
ardous to make firm predictions of the nature and discharge limits in any
final regulations. However, some possible scenarios for tight control of
cadmium wastes may be appropriately discussed.
9
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A NEW STRATEGY FOR CONTROLLING PRIORITY WATER POLLUTANTS
Ernst P. Hall, P.E.
U.S. Environmental Protection Agency
Effluent Guidelines Division (WH-552)
Washington, D.C. 20460
On June 7, 1976 the Environmental Protection Agency signed an
agreement which settled four law suits brought against the
Agency by the National Resources Defense Council and the
Environmental Defense Fund. These suits were aimed at forcing
the Agency to take action on and to expand the list of toxic
substances to be regulated under Section 307(a) of the Federal
Water Pollution Control Act (the Act) and to promulgate
previously proposed pretreatment standards. In reaching a
settlement, the Agency agreed; 1) to promulgate 307 (a)
standards for six pollutants on the 307 (a) toxics list
(aldrin-dieldrin, benzidine, endrin, PCBs, toxaphene and DDT);
2) to remove the remaining three materials from the 307(a)
toxics list (mercury, cadmium and cyanide); 3) to complete
rule-making of pretreatment standards which had been proposed
for eight industrial categories; 4) to review and revise
effluent limitations based on the best available technology
(BAT) and new source standards for a list of 21 industrial
categories, and 5) to revise or promulgate pretreatment
standards for 21 industrial categories. In these final two
steps, the Agency agreed to give special consideration to a
list of 65 compounds or families of compounds which we
commonly refer to as priority pollutants.
It is important to make clear a potential semantic problem
when we discuss toxic pollutants or priority pollutants.
Materials designated under section 307(a) of the Act are
designated as toxic pollutants. Materials so designated
require separate effluent standards to be established based
primarily on their toxicity. The list of pollutants in the
Settlement Agreement, while they may have toxic effects, have
not all been formally designated as toxic materials under
section 307(a). Rather they have been singled out for special
study and investigation by the Agency for appropriate control
under BAT and pretreatment authorities of the Act.
As I pointed out, the Settlement Agreement specified a list of
65 priority compounds and classes of compounds to be given
special consideration in our studies. The list contains
several classes of organic materials which must be expanded
into sublists or specific representative compounds in order to
remove ambiguity in our study effort. Thus, our working list
10
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actually contains a total of 129 chemicals (114 organics, 13
"heavy" metals, cyanide and as'bestos). These are the priority
pollutants for special consideration during the BAT review of
the 21 industrial categories (a copy of this expanded listing
is attached) .
Under P.L. 92-500 and within the terms of the Settlement
Agreement, there are a number of control options available to
the Agency for dealing with industrial discharges of toxic or
priority pollutants. The BAT standards and regulations called
for under the Settlement Agreement represent the first step in
dealing with such discharges. If it is determined that these
technology based effluent standards are not adequate, the
Agency may choose other control options. For instance, one
option is to designate a material as a toxic pollutant under
section 307(a). Under this section, standards more stringent
than those established under BAT might be developed since
307(a) does not call for the detailed economic considerations
required in the development of effluent limitations under
sections 301 and 304. There are other options also in the
area of water quality standards.
A variety of study efforts are involved in the implementation
of the Settlement Agreement. As with our previous effluent
guidelines efforts, we are conducting technical studies aimed
at characterizing the various industries and their discharges
as well as the technologies available for control and
treatment of various pollutants. Also, as in our past
efforts, we are conducting economic studies aimed at assessing
the cost and economic impacts of various control options.
However, there are two additional study efforts called for in
the Settlement Agreement which make this program radically
different from our earlier effluent guidelines efforts. These
studies deal with the toxicity and exposure levels for the
various priority pollutants and serve as the driving force
behind the basic principles of integration and prioritization
which we are attempting to incorporate into our strategy. In
terms of toxicity, we will be looking at the effects of
priority pollutants on aquatic life as well as potential harm
to human health. Added to this will be information on the
presence or absence of these pollutants in the Nation's waters
and in industrial discharges. This combination of toxicity
and exposure data will enable us to determine which pollutants
and industrial categories are in need of regulation under BAT,
new source and pretreatment authorities of the Act. In
addition, it will serve as a guide to these and other
authorities under P.L. 92-500 such as section 307(a). The use
of studies is not intended to end at this point. To the
extent we find the nature of a pollutant problem goes beyond
industrial discharges, we can recommend appropriate actions
11
-------
(either regulatory or additional analysis) under other
legislative authorities including Resource COnservation and
Recovery Act, the Toxic Substance Act, and the Safe Drinking
Water Act. It is our intent, because of the complexity of
these studies, to place much of our early efforts on the
screening of specific industrial discharges to identify those
categories which truly merit regulation under the Settlement
Agreement. Through thi s process we hope to narrow the number
of materials and industrial categories with which we have to
be concerned in the development of effluent limitations. Once
this is done, we will proceed on an industry by industry basis
to quantify more extensively the levels of discharge for
various pollutants and the proper control techniques on which
to bas e our regu la ti ons.
Obviously, this is a very ambitious and complex program. The
thrust of the Settlement Agreement and the Act is to set in
motion a continuing process for the identification of
pollutant problems, analysis of these problems, selection of
the proper regulatory mechanism and appropriate regulatory
action. We are attempting to add one or two orders of
magnitude of sophistication to environmental standards setting
never before accomplished on the national level on such a
broad scale. Many of the pollutants we are dealing with have
never been studied before and as a matter of fact, analytical
methods are still in the development stage for some of these
ma te rials.
Of particular interest to this meeting is the fact that
cadmium and its compounds is one of the 65 "materials and that
electroplating, the most common manufacturing unit operation
for applying cadmium to a base metal, is one of the 21
industries which must be studied. The stage therefore is set
by a court order and consent agreement of 15 months ago, which
deals directly with the problem we are considering in the
several sessions of this meeting. The consent agreement
schedule for electroplating requires that the Agency let a
contract for technical studies and economic studies not later
than October 1, 1977 and that the technical studies be
completed in 12 months while an additional three months may be
allowed for the completion of economic studies. The whole
revision and rule-making process is scheduled to be completed
not later than December 31, 1979 by the promulgation of
revised BAT, new source and pretreatment standards. At this
point in time, we are on schedule in this endeavor and have
selected Hamilton Standard Division of United Technologies as
the contractor for the electroplating technical study. I
anticipate that our modus operandi on this project will be
relatively similar to the approach used in the 16 preceeding
BAT studies which have already been initiated. This includes
12
-------
the collection of a substantial amount of information from the
industry itself, the sampling of a number of plants for
determining the presence or absence of priority pollutants and
more intensive studies of some of the industry concentrating
on the priority pollutants found to be present and on the
effectiveness of various technologies in removing these
undesirable materials.
Because the project is in its infancy - officially it was to
start last Saturday - I am not really able to tell you with
certainty how it may come out, but I might suggest the~ are
some things which we might want to examine closely and see if
they will result in substantial reduction in the discharge of
cadmium from electroplating.
First, there is the possibility of requiring that
wastes from cadmium plating be segregated and
treated separately from any other electroplating
wastes. This might have a number of advantageous
effects such as reducing the amount of waste water
which must be treated to remove cadmium and
providing a more concentrated cadmium waste for
treatment.
A second technology which almost immediately comes
to mind is to require multiple stage cascade rinsing
controlled by electronic meters in order to reduce
the amount of rinse water derived from the plating
process. I am told for example that a six stage
cascade rinse can provide the same level of product
cleanliness as a single stage flowing rinse with
about 1/1000 of the volumetric flow. Similar
consideration in reducing the amount of process
waste water from cleaning operations might need to
be considered if those cleaning or rinsing
operations result in the discharge of cadmium.
The third obvious area for applying technology would
be in the treatment of the greatly reduced volume of
process waste water. The present BPT concept of
neutralization and sedimentation most certainly will
be looked at to see if some more advanced pollutant
removal system will not be substantially more
effective. It appears probable, for example, that a
very simple treatment of lime and settle technology
followed by filtration would result in a substantial
reduction of metal content from the neutralization
and sedimentation technologies now being considered
at BPT. Additionally, more advanced but still well
known technologies of sulfide precipitation followed
13
-------
by sedimentation and good filtration would be even
more able to reduce the volumes of materials
discharged. If we presume that advanced rinsing
techniques are successful in reducing water flows,
it may even be possible to apply more advanced
pollution control techniques such as reverse osmosis
or evaporation to further concentrate the cadmium
salts and put them in such a concentrated form that
it would be economic to recover and reuse them or
convert them into a solid form and for
environmentally safe disposal.
Please do not interpret this as telegraphing what EPA is g9ing
to require as BAT for cadmium plating. I have simply
discussed some of the possible options which the Agency most
certainly will consider as it work through all of the options
and develops the most appropriate control considering all of
the relevant factors for cadmium plating.
TMnky~.
14
-------
Alternative Materials and Processes
Sesstion I
Tuesday Morning 10:10
COST EFFECTIVENESS IN THE TREATMENT
OF CADMIUM ELECTROPLATING WASTE
Kenneth J. Yost
InstituLe for Environmental Health
Purdue University
West Lafayette. Indiana 47907
Cadmium electroplating waste treatment, recovery, and "housekeeping"
measures are surveyed. Capital and operating costs are given for waste
treatment/recovery systems designed to reduce cadmium concentrations in
plant effluent to levels ran~ing from 1.5 ppm down to .3 ppm with a
water use factor of 4 gal/ft of area "processed" (as defined in the
EPA Development Document for the Electroplating Point Source Category).
Waste treatment/recovery alternatives considered are restricted to
those which have been proven effective in practice for cyanide plating
baths. These in~lude the conventional flow-through and batch chemical
destruct methods (alkaline chlorination for cyanide removal followed by
pH adjustment and settling of metallic solids), evaporative recovery,
filtration, clarifier sludge centrifugation, and housekeeping practices
such as waste segregation, drip tanks, still rinses, spill recovery,
etc.
Results of laboratory studies of cadmium precipitation in se5regated
as well as mixed metal electroplating waste are presented. Among the
variables shown to affect cadmium solubility/treatability at various
pH's are the initial concentration of cadmium in segregated waste, the
initial relative proportions of cadmium and other metals in mixed metal
wastes, the duration of "second stage" cyanide treatment, and the amount
of alkaline cleaner solution mixed with metallic waste. Some implica-
tions of these results for the de'sign and operation of chemical destruct
waste treatment systems are given.
15
-------
Cost Effectiveness for Cadmium Waste
Treatment in the Electroplating Industry
by
K.J. Yost
Purdue University
The purpose of this paper is to discuss results of a study performed
in late 1975/early 1976 for the Environmental Protection Agency Office of
Toxic Substances relating to Cd removal efficiencies for waste treatment
systems as a function of cost.
The study was designed to produce a
sequence of waste treatment systems made up of readily available, "proven"
components, which afforded progressively more complete Cd removal.
A
total of four systems were postulated. along with a variety of "House-
keepIng" measures such as drip tanks. still rinses. 3-stage counterflow
rinses. drip pans. and waste segregation.
The performances of each of the four systems were characterized i.n
terms of Cd concentrations in system effluent; these range from 1.5 ppm
down to 0.3 ppm Cd with water use factors ranging from 80 11m2 (2 gal/ft2)
2 2
area processed down to 60 11m (1.5 gal/ft). The corresponding Cd
discharge factors range from 120 mg/m2 area processed down to 18 mg/m2 area
processed.
The estimates of system performance were based upon in-depth studies
of operating waste treatment systems in over thirty electroplating shops
located throughout the eastern half of the U.S.
These studies were
sponsored by the MFF, NAMF. and NSF.
Performance estimates were frankly
intended to be conservative, i.e. the Cd levels in shop effluent just cited
are intended to reflect what can reasonably be expected from these systems
16
-------
operating in a "typical" job shop setting.
It is entirely possible, in
fact highly likely. that these performance criteria could be exceeded by
extraordinarily carefully managed, perhaps vendor nurtured, systems.
The hypothetical waste feeding the four waste treatment systems derives
from a hypothetical Cd platIng line consisted of caustic cleaner, acid
pickel, plating and chromating steps, each followed by a rinse.
The line
is shown in Figure 1.
For calculational purposes, water use was divided
equally among the four processes.
The use of counterflow rinses, in the process of reducing water use,
will of course result in a much more concentrated waste stream input to the
four proposed treatment systems.
Observations of waste treatment system
performance in field suggest that reduction of water use, and associated
waste concentrations, generally diminishes the treatability of plating
waste.
This diminishing of plating waste treatability as a function of
waste concentration has also been noted in our laboratory studies, as
indicated in Figure 2.
Figure 3 suggest that a Cd-water solution does not
exhibit this concentration effect.
The implication seems to be that the
concentration effect is a function of plating bath constituents and/or
bath contaminants.
Figure 4 exhibits the concentration effect for dilute
Cu plating solutions.
Another point relating to our choice of water use factors; counter-
flow rinse flow rates for rinses following the process steps in the
hypothetical Cd plating line were arrived at by multiplying the 160 1/m2
area processed special by EPA for the metal finishing industry in the
April 24, 1976, Federal Register by the ratio of flow rates observed for
3-stage counterflow rinses to those observed for single rinses in our
field studies.
17
-------
The four postulated Cd waste treatment systems are discussed below.
They are identified as systems A, B, C, and D, respectively in the order
of increasing treatment efficiencies.
Waste Treatment System A is specified in Figure 5 and Table 1.
Costs
are in 1975 dollars.
It is anticipated that Cd concentration can be
2
reduced to 1.5 ppmin system effluent with a water use factor of 80 l/m
area processed.
This is essentially a flow-through chemical destruct
system with 3-stage counterflow rinses after each process step, house-
keeping provisions for the containment of spills (process tanks placed in
containment sites with provision for directing spill waste for acid-alkali
tre~tment) and drip tanks and still rinses after the plating and chromating
steps. The specified ~ processed in Cd plating is relatively high,
2 2
corresponding to 1500 ft /hr Cd plating. This adds up to 12,000 ft Cd
plating/8 hour work day (plating and chromating are defined by EPA as
"steps" where treated area contributes to the area processed total).
The
relatively high Cd production figure is consistent with our contention
that if preferentially strict effluent guidelines are adopted for Cd as
now seems likely, Cd plating will be done by relatively fewer shops
specializing in Cd plating.
The specified cost of the system does not
include the CN destruct unit which was the subject of a separate study
for OTS.
Tank sizes are based upon 12 hour retention time.
The retention
time for the specified treatment level (1.5 ppm) is more or less arbitrary
and consultation with individuals (e.g. S. Gary, Dick Crain) in the
waste treatment business.
Labor costs for operating this system are
2
estimated to be $1.40/1000 ft area processed; chemical costs are $6.10/
1000 ft2 area processed; and sludge disposal costs are estimated to be
2
24C/1000 ft area processed.
18
-------
Waste Treatment System B is given in Figure 6 and Table 2.
I t is the
same as System A but with an evaporation recovery unit in place of the
cyanide waste treatment system and the drip tank and still rinse following
the plating tank.
The cost comparison with System A does not include
capital saving associated w~th the deletion of the CN destruct unit.
The
addition of the evaporative recovery unit is expected to reduce Cd concen-
tration in system effluent to 1.0 ppm, and reduce the water use factor of
2 2
2 ga1/ft to 1.5 gal/ft.
th:s system are $1.50/1000
2
.16/1000 ft processed.
Labor, chemicals and sludge disposal costs for
2 2
ft processed, $4.10/1000 ft processed, and
The relatively "small" Cd reduction factor is
associated with the containment of post-plating rinse by the evapor~tive
recovery unit.
Evaporative recovery units must recover cyanide to the point
that no supplementary cyanide treatment is required.
This was not the
case for several of the units we have surveyed.
Waste Treatment System C is the same as System B with the addition of
a filtration unit (with backup) to polish the Acid-Alkali clarifier effluent.
The componant list is summarized in Table 3.
Filtration units must be
shown to be practicable for the plating industry where water use factors are
low, and degree of waste concentration high, i.e. they must function with-
out excessive blinding or degradation of filter membranes/materials.
The
filter specified here is of the leaf type with a vibrator to shake off dry
cake.
The filtration unit (with backup) is expected to reduce Cd concen-
tration in system effluent from 1.0 ppm down to 0.5 ppm.
Chemicals and
sludge disposal costs for this system are assumed to be the same as for
Labor costs are estimated to rise from $2.10/1000 ft2 processed
System B.
2
to $2.48/1000 ft area processed.
The increase is associated with maintenance
of the filtration unit.
19
-------
Waste Treatment System D is summarized in Figure 7 and Table 4.
It is identical to System C but with three tanks for batch treatment of
acid-alkali waste.
Treatment tanks are sized to allow for 24 hour
detention time.
Each treatment tank is agitated at the time treatment
chemicals are added by paddle mixers with 2.5 HP turbine type motors.
Batch treatment of the acid~a1ka1i waste is expected to reduce Cd concen-
tration in system effluent from .8 ppm down to .3 ppm.
Chemica 1s and
sludge disposal costs are assumed to be the same with System D as with
Labor costs, however, are estimated to rise from $2.45/1000 ft2
System C.
2
are processed to $5.60/1000 ft area processed.
The increase in labor
costs are associated with the maintenance and monitoring associated with
the batch treatment system.
Sufficient floor space must be available for
trea tmen t tanks.
This may be a substantial problem for urban shops.
Recessed floor tanks may be a partial answer to this problem for shop
occupying ground floor area in urban building.
Chemicals and labor costs for the four proposed systems were in
part derived from data collected on our plant surveys.
Table 5 gives a
summary of some of these data.
Tables 6 and 7 summarize 1abort chemicals
and sludge disposal costs; and water use factorst Cd discharge (mg/m2 area
processed), and Cd discharge concentrations for the four treatment
systems.
20
-------
Figure #
1
2
3
4
5
6
7
Table #
1
2
3
4
5
6
7
Caption
Hypothetical Cadmium Plating Line
Apparent Solubility of Cadmium as
a Function of pH in a Plating
Solution Diluted to 1000, 500, and
200 ppm Cadmium. Shop # 4.
Apparent Solubility of Cadmium as a
Function of pH in Cadmium Chloride
Solutions. Samples Were pH Adjusted
and Allowed to Settle for One Hour,
then the pH of Each Sample was
Remeasured and the Sample Filtered.
Apparent Solubility of Copper as a
Function of pH in a Plating Solution
Diluted to 1000, 500, 200, and 50
ppm Copper. Shop #8.
System A Schematic
System Blc Schematic
System D Schematic
Caption
System A Component List
System B Component List
System C Component List
System D Component List
Waste Treatment, Labor, and
Chemical Costs.
Estimated Operating Costs for
Proposed Waste Treatment Systems.
Expected Performance of Proposed
Waste Treatment Systems.
21
-------
Caustic
Cleaner
N
N
Acid
Pickle
2 Stage
Counterflow
Rinse
2 Stage
~~
Counterflow
Rinse
Figure 1: Hypothetical Cadmium Plating Line.
3 Stag e
Cd
Platin
Counterflow
Rinse
.. Treatment
~ Chromate /
Bright 0 i P
~
-------
z
o
~
a:
.....
z
w
u
z
o
u
_1.0
"-
~~
=>E
--
~
a
«
u
a
w
>
-'
o
en
if!
o
Figure 2:
10
0.1
Initial Cd Concentration
6 1000 ppm
o 500 ppm
. 200 ppm
4
"
,
'4
,
,
. lr - -6- - -6- - -f:r. - '6-.
'. ,
'. ,
'. '6 I
~"'" 0 '--ls/ 0
'fI ..0..... .. 0 .
w'" -" -'" 0 :
. . "
'. .
-'0 .,'
'. O.
'"
~
8
J
9
II
12
10
pH
Apparent Solubility of Cadmium as a Function of pH in Cadmium
of pH in a Plating Solution Diluted to 1000, 500, and 200 ppm
Cadmium. Shop J4.
23
-------
Figure 3:
1000
Initial Cd Concentration
~IOOOppm
o 500 ppm
o 200 ppm
o 50 ppm
-
z
o
~
a:
f-
z
W
u
z
o
u
~
:::>
~
Q
<{
U
o
w
~
o
(/)
(J)
o
7 8 9 10 Iii 2 13
pH iMMEDIATELY PRIOR TO FILTRATiON
Apparent Solubility of Cadmium as a Function of pH in Cadmium
Chloride Solutions. Samples Were pH Adjusted and Allowed to
Settle for One Hour, then the pH of Each Sample was Remcasured
and the Sample Filtered.
24
-------
100
-
.......
~
E
-
z
0
~ 10
a:
I-
z
W
u
z
0
u
1.0
a:
w
a.
a...
0
u
0
w
> 0.1
-'
o
(f)
if)
-
0
0.01
7
Figure 4:
In1ttol Cu Concentration
~ 1000 ppm
o 500 ppm
o 200 ppm
o 50 ppm
.....o---o---a'"Q
,
"-
'q
\
\
\
\
q
\
\
\
\
\
\
\
~
\
\
\.
Q
"-
'8- - -0
.
Q
Q
.
.
.
.0
.
.
.
.
0....0
..
.0..
...
.
8
9
10
pH
.
.
.
o
.
13
Apparent Solubility of Copper as a Function of pH in a Platinr
solution Dilul~J to 1000, 500, 200, and 50 ppm Copper. Shop #B
25
-------
Cr. Reduction
Acid-Alkali Waste
Scavenger
N
C1\
CN Treated. Waste
Figure 5: System A Schematic
Supernatant
Sludge Concentrate
Acid - Alkali
Clarifier
Sludge
Sludge
CN Clarifier
Overflow
Overflow
Effluent
-------
Table 1:
System A
- Flow-Through Chemical Destruct System With Housekeeping Provisions for
the Containment of Spills. Drip tanks and still rinses after the
plating and chromate baths. Three-stage counter flow rinses for all
steps in plating line.
Components
Size
Capital Costs ($)
1)
2)
2 pH Adjust Tanks
500 ga 1.
1,600
3 gal/hr of 20% solids
sludge
Centrifuge
6.000
3)
4)
2 pH Controllers
5,600
Final pH Adjust Tank
1,000 gal
1,600
5)
2
18.000 gal/l,OOO ft
processed/hr
2
18,400/1,000 ft
processed/hr
Acid-Alkali Waste Clarifier
(rubber lined)
6)
2
6,000 ga1/1,OOO ft
processed/hr
2
4,100/1,000 ft
processed/hr
Cyanide Waste Clarifier
(painted)
7)
8)
2,000 gal/hr
13,600 (with ORP)
Chrome Reduction Unit
Cyanide Destruct Unit
2,000 gal/hr
Not included
9)
Acid for Caustic Tanks
for pH Adjust
Engineering costs for 3.000 ft2 Area Processed
in Cd Plating/hr. (10% capital cost does
~ include CN treatment capital)
500 ga 1.
1,600
10)
9.750
2 .
Total (3,000 ft Area Processed ~n
Cd plating/hr - ~ including
CN treatment capital costs)
107,250
27
-------
Cr
Reduction
Acid-Alkali
Waste
Supernatant
Condensate (to rinse)
N
00
CN Wa sh
(plating rinse)
Evaporator
Concentrate (to plating)
Figure 6: System Ble Schematic
Acid - Alkali
Clarifier
Sludge
Scavenger
HFiltration)-! /
Effluent
)!lor
Concentrate
-------
T.able 2:
System B - Same as System A but with an evaporative recovery unit in place of the
cyanide waste treatment system and the drip tank and still rinse
following the plating tank.
Components
Capital Costs ($)
Size
1)
2)
pH Adjust Tank
500 gal
1,000
3 gal/hr of 20% solids
sludge
Centrifuge
6,000
3)
4)
pH Controller
2,800
2
18,000 gal/l,OOO ft
processed/hr
2
18,400/1,000 ft
processed/hr
Acid Alkali Waste Clarifier
(rubber lined)
5)
6)
2,000 gal/hr
13,600 (with ORP)
Chrome Reduction Unit
100 gal/hr
Evaporative Recovery Unit
33,000
7)
Engineering Costs for 3,000 ft2 Area Processed
in C4 Platirig/hr (10% of capital)
2
Total (for 3,000 ft Area Processed
in Cd Plating/hr)
122,900
11,200
29
-------
Table 3:
System C - Same as System B with the addition of a filtration unit (with backup)
to polish the Acid-Alkali Clarifier Effluent.
Components
Size
Capital Costs ($)
1)
System B
-----
111,600 for 2
3,000 ft area
processed/hr
in Cd plating
2)
3)
2 Filtering Units
-----
24,000
Engineering Costs for 3,000
in Cd Plating/hr (10% of
2
Total (3,000 ft Area Processed in
Cd plating/hr)
2
ft Area Processed
capital)
13,600
149,200
30
-------
Cr Reduction
Acid-Alkali Waste
LV
I-'
Acid- Alkali
Treatment
Su per nata nt
Acid- Alkali
Treatment
Sludge Concentrate
Condensate (to rinse)
eN Waste
(plating rinse)
Evaporator
Concentrate (to plati ng)
Figure 7:
System D Schematic
Fi Itration
Effluent
Scavenger
-------
Table 4:
System D - Same as System C but with three clarifiers for batch treatment of
Acid-Alkali Waste. Clarifiers are sized to allow for 24 hour detention
time.
Components
Size
Capital Costs ($)
1)
System C less Acid-Alkali
Clarifier
-----
80,400
2)
3 Acid-Alkali Settling
Tanks (rubber lined)
2
1,500 gal/1,000 ft
processed/day
129,600 for 2
3,000 ft area
processed/hr in
Cd plating
4 - 5HP Turbine Paddle Mixers (1 back up)
3)
4)
12,000
Engineering Costs (10% of
2
Total (30,000 ft Area
in Cd plating/day)
capital)
22,200
Processed
244,200
32
-------
Table 5:
Waste Treatment, Labor, and Chemical Costs.
Shop
Labor
($/1000 ftZ Processed)
Chemicals
($/1000 ftL Processed)
System
1n 3.70 3.80 Batch
1t3 2.18 4.10 Continous
1t4 0.32 .15 Continous
116 0.23 .54 Continous
1f8 0.79 1.10 Continous
iHO 0.79 1.20 Continous
#11 0.02 .86 Continous
iH4 5.84 16.0 Continous
(Batch for Cr & CN)
;/:17 4.42 9.1 Continous
iH9 0.25 .10 Continous
33
-------
Table 6:
Estimated Operating Costs for Proposed Waste Treatment Systems.
Syste.l!!
Labor
($/1000 ftLprocessed)
Chemicals
($/1000 ft2processed)
Sludge Disposal
($/1000 ftLProcessed)
A 1.40 6.10 .24
B 2.10 4.10 .16
C 2.45 4.10 .16
D 5.60 4.10 .16
34
-------
Table 7:
Expected Performance of Proposed Waste Treatment Systems.
Waste Treatment
Water Use
Factor.
(1/m2)
Cd Discharge/Area
Processed in Cd Plating
(mg/m2)
Cd Concentration in
Clarifier Effluent
(mg/l)
System A 80 120 1.5
w System B 60 60 1.0
VI
system C 60 30 .5
System D 60 18 .3
EPA Effluent 160 36 .6
Guidelines Proposed
Standard-Existing Source
EPA Effluent 80 18 .6
Guidelines Proposed
Standard-New Source
-------
COST EFFECTIVENESS IN THE TREATMENT OF
CADMIUM ELECTROPLATING WASTE
DISCUSSION PERtOD
SPEAKER:
I assume you did all your work with
alkaline
cadmium solutions.
DR. YOST:
Yes.
SPEAKER:
Did you do any work with cadmium acid
solutions?
DR. YOST:
We have done the solubility
work, but
no field studies of acid.
SPEAKER:
Has anybody at all?
DR. YOST:
We have no field data.
We have seen in
the lab that we don't notice this concentration effect.
We
have done some laboratory work with acid copper and find
that we do not see the concentration effect with acid copper
solution, but that we do see it with the cyanide copper.
I
suspect that the situation would be the same with cadmium.
HR. POPE:
Dick Pope, the Weatherhead Company.
In
your experience, do you think it is possible to meet a .03
parts per million effluent limit on cadmium?
DR. YOST:
My personal opinion is that this requires
a closed loop.
There is no point in tracking down to those
levels.
Nobody could handle them.
!-iR. POPE:
Would this mean that you don't have
any effluents?
DR. YOST:
I think you can go to expensive closed
loop systems. I suppose you can throw back on your pickle
36
-------
rinse,
some of your chromates, your plating rinse.
I don't
know what to do about your cost.
MR. KRAFT:
Jerry Kraft, Kraft Chemical.
I wonder
if you would summarize your original work on the effect of
cadmium in the sediment and whatever effect that had on its
life cycle.
DR. YOST:
Basically, cadmium introduced into
aquatic systems is quickly precipitated and deposited into
bottom sediment.
We have found that as far as edible fish
species are concerned, even fish that are obtained from
heavily cadmium-contaminated areas do not show alarmingly
high cadmium concentrations in their edible portions. There
is Cd concentration in the fish liver and kidney.
DR. YOST:
We find that, generally, cadmium lies
relatively dormant in the sediment once it is introduced
into an aquatic system.
It is not like methylated mercury
or something of that nature.
We found cadmium concentration in sludge as high
as 1,000 parts per million, and the background in that area
is about two to three tenths.
SPEAKER:
It was hard to tell from the chart, the
total cost of the weight measurements, say, for 10,000
square feet of cadmium; was it the total of those figures
you had on the slide there?
DR. YOST:
Yes, that was the bottom figure.
SPEAKER:
Can one assume in the next to last table
that the higher labor cost would be the one that would be
the less likely to pollute the water streams?
37
-------
DR. YOST:
Yes, because the more complex and
costly systems require much closer monitoring and mainte-
nance in general.
SPEAKER:
But the guy who has the labor cost of
only 259 an hour, what is he doing?
DR. YOST:
As little as he can.
DR. YOST:
This survey was prompted by our inter-
est in the job shop component of the plating industry.
It
is this component that is going to be most totally affected
by the final EPA effluent guidelines.
SPEAKER:
Going back to your solubility curves,
you are showing a higher concentration which is less effi-
cient in bringing that down because you included chelating
agents.
Jumping over to systems that you proposed for waste
treatment, do you see a problem assuming higher concentra-
tions? How effective are these systems?
Down to what con-
centrations do you get the cadmium?
DR. YOST:
I guess I will have to dodge that one.
I think the jury is still out.
For this particular study,
we did specify a segregation of the cadmium waste, which
will do away with another effect which we have seen.
When
you mix cadmiurnzinc that seems to elevate the apparent solu-
bilities of each metal.
But I think it would probably meet
these limits, even with that effect.
SPEAKER:
On those studies, were you treating
cadmium and chrome at the same time?
DR. YOST:
Yes.
SPEAKER:
We are not just talking cadmium then?
38
-------
DR. YOST:
No.
The costs that were associated are
related to that hypothetical plating line which has the
chrome destruct system as part of it.
The Cd line had a chromating step, and we had in
those costs included a chrome reduction capability.
39
-------
Alternative Materials and Processes
Session I
Tuesday Morning 10:45
SURFACE ALLOYING BY ION IMPLANTATION:
AN ALTERNATIVE TO CADMIUM ELECTROPLATING
B. D. Sartwell
F. X. McCawley
College Park Metallurgy Research Center
Bureau of Mines, U.S. Department of the Interior
College Park, Maryland 20740
The Bureau of Mines is conducting research with the goal of
conserving critical alloying elemevts. This research includes
studies to develop a new class of corrosion--resistant alloys
that are fabricated by the implantation of energetic metallic
ions into either an iron or low-alloy substrate. The advantages of
using ion implantation over electrolytic plating are (1) the alloyed
surface region, extending to depths of up to 100 nm, is an
integral part of the substrate, thereby eliminating problems such
as interfacial weakness and dimension change, (2) ion implanation
produces no environmentally unacceptable byproducts that would
contribute to air or water pollution, and (3) the amount of elec-
trical power required to produce an equivalent corrosion- resistant
surface is estimated as being from 4 to 10 times less than required
for conventional electroplating techniques.
Surface stainless steels have been fabricated by implantation
of low-energy chromium and nickel ions into iron. 2The quantity of
chromium and nickel used was approximately 2 ug/cm of the substrate.
These surface alloys have been compared to ca"cJmium - plated steel in
corrosion tests involving exposure in several metallurgical process
environments. Results have shown that the relative corrosion rates
are comparable. Preliminary corrosion tests of iron implanted with
cadmium ions have shown that surface protection can be provided using
ion implantation.
41
-------
SURFACE ALLOYING BY ION IMPLANTATION:
AN ALTERNATIVE TO CADMIUM ELECTROPLATING
by
B. D. Sartwell
College Park Metallurgy Research Center
Bureau of Mines, U.S. Department of the Interior
College Park, Maryland 20740
Abstract
The Bureau of Mines has fabricated a new class of alloys by imp~anta-
tion of low-energy metal ions into the surface regions of iron to
doses ranging from 1.0 to 4.0 x 1016 ions/cm2. The alloy distribu-
tion as a function of depth (depth profile) has been determined for
polycrystalline iron samples implanted with either 25-keV chromium or
nickel ions, and the results have been compared with theoretical pre-
dictions. The resistance of these "surface alloys" to environmental
attack has been evaluated both by determining their anodic polariza-
tion behavior under potentiostatic conditions and by determining their
gaseous oxidation characteristics. Results of the electrochemical
studies have shown that the general corrosion resistances of the
surface alloys were comparable to those of nominally equivalent bulk
alloys and that the pitting-corrosion resistances for the surface
alloys were superior to that for iron, although generally not as good
as those for most equivalent bulk alloys. Gaseous oxidation studies
have shown that surface and bulk iron-chromium alloys exhibit
essentially identical oxidation kinetics, with a much higher rate of
oxidation observed for iron. In both the aqueous corrosion and
gaseous oxidation studies, the quantity of the alloying element used
to fabricate the surface alloys was six to seven orders of magnitude
less than that required to fabricate equivalent bulk alloys.
Introduction
To ensure the United States an adequate supply of critical materials,
the Bureau of Mines is conducting research to develop new, substitute
corrosion-resistant materials. The formation of alloyed regions near
the surfaces of metals using ion implantation is being investigated
as a means of providing corrosion resistance while realizing a sub-
stantial reduction in the consumption of expensive alloying materials
that are in limited supply. Ion implantation is a nonpolluting
process and, therefore, should also be investigated as a potential
substitute for standard electroplating processes.
42
-------
In this paper, the corrosion behavior of the surface alloys formed by
ion implantation will not be directly compared to that of cadmium-
electroplated steel. Comparisons will be made, however, between the
surface alloys and nominally equivalent bulk Fe-Cr and Fe-Ni alloys
which are known to be highly resistan~ to corrosive attack. It is
believed that if the surface alloys can be shown to possess corrosion
resistance comparable to the bulk alloys while using orders of magni-
tude less of the alloying elementt the surface-alloying process could
be a viable alternative to cadmium electroplating
Since its inception, the surface-alloying program at the Bureau of
Mines has been divided into three interrelated components: (1) the
development of the technology for the fabrication or production of
surface alloys, (2) the investigation of the physical properties of
surface alloys, and (3) the study of the aqueous and gaseous corrosion
characteristics of surface alloys compared to those of conventional
bulk alloys. The development of the fabrication technology has
involved the design and construction of two metal-ion implantation
systems. Using these systems, investigations have been conducted to
determine the rate of production of surface-alloyed material, what
types of metal ions can be implanted, and what size and shapes of
material can be surface-alloyed. The study of the physical properties
of the surface alloys has principally involved determining the
specific alloy concentration as a function of depth (depth profile)
and the effects of heat treatment on these profiles. Future work in
this area will be addressed to determining the alloy phases formed,
the number and types of defects produced in the substrate lattice by
the implantation process, and the effects of friction and wear on the
surface alloys. Corrosion characteristics of surface alloys have been
investigated in both aqueous and gaseous environments by comparing the
anodic polarization behavior and gaseous oxidation kinetics of sur-
face alloys to those of nominally equivalent bulk alloys. Preliminary
studies have also been conducted on determining the galvanic corrosion
and stress-corrosion-cracking behavior of surface-alloyed material.
Summary of Ion Implantation Theory
Ion implantation involves the injection of energetic ions into a solid
material. As ions penetrate a target material, they lose energy
through collisions with the target atoms, eventually coming to rest at
substitutional or interstitial lattice sites. The slowing-down pro-
cess for the ions is considered mathematically as a statistical pro-
cess, and the theories that have been developed to describe this
process generally predict that the final distribution of the implanted
atoms will resemble a Gaussian distribution (1). Figure 1 shows a
typical Gaussian distribution for low-energy ions implanted into an
amorphous material. The final concentration of the implanted species
is plotted as the ratio of the concentration, H(X). at a depth, X, to
the maximum concentration, N. The two parameters that describe the
p
43
-------
1
~-~-- Rp------
c.
Z
......
-
><
-
z
...
z
o
-
I-
<
a:
I-
z
W
(.)
Z
o
o
-ARp-
Alloyed region
Alloying element
di s tribution
--------------------------~-
SURFACE
DEPTH, X
Figure 1. - Typical Gaussian distribution for low-energy ions implanted into an
amorphous material.
""
""
BUREAU OF MME'
H 10,732 a»
-------
distribution are Rn, the "mean range" or "mean depth of penetration"
of the ions, and ~R , the standard deviation of the distribution,
sometimes referred ~o as the "range straggle."
The parameter that is normally used to describe the concentration of
implanted atoms is the dose, D, the number of ions per square centi-
meter implanted into the substrate material. However, in order to
compare surface alloy to bulk alloy systems, a designation for the
surface alloys has been obtained by averaging the concentration of the
implanted species over the region of the substrate extending from the
surface to a depth, R , that would include 95% of the implanted
species. Thfsdepth w~s determined experimentally for each alloy
system that was fabricated. The average concentration, N, of the
implanted species is calculated from N = D/R. The alloy designation
is then Fe-C(s)I, where C = N/8.5 x 1022 fortiron, and I is the
implanted element.
Experimental Techniques
This section describes the experimental techniques used for the
fabrication of the surface alloys and for the study of the corrosion
characteristics of the surface alloys. Part I of this section dis-
cusses the method used to prepare samples for either ion implantation
or for electrochemical and oxidation studies, Part II describes the
ion implantation system used to fabricate the surface alloys, and
Parts III and IV discuss the technique used in the anodic polarization
and oxidation research, respectively.
I. The iron samples that were used in the corrosion studies and as .
substrate metal in the fabrication of the surface alloys were cut from
high-purity (99.95%), cold-rolled iron sheet pruchased from the
Materials Research Corporation. 1 The bulk Fe-Cr alloys used in the
corrosion studies were fabricated by the Bureau of Mines, Albany
Metallurgy Research Center. Other metals and alloys used in the
electrochemical studies included high-purity nickel (99.5%) obtained
from International Nickel Company, type-9 nickel steel obtained from
the U.S. Steel Corporation, and a maraging steel (Vascomax-250)
obtained from Teledyne Metals.
Preparation of the nickel, type-9 steel, and Vascomax-250 for the
electrochemical studies consisted of mechanical polishing through 600
grit, cleaning with acetone and methanol, rinsing with l8-megohm
water, and drying in ultra-high-purity (UHP) nitrogen.
Preparation of the iron and the Fe-Cr alloys was more extensive.
This consisted of mechanical polishing through 600 grit, degreasing
lReference to specific trade names is made for identification only
and does not imply endorsement by the Bureau of Mines.
45
-------
with acetone and methanol, heat-treating at 6000 C for 2 hours in an
argon atmosphere, and then a rapid water quench. To remove the thick
scale resulting from the heat treatment, the samples were pickled in
20 vol-pet H2S04, rinsed with 18-megohm water, and then dried with
UHP nitrogen. Samples were then individually e1ectropo1ished in a
400-m1 solution of a 9:1 mixture of glacial acetic to 70 vol-pet
perch10ric acid. Following electropolishing, the samples were rinsed
with 18-megohm water, dried in a stream of UHP nitrogen, and then
mounted in the ion implantation system, the oxidation chamber, or the
electrochemical cell, depending on the type of test to be performed.
II. The surface alloys used for the corrosion and oxidation studies
were fabricated in the metal-ion implantation system shown schemat-
ically in figure 2. The principle of operation is as follows: a
solid metallic compound (for example, CrC13) called the "charge" is
placed in a short section of stainless steel tubing. During operation,
this charge is inserted in the ion source where the compound is vapor-
ized and ionized. The ions are "pulled" from the source by a nega-
tively charged extractor electrode, focused into an ion beam by the
focusing electrode, and then acce1ereated to the desired energy by
the accelerating electrodes. The ion beams are analyzed according to
the charge-to-mass ratio by the beam-analyzing magnet, providing fer
a high-purity beam of the metal ions entering the sample chamber.
The LN2-coo1ed section of beamline is designed to trap residual gases,
such as eh1brine, silicon, and hydrocarbons, generated either by the
ion source or the vacuum pumping systems and to prevent them from
entering the sample chamber and contaminating the surfaces of the
samples.
The fabrication chamber is constructed of stainless steel with meta1-
seal flanges and pumped with a 110-liter-per-second ion pump capable
of evacuating the chamber to a base pressure of 1 x 10-8 torr. The
metal samples intended for implantation are mounted on a carrousel,
with a diameter of 14 em, able to accommodate either twelve 2.5-em-
diameter samples or twenty-four 1.25-cm-diameter samples. The car-
rousel is insulated from ground and connected to a current integrator
that measures the total amount of ion beam charge incident on the
samples. From the value of the measured charge, the ion dose, D,
expressed in ions per square centimeter, could be calculated. There
are, however, several uncertainties involved in the measurement of
D in this manner. Therefore, the fiecessary quantitative determinations
of the total ion doses and also of any surface contaminants introduced
by the implantation process were obtained by proton-excited X-ray
analysis (PEX) (~).
III. The aqueous corrosion behavior of the surface alloys was
evaluated electrochemically under anodic polarization conditions in
a 0.15N boric acid solution (20.6 g/equiva1ent weight) containing
0.4 wt-pct NaCl (2,400 ppm C1-) and buffered to a pH of 8.5 with the
46
-------
OVEN SOURCE
~ECTRODES
CHARGE
HEATING FILAMENT
+--
"
ANAL YZING MAGNET
LN2 BEAM LINE BAFflE
ROTATING SAMPLE WHEel
MAGNETICALL Y COUPLED MOTOR
Figure 2. - Simplified schematic of Bureau of Mines metal-ion implantation system.
-------
addition of 0.15N ~a2B404'10H20 (5.5:1) (179.1 g/equivalent weight).
The solution was prepared using reagent-grade chemicals mixed in 18-
megohm water and was stored in a specially designed reservoir that
kept the solution free of atmospheric contaminants and provided for
direct transfer of the solution to the electrochemical cells.
The polarization measurements were conducted in a modified Greene-
type (1) electrochemical cell that had been thoroughly cleaned with
boiling HN03 and subsequently steamed with boiling l8-megohm water.
This cell, including the modifications, is shown schematically in
figure 3. Each cell consisted of a platinum counter-electrode, a
saturated calomel reference electrode, and the working electrode
(i.e., either a surface alloy, iron, or a bulk alloy). The working
electrode was mounted in a compression holder that, for the surface
alloys, isolated the nonimplanted regions of the sample from the
solution. High-purity helium (99.9%) entered the gas inlet and
stirred the solution in front of the working electrode in order to
minimize diffusion control of the reactions. The saturated calomel
reference electrode (SCE) was isolated using a Luggin-Haber probe.
The potential of the working electrode was controlled with a Wenking
70TS! potentiostat and a Wenking VSC72 voltage scan generator. Anodic
currents were measured with a Keithley 165 multimeter and recorded on
an XY recorder.
The anodic polarization measurements were performed identically for
iron, the bulk alloys, and the surface alloys. Prior to beginning
the potential scan, the metal sample was cathodically reduced using
the Wenking potentiostat in the galvanostatic mode. A cathodic
current density of 5 x 10-4 amp/cm2 was used to reduce the air-formed
oxide films on the metal surfaces. The samples were then allowed to
achieve a steady-state open-circuit rest potential (ER) for 10 to 15
minutes, following which the anodic polarization test was initiated
at -100 mV with respect to ER with the potential scanned at a rate
of 10 mV/min.
IV. The procedure used to determine the oxidation kinetics using
PEX has been extensively discussed elsewhere (~). and only a brief
description is given here. The sample to be oxidized was mounted in
the ultra-high-vacuum PEX analysis chamber and was heated radiatively
to the desired oxidation temperature of 3000 C by a tungsten filament.
At an ambient vacuum chamber background pressure of <1 x 10-8 torr,
research-grade-purity oxygen (10 ppm total impurities) was leaked into
the ya.auum chamber, through a sapphire seal leak-valve, to a pressure
of 4 x 10-6 torr in less than 2 seconds. Oxidation times .ranged from
25 to 2,000 seconds. At the end of each oxidation cycle. the chamber
was evacuated to 1 x 10-8 torr, the beam-line gate valve was opened.
and the thickness of the oxide film was measured by PEX.
48
-------
.j::-.
'"
/ Gas outlet bubbler
Counter electrode
Working electrode
Figure 3. - Schematic of the electrochemical cell used to determine the anodic polarization
behavior of the surface and bulk alloys.
-------
Physical Properties Studies
Since the technique of forming surface alloys by ion implantation is
considerably different from standard alloy fabrication techniquest an
understanding of the physical metallurgy of surface alloy systems andt
specificallYt the determination of the alloy concentration as a func-
tion of depth (depth profile) is required in order to interpret their
behavior in hostile environments. The theoretical depth profile
calculated from the theory of Lindhardt Scharff and Schiott (designated
LSS theory) for low-energy ions implanted into an amorphous material
was shown in figure 1. Since this theoretical description had not
been substantiated experimentally for metallic systemst it was impor-
tant that experimental profiles be obtained for the surface alloys.
Figure 4 shows the depth profile of 25-keV nickel ions implanted into
polycrystalline iron as determined experimentally using a combination
of PEX and low-energy argon ion sputtering (i). A comparison of the
experimental profile with the Gaussian-shaped profile of figure I
indicates that the distribution has been shifted toward the surface
and that the surface concentration is much higher than what would be
expected. This phenomenon was explained by considering the effects
of sputtering of the iron substrate during the implantation process
on the final depth profile. This sputtering results in an erosion of
the iron surface with removeal not only of iron atoms but also of
previously implanted nickel atoms. Using an iterative procedure (i)t
the LSS throretical profile was modified to include the effects of
sputteringt and the results are compared to the experimental profile
in figure 4. The agreement is quite good. with the maximum in both
o
profiles occurring at a final iron sample depth of 36 A. The dif-
ference in the amplitudes of the distribution is believed to be due
to the total uncertainty involved in the PEX profiling technique.
Figure 5 shows the experimentally determined profile for 25-keV
chromium ions implanted into polycrystalline iron. The theoretical
profile. modified to include the effects of sputtering. is also shown.
The agreement is not as good as for the Fe-Ni surface alloys. but the
effect of increasing the surface concentration caused by the sputter-
ing is still observed.
To determine the effects of heat treatment on the nickel distribution
in the Fe-Ni surface alloys. three surface alloys were heated to 5000 C
for 40 minutes, and the depth profiles of the nickel were subsequently
obtained after cooling to room temperature. The results are shown in
figure 6. with the theoretical annealed profile predicted by Fick's
laws of diffusion (6) also shown. The heat treatment has caused the
distribution of nickel to broaden more than what was expected by normal
laws of diffusion and also resulted in a shift of the maximum of the
distribution.
50
-------
~
Ul ..J
I-' l \J
~"
(J
~
..
E
u
-
(/)
E
o
-
@
c;;
o
't-
28
Nickel concentration depth profile
24
25 key Ni -+- Fe
~ - .......
// "
./ ,
,
"
'-
,
", / Experimental (PEX)
'\
"
,
,
,
,
,
"
"
,
20
16
12
L S S theory
(higher moments)
(corrected for sputtering)
8
4
o
l
20
180
40
60
80
120
100
140
160
DEPTHINIRON,~
Figure 4. ~ Nickel depth profiles as determined experimentally and calculated from
LSS theory modified to include sputtering of the metal substrate during
implantation.
200
BUREAU OF MINES
H 10,888 CP
-------
.,
E
(,)
--
(I)
E
o
-
CO
'"'
(\I
o
,...
..
Z
o
Ln i=
N
-------
:~l eN ,,5
o
~
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OC
~=
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m 1,,@ 'C=
«:)
~v
"-='
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01
lfd
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Anodic Polarization Studies
This section reports the results of the studies conducted in order to
determine the corrosion resistance of several binary surface alloys.
The technique, chosen from the many chemical and electrochemical
techniques available, was to make an electrochemical determination of
the critical corrosion current, ic, of the metal and the characteristic
pitting potential, Ep' of the passive film. These two parameters are
a relative indication of the general-corrosion resistance and pitting-
corrosion resistance, respectively, and can be compared to the same
parameters determined for equivalent commercial bulk alloys of known
corrosion resistance. A decrease in the ic and/or a shift of the Ep
in the noble direction for the surface alloys is interpreted as
indicating an improved overall corrosion resistance. A discussion of
the validity of using this technique to determine ic and Ep can be
found in reference 2.
To demonstrate how the parameters ic and Ep are determined, figure 7
shows the effect of several concentrations of C1- added to the buffered
boric acid solution on the anodic polarization of pure iron. The C1-,
added as NaC1, affected ie, Ep' and the passive-region current density.
The term ic is equivalent to the commonly used term "critical current
density" and is used here due to lack of a specific passivating poten-
tial for many of the alloys tested. The Ep is equivalent to the
potential at which passivity breaks down. The electrochemical behavior
of pure iron exposed to a pure buffered boric acid solution was
characterized by an increase in current density that occurred as the
potential was made more anodic than -520 mV vs. NHE (normal hydrogen
electrode), also referred to as Eo' the crossover potential between
the cathodic and anodic current regions. The current density peaked
at a value of 1.4 x 10-5 amp/cm2, representing ie, at -400 mV. This
was also the potential at which the active-passive transition occurred,
causing a subsequent decrease in the current density. The passive cur-
rent density remained constant at 1.2 x 10-6 amp/cm2, and the E oc-
curred at 1150 mV. Table 1 shows that the effects of C1- conceRtration
on the corrosion current and Ep of iron are quite complex and that the
effect of C1- on ic is not as significant as its effect on the passive
current densities (as shown by the onset of the Ep)
Table 1. - Effect of C1- concentratiou on elect~ochemic~!~?ra-
meters of hun in d. borate-buffered pH 8.5 solution
ic.
_amp/cm-
1.4 x 10-5
3.8 x 10-5
4.5 x 10-5
~--=-.-==.-
Ep,
mV
1150
800
-140
C1-,
Hill
o
10
2400
54
-------
10-1
Iron
10-2
-..- 2400 ppm CI-
In
V1
IN
:,E
'0
"'-
a.
E
-------
Figures 8 and 9 compare the anodic polarization curves obtained for
Fe-6(s)Cr and Fe-19(s)Cr, respectively, to those obtained from iron,
chromium, and three Fe-Cr bulk alloys. With respect to the bulk
alloys, the addition of chromium to iron results in (1) a reduction in
ic' (2) a shift of the crossover potential, Eo, towards the noble
direction, and (3) a shift of En towards the noble direction. It can
be seen from the figures that the same general effects are also obtained
for the surface alloys. The addition of chromium by ion implantation
(1) decreases ic, resulting in a cathodic current for the Fe-19(s)Cr
alloy in the region where anodic dissoluton is expected, and (2) causes
the Ep to be more noble. Two effects that differentiated the behavior
of the surface alloys from that of the bulk alloys were the elimination
of the passive region for the Fe-19(s)Cr alloys and the location of the
pitting potentials for surface and bulk alloys. The reason that the
surface alloys do not exhibit an Ep as noble as their equivalent bulk
alloy is probably the extreme thinness of the alloyed layer (250 A).
Figure 10 shows anodic polarization results for an Fe-25(s)Ni alloy
compared with those for iron, nickel, and two commercially available
steels. The bulk alloys tested were Type-9 nickel steel, a cryogenic
steel containing nominally 9 wt-pct nickel, and Vascomax 250 (V-250),
a high-strength maraging steel containing 18 wt-pct nickel and signif-
icant amounts of Co, Mo, Ti, Si, and Mn. The electrochemical behavior
of the Fe-Ni bulk alloys shows effects similar to those obtained for
the Fe-Cr bulk and surface alloys; however, the interpretation of the
behavior of the V-250 may be somewhat speculative since the effects of
the secondary elements (Co, Mo, Ti, etc.) have yet to be determined.
By comparing the Ep's of the two steels, it can be stated that the
V-250 has greater resistance to pitting than the Type 9 nickel steel.
The polarization curve for the Fe-25(s)Ni alloy indicates that implan-
tation of the nickel resulted in a significant reduction in ic and
caused the E~ to shift from -140 mV for iron to +80 mV for the Fe-
25(s)Ni. Th1s shift represents a substantial improvement in the
resistance to pitting corrosion.
The pitting potentials of the surface and bulk alloys are summarized
in table 2 in the order of increasing resistance to pitting corrosion.
In general, all of the Fe-Cr bulk alloys exhibited electrochemical
behavior that indicated better pitting corrosion resistance than any
of the Fe-Cr surface alloys. The Fe-25(s)Ni alloy, however, had a
greater resistance to pitting corrosion than all of the Fe-Ni commercial
alloys tested.
56
-------
10-2
10-3
...
E
(J
-
0.
E 10-4
co
~
~
en
z
w
C 10-5
\.Jl I-
......
Z
w
a:
a:
:::J
0
10-8
10-7
-0.60
0.0 ~~
POTENTIAL, v versus N H E.
1.20
- 0# ....
HI- CP
Figure 8. - Anodic polarization behavior (in a borate-buffered pH 8.5 solution
with 2400 ppm Cl- addition) of Fe~6(s)Cr compared with behavior of
polycrystalline iron, chromium, and three Fe-Cr bulk alloys.
-------
10-2
N
E
o
-
~ 10-4
CO
VI
00
~
~
en
z
~ 10-5
....
Z
w
a:
a:
::>
o 10-6
10-3
10-'
-0.60
0.0 0.60
POTENTIAL, v versus N H E
,1.20
IUREAU aF -
H 10.111 CI'
Figure 9. - Anodic polarization behavior (in a borate-buffered pH 8.5 solution
with 2400 ppm Cl- addition) of Fe-l9(s)Cr compared with behavior
of polycrystalline iron, chromium, and three Fe-Cr bulk &lloys.
-------
VI
1.0
10-1
N
E
o
-
c.
E
C'O
10-2
Type 9
Ni steel
10-3
~
~
U5
z
w
C
I-
Z
w
a:
a:
~
o
:"'- Fe-25(s)Ni
.
10-6
-0.60
-0.30 0.0
POTENTIAL, v versus N H E
0.30
0.60
IUIEAII 0#' -
H 10.171 ~
Figure 10.
- Anodic polarization behavior (in a borate-buffered pH 8.5
solution with 2400 ppm Cl- addition) of Fe-25(s)Ni compared
with behavior of polycrystalline iron, nickel, and two
commercial alloys.
-------
Table 2. - Summary of pitting potentials
for all alloys tested
Ueta1
Fe-6(s)Cr
Fe
Fe-5%Cr
Fe-19 (s)Cr
Type 9 Ni steel
Fe-12%Cr
V-250
Fe-25 (s)Ni
Ni
Fe-18%Cr
Cr
Ep'
mV
-260
-140
-140
-120
-120
-20
5
80
410
680
700
Oxidation Studies
Metal loss for iron-based alloys through gaseous oxidation processes
is a serious problem in most environments at temperatures greater than
about 3000 C. Unlike the problem of aqueous corrosion, where signifi-
cant metal loss can occur at low (200 to 500 C) temperatures, oxidation
in low-temperature, dry environments generally results in the formation
of a thin oxide film that prevents further metal loss. At higher
temperatures oxide films often separate from the metal substrate due
to mechanical stresses at the film-metal interface, with subsequent
significant metal loss due to the continuous reforming of oxide films.
In this study, the oxidation kinetics of Fe-22(s)Cr alloys were obtained
at 3000 C for an oxygen partial pressure of 4 x 10-6 torr with the oxide
film thickness obtained as a function of exposure using PEX. For compar-
ison, oxidation kinetics studies were carried out for Fe and an Fe-17.2
atomic percent Cr bulk alloy (4esignated Fe-17.2 Cr) under identical
conditions. Prior to oxidation, the surface of each sample was sputtered
with low-energy argon ions to remove any surface impurities.
Figure 11 shows the oxidation kinetics obtained for the Fe-Cr surface
and bulk alloys for iron. Each data point is the average value for the
oxidation of two samples. In calculating the oxide thickness from the
oxygen concentration in atoms per square centimeter as determined by
PEX, all of the oxides formed were assumed to be Fe304' This has been
shown to be the case for iron (4). If the oxide films on either the
bulk or surface alloys were completely Cr203 (worst case assumption),
the error in oxide thickness would be 15 percent. The oxygen eposure
in figure 11 is given in units of Langmuirs (10-6 torr-see).
From figure 11 it can be seen that the surface and bulk alloys exhibit
essentially identical oxidation results, ~Jhereas the rate of oxidation
tor the iron is considerably higher. The kinetics for iron are believed
60
-------
'"
f-'
0<
'"'
en
en
w
z
~
(.)
-
J:
~
W
C
-
><
o
120
3000 C Oxidation
4x10-e Torr O2
80
. Iron
. Fe-17.2Cr
o Fe-22(s)Cr
~--~--
. ~-_-it"--
rr-
8
12
16
40 -
o
o
4
OXYGEN EXPOSURE, 103L
Figure 11. - Oxide thickness as a function of oxygen exposure for iron, BUREAU OF MINES
Fe-17.2Cr bulk alloys, and Fe-22(s)Cr surface alloys H 10,506 CP
oxidized at 3000 C and 4 x 10- 6 torr oxygen.
-------
to represent an oxidation process where the rate of oxidation is limited
by the diffusion of iron ions or vacancies, whereas for the surface and
bulk alloys, the rate of oxidation is believed to be controlled by an
electronic transport mechanism.
The use of iron-chromium surface alloys at 3000 C is an ideal applica-
tion for surface alloying. Very small quantities of chromium are
needed to form the oxide films for oxidation protection since only
small quantities of chromium are needed to change the electronic prop-
erties of the metal-oxide interface.
Summary and Conclusions
Surface alloys have been fabricated by the implantation of low-energy
chromium or nickel ions into iron or commercial steel substrates.
Composition profiles of the alloy concentration as a function 6f depth
below the metal surface have been obtained for Fe-Cr and Fe-Ni surface
alloys. The profiles were found to be of a Gaussian-distribution char-
acter, agreeing reasonably well with profiles calculated using LSS
theory, provided that sputtering of the metal substrate during implan-
tation was taken into account.
The effect. of heat treatment at 5000 C on the alloy distribution has
been studied for the Fe-Ni surface alloys. The redistribuiton of the
implanted nickel generally followed Fick's law; however, a shift in
the maximum of the concentration profile away from the surface was
observed. This observation implies diffusion against a concentration
gradient, and the mechanism for this may involve radiation-enhanced
diffusion.
The aqueous and gaseous corrosion characteristics of the surface
alloys have been studied using anodic polarization techniques and
oxidation at 3000 C, respectively. Lhe results have shown that (1)
in terms of reducing gaseous oxidation and general corrosion, Fe-Cr
surface alloys are comparable to bulk Fe-Cr alloys, and (2) in terms
of reducing pitting corrosion, Fe-Ni surface alloys are comparable
to bulk Fe-Ni alloys.
In considering whether surface alloying by ion implantation can
potentially replace certain bulk-alloying or electroplating techniques,
the advantages and disadvantages should be considered. The principal
advantage of surface alloying is that enormous reductions in the con-
sumption of domestically scarce alloying elements would be realized.
In this report, the resistance of surface and bulk alloys to general
corrosion in an aqueous environment and to gaseous oxidation has been
shown to be essentailly equivalent. The amount of the alloying element
consumed in fabricating the surface alloy samples for these
studies ranged from six to seven orders of magnitude less than the
amount present in the bulk alloy sample.
62
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A second advantage is that the implanted elements become an integral
part of the base metal substrate. Surface alloying, therefore, would
be superior to other types of surface protection techniques such as the
application of coatings, since there would be no interfacial weakness
and no adherence problems, and the number of atoms implanted and their
distribution as a function of depth could be accurately controlled.
A third advantage is that alloys can be fabricated by ion implantation
that cannot be formed using conventional alloying techniques. Since
ions are forcibly implanted into the base metal, normal solid-solubility
limits can be exceeded. ITew alloy systems not available by present
state-of-the-art techniques can, therefore, be formed and studied by
ion implantation.
A possible fourth advantage exists in a comparison with conventional
electroplating techniques, which are known to produce toxic wastes that
contribute to both air and water pollution. Clean air and water stand-
ards are now restricting or eliminatng the use of electrolytic coatings
as an alternative to bulk alloying. Ion implantation, on the other
hand, produces no byproducts that contribute to air or water pollution.
One of the principal disadvantages of surface alloying by ion implan-
tation is that it is a "line-of- sight" process. Only surfaces that
are directly exposed to the incident ion beam can be alloyed. Another
disadvantage is that there is a limited depth to which the ions can be
implanted. In general, approximately 500 nm will be the maximum implan-
tation depth attainable, and the use of surface alloys may be limited
in abrasive environments. It should be pointed out, however, that
many bulk stainless steels can only be used in abrasion-free environments
because of susceptibility to pitting corrosion if the protective oxide
film is abraded away. A third disadvantage is that the surface alloys
must be fabricated in a vacuum environment. This may be a limiting
factor in using the surface-alloying technique for certain types of
metal structures.
References
1.
G. Dearnaley. J. H. Freeman, ~. S. Nelson, and J. Stephen. Ion
Implantation. North-lilliland, .~terdam, ~he Netherlands, 1973.
2.
P. B. Needham, Jr., B. D. Sartwell, and B. S. Covino, Jr., Ar.odic
Polarization Behavior of Fe-Cr Surface Alloys Formed by Ion Implan-
tation. J. Electrochem. Soc., (to be published).
3.
N. D. Greene. Experimental Electrode Kinetics.
technic Institute, Troy, New York, 1965.
Rensselaer Poly-
4.
P. B. Needham, Jr., H. W. Leavenworth, and T. J. Driscoll. The
Kinetics of Thin Oxide Film Formation on Iron Using Proton-Impact-
Excited X-ray Analysis. J. Zlectrochem. Soc., 120, 1973, pp. 778-783.
63
-------
5.
B. D. Sartwell, A. B. Campbell, and P. B. Needham, Jr. Formation
of Corrosion-Resistant Surface Alloys by Implantation of Low-
Energy Nickel and Chromium Ions Into Po1ycrysta11ine Iron. Ch. in
Ion Implantation in Semiconductiors and Other Materials, ed. by
F. Chernow, Plenum, New York, 1977, pp. 201-12.
6.
J. Crank. The Mathematics of Diffusion.
York, 1957.
University Press, New
64
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SUrface Alloying by Ion Implantation:
An Alternative to Cadmium Electroplating
DISCUSSION PERIOD
MR. DAGE:
Have you done any studies canparing this technique with
these netals to the use of cadmium or cadmium-plating.
MR. SARlWELL:
No, we haven't.
'Ihat is sarething ~ would like
to get involved in, but ~ haven't made any direct comparisons to cadmium
electroplated steel.
65
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Alternative Materials and Processes
Session I
Tuesday Morning 12:10
ION VAPOR DEPOSITED ALUMINUM COATINGS
E. R. Fannin
McDonnell Aircraft Company
St. Louis, Missouri 63166
A process for the application of dense, uniform, and very adherent
aluminum coatings has achieved production status. The process is a vacuum
coating process and is referred to as ion vapor d~position (IVD). It can
be used to replace cadmium coatings almost exclusively. Aluminum coatings
can be used at temperatures up to 92S.F, whereas cadmium is limited to 4S0.F.
The IVD process can be used to coat high strength steel without fear of
hydrogen embrittlement. It can also be used in contact with titanium
without causing solid metal embrittlement. Cadmium is prohibited for this
application. Finally, ion vapor deposition is a clean process and does
not contribute to any ecology problems. .
Details of the ion vapor deposition process, performance data,
current production applications at McDonnell Aircraft Company on both
and Air Force Programs will be discussed.
and
Navy
67
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MCDONNELL AIRCRAFT COMPANY
ION VAPOR DEPOSITED ALUMINUM COATINGS
by
E.R. Fannin
McDonnell Aircraft Company
Dept 247, Bldg 32
P.O. Box 516
St. Louis, Missouri 63166
Abstract
A process for the application of dense, uniform, and very adherent aluminum coatings has achieved production
status and can be used to replace cadmium almost exclusively. The process is a vacuum metallizing process and is re-
ferred to as ion vapor deposition. Aluminum coatings can be used at temperatures up to 9250F (496°C), whereas
cadmium is limited to 4500F (232°C). The process can be used to coat high strength steel without fear of hydrogen
embrittlement. It can also be used in contact with titanium without causing solid metal embrittlement. Cadmium is
prohibited for this application. Finally, ion vapor deposition is a clean process and does not contribute to any
ecology problems.
Details of the ion vapor deposition process, performance data, and current production applications at
McDonnell Aircraft Company on both Navy and Air Force Programs will be discussed.
MCDONNELL DOUGLAS CORPORATION
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MCDONNELL AIRCRAFT COMPANY
Introduction
Cadmium electroplating was the favored method for protecting steel on aircraft structure for many years.
Obvious problems with its use were minimal prior to the use of high strength aluminum and steel alloys. Cadmium
plated fasteners installed in high strength aluminum alloys helped promote exfoliation corrosion in the countersinks
and hydrogen embrittlement often occurred when electroplating cadmium on high strength steel. More recen tly it
has received further disfavor because it was found to cause solid metal embrittlement of titanium structure and
because of its toxicity and harmful effects on the environment.
However, it was mainly for the first two reasons that we at McDonnell Aircraft Company (a division of
McDonnell Douglas Corporation) started looking for a viable alternate for cadmium in the early 1960's. After
extensive paper studies, aluminum coatings were selected as the best substitute. Being the least dissimilar to
aluminum alloy structure, it is ideally compatible. Furthermore, aluminum is anodic to steel and provides galvanic
protection as does cadmium.
It was quickly found that available processes for applying aluminum coatings such as metal spraying, electro-
plating, cladding, hot dipping and others had severe limitations such as thickness control, adhesion, size and shape of
product that could be coated, and effect on substrate properties.
During this same period we had selected vacuum deposited cadmium as the coating for solving the problem of
hydrogen embrittlement of high strength steel. Our production experience with the vacuum cadmium coating process
was very favorable. For this reason we started looking at vacuum coating processes for aluminum. This included
physical vapor deposition, ion vapor deposition, and chemical vapor deposition. [on vapor deposition provided the best
adhesion and most uniform coating thickness and with other considerations was selected for further development.
The performance advantages of ion vapor deposited (IVD) aluminum have since been confirmed in both lab-
oratory and service tests and the process has reached production status. This high performance protective coating is
also environmentally clean. The following is therefore a description of the process, the equipment, the coating per-
formance, and illustrations of typical applications.
MCDONNELL DOUGLAS CORPORATION
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MCDONNELL AIRCRAFT COMPANY
Discussion
Description of the Equipment and the Process
The basic equipment required for ion vapor deposition, called IvadizerR at McDonnell, is a steel chamber, a
pumping system, an evaporation source, and a high voltage power supply. A schematic of a typical IVD unit is shown
in Figure 1.
NEGATIVE GLOW
SUBSTRATE
HOLDER
CATHODE
EVAPORATOR
POWER SUPPLY
ALUMINUM
EVAPORATORS
GP77-0982-12
FIGURE 1
SCHEMATIC OF AN ION VAPOR DEPOSITION SYSTEM
The process sequence consists of pumping the system down to about 10-4 Torr. The chamber is then back-
filled with an inert gas to about 10 microns and a high negative potential applied between the parts being coated and
the evaporation source. The gas becomes ionized and creates a glow discharge around the parts to be coated. The
positively charged gas ions bombard the surface of the parts and perform final cleaning. The clean surfaces resulting
are essential for good coating adhesion.
Following glow discharge cleaning, commercially available aluminum wire (1100 alloy) is evaporated by con-
tinuously feeding into resistance heated crucibles. As the aluminum vapor passes through the glow discharge, a portion
of it becomes ionized. This, in addition to bombardment by the inert gas ions, accelerates the aluminum vapor toward
the part surface. This results in denser coatings and also improves the coating adhesion. The ionization also provides
better throwing power and allows complex shapes to be more uniformly plated.
MCDONNELL DOUGLAS CORPORATION
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MCDONNELL AIRCRAFT COMPANY
A typical plating cycle for coating detail parts would consist of the following:
1. Pump down to 10-4 Torr 15 minutes
2. Backfill with inert gas - 2 minutes
3. Glow discharge clean - 15 minutes
4. Plate-IOminutes
5. Backfill to atmosphere - 3 minutes
The total coating cycle requires about 45 minutes.
After coating, parts are generally chromate trea ted in accordance with MIL-C-5541 (Reference 1). This pro-
vides additional protection against corrosion. It also provides a good base for paint adhesion and is a common
requirement for aluminum surfaces.
Technical Advantages
IVD aluminum coatings have several advantages over other coatings used to protect both steel and aluminum
alloy parts. Advantages include:
1. Useful temperature to 9250F (496°C). Cadmium is limited to 4500F (232°C) (Reference 2 and 3).
2. Replace diffused nickel-cadmium and provide better corrosion protection at all strength levels.
Diffused nickel-cadmium is limited to steels having strength levels below 200,000 psi because of
hydrogen embrittlement and has a salt spray requirement of only 100 hours.
3. Does not cause solid metal embrittlement of titanium. Cadmium plating is prohibited.
4. Can be used in contact with fuel. Cadmium is prohibited.
5. Provides galvanic protection to aluminum alloys and does not cause fatigue reduction. Anodize
coatings provide only barrier coating protection and cause fatigue reduction.
6. Can be applied thinner than alclad on aluminum alloys resulting in weight savings and is not limited
to rolled forms.
7. Neither the process nor the coating create toxic materials and therefore do not presen t any ecology
problems.
Coating Performance
An evaluation of 33 different coatings on fasteners was made by the Air Force and the Naval Air Development
Center on service aircraft (Reference 4). lVD aluminum was rated as one of the top three coatings. The other two
coatings were also metallic aluminum coatings that outperformed cadmium plated fasteners.
IVD aluminum is a soft, ductile coating and has properties nearly identical to pure aluminum. We use three
classes and two types of coatings. The classes reflect coating thickness and the types are I, as coated, and II, as
coated with a supplementary chromate treatment. Type 11 is generally used for reasons previously mentioned. The
corrosion resistance requirement for type 11 coatings is shown in Table 1 for the various class coatings.
TABLE 1
MINIMUM CORROSION RESISTANCE
REQUIREMENTS PER MIL-C-83488 (REFERENCE 2)
Class Thickness Corrosion Resistance
(mils) (hrs)
1 0.0010 Minimum 672
2 0.0005 Minimum 504
3 0.0003 Minimum 336
MCDONNELL DOUGLAS CORPORATION
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MCDONNELL AIRCRAFT COMPANY
Class I coatings are used for high temperature and exterior applications where severe corrosion environments
are encountered. Class 2 is recommended for interior parts where less severe environments are encountered, and
Class 3 is used only when close tolerances are required such as fine threaded parts.
Numerous corrosion tests have been performed on IYD aluminum coatings by McDonnell, the Air Force,
the Navy, the Army, and by other companies. As usual with corrosion testing, there is a wide range of results. Some
general conclusions can be drawn, however, using cadmium for comparison.
Corrosion testing of bright electroplated cadmium on steel panels along with IYD aluminum of comparable
thickness in 5% salt spray per Federal Standard No. 115 will generally show cadmium to be better. However, if a
scratch is made through the coatings to the substrates, the cadmium will generally sacrifice itself more quickly and
allow red rust to form before the IYD aluminum.
Results obtained in laboratory tests when cadmium and IYD aluminum coated steel fasteners were installed in
7075-T6 aluminum alloy and exposed to S02 - salt spray for 168 hours are shown in Figure 2. The cadmium plated
fastener heads are more severely rusted. More important is the condition of the countersinks in the aluminum. The
IYD aluminum has provided protection to the countersinks while the cadmium coated fasteners appear to have
promoted corrosion of the countersinks.
(Top View)
(6 x)
Aluminum Co\:ntersinks
Cadmium Plated
Fasteners
".Wg;--.&:
Q
Aluminum Plated
Fasteners
-#"--~;"W,-,~~""",,,,,",,,--,,,_'_h~~_""'''~~'"--'--
.
.
g~
~~
Q
.
, ,iX, ,1- rŁ );:"~,L'Ly.,%~,{j "A.i~"Ld/t~:~-Li;.--,;--"~";,,, j--:,,:::,:~~"--
(Side View)
(100 x)
Q
Q
GP77-0982-13
FIGURE 2
IVD ALUMINUM AND CADMIUM COATED STEEL FASTENERS
INSTALLED IN 7075-T6 ALUMINUM ALLOY AND EXPOSED
TO 168 HOURS OF S02 - SALT SPRAY
There are also advantages for IYD coating titanium fasteners installed in aluminum structure. A comparison was
made between IYD aluminum coated titanium fasteners installed dry, and bare titanium fasteners installed with wet
epoxy primer. The latter is a standard procedure used on aircraft. These fasteners were installed in 7075-T6 aluminum
alloy that had been MIL-C-5541 treated. After fastener installation the panel was sprayed with one coat of
MIL-C-23377 primer and exposed to S02 salt spray for 28 days. Yisual examination showed that the blistering
MCDONNELL DOUGLAS CORPORATION
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MCDONNELL AIRCRAFT COMPANY
of primer around the peripheries of the fasteners installed with wet primer was more severe than around the IVD
aluminum coated fasteners. Examination of the countersinks after fastener removal also showed less corrosion
resulted where the IVD coated fasteners were installed (Figure 3). Studies at McDonnell have also shown a cost
advantage of using IVD aluminum coated fasteners in lieu of wet installation.
- ,
..
...
~, ,
~ '..
..
. .
'-
, ..-
. .
(VD Aluminum Coated
Fastener
,-
, .
"
"
":
w
1
. "
.'
Bare Titanium Fastener
Wet Installed
GP77-G982-14
FIGURE 3
CORROSION TESTS OF IVD COATED AND WET INSTALLED TITANIUM FASTENERS
IN 7075-T6 ALUMINUM ALLOY COUNTERSINKS
Coating adhesion and thickness uniformity are comparable to electroplating, The adhesion requirements are
the same as those specified in Reference 3 for cadmium electroplating. An example of the coating uniformity on
a fastener is illustrated in Figure 4.
SHANK
THREAD CREST
1
HEAD
"
\
1':,
THREAD ROOT
FIGURE 4
IVD ALUMINUM THICKNESS DISTRIBUTION ON A FASTENER
MCDONNELL DOUGLAS CORPORATION
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MCDONNELL AIRCRAFT COMPANY
A lot of fastener qualification data has been generated on the use of IVD aluminum (Reference 5). A summary
of the tests performed is listed in Table 2. This data is too voluminous to present here, however the conclusions can
be summarized as follows:
1. IVD aluminum does not produce any detrimental effects on the mechanical properties.
2. The coefficient of friction of aluminum is higher than cadmium, therefore, higher installation forces
are required. These higher values, however, are within the working ranges presently used for cadmium
in most cases. Interference fit fasteners may require closer attention to the type of lubricants used.
TABLE 2
FASTENER QUALIFICATION TESTS
Mechanical Installation
T ensi Ie Strength Torque Tension
Double Shear Locking Torque
Tension Fatigue Reuseabi lity
Stress Durability Interference Fit
Stress Rupture
Production Status
The first production size coater was sponsored by the Naval Air System Command and delivered to the Naval
Air Rework Facility at North Island, San Diego, in April 1974. During this contract period a number of our aircraft
parts, both steel and aluminum components, were plated and evaluated. Coating uniformity, adhesion and corrosion
performance were all very satisfactory. This unit was 4 feet in diameter and 8 feet long and is shown in Figure 5.
At abou t this same time a new approach was conceived for coating small parts on a more economical basis.
The technique is similar to barrel electroplating in that parts are placed in rotating barrels over the aluminum
evaporation source. Following conceptual verification in the laboratory, a 4 foot diameter by 6 foot long system
was designed and fabricated. The unit has been used to demonstrate the process and as a test bed for design devel-
opment. The system has evolved from one barrel to two barrels per unit, doubling the output. Production capacity
was increased further by placing vacuum locks on the feed and discharge ends of the system (Figure 6). This allows
fasteners to be loaded and unloaded without breaking the vacuum and reduces the total coating cycle by about
50 percent. A similar unit installed this year at a fastener manufacturer, The Voi-Shan Corporation, is also shown
in Figure 5.
Early in 1976 a large detail parts coater 7 feet in diameter and 12 feet long was installed in our manufacturing
facility (Figure 5). Approval had been obtained from the Air Force to use ion vapor deposited aluminum coatings on
the F-15 Eagle. Fatigue improvement and economics were the motivating reasons. Sulfuric acid anodize coa tings
were replaced on fatigue critical aluminum wing skins. This resulted in a fatigue improvement without a design
configuration change. It also eliminated a shot peening operation, resulting in a cost savings. In addition, IVD coated
low alloy steel was used to replace higher cost stainless steel components.
IVD aluminum is presently being used on the FA Aircraft and is required for use on the Harrier and the F-18
Hornet. It will be the primary corrosion protective plating on the F-18. On this aircraft it will be utilized on all
fatigue critical aluminum structure, all high strength steel structure and on titanium and low alloy steel fasteners.
A unit has also been fabricated under contract with the Air Force Materials Laboratory, Manufacturing Technology
Division. This unit is presently at McDonnell and is being used to develop optimum parameters and fixturing for coating
both aircraft and engine parts. It will be utilized mainly as a replacement for vacuum deposited cadmium on high
strength steel parts. This unit is 6 feet in diameter and 10 feet long (Figure 5).
MCDONNELL DOUGLAS CORPORATION
7 Lf
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NlCDONNELL AIRCRAFT CONIPANY
McDonnell Production Coater
'I-
i
.~--. .'. ~
...... -
\I ...,
~, , ,"I
1
Barrel Coater
Air Force Coater
FIGURE 5
PRODUCTION COATERS
GP17-0982-1S
GP17-0982-16
FIGURE 6
SCHEMATIC OF BARREL COATER
A photograph of a few of the aircraft and engine parts that have been coated at McDonnell are shown in
Figure 7, There is also a lot of interest in aluminum coatings outside the aircraft industry. A few examples include
computer discs. comsumer hardw~He. automotive parts, space systems. electrical components, appliances. etc.
Examples Dr sample parts coated for evaluation are shown in Figure 8.
NlCDONNELL DOUGLAS CORPORATION
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MCDONNELL AIRCRAFT COMPANY
..'4:
~",~
~:,$J{
Engine Mount
Bellcrank
--------.----.
Wing Skin
Landing Gear
Stator Vane Assemblies
GP7HI982-17
FIGURE 7
IVD ALUMINUM COATED AIRCRAFT AND ENGINE PARTS
MCDONNELL DOUGLAS CORPORATION
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MCDONNELL AIRCRAFT COMPANY
. I
"~- I
.. I
I
II
FIGURE 8
IVD ALUMINUM COATED PARTS
Economics of the Coating System
Operating costs of the IVD equipment for the most part can be generalized into three categories-labor,
materials and utilities. Labor is the dominant cost factor and each system is designed to be a one man, or less,
operation. Materials and utilities costs are a function of coater size and plating requirements, but when combined
generally run between $5 and $15 per hour of operation.
In either the barrel or rack coater the plating rate is approximately 0.1 mil per minute.
Plating capacity of a 4 feet by 6 feet barrel coater is approximately 120 pounds of fasteners per hour. Plating
capacity for a rack type coater depends upon the size and shape of the parts. A 6 feet by 10 feet coater with a
translating evaporation source could coat all of the parts that could be practically racked in one 6 feet by 10 feet
plane area. A carriage rack rotating over a fixed evaporation source has higher capacity depending upon part size.
Conclusions
Ion vapor deposited aluminum is a high performance protective coating and is a viable alternate for cadmium
plating. It is more compatible with aluminum structure and minimizes t.he problem of galvanic corrosion when using
dissimilar metal fasteners such as stainless steel and titanium alloys. It does not cause hydrogen embrittlement of
high strength steel alloys or solid metal embrittlement of titanium alloys. It has a higher useful temperature than
cadmium and an all important consideration; it does not contribute to the pollution of the environment.
MCDONNELL DOUGLAS CORPORATION
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MCDONNELL AIRCRAFT COMPANY
References
1. MIL-C-554l, Military Specification, "Chemical Conversion Coatings for Aluminum Alloys"
2. MIL-C-83488 (USAF), Military Specification, "Coating, Aluminum, Ion Vapor Deposited"
3. QQ-P-4l6, Federal Specification, "Cadmium Plating (Electrodeposited)."
4. "Corrosion Performance of New Fastener Coatings On Operational Military Aircraft", Fred H. Meyer, J r.
Edward Jankowsky, International Corrosion Forum, NACE, March 1973.
5. MCAIR M&PD R&D Report No. 118, dated 6 February 1975.
MCDONNELL DOUGLAS CORPORATION
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ION VAPOR DEPOSITED ALUMINUM COATUJGS
DISCUSSION PERIOD
HR. HRATKO:
Bill Hratko, Slmdstrand Aviation.
I assune the
wing skins that you coated were aluminum.
MR. FANNIN:
Yes, sir.
MR. HRA'I'KO:
What did you gain by coating them with aluminum?
MR. FANNIN:
'Ihe highstrength aluminum alloys are not really
as corrosion-resistant as they should be, and we are putting out a
fairly pure aluminum.
It is very corrosion-resistant. So we are just
replacing a barrier coating with an anodic protective coating.
MR. GEISERT:
Ray Geisert, C-ould, Incorporated.
Gene, did you
say that you have the three-tenths mil process pretty Imlch under control
nON, that you are getting more unifonn corrosion results?
MR. FANNIN:
Yes.
~-ell, not as well as I would like because I
would like to get the 1,000 hours minimum all the tirre instead of 100,
200, 300.
We are consistently able to get the 300 to 336 minimum with
the Type II coating, and in a short period of tirre, I am sure we can
double that because the columnar structure that you get is directly
related to corrosion resistance, and that can be affected by several
things which we are trying to pin down and control during the coating
operation.
I can't consistently get three-tenths.
he say three-tenths
minimum, and we \~uld like to get between three and five-tenths for our
fastener applications.
79
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MR. FANNlli:
We can probably get only 85 percent of the fasteners
in a load to be wi thin that range.
Some of them ~uld be higher, and we
~uld rather have them on the high side than on the low side.
MR. WTl'LE:
Jim Tuttle, Rust Proofing and Hetal Finishing.
On
the salt spray hours that you referenced in the military specification, was
that the acidified salt spray?
MR. FANNlli:
No, that is the standard five percent ASD-117.
MR. COLE:
Frank Cole, Republic Steel.
I have tv.o questions on
the process.
Number one, how do you handle all that heat of condensation
of the aluminum on those thin wing skins?
MR. FANNIN:
Very good, and that was a problem.
If we go down
below, say, a tenth of an inch in gauge thickness, and we don't have much
mass to dissipate the heat, overheating can becorce a problem of aluminum
structure, and we are very, very concerned about that, of course.
There are only a few pockets in those wing skins that are less
than a tenth of an inch.
We have adapted what we call a convection cooling
system to our unit, and we will make maybe ~ quick passes before it will
get up to 300 degrees Fahrenheit.
We turn the volts off and we introduce gaseous nitrogen.
W: cool
the parts, and this takes about six minutes.
The heavy purrps are still
running, the mechanical and the bl~, and then we turn the nitrogen off,
Pt.1IT'P that down to pressure again, and make our second pass.
MR. COLE:
I didn't think the skins were that thick.
The second
question is:
What is the material on those bolts or crucibles you use to
evaporate the aluminum?
80
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MR. FANNIN:
.
It is a titanium ditoride ma.terial.
MR. OJLE:
Fram Union Carbide?
MR. FANNIN:
Well, we have several sources:
union Carbide,
Sylvania, and a rouple of smaller sources I can't renanber right now,
but they are basically that type.
MR. KOVELAN:
John Kovelan, Dianond Shamrock.
Gene, I wonder if
you would COlTIT.EI1t on your throughput or your production capability in numbers.
MR. FANNIN:
A good round number, depending on configuration, is
a1x>ut 120 FOtmds of fasteners per hour.
Of course, the big heavy fasteners
where you might danage the thread would have to be cooled just a little bit.
MR. SIMMJNS:
Gene Simrons, Senretel.
Can you tell us what surface
finishes are available as coated?
MR. FANNIN:
They are aOOut the same as the substrate that you
roat.
It is a ma.tte finish as coated.
I guess I have never checked the RMS
of the coating, but it looks the Sar:le as the substrate.
MR. Sll1MCNS:
So it is a ftmction of the starting substrate?
HR. FANNIN:
Yes.
On the barrel coating of fasteners, there is
sare rrechanical pick-up during the tumbling of the barrels, and you get
sare roughness as a result of that, especially on steel fasteners.
On the
titanium fasteners, coating is Imlch srroother.
MR. BAYNE:
Mike Bayne, Battelle-Northwest.
I was wondering what
the micro-structure in the "not strictly line of sight" areas was oorrpared
to the microstructure in the good line of sight areas.
MR. FANNIN:
I don't think I addressed that particular problem.
I have seen cross-sections where we would look down inside a hole for exa:rrple,
and see what the thickness was and the taper of the coating.
I haven't
81
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noticed any difference in the microstructure on a single part, but I guess
I have not intentionally looked for a difference.
I ~uldn't expect a difference, and it is not one of the variables
that we have found necessary to control to get the tightly-knit colurrnar
structure, but that is a good point.
I will check that.
MR. BAYNE:
Ibes the colurrnar structure grow in axis with the
crucible?
MR. FANNIN:
No, it is generally perpendicular to the substrate.
MR. SARIWELL:
Bruce Sartwell, Bureau of Mines.
Do you happen
to know what the po.ver consurred by your process is in terms of kilowatt hours
per square foot?
MR. FANNIN:
No, I don't, rot we did TIEke a study of the utili ties
I mentioned, and the cost for electricity was a little better than one
dollar an hour for that four by six foot coater, running on a continuous
basis.
HR. COOK:
I am Albert Cook fran the International Lead Zinc
Research Organization.
I ~uld have to confess to being IIDre interested
in the disadvantages of the progress than the advantages.
Could you ccmrent
on the difference as conpared to the cadmium plating, between conductivity,
inherent lubricity, galvanic protection, and corrosion resistance?
I
noticed your corrosion tests related to a lar.ge anode, sma.ll cathode,
large cathode, small anode relationship, where a cadmium plate ~uld show
disadvantageously.
82
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MR. FANNm:
We have not found this to be a severe problem in our
plasna application which is really the only concern that we have regarding
lubricity, the torque-up values that we get.
On disassembly we have run a
number of tests on reusability with the sane results, no problem.
On resistance, the coating, of course, oxidizes as pure aluminum
does and has a higher resiptance than cadmium, but if you put something like
a chromic treatrrent, one of the MIL-C 55481 treatrrents that is designed
for electric conductivity, you get satisfactory conductivity for grounding
applications.
we are looking at this electrical connector possibility now.
Whether or not that will VK:>rk, I don't knCM.
I think it will.
'IWJ connector
companies have evaluated it and indicated that it will 'WOrk.
On corrosion, we did an extensive study a few years ago on outdoor
exposure of IVD aluminum and cadmium, and the cadmium by its very nature
corroded .
These were on panels where we stripped different widths of the
plating down to the substrata and then exposed them to the outdoor environ-
rent, which we classified as industrial environment.
The cadmium sacrificed
itself in aOOut tv.D years, depending on the width of the strip that was
bared, whereas the aluminum did not sacrifice itself, but kept those bare
strips from rusting or fonning red rust.
I think the IVD aluminum will outlast cadmium because it VK:>n' t
sacrifice itself as quickly.
Also, the corrosion products of aluminum
are not as detrirrental as the corrosion products of cadmium, in my opinion.
MR. CCOK:
I think a careful assessment of the specific application
is needed to detennine whether the galvanic aspects are impJrtant or not.
If they are, then, of course, cadmium v,Duld be rrore beneficial.
63
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MR. FANNIN:
We let the people that want to use the coating
evaluate it for their own application.
We do not evaluate.
MR. maK:
I ~uld be very concerned about jamming possibilities
for this new coating and certainly electrical resistance for electronic
applications.
MR. FANNIN:
You can bet that we thoroughly evaluate it before
it is used.
HR. LE.VY:
Ibn Ii2vy of IDckheed Palo Alto Research labs.
Is there any particular problem with coating inside of the cavities, other
than the normal problem with small-diarreter, very deep holes?
MR. FANNIN:
Well, yes.
If you get a deep enough cavity, and
under certain configurations you can create a hollow cathode which ~uld
be very damaging to parts adjacent to where the ions were coming out, where
you are concentrating ions, so we are very careful about coating parts such
as that.
We would block off the hollow material.
we cannot coat the gear of the landing gear, but we can coat a
blind hole, that's in the landing gear, or the lugs where they have holes.
MR. LE.VY:
Is there SCIre di.nensional limit that gives you this
problem?
MR. FANNIN:
Well, as far as corrosion is concerned, we tell our
designers that we will not unifonnly maintain ITOre than one diarreter in
depth, and beyond that it starts to taper off.
It's very much like cadmium,
back cadmium, or the low bri ttling cadmium, as far as throwing power is
concerned .
MR. ISLER:
William Isler of Diam::md labs.
The heating problem
that you nentioned for the thinner pieces, was that source of heat primarily
your discharge system or your evaporative system?
84
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MR. FANNIN:
There are three areas where you get heat buildup.
In the order of magnitude, the glovrlischarge is least, the radiation is
second, and the heat of condensation is the bulk.
flffi. ISLER:
Is the glovrlischarge p:IWer level the same during
cleaning as during deposition?
f>.ffi. FANNIN:
Yes.
MR. ISLER:
IX> you have another source of ionization besides the
glow:iischarge system?
MR. FANNIN:
N:>, sir.
I might add that saretirres during evaporation, I guess the
conducti vi ty wi thin the system changes wi thin the plasma and sometirres
the potential does drop off, and if you want to maintain a constant potentia
or a constant current density, you have to adjust the voltage.
MR. WHITE:
Marty White, Cadmium Association.
Have you done any work on the deposition of aluminum on sintered
rcetal ccmponents, and, if so, what sort of theory could you carre up with?
f.ffi.. FANNIN:
We are presently using the IVD coating for sorce
tlmgsten alloy steels that are sintered netal.
~ffi. WHITE :
Have you any idea what the theoretical density on
this ccmponent is?
MR. FANNIN:
N:> , I have not.
'Ihey are very heavy.
MR. IAZARZ:
Mark Iazarz, Cutler-Hamrrer.
I-Iave you tried using IVD on copper substrate?
MR. FANNIN:
N:>t for a functional application.
~ have used
copper in sone of our developrent work, mainly to evaluate the effect of
glowdischarge cleaning, current densities and so forth, because you can
oxidize copper readily and see the effects.
85
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NR. FANNIN:
There is no problem getting adhesion of aluminum on
copper by this process, or any other conductive substrate of which I am
aware.
MR. IAZARZ:
What about diffusion?
MR. FANNIN:
You can get diffusion, but there is no diffusion
that I can detect \\rith the laborato:ry techniques that 'We have applied.
There are people evaluating it as a replace:rrent for pack cementation or
high temperature applications on engines.
We can get a fairly uniform
aluminum coating, and the diffusion is TIDre uniform.
Aluminum will diffuse
in TIDst iron-based and nickel-based alloys.
86
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Alternative Materials and rrocesses
Session II
Tuesday Afternoon 1:45
CADMIUM IN FOOD AND DRINKING WATER -
FDA CONSIDERATIONS
Samuel Shibko
George L. Braude
Division of Chemical Technology
Public Health Service
Food and Drug Administration
Washington, D.C. 20204
Cadmium in waste discharges fram plating plants may enter the food
chain directly via drinking water, or indirectly through crop irrigation and
use of sewage sludge on agricultural land.
The average human intake of cadmium in the U.S. is approaching maximum
levels recommended by the World Health Organization. Most of this intake
comes from food and water, especially for non-smokers. Different types of
foods vary greatly in their cadmium levels. Large differences also exist
in the total contribution each food group makes to the daily intake of this
toxic metal.
Long term hazards of cadmium to humans are due to the insidious nature
or this element. Accumulation in the body is gradual and occurs even at
relatively low exposure levels .over many years.
87
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CADMIUH IN FOOD AND DRINKING \JATER - FDA CONSIDERATIONS
By
Samuel I. Shibko and George L. Braude
Bureau of Foods
Food and Drug Administration
200 C Street) S. W.
Washington) D. C. 20204
88
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In talking to a group of people who are involved in electroplating like
yourself, the question obviously arises: ",hat is the relationship
between what you are doing and cadmium in food and water? The answer
is that use of cadmium in electroplating is one of the factors, probably
a major factor, which will determine whether the exposure of the general
population of the United States to this toxic element will be increasing
or decreasing in the years to come.
Let us first examine what happens when cadmium is allowed to enter a
plant I s ~vaste stream. If the outlet "pipe" leads to a municipal sewage
treatment plant, cadmium, with other waste materials, will be processed
by one of the several sewage treatment processes now in use. The result
will be that at least 50% of the total amount of cadmium present ~"ill be
precipitated or adsorbed and remain with the sewage sludge. The balance
of the cadmium which was introduced from the industrial activity or which
was present in water or other sewage components will remain in the
effluent water. The effluent in turn may be discharged to a river or
lake and thereby form our raw water supply for municipal drinking or
industrial use water or it may be used in agriculture as irrigation water.
Sewage sludge can be disposed of in landfills, it can be incinerated, or
used in agriculture as fertilizer and mulch. We are going to discuss this
latter use, which is of considerable importance in reviewing the fate of
cadmium in the environmen: and in the food chain later. But, first, let
us consider the possible ef=ects on the levels of cadmium in food and
water of that portion of tte cadmium which remains in the effluent which
usually enters rivers a~d la~es. When such water is used as a source of
drinking water, regulations ?=o~lgated by the Environmental Protection
Agency wi.ll 8.?ply. T12S~ s'J2c:..fy that such water shall not contain more
than O.C~ ~lligraws 0= ::.a22:"u~ per kilogram of water or 10 parts per
billio:1. :!ost potable ';;8.::e:::- 5'''::Jplies in the United States are well below
this li~it (though a fe~ ~~::'22C it at times) and it would be very
u~=ortu~at2 if sig:lifi::.a~= i~::'~2ases ,,,ere to occur. Then there is the
prob~e2 ~f t~e possi~ilit: ~= accu~ulation of cadmium in edible aquatic
species. S~~cies i~dica== ~~a~ cadwiu~ accumulation in fish occurs
priI:'Eril.Y i:1 ~iciney, lic;=:::-, ~i::'l and the gut with lesser amounts in
bone a~d 2USCl.e. Accu=u~a~io~ ~ccurs through exposure to cadmium
dissolved i~ :0e ~ater, ~a=~== than the intake of cadmium-containing
food, i.e., it is likely :iat t~ere is no marked food chain accumulation
of this ele~ent and t~at ~~e hish levels of cadmium observed in fish
fro3 conca~i~ateG areas ar= c~e to direct concentration from water (1).
The greatest concentratio:1 8= cadmium is observed in estuarine species,
primarily shellfish, where cO:1centration factors - based on a sea water
concen:ratio~ of 0.1 ppb - range from 1000 - 14,000 (2). There is also
the ecological concer:1 that if cadmium pollution in freshwater areas is
high enough, it may eli~i~a=e the normal aquatic life completely. These
ecological problems will be discussed in detail tomorrow.
89
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Water is also used extensively in the South West and in California and
other arid or semi-arid areas to irrigate a variety of crops. The
cadmium, being readily available in soluble form, is taken up by the
crops planted, and becomes part of the plant and, if these are food
plants, of the human and animal food chains. Cadmium in normal irri-
gation water may be limited to acceptable levels. Of most concern,
however, is the presence of excess cadmium in sewage sludge (3,4).
The Federal Water Pollutibn Control Act in 1972 (PL 92-500) mandates
that all municipal sewage will have to undergo at least secondary
treatment. An extensive building program is underway, largely financed
by the government, to construct sewage treatment plants allover the
United States, or provide secondary and sometimes tertiary treatment
facilities for existing plants. The results will be cleaner rivers
and lakes, but also vast and increasing quantities of sewage sludge.
This sludge has to be disposed of, and with strict limitations on
ocean dumping and incineration, land application is becoming a logical
alternative. To make such land application economical it must be used
on land where crops are being grown which in many cases are destined
for human or animal consumption.
The cadmium content of sewage sludges ranges, on a dry weight basis,
from a few parts per million (ppm) to several thousand ppm. Many large
and small cities produce sludges in which the cadmium levels exceed
100 ppm, while other ~nicipalities of similar size have relatively low
levels of cadmium, often below 10-15 ppm. The difference is the input
from industrial effluen~s, including electroplating.
Table 1 shows what happens when crops are grown in soil to which sludge
containing excessive ~oun~s 8Ł cadmium had been applied. As you will
notice, the cadDiuill c~nten~ of all the crops has increased greatly as
compared ~c the contro~s> ~~ic~ were grown in soil fertilized with
ordinary fertilizer. Leafy vegetables, forage for domestic animals and
SO::le gra:.;::s are especi.ally li~~eiy to accumulate excessive quantities of
cadmiu~, ~hen planted in sl~dge-amended soils. Over the last several
years, iliUch resea~ch ~~S b~~n conducted, some supported by FDA, to
define the \~riables a~=ec=i~g the uptake of cadmium and other metals
~y food creps (5). I: has ~ee~ shown that many fa,ctors are involved,
including ~y?es or 30i~s CLct ?~> rates and tiDing of sludge applications,
interaccion of cad~i~ill wic~ other elements (especially zinc), type of
crops planted and thei~ age, etc. It is possible to reduce the level
of cadmi~ uptake by crops ~y good agricultural practice, including
liming and selection of t~ose crops which are less likely to accumulate
this element. However; ,,,hen large amounts of high cadmium sludges are
used, crops will nearly always show increased cadmium concentrations
in plant tissues, including the edible parts.
The question may be asked, why should we be concerned about low levels
of c.admium entering our food supply? The concern is two-fold. First,
there is the available information on the possible toxic effects of
chronic low level exposure to cadmium and secondly> the information on
~he present level of ~xposure of the general population of the U. S.
to cadmium from food.
90
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First, I will discuss the toxicological information. Cadmium is generally
considered to be a non-essential element, i.e., it has no known function
in living systems. In mammals it is essentially absent at birth but
accumulates in the body primarily in the liver and kidneys during a life-
time. Although only a small amount of ingested cadmium (between 4 - 7.0%)
is retained, only a very small percentage of the daily absorbed dose will
be excreted. Thus, there will be considerable accumulation with time even
at relatively low dose levels. Exposure to high concentrations of cadmium
in the air, in the industrial setting, is characterized by anemia, damage
to the lungs, and kidney damage which is characterized by the excretion
of low molecular weight proteins commonly characterized as tubular
proteinuria. Cadmium poisoning had previously been thought of as
primarily an industrial exposure problem.
However, the identification of cadmium as one of the causative factors of
the so-called Itai-Itai disease, reported from Japan in the '60s although
it was probably occurring at a much earlier date in the affected areas,
indicated the possibility of the types of problems that could arise for
the general population if widespread contamination of the environment
,~ith cadmium occurs. The cadmium contamination in this incident was due
to a mining operation which polluted river water used for irrigation of
the rice fields. The Itai-Itai disease was associated with the ingestion
of the cadmium-contaminated rice by a particularly sensitive population,
deficient in both calcium and Vitamin D. In general, the typical cases
reported consisted of wODen ~ore than 40 years old and with multiple
childbirths. The disease is characterized by severe osteomalacia or
bone softening leading to ~ltiple fractures. Kidney damage (tubular
proteinuria) of the sa~e ~)7e as that observed in industrially exposed
workers ~as also roune. ll,e cadDium intake was estimated to be 600 pg/
day, which is 10 tises hi;he~ than that in the non-contaminated areas.
The cad~i~2 in irriga=io~ wa~e~ in this area reached a concentration of
U? to 0.09 ~g/l. Veseta~iQn grown in fields served by the contaminated
wa~er ha~ si;~ 1~\21s 0= ca~~~~2, e.g., rice 0.44 - 3.6 ppm and soybean
1 P?m, ane ~st have :22~ :~2 =ajor source of the intake of cadmium by
the affected indiviQ~2~s.
The firs~ ce~ailed revie~ ane evaluation of the problem of estimating
tole~ac~e ~evels of e:~o5~re ~= the general population to cadmium was
published by ~rofessor =ri~e~g and his co-workers at the Karolinska
Instit~~e, Sweden in 197J under a contract between the U. S.
Enviro~ental Protection A;ency and the Department of the Environment
or the Karolins~a Instit~te (6). The most important considerations in
this evaluation were (aj cad~um has an extremely long biological half
life in 2an, (b) low level ~xposure to cadmium with time results in
considerable accuDUlation of cadmium in the kidney, (c) the critical
level or cad~ium in the cortex or the kidney (based on animal studies and
human autopsy data) associated with development of long lasting
proteinuria, i.e., kidney daWEge, is about 200 ppm wet weight, (d) the
present mean levels in the kidney cortex in 50-year old people not
known to be exposed to excessive amounts or cadmium are 25 - 100 ppm,
91
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and these levels were obtained by daily intakes of cadmium varying
betwaen 25 - 100 ~g, (e) it was calculated that the necessary daily
intake of cadmiu~ from food to reach the critical kidney cortex
concentration over a 50-year period would be 250 - 350 pg. (Table 2)
In 1972 the WHO/FAa examined the available data, and concluded that the
maximum level of cadmium that can be considered tolerable by man within
the present state of knowledge is 400-500 micrograms per week, (equivalent
to 57 to 71 micrograms per day)(7). Recently, Kjellstrom has published the
results of his studies with cadmium-exposed Swedish workers and Japanese
farmers, using the range of exposure levels and duration of urinary
excretion of a specific protein associated with kidney damage. The results
support the previous assumption that the critical concentration of cadmium
in the kidney cortex is 150 - 300 pg cadmium/g (8,9), and this provides
additional support for the low margin of safety of the present daily intake
of cad~ium and levels that could cause minimal toxic effects. Again, I
would emphasize that the concern for exposure to cadmium from food is not
the acute and rapid poisoning, but the effects due to chronic low level
exposure which is slow and insiduous, requiring many years, 20 or 30 or
more, until the deleterious effects manifest themselves.
Now that I have discussed the hazard associated with chronic exposure to
increased levels of cadmi~, it is important to relate this to present
day levels of cadmium in the diet. The present average dietary intake
of cadmium in the United States is about 72 pg/day, and thus either is
approaching the tolera~:e caily intake or may already have reached it.
The basis for these in~a~e values are the Total Diet Surveys, which are
co~ductec by ~he Food a~c Jr~~ _~ministration (10,11). These surveys,
which are also called t22 ~2rket Basket Studies, have been performed
ar:n~ally s~cce 1965. =r_ey are based on food consumption information
de,:21~?ed ~so~t 10 Y22=5 ~~~ by the U. S. Department of Agriculture and
cor=e3?o~~ :~ the d~c= ~: 2 :5 ~o 20-year old male, the heartiest eater.
A to~al 0= 1~7 dif=era~= z~~ds are included and the foods are cooked or
otherwise ?re?ared as ~o==z~:y eaten. The 117 foods are divided into
~welve dif~erent =oo~ C:2~S ~o=?osites which are analyzed for the various
contami=a~ts- ~he tot~: i~~~e, including drinking water, is about 3,000
gra~s per day.
In the overa:l eX703~re cf urban populations to cadmium it has been
esti~~ted that foods provide roughly 80-85%, drinking water 15-20%, and
airborne contaninants 1% of this element (12). In addition, an average
smoker is expected to be absorbing an additional 15-20 micrograms per
day from Lte to~acco s~oke ~y inhalation.
The cadmium content 0= the various foods differs greatly, even though
grown on ordinary (not sludged) soil. Highest cadmium concentrations
can usually be found in so~e leafy vegetables, grains and fruits.
92
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However, because of the magnitude of the intake of, for instance, the
grains, their contribution to the total dietary intake of cadmium presents
a somewhat different picture, as s11o\vn in Figure 1. Here, grains,
vegetables, potatoes and fruits make the largest contribution.
In the total diet survey and in other studies of a similar nature which
are conducted by FDA, we are usually dealing with the "average person."
However, there are population groups in the United States which because
of dietary habits or preferences are exposed to both higher and lower
cadmium levels. Vegetarians, especially strict vegetarians who exclude
meat, milk and eggs, consume large amounts of those food items which
may be cadmium cumulators, such as grains, green vegetables, and various
nuts and seeds. There is no survey available which has measured the
cadmium intake of vegetarians as yet. However, estimates have been made
which show the possibility of potentially increased exposure to cadmium
compared to that of the general population (13).
The Food and Drug Administration is concerned that the level of cadmium
in our present diet is close to or has reached the tolerable limits
established by the WHO/FAD. In order to minimize any potential increase
in dietary intake of this toxic element, consideration is being given to
establishing tolerances or guidelines for cadmium in various foods. However,
cadmium is naturally present at low levels in our soils, in water and
food and even in the air. It has been properly defined as the dissipated
element (14). The Food and Drug Administration is now conducting annual
surveys of raw agricultu=a1 cocmodities, which are being collected in
different parts of the Lnited States and analyzed for cadmium, lead and
zinc. This will provide the baseline needed so that, if considered
desirable a~d feasible, ii8~tations or tolerances can be developed in
the future. Haweve=, e"eD if limitations were available, controls will
still have to be exe=cised at the source prior to the introduction of
this toc-:::.c el.e::J.ent into s:>ils 2nd water and ultimately into human and
ani~~l i~o~. S~bst2n~i211y re~~cing the amount of cadmium entering the
enviro~en~ ==o~ e:ect=op12~i~5 ?lants is a major step towards the
co~trol c: t~is p=obl~~. ~is is the reason why this conference is 80
valuable, as Łt ~AY hel? =e~~ce the widespread distribution of cadmium
fro~ ind~s~=~al processi~g a~c provide for better and safer food and
water.
93
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REFERENCES
1.
Landner, L., and Jernolov, A. (1969). Cadmium in Aquatic Systems.
In Metals and Ecology, Symposium, Stockholm 1968. Ecological
Research Committee Bulletin No.5. Swedish National Science
Research Council. Sveavagen 166 VIII, S-133, 46, Stockholm, Sweden.
2.
Pringle, B. H., and Shuster, C. N. (1968). A
in Shellfish. 1968 Workshop. N. E. Shellfish
Center, Shellfish Sanitation Branch.
Guide to Trace Metals
Sanitation Research
3.
Braude, G. L., Jelinek, C. F., and Corneliussen, P.: "FDA's OVerview
of Potential Health Hazards Associated with the Land Application of
Municipal Wastewater Sludges". Proc. of the 1975 Nat. Conf. on Mun.
Sludge Mgmt. and Disp., Aug. 18-20, 1975, Anaheim, Cal.
4.
Jelinek, C. F., and Braude, G. L.: "Management of Sludge Use on Land;
FDA Considerations Proc. of the 3rd Nat. Conf. on Sludge Mgmt. Disp.
and Utiliz., Dec. 14-16, Miami, Fla.
5.
Chaney, R. L., Hornick, S. B., and Simon, P. W. "Land as a Waste
Management Alternative", Proc. 8th. Ann. Waste Man. Conf.,
Rochester, N. Y., 1976.
6.
Friberg, L., Piscater, M., Nordberg, G. F., and Kje11strom, T. (1974).
Cadmi~ in the Enviromment. Published by CRC Press Inc., Cleveland,
Ohio.
7.
16th Re:>ort of Joi:-.t FAO/~-t:lO Expert Cormnittee on Food Additives,
Geneva ::'972.
8.
Kjel.::"s::r:::::, T., E,;ri::, ?-:::., and Rahnster, B. (1977). Dose-response
relatiocsnip of ~ac~~-~niuced tubular proteinuria. A study of
workers exposed to cadmiu~ in a Swedish battery factory.
Env. Res., 13(2), 303.
9.
Kjellst.ro:r:, T., Sh::..::-oi32.i, K., and Evrin, P. -E. (1977). Urinary
P2-micrcglobulin excretio~ among people exposed to cadmium in the
general enviro~ent. An epidemiological study in co-operation
between Japan and Sweden. Env. Res., 13(2), 318.
10.
FY 73 Total Diet
Studies, No.
7320.08 Bureau of Foods, FDA, Jan. 9, 1975.
11.
FY 74 Total Diet Studies, ~o. 7320.08 Bureau of Foods, FDA, Jan. 21, 1977.
12.
Compliance Program Evaluation, FY 1974, Heavy Metals in Foods Survey
732-136. Bureau or Foods, FDA, June 19, 1975.
94
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13.
Braude, G. L., and Jelinek, C. F. "FDA's position on municipal sludge
application on agricultural land." Presented at 1977 Summer Meeting
of the American Society of Agricultural Engineers, Raleigh, N. C.,
June 26-28, 1977.
14.
"Cadmium, the Dissipated Element") Ed. by William Fulkerson,
H. E. Goeller ORNC-NISF-EP2l) Oak Ridge National Laboratory,
Oak Ridge, Tenn. 37830) Jan. 1973.
15.
Giordano, P. M.) and Mays, D. A. "Biological
the Environment", 15th Ann. Hanford Life ScL
(in press).
Implication of Metals in
Symp.) Richland, Wash.
95
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TABLE I
CADHlUN CONTENT OF CROPS GRmm ON SOIL WITH Ai\fD
IHTIlOUT ADDED SLUDGE PPH, DRY NATTER BASIS
Soil
Crop Sludged Not Sludged
Soybeansa) 3.7c) 0.4c)
1.5 0.3
Oatsa) 2.lc) 0.2c)
0.4 0.04
Swiss Charda) 73.0c) 3.6c)
5.5 1.2
Tomato-esb) 1.1 0.3
Squashb) 0.7 0.3
Lettuceb) 7.0 1.2
a) Chaney. ~. ale (5)
b)Giordano, et. a1. (l5)
C)Soil pH <5.3; all other >6.4
96
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Table II
! ----
iFactors considered for evaluating tolerable daily intakes of
!Cadmium.
i
,
1(1)
I
1(2)
1(3)
!
1(4)
\
i (5)
I
I
1(6)
Cadmium has an extremely long biological half life (18-35 yrs)
Low level exposure to cadmium with time results in con-
siderable accumulation of cadmium in the kidney.
The critical level of cadmium in the cortex of the kidney
associated with development of long lasting proteinuria,
i.e~, kidney damage is about 200 ppm wet weight.
The present mean levels of cadmium in the kidney cortex in
50-year old people not known to be exposed to excessive
amounts of cadmium are 25-100 ppm.
The levels were obtained by daily intakes of cadmium varying
be~en 25-100 pg.
It was calculated that the necessary daily intake of cadmium
f=o~ food to reach the critical kidney cortex concentration,
over a 50-year pariod would be 250-350 pg.
97
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Fig. I
Contribution of Food Groups to Cadmium Intakes
1) Legu:ne
Vegetables
.8%
2)Root Veget~les
1. 5%
3)Garden Eru.its
3.4%
) Sugar &
Adjuncts
1.3%
)Oil, Fats &
Shortenings
2.7%
98
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Cadmium in Food and Drinking Water
DISCUSSION PERIOD
MR. YOST:
Jack Yost, Purdue University.
Dr. Shibko, you errphasized that the cadmium contents of various
classes of foodstuffs vary markedly and that this might llnpact on various
ethnic groups who consume one type of food to the exclusion of other
types of foods.
Have you nade any studies at FDA on the dietary habits
of various population, ethnic, or socioeconomic groups?
DR. SHIBKO:
So far at FDA we have not carried out the study
although we are aware of the problem.
I think the MRC is presently carrying
out various detailed surveys we hope to use in order to get better i:nforrration
so we can see which groups of individuals will be greater risks.
As you nay knc:M, the USDA is also about to undertake a new survey
of dietary habits of the general population and this probably will be a
much larger survey than the one which was previously carried out in 1965.
In that survey, I think the eating habits of individuals were studied for
only a single day, whereas, in this new survey, the eating habits over a
period of three days will be studied with particular attention to the
various ethnic groups.
MR. LYMAN:
Don Lyrran of the International Lead Zinc Research
Organization.
Two rronths ago in East Gerrrany, Harlan, et al, of FDA
presented a paper on "Cadmium in the American Diet," in which they said
there had been fluctuations in cadmium levels in diet through the years,
but there had been no detectable trend indicating increased levels of
exp:>sure to cadmium in food.
I think they were referring to the market
basket surveys.
99
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MR. LYMAN:
Based on these considerations, the present levels
of cadmium in food do not pose a toxicological problem to man.
HCMever,
continued rroni toring of the food supply for cadmium trends is necessary.
You seem to paint a Imlch darker picture.
DR. SHIBKO:
There is a very small margin of safety between
what man is presently eXFOsed to, and the levels that cause the minimum
toxic effects.
We are very anxious to insure no increase in the general
level of cadmium in the food supply.
MR. LYMAN:
But evidently there is no evidence to indicate
that there has been an increase in cadmium in foods.
DR. SHIBKO:
No, but we feel that the possibility of the use
of large arrounts of cadmium-containing sewage sludge, particularly on
certain crops, could result in a drama.tic increase in the levels of
cadmium in food supplies, which would be reflected in the levels of
cadmium in the total diet.
~ LYMAN:
But actually there has been no indication to date?
DR. SHIBKO:
No, this has not occurred so far and I don't think
that the present use of cadmium sludge is very wide-spread in this country.
It's in the experimental stage.
MR. GLEASON:
'Ibm Gleason of EPA.
If you take the 33-microgram value that was quoted, the mean
average of all the values that FDA has carpiled since 1967, this will give
you this particular value.
But, you have to consider the lCMer accuracy
of the rrethods used in earlier surveys and the small safety factor in using
the WHO tolerance level.
100
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DR. SHIBKO:
I think it is very :irrqx>rtant to consider all or
much of the earlier analytical studies in view of the very difficult
problems in analysis.
101
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Alternative Materials and Processes
Session II
Tuesday Afternoon 2:20
CADMIUM PLATING WITH ENVIRO~~ENTAL RESTRICTIONS
L. E. Vaaler
J. Gurklis
BATTELLE - Columbus Laboratories
Columbus, Ohio 43201
From a practical standpoint it must be assumed that cadmium is
toxic at extremely low concentration levels. However, caamium electro-
plate is very useful and is required for specific applications. For
protective coatings on gray iron castings, cadmium is considered indis-
pensible by many authorities. Corrosion products of cadmium are less
volumin0us than those of zinc and less likely to iTl'terfere wi th the func-
tion of moving parts. Cadmium corrodes at a much slower rate than zinc
in marine atmospheres. A coating composite of tin over cadmium has a
durability and service life under some conditions that is not equalled
by a single metal or other simple composite, including tin-zinc. There-
fore, the problem is to electroplate cadmium and still satisfy the en-
vironmental restrictions.
Specifically tailored recovery methods, provision for handling
spills, segregated treatment of unavoidable waste-water, and careful
control of the complete operation will be required. With these require-
ments cadmium should be plated only in installations that specialize in
it and that have sufficient production volume to justify the appropriate
control procedures. Cadmium plating as an intermittently used process
in a general plating shop will not be economically feasible.
The paper discusses the technology
function of production volume for plating
that will probably be imposed.
and estimated costs as a
cadmium under the restrictions
103
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CADMIUM PLATING WITH ENVIRONMENTAL RESTRICTIONS
J. A. Gurklis and L. E. Vaaler
INTRODUCTION
This conference on cadmium is one of an increasing number of
discussions on substances or processes known to be or suspected of being harmful
to the environment. The ideal goal is to completely eliminate the substance
or processes in question and find completely satisfactory and safe alternatives
for all applications. Another possible temporary goal, however, is to contain
the substance in manufacture and use.
We believe that a practical objective for cadmium is to find substi-
tutes where it is possible, technologically and economically, and to practice
containment where the properties of cadmium lead to unique applications.
Special Uses of Cadmium
The performance of cadmium has often been compared with that of zinc,
which has similar properties and chemistry and is cheaper and more acceptable
to the environment. There is evidence that cadmium affords better protection
to steel in humid, tropical, and certain marine environments, and provides a
more integral plate on cast iron than does zinc. Cadmium appears more suitable
than zinc for soldering operations, for making electrical contacts, and for
providing a low coefficient of friction. However, one should not be too
dogmatic in citing unique uses. From a practical standpoint, it is not possible
to find a substitute for cadmium plate in a relatively short time for many
manufactured items. The field testing and changing specifications can require
years before the modified product can be sold or used with confidence. We
have personal experience with this situation. From published results it
appeared that a tin-zinc alloy plate might be used for components in an assembly
that were normally plated with cadmium and tin. However, accelerated corrosion
tests did not support the substitution. Perhaps the substitution would have been
104
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satisfactory under actual conditions of use but there was certainly no rationale
for risking such a change.
Containment of Cadmium-Analogy with Mercury
As a precedent for using and containing cadmium. the situation with
mercury can be considered. Mercury came under scrutiny as the result of
adverse consequences of its release into the environment in Japan and Sweden
and determination of high levels in fish in the Great Lakes. Mercury is used
in large amounts for a flowing cathode in chlorine-caustic production. The
result of environmental limitations in the U.S. was: (1) the phasing out of
old, inefficient plants for which a substitute technology was available,
(2) no sales of new mercury cathode cells, and (3) development of methods of
mercury containment for modern mercury cell installations. In Japan a deadline
was set for elimination of mercury cells, but the huge cost of such a replacement
and the development of more efficient methods of mercury containmnet has caused
MITI to have second thoughts about following through on this.
Specializing in Cadmium Plating
Although cadmium plating is frequently included as a routine operation
in typical job shops, some shops have now eliminated cadmium. They have found
that the amount of business derived from cadmium plating is not worth the trouble
and cost of meeting present and anticipated pollution requirements. However,
it is reasonable to assume that with some critical size and continuity of
operation plating and containment operations can be justified.
A couple of examples will be used to approximate the cost of a modest-
sized cadmium line which is operated at full capacity and uses a recovery
technique to minimize waste. The first example will use evaporative recovery.
A two-stage (double effect) recovery unit will be assumed rather than the more
common single stage unit in order to save steam (energy).
The second example will assume reverse osmosis recovery in place of
evaporative recovery. This technique is less established for cadmium cyanide
baths than is evaporative recovery. Nevertheless, it is a very promising
method that will probably be established in the future.
105
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To provide a basis for modelling and costing a recovery system, a
plant producing 2,000 sq ft/day (186 sq m/day) of cadmium plate will be assumed.
An outline of the process steps and volume of riAse water used is shown in
Table 1.
The amount of dragout from a cadmium plating bath is important in
establishing the economics of a cadmium plating recovery and waste treatment
system. We have assumed dragout values of 5 ga11ons/l000 sq ft (0.2 1iter/sq m)
for barrel plating and 3 gallons/lOOO sq ft (.12 liter/sq m) for rack plating
to be typical. Of the 2,000 square feet (186 sq m) of plated product, 2/3 of
the area is barrel plated and 1/3 rack plated. The average dragout for the
daily production is then 4.33 ga110n/1000 sq ft (0.18 liter/sq m).
The volumes of rinse water going to treatment or recovery were
calculated using ideal mixing formulae modified by an efficiency factor of
50 percent. This means that if the desired concentration of chemicals in the
final rinse .assuming ideal mixing is, say 15 ppm, the dragout film on the part
will be of this concentration but the rinse water itself will have a concentration
of only 8 ppm and will be twice the volume of rinse water needed than if ideal
mixing occurred.
Cadmium Plating with Evaporative Recovery
An evaporation of 50 gal/hr (189 liters/hr) will handle the daily
400 gallon (1514 liters) for the cadmium rinse in 8 hours. Cost estimates
for purchase, installation, and operation of a two-stage 50-gallon evaporative
recovery unit are given in Table 2.
Recovery by Reverse Osmosis
Evaporative recovery is an established technique for cadmium cyanide
baths. Reverse-osmosis with this bath is less well developed and there is
promise that suitable membranes are or will soon be available to make it
practical. There is also promise that reverse-osmosis will be cheaper and less
energy consumi ng than evaporative recovery. Therefore, costs have been
projected for this system in Table 3, even though it is not an established
technique.
106
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TABLE 1.
PROCESSING STEPS FOR CADMIUM PLATING
Process
Anodic al kal ine
clean
Single rinse
Acid pickle
Double countercurrent
rinse
Caustic dip
Double countercurrent
rinse
Cadmium plate
Triple countercurrent
rinse
Chromate di p
Double countercurrent
rinse
Item
Bath Composition
Concentration,
9/1
Time,
min
1.25
.75
1. 00
1. 25
1. 00
0.75
20.0
2.25
0.5
6
Solids Conc(l)
in Final
Rinse, ppm
750
750
50
15
37
Act ua 1
Rinse
Water
Use, l/day
5246
797
1135
1518
779
(a) This value is for ideal mixing where rinse water volume would be half of actual use.
Alkaline salts
60
HCl
111
NaOH
15
Cd
NaCN
NaOH
Na2C03
20
100
14
52
Na2Cr207;2H20
HN03
15
7.5
107
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TABLE 2. COSTS FOR EVAPORATIVE RECOVERY OF
CADMIUM CYANIDE SOLUTION DOUBLE-EFFECT
50 GAL/HR UNIT
Item
INVESTMENT COSTS
Purchase Cost
Cost of Installation and Auxiliary Items
OPERATING COSTS
Interest/Year (10 percent)
Depreciation/Year (20 percent)
Steam at $4.00/1000 lb., 800,000 lb.
Electricity at 4~/kwh, 42000 kwh
Labor at $12.00/hr, 240 hrs
TOTAL OPERATING COSTS
Area Plated/year (240 days)
Recovery Unit Cost
480,000 sq ft (44,600 sq m)
$.037/sq ft ($0.40/sq m)
$30,000
1 0,000
2,000
8,000
3,200
1 ,680
2,900
$17,780
108
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TABLE 3. COSTS FOR RECOVERY OF CADMIUM CYANIDE
PLATING SOLUTION BY REVERSE OSMOSIS
INVESTMENT
Cost
OPERATING COSTS
Interest/Year on Initial Cost (10
Depreciation/year (20 percent)
Electric (50 kwh/day)
Maintenance (5 percent)
percent)
Membranes
TOTAL OPERATING COST
Area Plated/Year
Unit Recovery Cost
480,000 sq ft (44,600 sq m)
$.017/sq ft ($.18/sq m)
$20,000
1 ,000
4,000
500
1 ,000
1 .500
$8,000
109
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Savings in Chemicals by Use of Recovery Systems
Without a recovery system the amount of solution dragged out of the
plating bath annually is:
(4.33)(500) = 2165 gallons (8200 liters).
The saving in chemicals by use of a recovery system is a credit against the
cost of operating the cadmium system itself. The amounts of chemicals lost
in this way and their cost are shown in Table 4. Furthermore, chemicals are
required to treat this dragout and are also included in Table 4.
Treatment of Cadmium Wastes
Even with a recovery system, waste water and other solutions requiring
treatment to remove cadmium (and possibly other metals) can come from:
(1) Rinses following chromating
(2) Dumping of the chromating solution
(3) Purging of the plating-recovery loop or
other losses from this system.
The cadmium dragged out of the cadmium rinses into the chromating
system is only 0.5 g/day (8.66 gallons or 33 liters/day containing 8 ppm of
cadmium). If the chromating solution has a volume of 200 gallons (757 liters)
and is dumped every 10 days, the average volume/day of waste chromating solution
plus chromate rinse water is 20 + 206 = 226 gal (856 liters). The average
concentration of cadmium in this wastewater (assuming the work is not
significantly etched in the chromating bath) is 0.6 ppm. Chromium concentration
assuming no loss from chromating would be 480 ppm.
Directing the wastewater and purge from the cadmium line to the plating
chemical waste treatment system will dilute the cadmium in a larger volume.
Even after treatment to precipitate as much cadmium as possible the total
cadmium discharged in the effluent may be larger than if the water from the
cadmium line were treated separately. A separate waste treatment system would
gain some economics from sharing personnel, testing, and possibly some control
equipment with the larger treatment facility but could cost from $25,000 to
$50,000 and increase production costs up to $.05/sq ft.
110
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TABLE 4.
CHEMICALS CONSERVED WITH A RECOVERY SYSTEM
Annual Loss Unit Price Total Saving,
Process Chemical or Use, kg $/kg $
Dragout Cadmium 164 8.25 $1 ,356
Sodium Cyanide 820 1.00 820
Sodium Hydroxide 115 .60 68
Sodium Carbonate 426 .44 188
Chemical Chlorine 2968 .18 534
Waste Treatment Sodium Hydroxide 564 .60 338
TOTAL $3,304
111
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If the main treatment plant operates in a batchwise mode it can be
suggested that cadmium-containing waste be collected in a holding tank to a
volume sufficient for batch treatment. This can then be transferred to the
main plant for separate treatment, thus avoiding dilution with other waste water.
Other end-of-pipe treatments for the small amount of cadmium-containing
wastewater from the plating line can be suggested but we will not speculate
further. It may be concluded that cadmium plating with containment is possible
with a moderate economic premium, providing a full production schedule can be
maintained.
112
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Alternative Materials and Processes
Session II
Tuesday Afternoon 2:55
OUTSTANDING CORROSION PROTECTION WITH ZINC FLAKE
IN A WATER-BASED COATING
Jon A. deRidder
John R. Kovelan
Diamond Shamrock Corporation
Metal Coatings Division
Chardon, Ohio 44024
A new and cost competitive, corrosion-resistant coating for ferrous
and other substrates has been commercialized. The coating, developed
and\marketed by Diamond Shamrock Corporation, is a new addition to their
family of corrosion-protection systems. The coating contains zinc flake,
chromium and proprietary organics in an aqueous dispersion. Applied by
immersion, the coating is essentially inorganic after being baked to an
adherent, metallic gray finish. The average dry film thickness is 5.0 -
8.0 microns which is equivalent to a coating weight of 1500-1800 mg per
square foot.
Outstanding corrosion resistance is obtained by the combination of
barrier protection and controlled cathodic protection afforded by the
zinc flake, which is passivated and bonded by the chromium. The coating
is also completely resistant to solvents, gasoline and brake fluids and
will withstand temperatures in excess of 300.C.
Unlike cadmium, the coating application process is completely free
of hydrogen embritt1ement and pollution, in that is uses no acids, elec-
trolysis, or post rinses.
The main users to date have been the U.S.A. and Japanese automotive,
appliance and building industries. Chrysler Corporation, General Motors
Corporation, General Electric Company, Nissan Motors and Toyota have
issued specifications. The coating is currently being used to protect
fasteners and other small metallic items, although larger parts and assem-
blies can be rack-coated using an overhead conveyor system.
113
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OUTSTANDING CORROSION PROTECTION PROVIDED WITH
ZINC FLAKE IN A WATER-BASED COATING
J. A. deRidder and John R. Kovelan
Diamond Shamrock Corporation
Metal Coatings Division
P. O. Box 127
Chardon, Ohio 44024
114
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A new corrosion-resistant coating for ferrous and other metal
substrates has been commercialized.
The coating, developed by
Diamond Shamrock Corporation, is a new addition to their family of
corrosion protection systems.
The coating is marketed by Diamond
Shamrock and its Joint Venture Companies, Nippon Dacro Shamrock in
Japan and Dacral in Europe.
The Coating
The coating, as applied, looks very much like zinc plate, but
it is not a plating.
The coating is applied by immersion and then
baked to an adherent metallic gray finish, which is essentially in-
organic.
By definition, the coating is an aqueous dispersion of zinc
flake, containing chromium and proprietary organics.
The organics
are used to derive the proper chemistry during the bake operation
and then are essentially destroyed at the peak metal temperature.
(Slide #1)
The most unique physical aspect of the coating is that it
contains zinc flake.
The zinc flake is typically 0.2~-0.4~ thick
and averages 20~-30~ in length.
It becomes obvious that with
reasonable orientation, a small amount of zinc flake will cover a
large surface area as compared to zinc dust. (Slide #2)
The applied coating has a typical dry film thickness of 5~-8~
or 0.2 mil, which is equivalent to 1600-1900 mg per square foot.
(Slide #3)
Outstanding corrosion resistance is provided by a combination
of protective mechanisms. (Slide #4)
First, the large number of
115
-------
laminated zinc platelets provides good barrier protection due to the
critical pathway required for water and oxygen to reach the substrate
surface.
Second, the chromium +6 in the coating solution ensures
that all the zinc platelets and the substrate surface are passivated.
Thus, unlike zinc or cadmium plating, which is given only a dichro-
mate surface treatment, DACROMET@320 has through-film passivation.
Finally, the zinc in the coating, which is free of any organic poly-
mer, will provide cathodic protection of the basis metal.
It is then
this combination of protective mechanisms , barrier protection, Cr pass-
ivation and cathodic protection, that provides such outstanding corro-
sion resistance.
Application,
Now that you know what DACROMET@320 is and how it protects, let
me explain briefly how it is applied. There are two basic methods of
application.
First, there is the dip-spin process which is designed to apply
the DACROMET@320 to bulk fasteners such as nuts, bolts, clips, etc.
It consists of three basic steps -- cleaning, coating and baking.
Like with all other metal finishing processes, cleaning is of
fundamental importance. With the DACROMET@320 process, we are dis-
couraging the use of acid pickling.
We currently require our Licen-
sees to use vapor degreasing or alkaline degreasing to remove normal
oils and soils.
Dry honing is recommended to remove mill scales, etc.
On this slide showing the dip-spin process you will note several
cleaning options. (Slide #5) What is best is determined by the typical
product mix to be coated and personal preference.
Basically, alkaline
ll6
-------
spray washing is used to remove the oils.
Loose heat-treat scale
can be removed by vibratory cleaning with preformed aluminum oxide
media, or by dry honing with 120 mesh glass beads.
The latter
method is very effective for cleaning a wide variety of parts,
especially threaded fasteners.
Following the cleaning, the parts are rinsed and dried.
Dry-
ing is required to avoid dilution of the aqueous DACROMET@320 and
because the surface tension of the rinse water and DACROMET@320 are
different, which can result in a non-uniform coating.
The clean, dry substrate is then metered into coating baskets
for application of the DACROMET@320.
Conventional dip-spin coaters
are used for this job.
The baskets containing the parts are simply immersed in the
DACROMET@320 and then raised above the liquid level and spun to re-
move the excess coating.
No critical residence time is required.
The coating weight is regulated by controlling the DACROMET@
320 viscosity and the coating basket r.p.m.
The coated parts are then discharged into the first conveyor-
ized oven and the metal temperature is raised to about 2000C to set
-the coating and render it water insoluble.
The parts are then cooled,
using ducted air, and the second coat of DACROMET@320 is applied.
I
The second coat is necessary to cover contact or nesting marks
caused by part touching part as in any immersion process.
o
The final bake is to a metal temperature of 300 C to completely
cure both coats of DACROMET@320.
The time-to-temperature is deter-
mined by part mass and oven efficiency.
The time at temperature is
117
-------
typically 3-10 minutes.
The second application method, called the dip-drain process,
consists of the same steps of cleaning, coating and baking. (Slide #6)
However, this method is designed to apply DACROMET@320 to parts which
are too large to treat in a coating basket.
In this process, the
parts are individually hung on an overhead conveyor and transported
through a dip tank and oven.
Only one heavy coat of DACROMET@320 is
required since there is no contact between parts.
If acid cleaning is avoided, both these application methods are
free of hydrogen embrittlement and pollution. There is no electroly-
sis, no acids and no post rinses.
Competitive Coatings
Before discussing the advantages of the DACROMET@320 coating per
se, let me briefly review some of the competitive coatings for later
comparison. (Slide #7)
You are all familiar with phosphate and oil - a good and rela-
tively inexpensive coating for mild corrosion resistance. The pro-
blem with this system is that, prior to end-use application of the
.coated parts, you end up with either too much oil or not enough. With
not enough oil, there is little or no corrosion protection, and with
too much oil you have the problem of the oil running out of the con-
tainers.
Phosphate and paint can provide fairly good corrosior protection
at a medium price.
It is used rather extensively on spring steel fas-
teners.
Its biggest problem is that the paint polymer freezes up bolt-
washer assemblies, etc.
Phosphate and paint are also sensitive to
118
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higher temperatures and many solvents.
Mechanical peen plate is a newer coating in the marketplace.
At higher coating thicknesses, it can provide fairly good corrosion
protection.
Its biggest claim to fame is that it eliminates most of
the hydrogen embrittlement problem because the zinc or zinc alloy
coating is physically peened on by glass beads.
Its big disadvantage
is simply that it is largely limited by part configuration.
If the
glass beads can't get into a hidden area, then that area doesn't get
coated.
Galvanizing is still widely used on small stampings.
It's rather inexpensive, but provides only limited protection, partic-
ularly in a salt environment.
Usually some post treatment, such as a
dichromate or phosphate and paint, is required to obtain good corrosion
resistance.
The most common of protective coatings, certainly in the automo-
tive market, are zinc and cadmium plating.
The corrosion resistance
will vary from poor to very good, depending on the coating thickness
and quality.
Price will also vary.
The biggest problems with both of
these platings is pollution and hydrogen embrittlement. (Slide #8)
In summary, all of these competitive coatings have at least one
major advantage, but they also have one or more major disadvantages.
Advantages of DACROMET@320
Now, let's go back and look at DACROMET@320.
This slide shows
an array of untested DACROTIZED@ parts, some of which are currently
being coated for automotive end use in the United States (coil spring
and single-thread spring steel nuts). (Slide #9)
119
-------
This slide shows a similar array of DACROTIZEQ@ parts after ex-
posure to 500 hours salt spray (ASTH B-117 5% salt fog).
(Slide #10)
You can see that the DACROMET@320 coating provides excellent salt
spray resistance. There is no red rust and very little white corro-
sion.
In addition to accelerated salt spray testing, let's look at
some other test results.
On this slide you see both zinc plated and DACROTIZEDID bolts
after one year's weather exposure at Kure Beach, North Carolina, a
marine environment.
(Slide #11)
The next slide shows the results of an independent study con-
ducted by Standard Pressed Steel Corp. 75-T6 Aluminum alloy was
drilled to accept 1/4 inch bolts coated with Cadmium and Zinc Electro-
plating and DACROMET 320. The entire assembly was subjected to 1000 hours
of testing in salt spray (5%).
The purpose of the test was to de-
termine the amount of dissi~ilar metal corrosion between the coated
bolts and bare aluminum.
Note how little galvanic action has occured
in the area whe~e the DACROTIZED bolt was fastened.
In addition to providing outstanding corrosion resistance,
DACROMET 320 is resistant to solvents, gasoline, brake fluids, and
~ustained temperatures of up to 300°C.
DACROMET 320 also provides
a good base for both conventional paints or electrodeposlted paints
with no additional post treatment.
(Slide #13)
Potential
Looking to the future, we see DACROMET 320 being applied to
whole assemblies by the dip-drain method.
120
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For examplet an automobile door latch assembly containing five
springst a number of moving cams and leverst is usually assembled
after the individual parts have been coated; often with different
coatings.
(Slide #14) With DACROMET 320, the latch could be assembled
first and then coatedt eliminating costly time-consuming individual treat-
ments.
Because DACROMET 320 is essentially an inorganic coating after
baking, there is no organic polymer to interfere with the free move-
ment of assembly parts after coating.
Large, heavy parts can also
be coated by immersion in dip tanks while suspended from overhead
conveyors.
Marketing
The DACROMET 320 process is licensed in the United States by
Diamond Shamrock and in Europe and Japan by its Joint Venture Companies,
Dacralt S. A. and Nippon Dacro Shamrock Co., Ltd.t respectively.
The principal target area so far is the one of automotive fasteners because
of its extremely high potential.
However, the Metal Coatings Division
is making a concerted sales effort to penetrate the appliancet building,
marine and military market.
To datet General Motors, Chevrolet, Bendixt Deleo, Chryslert Ford
(interim)t Holly Carburetort Nissan and Toyota have issued specifications
for DACROMET 320.
In the appliance industry, General Electric has
specified DACROMET 320. A Federal specification was recently issued
for use of our coating on nailst staples, brads, and spikes.
Before
the end of 1977 we hope to have published a tri-service military speci-
fication.
Further specifications will be written within the coming
months. (Slide #15)
121
-------
In conclusion, DACROMET 320 will not solve all of the metal
finishing problems, but it does offer more advantages and greater
flexibility to the engineers and designers in metal finishing.
122
-------
SLIDE NO.1
SLIDE NO.2
(ZINC FLAKE)
~
~-f
~.
123
-------
SLIDE NO.3
'~
SLIDE NO.4
DACROMET@320 EXHIBITS OUTSTANDING CORROSION RESISTANCE UTILIZING A
COMBINATION OF 3 PROTECTIVE t1ECHANISMS.
BARRIER (OVERLAPPING PLATELETS)
CATHODIC ACTION (SACRIFICIAL ZINC)
THROUGH FILM PASSIVATION
124
-------
SLIDE NO.
5
@
DACROMET
320
. -"'\ ,~~-::- -....... -: ~.....- --r. .
'. ~ '., .- -f"""'''.-'
._~~",-:~-:
", r~-'C'.' ,.--".~',
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SLIDE NO.
6
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;' DACROMET ; '~. -. .'..--- .-'. .
L <~ 320 '; . -Ere t~G}:JrrT7.G?~i'(~'f~<.',:
r ...;~;~~:ft"~ . .~.-;.)?:':'-;~JI:..' ~- - -,.. ..- ..,. .,..do,".:" '-:~~<.::: ".: ..~ ,-
125
-------
SLIDE NO.7
COMPETITIVE COATINGS
Untested
-. 96 hr;. Salt Spray"
----
Phos.fPaint
--
-
,
,
...
.--,r;I-~
,;...~ \) '...: ( -- ~
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-
-
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~
Electro~ Galvanized
o
;- -~~- ~ i:\t,~,
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-.-
SLIDE ~O. 8
-------
SLIDE tW. 9
DACROMET 320
. U nte~ted
1
-..-, '.
- "-"-' ~--:.-~...~-;"'};;,...".,. ~.":-~-->".'--.---'. '.7" -.~
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, .. ~ ..'
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SLIDE'NO. 10
DACROMET 320
500 hr. Salt Spray
.: :;, ~': ~,' ~~
. "':1
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-------
SLI DE NO. 11
SLIDE NO. 12
(INDEPENDENT TESTS BY SPS CORP.)
UNAVAILABLE AT TIME
OF
PUBLICATION
128
-------
SLIDE NO.
13
.DACROMET@320
h-~....
"
~.
ummary "'-'~-:'.'~
,,~~~ftJt::ct:;':.;:V!::;~'-~~:-j'~,':,.
..-: ~~~~...t"~~~'~j.....__.::----- --:.A'Of ,.i :&,,-,' 4
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"!~~~'"!..!'@i~:td:-.L:-'/ ~~..-'.:...~,..--:t :"F -
.~ - ~~f~:~1;*t1f~ifi:~;)?
l.Superior Corrosion Resistance' ::>,-~::'~-;~~~~~/-~-~;'
~~~~: ~ :~~~~~~l{y~~;,2t:?::;;~. .;: ~.':
2 Pollution Free '>~t~~~. ~~T~~-Ą;;Z;:;-"7:1~";:;-:_.~~~:'~::'
. ,.~,:.~'~ - ,'.. - -~~~~;jE~Ł:j~a~~~::~:>:';
3.Hydrogen Embrittlement Free . :r:/i'~~=~:~~::!:?,~-.~:
. -' . . -'.~~~ )-~- -" J -' ~r' ~~~::~;~;*~~~~ ~? ~~~.~~~'
4. Good Base for Further Painting ~_.:'/J{l\~~t.:..:~-'~
- '~~Jii!~~~~"""--'':'>,~"":~~",,,-:-;,~'' '.r'.
5.Controlled Galvanic Action~"L~~~~~~~~~::=
. - _. -. ' '0 - , . , ", ~~<..- -:,;~~~::;,~,,,,'Ą:'.-;';'~i'::;-2:'::':>
6 I '0: "..r.<'~"';1"!O;;;'~W~~""~"':o;..",. ,.Ąi..-. (~:,..-",
.So vent Resistant .",j~~~~~~~~~~J~:w~..~;\t7/r;~:.
.. . " - -, -. . ;&'!.;~~'J6iB"'~»~~.~0"'" '..~ <. ,,--
7. Higher Tempera ture Compatiibility ;\J~~?~~~':;:
- -. .~. . ~. ._~ -;~~~~~i~~f~~
a.Electncaily Conductive . ~::'i~~;~~~~""- -:- '3'ŁŁA~/j~J'
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9.Cost C ompetfJtlve ";f': );'~~~Ą"~~~-".- ~ :.>f~~
'..
!:
;
SLIDE NO.
14
(DOOR LATCH ASSEt1BLY - DACROTIZED BY DIP-DRAIN)
12~
-------
SLIDE NO. 15
SPECIFICATIONS ~y~;.
!.:.,'!.~
130
-------
OUTSTANDING mRROSION PRaI'OCTION \VITH ZINC FlAKE
IN A WATER-BASED mATING
DISCUSSION PERIOD
MR. WHI'IE:
M3.rtin \mte, Cadmium Association.
I v.Dnder if
you could clear up "b.\D points on your process.
Your system seems to have a trenendous energy input.
You are
heating the alkaline cleaner.
You are heating the degreasing.
You have
two heat processes.
I I m interested to know how it is costcornpeti ti ve
for people paying you a license fee on top of that.
r1R. KOVELAN :
I think one of our disadvantages is that we do
have a high temperature cure.
As I rrentioned, it's a.l:Dut 575 degrees.
I was just talking with our manager of research and develop-
rrent, John deRidder, and we feel that we are costcompetitive with the
phosphate oil line.
We are talking a.l:Dut three to ten minutes on that final cure.
On the first cure, we are just passing it through to set the Dacrorret
and render it water-insoluble.
Dacrarret 320 can be sold for from nine to ten cents a pound;
polyshield goes for a.l:Dut nine or ten cents a pound; phosphate oil, for
about three cents a pound; zinc or cadmium, seven to eight cents a
pou.l1d.
We also know we are selling a license, and I might add at this
juncture that one gallon of Dacrarret 320 coats a.l:Dut a thousand square
feet. 'Ihis v.Duld be 1.3 cents per square foot, I guess, because it costs
$13 a gallon, so this is no rrore expensive than ordinary house paint.
Have I answered your question?
131
-------
MR. WHITE:
A couple of other small points.
First of all, you
are saying that corrosion resistance is a fmction of coating weight,
but there is also the question of coating uniformity.
I am ~ndering what happens to the threads of bolts - what
is the coating --
MR. KOVEIAN :
I mentioned that the zinc dichr0ffi3.te was a
heavier coating than ours, and we gave you twice the salt spray resis-
tance of the zinc plate for half the coating weight.
I don't think I said the coating weight was a fmction,
because we use on! y two-tenths or three-tenths of a mil when there are
many coatings that use either four-tenths or five-tenths.
MR. vlliITE :
t-1hat I'm trying to get at is how unifom is the
coating?
MR. deRIDDER:
DacroJret 320 can be carpared very much with
phosphate paint.
We are fighting gravity, and I guess as corrpared to,
say, cad plating where you filled up on the thread pitches, we had just
the reciprocal, we tend to build up ITDre in the thread roots and less on
the thread pitch.
We have been looking at the rayology of the canposi-
tion very closely, trying to iIrprove that situation, but overall I think
the distribution of coating weight is fairly good.
HR. ~'lliITE :
I'm interested in the torque characteristics of
the coating, because if you have got a flake, you must have a low show
of force between the flake.
t'1hat' s your torque characteristics of the
coating, because all the fasteners you have shown have been before they
have actually been put into position.
MR. deRIDDER:
Based on production evaluations by a variety of
people using the coating, I ~uld guess it is very comparable to zinc
plate; certainly not the lubricity of cadmium.
132
-------
v.e have been compared to cadmium, though, on a one-to-one by
autarDtive users using dynamic torque tension equipnent with load cells
and strip charts.
The whole thing, starting, prevailing and plant force
can be corrparable to cadmium with a friction rrodifier.
Usually we use a
very dilute water emulsified wax.
MR. WHITE: Thank you very much.
MR. VAALER:
Luther Vaaler, B3.ttelle-Columbus.
All right, perhaps CAdmium has sorre lubricity, or whatever it
may have in unique applications.
Can't you use this technique with
cadmium plate? Why wouldn't it --
MR. KOVELAND:
You mean plate over cadmium?
MR. VAALER:
I:b, just use cadmium instead of zinc plate to
start with.
MR. KOVEIAN:
I think again I'm going to have to thrCM that to
John, because John-- I' 11 give you some background.
John has been \"i th this for arout 12 or 13 years and he has
looked at all the things that have been added to Dacrorret 320, including
aluminum for the cosmetic effect, but I think John will tell you sorre of
the things that can't be done.
MR. deRIDDER:
I checked into this years and years ago, before
we ever got involved with zinc, and the initial res:r;x:>nse was for arout
$25 a pound they Vl:>uld flake the cadmium, and that dampened our enthusi-
asm, to say the least.
We have since Vl:>rked very closely with several of the rrajor
metal corrpanies that are in the process or business of making very
highly classified dust and i.lakes and so forth, and cadmium is still
alrcost prohibitive cost-vvise as a flake.
133
-------
vIe are currently looking at cadmium and other metals blended
to find other properties or to prove sorre of the existing properties.
MR. KOVELAN :
I might add that \'ie meet the prevailing torque
of the autOITDbile industry, spins five on and five off.
HR. BARTEK:
Charlie Bartek, RCA, Cherry Hill, New Jersey.
Hovv do you check for cure of this coating?
I am asking you
that because at one point in your talk you mentioned the lock assembly
that was free of polymer and yet your fonnulation is based on organic
proprietary material.
lVhat happens?
Ibes that polymerize in some way?
f.iR. KOVELAN :
v\1ell, it cares out in the stack.
vIe actually
destroy all of the polymers and there is no pollution corning out of that
stack.
There is some glycol, but nothing that is harmful.
HR. BARTEK:
What is the mechanism that holds those metal
plates together?
MR. KOVEIAN:
\\ell, the chromic acid binds the Dacromet 320 to
the substrate, and there is sorre form of oxidation that takes place, and
the cure, of course.
Have I answered everything, John, or can you amplify on that?
MR. deRIDDER:
Briefly, I wish we knew what the structure was.
All we can tell you is that it is some type of chromium matrix with the
surface iron and between the zinc flakes.
l'1e have a lot of the parts of
that puzzle, but not the whole thing.
'!he chromium is the key binding agent.
'!he organics are
shortchanged and completely destroyed.
Essentially there J.s nothing
left, maybe a little carbon residue, at best, but really nothing in the
way of an organic.
134
-------
Alternative Materials and Processes
Session II
Tuesday Afternoon 3:45
A PRACTICAL WET IMPACT ALTERNATIVE TO
CADMIUM ELECTROPLATING
Lester Coch
Waldes Kohinoor, Inc.
Tru-Plate Division
Long Island City, New York
11101
An improved system for coating base metal parts with co-deposits
of zinc, cadmium and tin and cadmium-tin by wet impact plating: The
several solutions used in cleaning or otherwise preparing the work, in
plating it and rinsing it, are individually segregated after use and
re-used in consecutive plating cycles; chemical and metal components
fed into the process are conserved instead of being discarded after
each plating cycle. No effluent is discharged into sewers. Fresh
water use is about 1 volume of water for 25 volumes of parts to be
plated. Pollutants are removed as a concentrated slurry.
Coated part corrosion resistance is comparable to cadmium
plating for most environments. Parts with Rockwells as high as Rc 55,
coated by this process, are always free of hydrogen embrittlement; no
energy-consuming stress relief is required after plating. Process is
in line with environmental goals of 1) conservation of all materials
used, especially water, and 2) no outfall of liquid effluent into the
ground via sewer or other conduit. The process is lower cost than
cadmium electroplating in most cases.
135
-------
A PRACTICAL WET IMPACT ALTERNATIVE TO CADMIUM ELECTROPLATING
LESTER COCH
WALDES KOHINOOR, INC.
47-16 AUSTEL PLACE
LONG ISLAND CITY, NEW YORK 11101
136
-------
Cadmium electroplating, the venerable and excellent standard of corrosion
resistance spanning the working lifetime of most of today's corrosion
resistance specialists, is truly a carry-over of a less sophisticated age.
In today's sharpened climate of expanding demand, limited resources,
sensitivity to potential ecological hazards, and heightened competition,
the old standby no longer measures up in many ways to current demands and
new ways must be found. In finding these new paths, we must never forget
that the primary purpose of corrosion protection is just that, and that
cadmium electroplating survived all rigors of the marketplace for many
years because it was cost-effective in terms of marketplace quality re-
quirements.
We, at Waldes, were among "the early birds" in abandoning electroplating
of all coatings, including cadmium. Many of the parts we manufacture
are stamped annular springs with minimum virtually square sections of
.025" and .035", hardened to Rc 55, and expanded diametrically in use
over 10%. Obviously, hydrogen embrittlement was and is a source of real
concern to our engineers, and efforts to relieve it by heat treating
procedures after electroplating were unreliable at best.
We replaced our zinc and cadmium electroplating with mechanical plating.
We started with a purchased system and chemistry: Gradually over the
intervening 15 years since that tentative start, we have evolved our own
systems, including methods, machinery and chemistry which have been
responsive to the changing environmental climate. It is this system,
and our new concepts (both in using old materials and new approaches)
which form our recommended methods for replacing cadmium electroplating.
First, we will describe in some detail a new system of wet impact plating
in which there is no liquid effluent outflow into a sewer. All liquids
and the materials they contain are used again and again. Rectification
of liquids when required, is done as a part of the machine function, and
waste products are removed as a slurry. Water consumption is about 5% of
that required by most conventional mechanical plating.
Second, using this new self-contained eccosystem of impact plating, we
will show how discreet layers of metals can be used as coatings to engi-
neer protective coatings to meet requirements of corrosion protection,
lubricity, etc., with no materials, toxic or non-toxic, being discharged
into the environment. Further, we will show how virtually any desired
degree of corrosion protection can be achieved by the peculiar ability of
this process to achieve any desired degree of thickness.
Third, we will document the corrosion resistance of the coatings by salt
spray testing of parts, both unmounted and mounted in a simulated use
condition in which plated retaining rings will retain aluminum bushings
mounted on various stainless steel shafts. Test results will also be
shown as conducted in the harsh real-life conditions of seaside south
Florida.
Fourth, we will demonstrate with our test samples that thin metal stamp-
ings \Hth fragile minimum sections, heat treated to Rockwell. C 55~ can be
safely plated by our system and heavily stressed in applicat~on W1th no
fear of failures due to embrittlement or stress corrosion.
137
-------
Fifth, we will show by comparative dollar figures that our proposed coat-
ing, applied by conventional mechanical plating techniques with our
recommended chemistry, compares favorably with the economics of cadmium
electroplating. This coating, when applied with our recommended Pollex
anti-pollution system, not only compares favorably with cadmium electro-
plating in the narrower sense of dollars but, more importantly, in the
larger sense of much lower water and energy consumption.
Summing up, we will present a plating program responsive to the demands
of 1977 for non-toxic coatings of a balanced quality previously obtain-
able only with cadmium, low in water and energy consumption, free of the
traumatic failures often associated with electroplating, with economics
which compare favorably with cadmium electroplating, and which has no
effluents to even minimally contaminate the watershed.
Mechanical plating is now practiced on a wide-spread commercial scale in
two basic forms.
The older of the two forms we call the "interrupted plating method". In
this method one or more tanks of cleaner, several rinse tanks and a tank
of coppering solution are utilized. One cleaner tank is frequently at an
elevated temperature, normally 150°-170°F.
The parts to be plated are placed in a rotating drum of perforate con-
struction (the parts having previously been degreased). The drum is lower-
ed into th~ cleaner and rotated for several minutes until the cleaning
operation is satisfactorily performed. The rotating drum is then lifted
from the cleaner tank and lowered into one or more rinse tanks, where it is
again rotated briefly. The drum is then taken from the rinse tank and
lowered into a copper tank, where the parts receive their copper-flash
treatment, again followed by a rinse.
The parts are then emptied into a rotating mill, normally. (but not always)
a horizontal plating barrel. Glass beads, water, plating accelerator and
powdered metal are added, the door is clamped on and the mill is rotated
for approximately 30 minutes, at which time the plating cycle is complete.
The parts are then emptied from the mill, normally into a large hoist pan,
which is then taken to a separating station, at which point the parts are
rinsed and separated from the glass beads. The expended plating liquid and
everything else that was in the mill except for the glass beads and the
plated parts are carried along with the rinse water into a sump, holding
tank or directly into the sewer. See Figs. 1, 2, 3 below.
138
-------
CONVENTIONAL (INTERRUPTED) PROCESS
FOR MECHANICAL PLATING
METAL
PARTS
I-'
W
1..0
FIG. 1
CLEAR RINSE
COPPER
CLEAR RINSE
ACID CLEANER
-------
I-'
~
o
GLASS
BEADS
\
PLATING
DRUM
PLATING
CHEMICALS
CLEANED AND
COPPERED PARTS
FIG. 2
-------
GLASS
BEADS
PLATED
PARTS
PLATING
LIQUID
SEWER
FIG. 3
141
-------
As generally used, this process depends upon a strong charge of citric acid
in the plating accelerator for the driving force of the process and it
normally operates in the range of pH 3.0 to 4.5. The process has the
advantages of comparatively very low capital expenditure, recovery of the
cleaning and coppering fluids and the fact that it tends to bring up a
rather bright finish as mechanical plating goes. It has the disadvantages
of being rather expensive from the standpoint of material handling and
being rather expensive in the expenditure of plating accelerator, compared
to more modern systems. Discharge of metal both in solution and in suspen-
sion occurs after each plating load; additionally, because of the rather
rapid build-up of particulate plating metal on the glass beads, these beads
must be stripped in acid frequently with consequent additional discharge of
metals in solution.
Many of these disadvantages have been engineered out in various installations,
in others platers choose to live with them, but one disadvantage all practi-
tioners of mechanical plating using this system share is the higher cost of
chemistry inherent in the system. Despite this real drawback, the system
continues to enjoy wide popularity, especially among platers of low-bulk-
density parts (parts less than 80 lbs./cubic foot) and tangling parts.
Many plating shops have replaced this interrupted method with an "uninter-
rupted plating method". In this procedure the de greased parts to be plated
are loaded directly into the plating mill, the cleaner is added along with
the glass beads and water and the driving force for the plating process
comes directly from the acid used in the cleaner, so that the copper solution,
the plating accelerator and the powdered metal are added directly in sequence
with no interruption or material handling. This process normally operates
at pH 1.0 to 1.5 and in general is lower in cost with very much less material
handling than the older method. The plating tends to be somewhat coarser on
certain part types using this method than when using the interrupted method.
At the conclusion of this plating process the total liquids used in the
process are again dumped into the sump or sewer along with the very great
volumes of water which are used to separate and rinse the material. When
this method is used little in the way of metal adheres to the beads, so that
additional stripping, while sometimes required, is quite rare. See Figs. 4,
5, and 6 below.
142
-------
f-'
.I'--
W
FIG. 4
PLATE-THROUGH (UNINTERRUPTED)
PROCESS FOR MECHANICAL PLATING
-
.. ..
..~.. I~ ,~/
~ ~
WATER
META~
PARTS
-------
POWDERED METAL
I-'
.j:'-
.j:'-
CHEMICAL TO
INDUCE PLATING
COPPER FLASH
CHEMICAL
INORGANIC ACID
CLEANER CHEMICAL
METAL
PARTS
BATH OF
GLASS BEADS
AND WATER
FIG. 5
-------
GLASS
BEADS
PLATED
PARTS
PLATING
LIQUID
SEWER
FIG. 6
145
-------
There are many variances of the above two processes and many combinations,
but basically virtually all mechanical plating done in this country today
is done by one. of these two processes. Both processes are distinguished
by the following common characteristics:
1)
With wide variations, they both use several volumes of water
for each volume of parts plated.
2)
Substantial quantities of metal, both in solution and in
suspension, are residual after plating and these must either
be treated before discharge into the sewer or this discharge
will have substantial quantities of metal in suspension and
in solution. While the very high water consumption obvious-
ly lowers the parts per million of metal content in any given
volume of the waste, even this dilution is not sufficient to
give reliable low metal concentrations in the process effluent.
3)
Both processes are wasteful of chemistry and metal, since both
essentially throwaway liquids which have large amounts of
usable and recoverable material.
A new method by which
Plate Pollex System".
beads are plated in a
the process:
mechanical plating may be done is the "Wa1des Tru-
In this system the de greased parts and the glass
semi-automatic tumbling mill. In automatic sequence,
a)
Adds a room-temperature cleaning solution, rotates the mill
for several minutes, drains the solution off and back into
the cleaning solution tank.
b)
Adds a coppering solution, rotates the mill for several
minutes until the parts are coppered, and then drains the
coppering solution back into the copper solution tank.
c)
Ends the automatic cycle by adding the plating liquid from
the plating accelerator tank. Manually, powdered plating
accelerator and powdered metal are added, the mill is
rotated until plating is effected. The plating liquid is
then drained back into the plating accelerator liquid tank,
the parts are then separated from the beads with rinse water
which is caught and recycled continuously. Parts are always
dried by centrifuge in this process.
This unit is operated with no outlet valve to a sewer or sump connection;
none is ever required so far as we now know. Since the process is exothermic,
there is some liquid lost by evaporation and by dragout; these losses must
be made up by addition of clear water. However, no liquids are discarded
into the sewer at any time.
All plating fluids, including the rinse water, are rectified from time to
time chemically in their tanks-with sludgy materials being removed to an
evaporating pan. Waste materials are alternately removed as a thick sludge
or dried solid material. See Figs. 7, 8, 9, 10, 11, 12, 13 below.
146
-------
f-'
.j>.
"'-J
FIG. 7
WALDES TRU-PLATe NON-POLLUTING
SYSTEM FOR MECHANICAL PLATING
GLASS
BEADS
/PUMP
METAL
PARTS
CLEANING
LIQUID
MIXTURE
-------
f-'
~
co
FIG. 8
GLASS BEADS
AND CLEANED
METAL PARTS
CLEANING
LIQUID
MIXTURE
-------
i-'
~
\D
FIG. 9
GLASS BEADS
AND CLEANED
METAL PARTS
COPPERING
LIQUID
-------
t-'
Ln
o
GLASS BEADS
AND COPPERED
METAL PARTS
FIG. 10
COPPERING
LIQUID
-------
i-"
\J1
i-"
FIG. 11
PLATING
CHEMICALS
GLASS BEADS
AND COPPER ED
METAL PARTS
POWDERED
METAL
LATING
LIQUID
-------
t-'
V1
N
FIG. 12
GLASS BEADS
AND PLATED
METAL PARTS
PLATING
LIQUID
-------
f-'
\Jl
v.:>
FIG. 13
PLATED
METAL
PARTS
SCREEN
BAFFLE
GLASS
BEADS
RINSE
WATER
-------
Expenditures for chemistry in this process are only about 60% of the
expenditures of today's lowest cost method and much valuable material is
reused rather than ending up as a noxious effluent to be removed by the
producer or the community or to foul the watershed. Water consumption
is approximately 1 volume of water for each 25 volumes of plating and
the nature of the machine and the process is such that it -lends itself
well to partial automation, thereby making larger machine assignments
possible.
It seems clear that the development of the "closed loop"Pollex system
of mechanical plating, from which no effluent is discharged into the
watershed, is a giant step forward in the protection of our streams and
rivers. It is also clear that its unique economies in the conservation
of energy, water, metal and chemistry is in tune with the times and opens
new vistas to the corrosion protection engineer. It is an idea whose time
has come!
Market analysis of specific coating function requirements by manufacturers
presently using cadmium electroplating shows that while all users expect
good protection against rust from this coating, other characteristics
frequently have great weight in their choice of cadmium electroplating.
Foremost among these is lubricity, which may greatly affect the torquing
.of threaded fasteners, the application and function of spring-type
electrical fittings, the insertion of radial-type retaining rings in
grooves, etc. Another significant virtue of cadmium is its good prl\tec-
tion against white corrosion products. A very important requirement
frequently encountered is that it be inert when in contact with various
alloys such as aluminum, stainless steel, etc. Proposed alternatives to
cadmium electroplating must consider these requirements as well as extend-
ed resistance to red corrosion, to truly meet all market requirements,
hopefully at no increase in cost.
The simplest and most straightforward alternative possible to cadmium
electroplating, which will meet all these requirements and protect the
environment against cadmium-bearing effluents as well, is cadmium mechan-
ical plating done according to the Waldes Tru-Plate Pollex system. Since
there is no effluent from this process, the requirement that no cadmium
enter the watershed is fully met by this plating process. (Since the
plating is cadmium, it will have the characteristics of cadmium electro-
plating and surely meet all requirements. Indeed, mechanical deposition
of cadmium offers expanded possibilities in corrosion protection by means
of heavier thicknesses of coatings; coatings up to 50~ are practical, as
are co-deposits with other metals such as tin.) For the ultimate in
corrosion protection, coatings using cadmium have no peer.
We feel that there will be an ongoing requirement for mechanical cadmium
plating, done in a non-polluting process in selected plating stations,
carefully monitored. But it is clear that the greater the volume of
cadmium plating done, the greater the danger of some cadmium entering the
eccosystem, perhaps by careless handling of a stripping solution or some
"goof" not presently foreseen. But there are many applications existing
today which are routinely specified as cadmium electroplating which do not
require the supreme rust protection of cadmium but which do require some
or all of the other virtues of cadmium.
154
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One way in which less cadmium is used today in mechanical plating is by
plating co-deposits as, for example, 50% cadmium, 50% tin. Mechanical
plating of co-deposits is done by any of the mechanical plating systems
previously described, making each required metal powder addition half
cadmium, half tin. The agitation of the mass assures a reasonably
uniform distribution of the cadmium and tin in the coating. Since the
properties of cadmium and tin are supportive in most cases, the value
of the coating in most cases is as good as cadmium alone; in many
applications, the coating values are enhanced.
Certainly, this is one way in which the amount of cadmium used
reduced by half. Unhappily, the cost of tin makes this finish
costly than cadmium alone, adding about one-and-one-half cents
foot for a 7 micron coating over cadmium'alone.
can be
more
per square
However, since tin worked well in co-deposit with cadmium, we should not
overlook the possibility that the use of lower-priced and less toxic zinc
will be effective as a co-deposit with tin. Certainly the economic prob-
lem will be overcome; the resultant coating will be less expensive than
cadmium alone. But it is at this point that we run into a limitation of
the melange approach: The properties of the co-deposit are the properties
of both the components all through the coatings. The synergism of the
cadmium-tin mixture is noticeably absent in the tin-zinc mixture.
Zinc tends to have two basic drawbacks as a replacement for cadmium, even
in the cases where protection requirements against rust are moderate: It-
has poor lubricity, which makes it a less desirable coating for many
threaded and other fasteners requiring good lubricity and it has a tendency
to form white corrosion products after a comparatively short exposure to
many atmospheres. The tin in a zinc-tin co-deposit does assist in giving
the coating a greater lubricity than zinc alone, but the resultant lubric-
ity of the zinc-tin combination falls far short of the desired standard
for lubricity, that of cadmium plating. Further, in most tests, the tin
portion of the coating seems to do little in extending the coating life to
white corrosion failure.
Understanding clearly that in the nature of things, there will be some
applications for which the tin-zinc co-deposit will be useful, we believe
we "have found a better way".
One technique used in mechanical plating is adding the required amount of
metal powder in small doses to achieve a smoother, more cohesive finish.
For example, a 12 micron thick zinc plating on a part having 1 square foot
of surface area per pound of parts requires 9 grams of zinc powder per
pound of parts. Good mechanical platers ordinarily apply the metal powder
in two equal additions of 4.5 grams per square foot each to the plating
barrel at about 15 minute intervals. In effect, they plate two separate
layers of zinc with perfect cohesion.
There is, of course, no reason that the separate layers have to be the
same metal or the same thickness or that we could not have several layers
rather tha~ two. For example, one practical alternative to a ~2 micron
co-deposit of tin-zinc might be a 10 micron thick coating of z~nc covered
155
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by a 2 micron thick coating of tin. That would have the effect of
putting the tin "up front" so to speak, where it would certainly improve
the lubricity of the product to the equivalent or better of cadmium
plating, and exert a benign effect in resisting the formation of white
corrosion products.
Such a treatment is, in our opinion, a better treatment than co-depositing
tin and zinc and, obviously, uses only 1/3 the tin of the co-deposit on a
13 micron coating, saving about $.04 in metal per square foot at current
tin prices. The time per plating run would be extended several minutes,
which is a cost adder. There is a more serious criticism of this technique
as I have described it; it applies equally to putting on a final layer of
tin using powdered metal and to co-depositing tin with zinc. The plating
is rather lumpy as a rule; far more so than is common with quality mechan-
ical plating. This is especially noticeable with low bulk density parts
(less than 80 lbs./cubic foot) of high surface area. This is caused in
part by the coarse particle size of powdered tin.
There is another approach to the same problem that plainly seems tailor-
made for mechanical plating. Returning to our previous example of the
12 micron coating, we can take the 2 microns of tin from tin salts. This
top layer, put on in a proper chemical ambience over a quality mechanical-
ly plated base of zinc, yields the smoothest and most lubricious mechan-
ically plated surface we have ever seen, and one which functions in many
key ways as well as or better than the finest cadmium electroplating,
particularly with regard to uniformity and ease of torquing threaded
fasteners so plated. Costs of the process and materials are competitive
with all other mechanical plating approaches to the problem of replacing
cadmium electroplating and, in most cases, with cadmium electroplating
itself.
The concept of layered plating has additional value in the search for a
replacement for cadmium electroplating. Using our effluent-free Pollex
process, it is possible to effectively coat parts with, for example, 2.5
microns of zinc as a base, a second layer of 2.5 microns of cadmium and a
top layer of 2 microns of tin as previously described. Such a coating
retains all of the lubricity values previously described, further improves
the corrosion resistance against both white and red corrosion and still is
attractive economically.
This zinc-cadmium-tin layered coating has an attractive bonus plus. The
nature of mechanical plating is such that a failure in the plating process
is almost always caused by one of several possible errors, the effect of
which would be clearly visible on the first layer of zinc. Thus, a plater
who always used a first layer of zinc, before putting on a layer of cadmium,
and who inspected the plating deposition of the zinc layer carefully before
putting the cadmium powder in the plating barrel could largely avoid the
problem of stripping, since success through the stage of the first layer
virtually assures successful completion of the plating. To the extent that
cadmium plating is required, the combined practice of using the Waldes
Pollex mechanical plating system and the use of a zinc first layer of plat-
ing would certainly minimize danger of any entrance of cadmium into the
watershed. We feel, however, that the bulk of existing cadmium electroplat-
ing can be replaced by a zinc coating with a layer of tin on the surface.
This layer of tin will normally be 2.5 microns thick over 5 microns of zinc;
Exact tin-top thicknesses specified will always be a function of the end
product requirement.
156
-------
The use of chromates is not always necessary with the tin-top plating de-
scribed above but it does greatly further enhance the corrosion resistance
of the plating. Depending on the thickness of the tin coating it is fre-
quently not visible and rarely assumes a full yellow chromate ~olor but its
use, particularlĄ with coatings of 5 to 7 microns of thickness assures
good corrosion resistance against both red and white corrosion: Clear
chromate coating over mechanical plating does not add the corrosion resis-
tance it does to electroplating. To get a significant effect reliably from
lot to lot, it is necessary to use a yellow chromate and leach. This is
distinctly less of a problem with the tin-top coating, since normal chromat-
ing over tin-top plating frequently shows only the n0ldest tawney coating
and leaching where required should not be difficult.
Summing up, we believe that the Waldes Pollex mechanical plating system can
deliver several coatings to serve as viable alternates to cadmium electro-
plating with no danger of polluting the watershed. These are:
1)
Cadmium mechanical plating
2)
Cadmium co-deposited with tin mechanical plating
3)
Layered plating, designed by specific requirements of
corrosion resistance and lubricity, in which a base
layer of zinc would be covered with a top layer of tin,
with an intermediate layer of cadmium as an optional
additional .possibility where corrosion requirements
demanded it. Tin-top plating, which uses only tin and
zinc to replace cadmium electroplating, can be made by
many existing mechanical plating installations, requir-
ing only a new chemistry and technique.
Setting up a test program by which the virtues of the various platings might
be assessed, it is advantageous to work with non-threaded as well as thread-
ed fasteners, since certain key parameters such as hydrogen embrittlement
and stress corrosion are far easier to evaluate in a spring-type fastener
than a threaded fastener. Obviously, lubricity is best evaluated for most
purposes in threaded fasteners.
The spring steel part chosen for our test is a radial type retaining ring of
a new and hard-working type. It is made of 1075 steel, .050" thick and
designed to work in a groove cut into a half-inch shaft. The basic part is
stamped at high speeds in blanking dies and heat-treated to Rockwell C52-55.
The part was originally designed for the farm implement industry and is widely
used in both automotive and the farm implement industries as a workhorse when
extra strength is needed. Loading on these parts is always bi-axial, with
static thrust load and frequently some impact in the axial direction, and
working stresses in the area of 170,000 P.S.I. in the radial direction to
clinch the ring in its groove.
The parts are heat treated isothermally, austenitized at l500°F in a neutral
atmosphere with a dewpoint of 35°F and quenched in violently agitated nitrate-
nitrite salts at 540°F for one hour. Normally, plating is done directly after
heat treating: however, some lots require a special intervening deburring.
The actual distribution of Rockwells shows a mean Rockwell of roughly 54.5,
with a low of 53 and a high of 55.5 - a good typical distribution from our
157
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isothermal heat treating process. All samples which were Rockwelled were,
of course, discarded, since the penetration mark does constitute a notch
at these Rockwells.
ROCKWELL "c" DISTRIBUTION
TEST SAMPLES
53 - X
y
:j
~
t)
~
54 - XXXXXXXXXXXXXX
- XXXXXX
55 - XXXXXXXXXX
-xx
EACH "X" REPRESENTS 3% of I:
ROCKWELL "c" DISTRIBUTION
TEST SAMPLES
MEAN = 54.44
S.D. = 0.58
N = 50.00
MIN = 53.00
MAX = 55.50
RANGE = 2.50
Tin-top plating samples were prepared by all three mechanical plating
methods - the uninterrupted, the interrupted and the Pollex method. Other
samples which were prepared, such as tin-zinc mixtures, cadmium, etc., were
generally prepared by the uninterrupted method.
Our bitter experience has shown that on these part types, heat-treated to
RC 55, there is no combination of electroplating, pre-treatments and post-
treatments which will give any real degree of security against hydrogen
embrittlement. Thus, the first test requirement in our program is to dem-
onstrate by overtesting that all parts plated by this process are free of
emb ri t tlemen t.
Our normal test for this is to mount the ring in such a way that the stresses
in the radial direction are raised to about 200,000 lbs. P.S.I. and hold it
at this stress level for 8 hours. No failures are permitted from a 20-piece
sample.
For this test, we turned 200 test shafts, each containing 2 grooves of a
diameter which raises the working stresses of the rings in the radial direc-
tion to 205,000 lbs. P.S.I. The 400 rings so tested, about 20 each from the
20 test lots made, remained on the grooves for various lengths of time from
4 to 14 weeks.
158
-------
100 of the test shafts were made from 430 stainless, 100 were made from
304 stainless. For each shaft, a bushing of 7076-T6 aluminum was turned
so that it was a close fit on the stainless shaft and so that it was
retained tightly by the two plated retaining rings.
It ~s clea~ from the chQice o~ materials fo~ our test assemblies that we
~sh.ed thi,.$ te~t to s.h.QW mo;t;e than just e1I\b;t;ittle1I\ent. Cadmium~ whether
electroplated or mechanically plated, is ~elatively inert to the bi-
metallic influence of common steel, stainless steel and aluminum alloys,
even in highly corroding atmospheres, and all of the test platings we ran
were subject to this bi-metallic assembly test.
One further note on the use of the assemblies as a test fixture: You will
recall that the rings are loaded in the radial direction to some 205,000
lbs. P.S.I. Since each assembly was corrosion-tested, it is obviously a
very good test for stress-corrosion as well: Did the high working stresses
increase the rate of corrosion on the plated parts or, alternately, did
any corrosion which occurred increase the stresses to a failure point?
Threaded parts were also plated, assembled in 6064-T4 aluminum threaded
blocks with pH 15-7 Me nuts. These tests were run as part of the bi-
metallic tests only.
All assemblies, as well as individual plated pieces, were tested in one of
two salt spray cabinets: Ours. in our Long Island City laboratories and New
York Testing Laboratories' cabinet at Westbury, New York. In effect, we
ran duplicate, simultaneous tests, both as a replicate and to eliminate
any test bias. Both cabinets and test procedures meet all requirements of
ASTM-B-1l7-64.
Various other parts, threaded and non-threaded, were included in the test
for various reasons. Some test parts weighed 600 grams, some test parts
were 10" long, many 1-1/2" diameter doughnut-shaped chips were used. We
included these parts to make sure our conclusions had general rather than
narrow validity.
"Real-life" corrosion testing was done at a testing station located at
Jupiter Beach, Florida. The results of tests done at this station vary
significantly from the accelerated salt spray tests in several ways, which
will be noted as we discuss the results.
The Florida testing station itself was located along the inland waterway
approximately 300 yards from the Atlantic Ocean, with a reef overgrown with
Australian pines intervening. The location is an interesting one and fenc-
ing elements made of hot-dipped galvanized wire frequently have to be
replaced in less than two years. Also of general interest, the testing
station is located only a short distance from a principal outboard motor
manufacturer's testing station.
The Florida tests which were run in the general period of late June, July,
August and early September of this year, included exposure to sun, rain and
the very humid salt atmosphere of south Florida in the summer. We ,were able
to establish a very rough correlation to failure of some of the thlnner .
plated parts of roughly one hour in the salt spray cabinet to seve~ hours ln
the Florida atmosphere. However, for the heavier plated parts, ~hls.corre-
lation is not clear, since failure in many cases on the same basls wll1 take
almost a year and we simply do not have enough experience.
159
-------
It is clear, however, particularly in the case of the assemblies, that the
Florida tests give far more meaningful results than the salt spray tests on
the relative inertness of a plating to bi-metallic influences and certainly
come closer, at least, to relative kind of performance which may be antic-
ipated in real life. On the other hand, the repeatability of specific
results in salt spray is Unlikely to be matched by any test run in Florida.
The test program, in addition to considering the mechanical properties of
the part after plating, the part's corrosion-resistance and the part's
inertness in the presence of various metals, considered one of the most
significant of all properties of cadmium electroplating, lubricity. Because
of the very particular requirements of lubricity and the multiple require-
ments of various consumers, no standard test was attempted at Waldes; rather
we worked through prime producers of threaded fasteners who were able to
test the various treatmenmon the surface of the threaded fasteners to
determine whether or .not they met specifications for lubricity of cadmium
electroplated fasteners. Using GSE test equipment, five large producers
determined that the Pollex tin-top plating did, indeed, meet the requirements
of a principal automotive manufacturer, both for the amount of torque requir-
ed to drive the fasteners and for the uniformity of torque requirement from
piece to piece and lot to lot. Since we at Waldes are not expert in the tests
involved or in the varying requirements of this industry, we will let the
test reports speak for themselves.
We are very keenly aware of the desirability of high lubricity on parts such
as retainer rings and on parts which are hoppered prior to assembly and in
this respect the non-threaded parts performed in an outstanding manner,
albeit a subjective evaluation, both in terms of being easier to insert a
part in a tight clearance fit and also in terms of speed of hoppering feed
compared to other finishes or no finishes at all.
Any discussion of plating quality starts with an assessment of its unifor-
mity of coverage. Our basic device for measurement of thickness is a
Dermitron unit. Cadmium-tin mixtures, zinc-tin mixtures and tin-top plating
were all measured using the probe designed for measuring cadmium: Pre-test
experiment had indicated that this probe most nearly correlated with micro-
scopic thickness measurements of sectioned coated pieces. We believe that
this probe is sufficiently accurate for production and quality control of
tin-top plating as well as the zinc-tin co-deposit. .
The part itself has some tendency to tangle during plating which reduces
plating uniformity. It has the reputation in our plant of being a "difficult
part" to plate uniformly and smoothly. A typical example of the thickness
distribution obtained in measuring a 50-piece sample taken from a lot of
Pollex tin-top plating which we intended to be 7 to 8 microns thick (5 to 6
microns of zinc plus 2 microns of tin) can be seen in Fig. 16 below.
TYPICAL DISTRIBUTION OF THICKNESS, POLLEX TIN-TOP PLATING
5~ zinc + 2.5~ tin = E 7.5~
6.5~ = 2
7.0~ = 12
7.5~ = 15
8 . O~ = 17
8.5~ = 4
x = 7.57
cr = 0.54
160
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4% of the pieces were in the range 6.5-7.0 microns (undersize) and 8% were
in the range 8.0-8.5 microns (oversize). This kind of range is somewhat
better than we normally experience in mechanical plating of these parts, but
was typical of the test lots and about the same variance as two small cadmium
electroplated samples of the same part.
No special treatments prior to plating were given to the rings to prevent
embrittlement nor was any attempt made after plating to relieve embrittlement
by any known method. The parts were raised to a working stress of 205,000
lb./sq.in. in the radial direction and many parts were held at this load for
as long as 12 weeks (in fact, at this writing, most of the parts are still
being held under this condition). No failure occurred.
This is no unique incident. In the several years that we have been using
our own chemistry and systems for mechanical plating, of the tens of millions
of pieces that we have plated, no piece has ever failed in embrittlement test-
ing at Waldes and we know of no customer complaint involving embrittlement on
these pieces. We consider this to be a truly remarkable record and we believe
that the Pollex plating can be used with no fear of embrittlement and no re-
quirement for post-plating stress relief.
The salt spray corrosion testing in a systematic manner was done in two salt
spray cabinets - one in our own laboratory, the second at New York Testing
Laboratory - using duplicate sets of samples. Both salt spray tests conformed
in every way to ASTM-B-117-64.
ln general order of magnitude, for equivalent
tin-top plating to give consistantly superior
mixtures in hours to white corrosion; neither
cadmium.
thicknesses, we find the Pollex
performance over tin-zinc
has the corrosion resistance of
A fair and repeatable evaluation of our salt spray data for the Pollex tin-top
plating is summarized in Chart #2, which we believe shows that the Pollex tin-
top pl~ting has a usable corrosion resistance for most applications. Many
things can be done to improve certain corrosion properties of the Pollex tin-
top plating. For example, in the development of a 12 micron thickness, we
could improve the resistance to white corrosion by having an 8 micron layer
of zinc plus a 4 to 5 micron layer of tin. Systematic evaluation, which is
continuing, has not gone far enough to provide us with an equation by which
we might estimate the benefits of such a move.
Chart #2
SALT SPRAY CORROSION RESISTANCE
Resistance to
Neutral Salt
Spray
Minimum Coating Thickness* Type of Plating and To White I To Red
um in. Supplementary Treatment Corrosion
50.0 .002 Zinc 196 800
25.0 .001 Plus 160 400
.
13.0 .0005 Tin 120 168
8.0 .0003 Plus 96 140
5.0 .0002 Chromate 72 96
* The top 2.5U (.0001") of coating is tin
161
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The bi-metallic assemblies in salt spray show clearly that the Pollex tin-top
plating performs identically alone or in the bi-metallic ambience under the
severe corroding conditions of salt spray. No battery action or white
corrosion appeared prematurely due to the bi-metallic ambience.
The tests in Florida were more interesting and informative in many ways than
the tests run in salt spray. Though the general relationships were the same
in salt spray and in the Florida tests, we were able to see more clearly what
was happening in Florida. For example, the rate at which white corrosion
products were formed and the way in which they spread over both the plated
part and the surrounding parts was not impeded by masses of salt caked all
over the parts and assemblies, and thus we were able to see very clearly
that
1)
The formation of white corrosion products on the tin-zinc
mixtures was about the same as the formation of white
corrosion products on zinc alone, and both occurred much
earlier than on the Pollex tin-top plating, and
2)
In the bi-metallic assemblies, white corrosion products
were far more severe for the tin-zinc mixture than they
were on the parts plated with the tin-zinc mixture but
tested alone rather than in an assembly. The white
corrosion products spread over the 430 stainless shafts.
From the data it appears that the bi-metallic ambience
increased the rate at which white corrosion products
formed on the tin-zinc plating mixture and also affected
the amount of total white corrosion products formed in
any time period. The Pollex tin-top plating again per-
formed well in these circumstances, showing no tendency
to form white corrosion products prematurely as a result
of the bi-metallic ambience.
We tested a few pieces coated with a popular organic coating in this test and
found a most severe battery action which occurred very rapidly, most partic-
ularly again with the 430 stainless steel in the presence of aluminum.
It seems to us that this test of performance in a bi-metallic ambience is a
most important one in trying to evaluate the performance of an alternative ~o
cadmium electroplating. For example" many of our snap ring parts are used on
die cast aluminum and magnesium housings, on stainless steel shafts or hous-
ings, and in mixed metallic ambiences in both the automotive and marine motor
industries. Many of our customers have traditionally insisted on cadmium
plating because of this and our Florida tests have showed how correct they
are.
Summing up the corrosion testing, we think that both the salt spray and the
Florida testing show that the Pollex tin-top plating has a good corrosion
resistance, that it is relatively inert in the presence, of a bi-metallic
ambience and that for most instances, it appears that it will be a very good
real-life replacement for cadmium electroplating.
Lubricity tests were
tests were performed
ent deformations. A
plating for the five
performed by five major manufacturers of locknuts. Basic
on 8 mm, 10 mm and 14 mm size locknuts in several differ-
total of 40 lots were plated with the Pollex tin-top
manufacturers.
162
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It has been reported to us that all of the samples evaluated by the five
manufacturers from the 40 lots fall within the torquing limits of cadmium
on the particular product involved and that performance was reliable from
lot to lot and from piece to piece within the lots. The test report of
one of the manufacturers is appended to this paper.
As a result of the testing done for lubricity, a major automotive manufac-
turer has indicated acceptance of this finish for the threaded fastener
industry as an alternative to cadmium electroplating and we have been
invited to propose a tentative standard for the finish. I think that this
speaks loudly for the lubricity quality of the process and tells more than
anything else I can state.
One very important consideration in evaluating any plating is the cost ratio
of this plating in comparison with cadmium electroplating. A careful one-
week analysis of an automatic cadmium electroplating line with a basket
capacity of 1/2 cu. ft. was made at the Empire Plating Company in Cleveland,
Ohio. A further very exhaustive analysis of the costs of the Pollex tin-top
plating of almost a comparable thickness was made. All costs were related
to a cap screw with a. surface area of .8 sq.ft./lb. and a bulk density of
200lbs./cu.ft. Referring to Chart#17, we assume certain standard costs for
the metals involved, for electricity, for water and for labor. We then con-
structed a weighted cost for the cap screws, using all available data since,
unhappily, there were not enough cap screws to run both processes for a week.
Both lines were capable of producing in the neighborhood of 1800 lbs. per
hour with approximately the same amount of labor. Again, referring to Chart
#17, we see that the costs of the two operations are not distinctly different
for the basic groups of chemicals, metal, water, labor, maintenance, and
there is a small additional charge which accrues to mechanical plating for
beads and defoamer; the largest single difference in the costs comes in the
electricity. With rising costs per kilowatt hour, electricity has now
become a preponderant factor in the cost of electroplating.
The cost bias in favor of the Pollex plating over the cadmium electroplating
is very real and very genuine, but it assumes a minimum thickness of 7 to 8
microns and it assumes a relatively large load. This cost analysis is based
on 1800 lbs. and for cost parity, at least 1200 or 1300 lb. loads would have
been necessary.
Since the cost of the Pollex plating is virtually the same for 5 microns as
for 7.5 microns but the cost of cadmium electroplating goes down for a lower
thickness, it becomes clear that the cost advantage of Pollex over cadmium
electroplating will start only with platings thicker than 6 or 7 microns.
However, the additional cost, for example, of 12 microns over 7.5 microns for
Pollex is small, being only the additional cost of the zinc powder; thus, the
advantage of the Pollex plating over cadmium electroplating will increase as
the plating requirement becomes thicker.
The same figures developed for other parts during this study showed approx-
imately the same advantage of the Pollex plating, noting only that as the
part grows substantially larger, the advantage of the Pollex plating would
probably increase. In general, it is fair to say that as a sub~titute for
cadmium electroplating, the Pollex plating with coatings of ~ mlcrons or
thicker will enjoy a cost advantage over cadmium electropla~lng and t~is .
advantage will increase rapidly as the coating requirement lncreases In thlck-
ness.
163
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......-
CHART 1/17
PLATING - DIRECT COSTS PER LB.
CAP SCREW, .8 SQ.FT./LB., 200 LBS./CUBIC FOOT
*
7.5}.! POLLEX 6. 5}.! CADMIUM
TIN OVER ZINC ELECTROPLATE
CHEMICALS .0128 .0079
METAL .0360 .0335
WATER .0001 .0010
LABOR .0097 .0097
MAINTENANCE .0013 .0018
BEADS & DEFOAMER .0018
ELECTRICITY .0010 .0229
l: .0627 .0768
* Based on 1800 lb. loads
ASSUME
ELECTRICITY
= $. 06 /ĄIN HOUR
CADMIUM POWDER - $3.54/LB.
ZINC POWDER
= $.52/LB.
WATER
= $.72/100 CUBIC FEET
LABOR
= $10/HOUR
= $5.20/LB.
TIN
164
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Again, since it seems probable that because
1)
the ability to handle larger and larger loads of mechanical
plating will increase in the future, and
2)
the cost of energy will probably increase at a somewhat
faster rate than most of the other plating costs
it seems probable that in the near and distant future the cost effectiveness
of the Pollex plating will grow relative to cadmium electroplating.
One last point concerning costs: Many heat-treated parts require energy-
consuming stress relief after electroplating. All of our experience and all
of our test results indicate that no one need stress-relieve any Pollex plat-
ing after plating in any circumstances of which we can conceive. This is an
important cost consideration, both for material-handling and energy consump-
tion. These have not been evaluated in our cost comparison, but it is
obvious that this factor increases the cost effectiveness of the Pollex tin-
top plating over cadmium electroplating.
In considering cost effectiveness of this plating, two significant factors
have been omitted:
1)
The cost of the capital equipment involved. Based on current
costs, the capital equipment needed to perform at a rate
comparable to the automatic cadmium electroplating line we
studied at Empire Plating Company, completely installed, is
in the range of $125,000 to $130,000. The replacement cost
of the electroplating line is estimated at $300,000.
2)
Overhead in any fair cost assessment will be in large part a
function of the floor space used; while the particular work-
handling requirement of any system has to be accounted for to
fairly evaluate all the floor space required, the machinery
described in item I above will occupy approximately 660 sq.ft.
of floor space, approximately the same as the automatic cad-
mium electroplating line.
It seems probable that basic overhead cost assignment per pound would be
approximately the same as the existing cadmium electroplating line and that
amortization of equipment would be approximately half that required for an
automatic cadmium electroplating line.
We draw the following conclusions from our search for a replacement for
cadmium electroplating:
1)
That we have found a worthy successor for many applications
presently done by cadmium electroplating. In our Pollex
tin-top plating, this plating should cost slightly less than
cadmium electroplating for large bulk orders. It shoul~ have
equal or greater lubricity. It should have goo~ corros~on-
protection against white and red corrosion and ~s relat~:ely
inert against aluminum, stainless steel and variou~ al~~ums
and stainless steels and combinations thereof. Th~s plat~ng
165
-------
has the advantage that it can be done in many of the
existing mechanical plating set-ups, requiring only
know-how and chemistry, so that it can truly become
available in various areas within a reasonable time
period.
2)
Basic zinc and tin thicknesses can be manipulated to
increase lubricity, increase resistance to white
corrosion, increase dielectric properties, to cover
any needs.
3)
The Pollex plating can be produced with absolutely
no liquid effluent. Equipment and techniques for
doing this plating are commercially available at
this time and await only sufficient interest on the
part of producers. The economics of the pollution-
free process are cost effective in every sense of
the word.
4)
We believe there will be some continuing need for
cadmium plating where extreme corrosion protection
is required and organic finishes cannot be used
because of the lubricity requirement, dielectric
requirements, temperature requirements, etc. Such
plating can be produced in our pollution-free
system and can be produced in any desired thickness,
thus for the first time extending the possibility of
almost infinite corrosion protection. The Pollex
tin-top finish~ which can also be extended to great
thicknesses, also provides greatly extended protec-
tion.
We have a process which can be done in many existing mechanical plating
stations, in a uniformly good manner, producing a uniformly high quality
product. Happily~ the process is not a difficult one and is not sensitive
to the kinds of things which cost a great deal of money.
The Pollex anti-pollution system is a patented process of Wa1des Kohinoor~
Inc. The Pollex tin-top plating is in a "patent applied for" status.
Attach.
166
-------
APPENDIX I
LUBRICITY TEST WITH AIR STALL GUN
M 14 LOCKNUT - FIRST INSTALLATION
TYPE
RANGE IN INCH LBS.
Max. Allowable: 274 in. lbs.
A
A + wax
234-528
168-336
B
B + wax
232-488
156-288
C
C + wax
192-396
156-318
Pollex tin-top, 8~
Pollex tin-top with wax, 8~
102-180
90-165
D
D + oil
D + wax
240-540
244-576
144-420
Twenty pieces of each finish were tested.
Note:
Johnson's III Wax used in all instances
where wax is used.
167
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A Practical Wet Impact Alternative to Cadmium Electroplating.
DISCUSSION PERIOD
MR. GROBIN:
Allen Grobin, IBM Corporation.
I notice that you have a sacrificial rretal, zinc, between two
other rretals.
Now, is there any bake process in there that would account
for any alloying of tin and zinc layers, so you don't get creeping corrosion
separation of the layers.
MR. coeH:
Yes.
I can bring that out just a little bit for you.
The zinc in this particular case was taken from pcMdered zinc, which is
approxinately three microns in diarreter.
The rrechanical plating process,
as you knON, basically irrpacts against the grain of the zinc and elongates
it and it is in effect stuck with glue onto the part.
The tin is taken from atomic tin, not by simple reaction.
The
whole chemical ambience is such that you get the kind of alloying that you
are talking about.
I cannot possibly corrm:mt on the thickness, but there is the
kind of alloying you are talking about.
The coating was completely
unsuccessful with the pcwdered tin.
MR. GROBIN:
I would agree with your observation.
Once there is
alloying, you are going to get creeping corrosion separation.
We have
observed this ourselves.
You do recognize you have alloying there.
MR. COCH:
Yes.
Incidentally, we tried to guard against this.
We have done a number of other tests.
A part of contraction expands very
severely under trerrendous load.
Both adhesion and cohesion of all plating
layers is always a problem to us.
168
-------
For example, the ten-inch part that you saw which goes into
aerospace has a diarretric contraction in the neighborhood of over an inch,
and, of course, you have trerrendous loading.
The inside diarreter loads
very severely in conpression, the outside tension.
We did a tremendous
arrount of these flexion tests looking for just this kind of a problem, and
we didn't find any.
The tests are ongoing in Florida.
We put out the first pieces
on the first of July, but we will continuously update the reports on what
we find there.
MR. HEIDERSBACH:
Bob Heidersbach, Ocean Technology Incorporated.
I have two questions.
One, as I understand it, you are talking
about a ferrous or aluminum substrate with zinc topped by tin.
MR. coeH:
No, sir.
I am talking about only a ferrous substrate
wi th zinc topped by tin.
We have not done this with aluminum.
MR. HEIDERSBACH:
Why don't you compare that to a simple tin
coating as well?
MR. coeH:
In what way?
MR. HEIDERSBACH:
Well, as I understand it, you have a tin surface.
MR. coeH:
A tintop surface, yes, Slr.
MR. HEIDERSBACH:
Is this essentially a noble metal coating, which
you are comparing with sacrificial coatings, such as any of the other metals
that have been discussed so far today?
MR. coeH:
Yes.
MR. HEIDERSBACH:
Okay, and you have two different situations
there.
Have you tried deliberately induced stress environmental tests of
any sort?
169
-------
MR. COCH:
We have not.
We have talked about the possibility
of eroding our parts intentionally.
That would be to take one of the
large parts, and draw it in with a pair of pliers until the points were
touching.
Then put a deliberate scratch through it to see what the
results are.
One of our customers uses such a part.
It's about an inch and
a half at the end of a long tube.
It's on an inboard-outboard IIDtor
and it's subject to repeated iTIpacts at an ambience of 200 degrees
Fahrenheit.
It is sometimes sprayed.
You are all familiar with the
beautiful blue they spray it with that doesn't coat the snaplink conpletely.
This is alrrost the situation you are talking about, in many ways, because
it lets all the action go to one place.
NCM, I have induced these people
to try three or four of these parts, which I think will come very close
to what you are talking about.
All of our parts get a certain arrount of
scratching when they are installed because they have to be done with pliers
or some other way.
We are very conscious of this problem.
170
-------
Alternative Materials and Processes
Session II
Tuesday Afternoon 4:20
ELECTRODEPOSITION DF ZINC-NICKEL ALLOY COATINGS
J. W. Dini
H. R. Johnson
Sandia Laboratories
Metallurgy & Electroplating Division
Livermore, California 94550
One possible substitute for cadmium in some applications is a Zn-Ni
alloy electrodeposit. In the past, thermally prepared coatings of Zn-Ni
coatings have been used under the trade name Corronizing. They were
prepared by the interdiffusion of separately deposited Ni and Zn coatings.
The fact that the diffusion coating has had applications indicates that
an electrodeposited Zn-Ni coating would also have applications if a
convenient method of deposition could be developed. One of these applica-
tions could be as a substitute for cadmium.
Earlier work has already shown that electrodeposited alloys containing
about 85% zinc and about 15% nickel provide noticeably better corrosion
resistance than pure zinc. Present work supports this finding and also
provides a comparison with electroplated cadmium in salt spray. Data on
operation of the solution is presented including influence of current
density and temperature on deposit composition and corrosion resistance.
A method of chromating the deposits was developed and this also improves
corrosion resistance.
Based un the work reported in this paper, future efforts
deposited Zn-Ni coatings are warranted since this deposit looks
viable substitute for cadmium.
with electro-
like a
171
-------
ELECTRODEPOSITION OF ZINC-NICKEL ALL OY COA TINGS*
J. W. Dini
H. R. Johnson
Metallurgy and Electroplating Division 8312
Sandia Laboratories
Livermore, California 94550
ABSTRACT
One possible substitute for cadmium in some applications is a zinc-
nickel alloy deposit. Previous work by others showed that electrodeposited
zinc-nickel coatings containing about 85% zinc and 15% nickel provided
noticeably better corrosion resistance than pure zinc.
Present work sup-
ports this finding and also shows that the corrosion resistance of the alloy
deposit compares favorably with cadmium.
':'This work was supported by the United States Energy Research and Develop-
ment Administration. Contract Number AT-(29-1)-789.
172
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Dini, Johnson
ACKNOWLEDGMENTS
The authors would like to acknowledge the assistance of the following:
J. R. Helms, 8312, plating, T. L. Bryant, 8312, metallography, G. M.
Giovacchini, 8313, X-ray diffraction, and P. Dean, 8265, technical writing
173
-------
Dini# Johnson
ELECTRODEPOSITION OF ZINC-NICKEL ALLOY COATINGS
Introduction
Thermally prepared coatings of Zn-Ni have teen obtained by the inter-
diffusion of separately deposited nickel and zinc coatings and used as a
protective coating for steel under the trade name Corronizing. 1 The com-
mercial use of the diffusion coating indicates that electrodeposited Zn-Ni
coatings also should have applications# if a convenient method of deposition
could be developed.
One of these applications could be a substitute for
cadmium.
The literature on the topic of Zn-Ni plating up to 1960 was covered by
Brenner2 in his treatise on alloy deposition.
Since 1960. very little has
appeared on this subject.
Hammond and Bowman3# 4 were granted patents in
1961 and 1962.
Kudryautsev5 reported on deposition from cyanide and am-
moniacal solutions in 1964.
Domnikov6 reviewed some Russian work in 1965.
Roehl7 was granted a patent in 1969# and Roehl and Dillon 8 a patent in 1971.
These latter two patents were the starting point for the work described in this
paper. Roehl7 reported that in salt spray tests# 92 % Zn-8% Ni alloy coating
was three to four times as corrosion resistant as electrodeposited zinc or
hot-dipped zinc (Figure 1).
Based on the results reported in the literature
174
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Dini, Johnson
and the fact that zinc-nickel coatings have shown promise at Sandia Labora-
tories, Livermore, in protecting uranium alloys from corrosion, it was
deemed worthwhile to investigate zinc-nickel alloy plating in further depth.
The present study was divided into two parts.
The first portion consisted
of determining the optimum operating conditions for the electroplating process.
The factors evaluated were the influence of current density and temperature
on deposit appearance, composition, stress, and efficiency.
The second
portion of the study evaluated the proposed zinc-nickel coating in a salt fog
environment.
To provide comparison data, unalloyed zinc and cadmium coat-
ings were also evaluated in the same environment.
A salt fog environment
was selected for this study because previous investigations had demonstrated
the superiority of cadmium over unalloyed zinc in this test.
Selection of Operating Conditions
General
The work reported herein was done with lO-litre solutions of the
7
composition listed in Table I. The solution is basically Roehl's with some
changes.
He used the chloride salts of zinc and nickel whereas we used
zinc sulfate and nickel sulfamate.
The reason for this change is that one
potential application for Zn-Ni coatings is corrosion protection for uranium
and its alloys, and these materials are notoriously attacked by chlorides.
175
-------
Dini, Johnson
A few cursory experiments revealed that nickel sulfate could be substituted
for the nickel sulfamate.
If this coating system were to be used in production,
the sulfate would be less expensive than sulfamate.
Roehl 7 recommended a
small amount of acetic acid as a buffer to promote ease of pH control. We
found this to be unnecessary, and furthermore discovered as a result of some
Hull cell tests that acetic acid reduced the covering power of the solution.
Zinc anodes were used for most of the work, but alloy anodes of the approxi-
mate composition Zn-10 Ni would probably be quite suitable.
A wetting agent (sodium lauryl sulfate) was used to lower the surface
tension of the solution to eliminate pitting.
The importance of this ingre-
dient is shown in Figures 2a and 2b, which compare deposits produced in
solutions with and without wetting agent.
Heavy pitting was evident in the
deposit obtained from the solution containing no wetting agent, whereas no
pitting was evident when the wetting agent was present.
An additional benefit
of the wetting agent is that it improves the appearance of the deposit and has
a grain refining effect.
Steel panels 6.4 x 10.2 cm (2.5 x 4 in. ) were used as the plating sub-
strates.
Steel was selected because the red rust produced on unprotected
surfaces in salt spray gives a good indication of the corrosion process oc-
curring.
The parameters used to evaluate the operating conditions were:
influence of current density and temperature on deposit appearance, com-
position, stress and efficiency.
176
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Dini, Johnson
Influence of Current Density and Temperature
As illustrated in Figure 3, deposits with the highest nickel contents
were obtained at the lowest current densities. Likewise, the higher the
plating temperature. the higher the nickel content of the deposit.
The ap-
pearance of the deposits produced at 27 and 50°C did not change much over
the current density range of 54 to 538 A/m2. However. a noticeable differ-
ence was obtained at 93°C. Figure 4 shows that deposits plated at 93°C were
2 2 2
black at 54 AIm. grey at 538 AIm and grey-black at 269 AIm. The black
coloration is attributed to the higher amounts of nickel plated out at the lower
current densities.
Repeated measurements revealed that efficiency':' at 54 A/m2 was
greater than 100%. which is indicative of either material being occluded in
the deposit or autocatalytic deposition; we choose to believe the former.
There are indications that deposition at the lower current densities was
accompanied by heavy oxides and hydroxides.
Gas and carbon analysis of
some deposits revealed noticeably higher impurity content at lower current
densities.
This is especially evident when comparing deposits produced at
2
54 and 538 AIm (Table II).
There was no weight change in the deposits
':'The efficiency measurements were based on the standard established by a
copper coulometer connected in series with the Zn-Ni plating solution. The
coulometer contained 200 gll of copper sulfate. 100 ml/l (specific gravity
1.83) of sulfuric acid and 50 ml 11 of absolute ethyl alcohol. To calculate
the efficiency. the deposit composition was first determined by atomic ab-
sorption analysis. and then electrochemic~ equivalents of.the 9allOy were
calculated by the reciprocal method descrIbed by Lowenhelm.
177
-------
Dini, Johnson
after heating at 150°C for 24 hours, which ruled out trapped moisture. For
the 54-A/m2 samples, deposition above 60°C was accompanied by heavy gas
evolution and efficiency increased with temperature (Figure 5). This phe-
nomenon was not as obvious at 269 A/m2 because at this current density
efficiencies greater than 100% were not obtained until plating temper-
2
atures greater than 70°C were used. At 538 A/m , efficiency was 100% over
the temperature range of 27 to 93°C (Figure 5).
X-Ray Diffraction
The Debye-Scherrer method was used to obtain X-ray information on
some Zn-Ni deposits. The results of this analysis, along with the results
from the computer program SEARCH10 revealed a major line of zinc sulfate
hydroxide hydrate, ZnSO 4. 3Zn(OH)2. 4H20, some minor probable Zn lines.
and some unidentified lines. In addition. the SEARCH program also indicated
that NiO and NaNi02 could be present in the sample.
Stress
Stress in the deposit was measured with the rigid-strip technique
described by Borchert. 11 Temperature was varied from 49 to 88°C and
current density from 27 to 269 A/m2. The data. included in Table III. show
that the stress was quite low. less than 35 MN/m2 (5000 psi) and influenced
very little by variations in current density or temperature.
178
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Dini, Johnson
Salt Fog Tests
Samples and Plating Solutions
For the salt fog tests, steel panels were plated with 2.5, 7.5, 12.5,
and 25 /.tm (0. 1, 0.3, 0.5, and 1. 0 mil) of cadmium, zinc, and zinc-nickel
alloy. The cadmium was plated in a cyanide solution and the zinc in an acid
chloride solution according to formulations and operating conditions listed
in Table IV.
Some of the panels from each set were chromated prior to salt
fog testing.
Some comment should be made on the chromating of zinc-nickel
deposits.
A number of proprietary immersion processes were tried with no
success, inasmuch as either no apparent chromate film was formed or if
one was formed it was non-uniform and lor non- adherent.
Use of electrical
current in Macro Drab No. 6>:< which is a proprietary process for zinc and
cadmium, did provide a uniform adherent film similar in appearance to the
films typically seen on zinc.
Parts were cathodically treated in this solution
at 9 volts for 1 minute at 32°C.
All samples were placed in plastic holders that inclined them 15
degrees from the vertical.
They were exposed up to 500 hours in a cabinet
with a 5 percent salt fog environment at 35°C (95°F), per ASTM B117-49T.
*Mac Dermid, Inc.. Waterbury, Conn.
179
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Dini, Johnson
Results
Unchroma ted Panels
The salt spray results are summarized in Tables V and VI and presented
pictorially in Figures 6 -11.
The panels with no chromate clearly showed the
inferiority of unalloyed zinc when compared with cadmium or zinc-nickel alloy
coatings in salt spray.
Heavy white corrosion products commonly referred to
as "white rust "* were obtained very quickly on the pure zinc-coated panels,
and rusting started much quicker than on the cadmium or zinc-nickel coated
panels.
Corrosion was so heavy on the pure zinc panels that none of these
were left in salt spray for more than 192 hours, whereas all but the thinnest
cadmium and zinc-nickel coatings were exposed for 500 hours.
The zinc-nickel
coatings exhibited a moderate amount of white corrosion products, consider-
ably less than the pure zinc coatings but more than the cadmium coatings.
Figure 6 compares the white rust on unchromated panels after 24 hours. The
red rusting on the zinc-nickel deposits was about equivalent to that observed
The zinc-nickel coating deposited at 54 A/m2 was
on the cadmium panels.
slightly more corrosion resistant to red rusting than the panel plated at 269 A/m2,
Chromated Panels
The chromated zinc-nickel panels plated at 32°C were not as corrosion
resistant during 500 hours of salt spray as those plated at 60°C.
This is
probably because less nickel is included in the alloy when deposition takes
place at lower temperatures (see Figure 3).
For the samples plated at 60°C,
,,-
"'These corrosion products are mixtures of zinc hydroxide and zinc carbonate.
180
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Dini, Johnson
some rust was evident on the panel with 2.5 /.lm of coating plated at 54 A/m2;
no rust was evident on the companion panels plated at 269 A/m2.
The zinc-nickel panels plated at 60°C were more corrosion resistant
than the acid zinc deposit. Zinc-nickel coatings plated at a current density
of 269 A/m2 exhibited no rusting for the duration of the test, whereas acid
zinc coatings and the zinc-nickel coatings plated at 54 A/m2 did show some
rusting. A coating of 2. 5 /.l m of acid zinc started to rust at 360 hours, and
at 500 hours the 7. 5-/.lm thick coating of this deposit also started showing red
rust. The zinc-nickel deposit plated at 54 A/m2 showed red rust on the 2.5-
pm thick coating at 360 hours but no red rust on the remainder of the panels
after 500 hours.
Comparison of zinc-nickel samples with cadmium plated samples showed
that the zinc-nickel deposits plated at 60°C performed better than the cadmium
panels, especially for a deposit thickness of 2. 5 /.l m.
Zinc -nickel deposits
plated at 32°C, however, were slightly inferior to the cadmium plated panels.
After 500 hours of exposure, heavy red rust was evident on the 2. 5-/.lm thick
cadmium panel; no rust appeared on the zinc-nickel coating plated at 269 A/m2,
and only a small amount of rust was evident on the zinc-nickel panel plated at
54 A / m 2.
Summary
Zinc-nickel alloy coatings appear to be a potentially viable substitute
for cadmium coatings.
Salt fog exposure tests showed that zinc -nickel
coatings performed at least as well as cadmium in protecting steel from
181
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Dini, Johnson
corrosion.
Data on operation of the solution is presented, including the in-
fluence of current density and temperature on deposit composition and stress.
Although this effort has demonstrated that Zn-Ni coatings are a poten-
tially viable system for protecting steel from corroding, much work remains
to be done to economize the process.
Further work is needed on the compo-
sition and operating conditions of the solution. Nickel sulfate can be sub-
stituted for the nickel sulfamate used in this work but compositional ranges
of both the nickel and zinc salts are presently unknown.
The solution can
probably be operated with much less nickel and still produce satisfactory
deposits, but this would have to be proved.
Additional effort should also be
expended to define the most economical current density and temperature.
Also, it is very important to evaluate the potentiality of barrel plating Zn-Ni,
since much of the cadmium is plated in this fashion.
Further work would
also be needed to determine the anode system (pure zinc with occasional
additions of nickel, or zinc-nickel alloy anodes) most economical for this
solution. Lastly, and perhaps most important, a brightener system would
have to be developed if this deposit is ever to really compete with cadmium.
Most of the applications for cadmium call for a bright deposit and to try to
replace these with a dull zinc-nickel deposit could be an insurmountable task.
A bright zinc-nickel deposit would be much easier for users of plated products
to accept as a substitute for cadmium.
182
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Dini, Johnson
REFERENCES
1.
G. Black, Metal Finishing, 44, 207 (May 1946).
2.
A. Brenner, Electrodeposition of Alloys, Volume II, Academic
Press, 1963.
3.
M. B. Hammond and G. B. Bowman, U. S. Patent 2, 989,446,
June 1961.
4.
M. B. Hammond and G. B. Bowman, U. S. Patent 3,064,337,
November 1962.
5.
V. A. Averkin, Editor, Electrodeposition of Alloys, Israel Program
for Scientific Translation, Jerusalem, 1964, pp. 102-115.
Available
from Office of Technical Servi ces, U. S. Department of Commerce,
Washington 25, D. C.
6.
L. Domnikov, Metal Finishing, 63, 63 (March 1965).
7.
E. J. Roehl, U. S. Patent 3,420,754, January 1969.
8.
E. J. Roehl and R. H. Dillon, U. S. Patent 3,558,442, January
1971.
9.
F. A. Lowenheim, Electroplating and Metal Finishing, 15, 358
(1962).
183
-------
10.
M. C. Nichols,
Dini, Johnson
A FORTRAN II Program for the Identification of
X-Ray Powder Diffraction Patterns,
Univ. of California, Lawrence
Radiation Laboratory, UCRL-70078, October 17, 1966.
11.
L. C. Borchert, 50th Annual Proceedings American Electroplaters'
Society, p. 44, (1963).
184
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Dini, Johnson
T A BL E I
ZINC-NICKEL SOLUTION FORMULATION
Zinc
266 g /1
60 g /1
Zinc Sulfate (ZnSO 4. 7H20)
Nickel Sulfamate';'
190 ml/l
Sodium L auryl Sulfate
34 g /1
0.375 g/l
Nickel
Surface Tension
35-40 dynes/ cm
pH
5. 0
':'SNR 24 sulfamate nickel concentrate, Allied-
Kelite Products Div., the Richardson Co.,
Des Plaines, Ill.
185
-------
Dini, Johnson
TABLE II
GAS AND CARBON CONTENT OF ZINC-NICKEL DEPOSITS
Current Density Carbon
-------
Dini, Johnson
TABLE III
INFLUENCE OF TEMPERATURE AND CURRENT DENSITY ON STRESS
Current Density Temperature Stress CD
A/m 2 A / ft 2 Co FO MN/m 2 psi
27 2.5 88 190 24. 1 3500
270 2.5 49 120 35.2 5100
270 2.5 88 190 33.4 4850
CD Measured by the rigid strip method, Reference 11.
187
-------
TABLE IV
FORMULA TION AND OPERATING CONDITIONS FOR CADMIUM AND
ZINC PLATING AND CHROMATING SOLUTIONS
Cadmium
Zinc
Pl ating Solution
Cadmium
g/l
22.5
Sodium Cyanide
Caustic Soda
124
19.5
Udylyte Bry-Cad #53 Brightener':'
As Recommended
by Supplier
161 A/m2 (15 ASF)
27°C
f-'
0::>
0::>
Current Density
Temperature
Chromating Solution
Sodium Dichromate
200 g /1
6 ml/l
1.0
Sulfuric Acid
pH
Temperature
Time
25°C
15 s
Plating Solution
Zinc (as zinc chloride)
Ammonium Chloride
Maz Brightener 8480**
Maz Brightener 8482*>:'
Current Density
Temperature
Chromating Solution
Macro Drab No. 6**
Temperature
Time
g/l
46
190
As Recommended
by Supplier
"
259 A/m2 (25 ASF)
27°C
27°C
30 s
':'The Udylyte Corp.. Detroit Mich.
>:":'Mac Dermid. Inc.. Westbury. Conn.
t:I
.....
~
.....
..
C-.f
g.
~
m
o
::s
-------
TABLE V
A
SALT SPRAY CORROSION RESULTS FOR CADMIUM (CYANIDE) AND ZINC (ACID) DEPOSITS
Cadmium
Chromate Chromate
Thickness Treatment Hour 5 in Te 5t Treatment
'VIlis Microns 48 192 360 500 24
0.1 2.5 None Red Rust C None Red Rust D
0.3 7.5 None No Corrosion Red Rust Red Rust Red Rust None Heavy 'J/hite Rust
0.5 12.5 None No Corrosion No Corrosion Red Rust Red Rust None Heavy Wh ite Rust
1.0 25.0 None No Corrosion No Corrosion White Edge White Edge None Heavy White Rust
Corrosion Corrosion
Zinc
Hour s in Te st
72
168
182
Red Rust E
Red Rust F
Heavy White Rust
Heavy vVhite Rust
Heavy \:V'hite Rust
Red Rust G
0.1 2.5
0.3 7.5
I-'
00 0.5 12.5
/o.C
1.0 25.0
48 192 336 500
Yes B No Corrosion Red Rust Red Rust Red Rust Yes B
'{es Ii No CorroslOn No Corrosion White Edge White Edge Yes B
Corrosion Corrosion
Yes B No Corrosion No Corrosion No CorrosIOn White Edge Yes B
Corrosion
Yes B No Corrosion No Corrosion No Corrosion No Corrosion Yes B
240
360
500
Red Rust
ned Rust
Slight ned nust
Slight \Vhite Corrosion
Slight Vilhite Corrosion
Slight \'\'hite Corrosion
Slight White Corrosion
Slight \\'hite Corrosion
\\'llite Corrosion
Slight 'Nhite Corrosion
Slight White Corrosion
\Vh ite Corrosion
.'\ See TQblc I\' for solution composition and operating conditions.
It Sl'C Table IV for chromating details.
C Tested for orU,. 72 hours.
\) Tcstl'd for anI)' 24 hours.
}': TC'stl'd for only 1-14 hours.
'l'cstC'(] for only lIi 8 hours.
(; Tested for only 1~)2 hours.
t1
5'
....
..
y
o
::r
/:j
rn
o
/:j
I
......
00
-------
TABLE VI
SALT SPRAY CORROSION RESULTS FOR ZINC-NICKEL DEPOSITS A
Plating Current 54 Aim 2 2 2
Density 269 Aim 269 Aim
Plating Temp. 60"C 600C 320C
Chromate Chromate Chrorn ate
Thickness Treatment Hours in Test Treatment Hours in Test Treatment
;\Iils l\Iicrons 24 48 360 500 24 48 240 336 500
O. 1 2.5 ::,\1 one Light \\llite Red Rust C None Light White Red Rust Red Rust Red Rust Red Rust
Rust Rust
0.3 7. .5 :\ one Light \\llite Light White Red Rust Red Rust None Light Wh ite White Rust Red Rust Red Rust Red Rust
Rust Rust Rust
0.5 12. 5 :\ one L 19ht White Light \Illite Light \11, ite Red Rust None Light White VVhite Rust \Vhite Rust Red Rust Red Rust
Rust Rust Rust Rust
1.0 25.0 =-
-------
Figure 1.
Figure 2 a.
Figure 2b.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Figure 7.
Figure 8.
Figure 9.
Figure 10.
Figure 11.
Dini. Johnson
FIGURE CAPTIONS
Salt Spray Test Comparison of Hot Dipped Zinc. Electroplated
Zinc. and Electroplated 92% Zn-8% Ni Coatings on Strip Steel
Surface Appearance of 100 fJ. (4 Mil) Thick Zn-Ni Alloy Deposits
Cross Sections of Zn-Ni Alloy Deposits
Influence of Current Density and Temperature on Composition
Influence of Current Density on Deposit Appearance (Plating
Temperature = 93°C)
Influence of Temperature and Current Density on Efficiency
Unchromated Panels After 24 Hours in Salt Spray
Samples Plated in Acid Zinc Solution
Samples Plated in Cyanide Cadmium Solution
(54 A/m2. 60°C)
(269 A/m2. 60°C)
Samples Plated With Zinc-Nickel
Samples Plated With Zinc-Nickel
Samples Plated With Zinc-Nickel (269 A/m2. 32°C) After
500 Hours Salt Fog Exposure (all were given a chromate
treatment)
193
-------
f-'
\0
.po.
en
~ 200
o
I
I
>-
« 150
a:
a..
en
I-
...J
«
en 1 00
300
250
V ELECTROPLATED
92% Zn - 8% Ni
~ HOT DIPPED ZINC AND
ELECTROPLATED ZINC
50
0.0002
5
0.0006
15
0.0012
30
0.0008
20
0.0010
25
0.0004
10
COATING THICKNESS
0.0014
35
0.0016
40
0.0018
45
(INCHES)
(MICRONS)
t::J
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..
~
::r
~
(/)
o
~
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t'Ij
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-------
I-'
\0
VI
(a) Plated in Solution
Containing No
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(b) Plated in Solution
Containing Wetting
Agent
tJ
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~
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'1
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-------
(a) Plated in Solution
Containing No
Wetting Agent
(b) Plated in Solution
Containing Wetting
Agent
196
Dini. Johnson.. Figure 2b
Cu Overplate
Zn-Ni
Steel
Cu Overplate
-
Zn-Ni
Steel
-------
~
I- 15
(f)
I-' 0
\0 0..
-.J W
0
Z
..J
W
::w:::
()
z
25
20
10
5
50°C
/
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/
o
100
200 300 400
CURRENT DENSITY (A/m2)
500
tj
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..
600
~
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o
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w
-------
Dini. Johnson - Figure 4
5 asf 2
54 Aim
25 asf
269 A/m2
50 asf
538 A/m2
198
-------
. 54 A/m2 (5 A/ft2)
. 269 A/m2 (25 A/ft2)
. 538 A/m2 (50 A/ft2)
200
160
-
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>-
u
z 120
LlJ :
u :.
I-'
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80
40
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TEMPERATURE (OC)
tj
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11
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=
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-------
Dini, Johnson - Figure 7
.' ~"" ,r.........." ;>,' "
. ~~:~"':',~i1"{.'~'%i~,11,
. ~-r, ,." ~, \\, "-.J .. ,
iJ. ~~,..'? i'(."~\ "'\"1
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r. '.I~ ' "/~ t",". '[{H ,
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No Chromate Treatment (salt fog exposure time as indicated on panels)
Chromate Treatment (500 hours salt fog exposure)
201
-------
Dini. Johnson - Figure 8
No Chromate Treatment (salt fog exposure time as indicated on panels)
Chromate Treatment (500 hours salt fog exposure)
202
-------
Dini. Johnson - Figure 9
No Chromate Treatment (salt fog exposure time as indicated on panels)
Chromate Tre atment (500 hours salt fog exposure)
203
-------
Dini. Johnson - Figure 10
No Chromate Treatment (salt fog exposure time as indicated on panels)
Chromate Treatment (500 hours salt fog exposure)
204
-------
Dini, Johnson - Figure 11
205
-------
Electrodeposi tion of Zinc-Nickel Alloy Coatings
DISCUSSION PERIOD
MR. GROBIN:
Allen Grobin, IPM Corporation.
I think the authors have made a case for the alloy.
However,
I would like to point out that the use of the salt spray test, ASTM B-117
is being incorrectly interpreted here.
The salt spray test is not a corrosion test.
It's a quality
control test which is used to show that the plating you did today is
equivalent to the plating you did yesterday.
It provides no means of
corrparison between different materials.
It represents a five percent
salt environment.
MR. LEVY:
I would guess that they wanted some standard tests
for corrparison.
I'm sure the p:>int is valid.
MR. GROBIN:
I would then suggest that they look at temperature
and humidity tests, which appear to be much rrore representative of the
tyPes of corrosion that we see in the United States.
MR. DROSTEN:
Fred Drosten, Army Aviation Research and Development
Cormand, St. Louis.
I notice from your slides that the alloy platings rrost of the
time will erupt.
Is that just an appearance or was it rough, or is this
a crystal structure we are looking at?
MR. LEVY:
That's probably a question that will have to be
deferred to the authors.
It certainly had that appearance, yes.
206
-------
Alternative Materials and Processes
Session II
Tuesday Afternoon 4:55
CORROSION RESISTANT COATINGS CONTAINING
LUBRICATING SOLIDS AS AN
ALTERNATIVE TO CADMIUM PLATING
G. R. Kliemann
D. J. Sargent
ElM Lubricants, Inc.
A Subsidiary of
Lakes Chemical Corporation
Lafayette, Indiana 47906
Great
West
Corrosion resistant coatings containing lubricating solids'have
been used effectively as an alternate to cadmium plating on
fasteners, carburetor parts, electrical connectors, gears,
shafts, splines, bushings, bearings, etc. On fasteners, drive torque
to clamp loads are maintained. Corrosion resistance is maintained.
Costs for these coatings and their application is competitive. These
coatings are currently in the market place, and major users are aware of
their viability. Comparative data is discussed regarding corrosion re-
sistance, wearability, friction, costs, etc.
207
-------
CORHOSION RESISrr1\NT COATING~~ CONT1\INING LUBIUC1\'1'ING
SOLIDS 1\f; AN 1\LTERNATIVE TO CADIvlIUH AND
ELECTROPLATINGS ON FASTENERS AND OTHER HII.RDW\EE
Colonel R. Kliemann
Midwestern Regional Manager
E/M LUBRICANTS, INC.
129 Eisenhower Lane South
Lombard, IL 60148
Vice
Donald J. Sargent
President-Technical Director
ElM LUBRICANTS, INC.
P. O. Box 2200
West Lafayette, IN 47906
208
-------
CORROSION HESISTANT COATINGS CONTAIliING LUJ:1~JC/\.T:ll1c;
SOLIDS AS AN l\L'rERNATI'JE TO CI"Dl'lIUr-1 AND
ELECTROI?LATINGS ON FAS'l'ENEP,S AND OTHER lI!1.H[J\':;,\Hl.:
For the past quarter century, the use of soljd film lubricants
(also referred to as dry film lubricants, bonded solJd lubricants,
resin bonded lubricants, dry films, bonded coatings. or solid films)
has grown substantially- Variations of these coatin0s have been
successfully used on DOD and industrial applications on a wide variety
of hardware.
A broad range of military and industrial specifications
cover many solid film lubricants. Solid lubricant cOutings have found
utilization in a wide range of applications requiring friction reduc-
tion/anti wear, load carrying/anti-galling and corrosion resistance.
Lubricant coatings for such applications (meeting militury
and industrial specifications) have not found wide acccptunce in the
fastener industry, however, for a number of reasons:
1)
2)
3)
High application costs;
Limited corrosion resistance;
Torque ranges for coatings: )ntaining conventional solid
lubricants unpredictable;
High processing volumes;
Little real technical incentive.
4)
5)
For the past two years, our firm has been engaged in a develop-
ment program to produce coatings that would meet the needs for the
mechanical fustener industry, in a broad sense, uS well uS serve as a
superior substitute for various platings.
A review of the needs for mechanical fasteners disclosed the
following basic user criteria:
1)
Extended corrosion resistance
Especially in the automotive,
struction industries;
aircraft, marlne and con-
2)
Consistent pre loading
Standard deviation for
is generally less than
(clamping torque)
pre loading of lubricutcd fasteners
half that of dry fasteners;
209
-------
3)
consistent driving torques -
Driving torque of unlubricated
increase and are unpredictable
fasteners generally
with fastener reuse,
4)
causing inaccurate preload on reused fastenersi
Reliability -
Half the "in-place" cost for a fastener results from
time to assemble. This promotes automated assembly
systems. Lubricated fasteners are more reliable in
5)
automated assembly systemsi
Cleanliness -
Lubricated fasteners, currently, are essentially of
two type s :
a) waxed metallic platings;
b) oil impregnated conversion coatings.
Problems common to fasteners of either type are staining
of dry wall and fabrics, painting problems, limited shelf
6)
lila, galling, etc.
Environmental impact -
Many electroplatings are undesirable in terms of
effluent pollution.
Coating uniformity -
Uniformity of deposition on threads, thread roots,
and heads is important.
7)
Consumer demands, government regulatory requirements, and
associated potential liabilities are increasing the need for alternates
to current day electroplatings. One such alternative and a very viable
one, is the use of solid lubricant containing coatings. Such coatings
have been developed and have been evaluated and found, by the fastener
industry, to satisfy most fastener industry needs. For example:
1)
Torque performance -
a) prevailing torque to clamp torque ratios are in the
range of cad plate and wax;
b) driving torques are comparable to cad plate and in
c)
most cases much narrower in range;
torque is unaffected by lapse time before use;
d) on-off torque remain relatively stable, assuring
210
-------
2)
consistent clillnping torques for many reuses;
e) coated self-drilling screws perform well within the
three second max drill time specifications.
No galling, even on self-drilling/self-threading and
deformed locknut applications.
Corrosion resistance is a function of Ll number of fac.tors
3)
including part configuration; therefore, it is difficult
to give precise and meaningful data in a generalized dis-
cussion. We will, however, make some generalized state-
ments:
a) Using a criteria such as typical phosphated automotive
fastener performance, i.e. failure is ludged as three
rust spots over 1/16 inch in diameter per square inch,
on significant surfaces, 48 hours is very achievable
for coated fasteners that have been set or driven in
place.
b)
240 hours
(on driven fasteners)
is achievable at
c)
fractionally higher processing and/or coating costs.
3000 hours have been achieved on hardware, after
installation.
Evidence obtained to date indicates that these coatings generally
limit rust creep past the initiating spot.
The coatings are still under development department control
and are undergoing product improvements; however, we have processed
production parts in substantial quantities during the last year.
Many of the large cold headers were introduced to the coatings
and are using them in problem solving. coating variations are under
evaluation by several automotive manufacturers and their suppliers.
Results are extremely promising. Appliance manufacturers are using
the coating in many critical applications.
The applications, while not proprietary or confidential, do
involve tradenames and other characteristics that would require formal
211
-------
releases if published. Therefore, Tde are not lis-tingtradenames
or firms. We would be pleased to discuss, on an informal basis, the
company names and personnel that could be contacted for user details.
We believe, as do a growing number of people in the fastener
industry, that our coatings offer great potential as replacements
for electroplate, parcicularly cam1ium plate, on fasteners and other
hardware, and we certainly appreciate this opportunity to present
our story.
212
-------
CORROSION RESISTANT COATINGS CONTAINING LUBRICATn~ SOLIDS
DISCUSSION PERIOD
VOICE :
Yes, my question was, what were the naterials in the
solid lubricant you were talking a}xmt, and what are sane of the inhibi-
tors that may have been used with them.
MR. SARGENT:
I have to resr;ond to your question by saying
that is in the realm of propriety, and Ilm afraid I can I t answer that.
213
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Alternative Materials and Processes
Session III
Wednesday Morning 9:30
ARTIFICIAL SHELLFISH FOR MONITORING AMBIENT
CADMIUM LEVELS IN SEAWATER
William B. Kerfoot
Environmental Devices Corporation
Marion, Massachusetts 02738
The adsorption kinetics of artificial oysters (METRO-DISC* TYPE 140)
are compared with the accumulation of cadmium by natural populations of shell.
fish reared in a prototype tertiary treatment-aquaculture system. Accumula-
tion of m~tal in the aquaculture system was studied with two types of photo-
plankton, a green platymonad (Prasinocladus tricornutum) and a mixture of
diatoms (predominantly Phaeodactylum tricoInutum and Chaetocerus simplex),
and two species of shellfish, the American oyster (Crassostrea virginica)
and the hard clam (Mercanaria mercenaria). The algae showed a rapid increase
in metal concentration until an equilibrium was reached, proportional to the
initial concentration introduced. Shellfish species exhibited a continual
increase in concentration when exposed to seawater and algae mixtures con-
taminated with cadmium. Separation of the two pathways of transfer identi-
fied the algae as a principal source of accumulation in the aquaculture
system, while direc~ adsorption of soluble cadmium was the dominant pathway
of accumulation by shellfish in natural waters. Adsorption of the direct
pathway can be monitored by laminate discs containing a chelate matrix sand-
wiched between membrane filters. The discs act like artificial shellfish by
integrating ambient metal concentrations with time.
*Commercial Name
215
-------
ARTIFICIAL SHELLFISH FOR MONITORING
AMBIENT CADMIUM LEVELS IN SEAWATER
William B. Kerfoot
Environmental Devices Corporation
Marion, Massachusetts 02738
ABSTRACT
The absorption kinetics of artificial oysters (METRO-DISC*
sensors), are compared with the accumulation of cadmium by natural
populations of shellfish reared in a prototype tertiary treatment-
aquaculture system. Accumulation of metal in the aquaculture system
was studied with two types of phytoplankton, a green platymonad
(Prasinocladus tricornutum) and a mixture of diatoms (predominantly
Phaeodactylum tricornutum and Chaetocerus sim lex), and two species
of shellfish, the American oyster Crassostrea virginica) and the
hard clam (Mercenaria mercenaria). The algae showed a rapid in-
crease in metal concentration until an equilibrium was reached,
proportional to the initial concentration introduced. Shellfish
species exhibited a continual increase in concentration when
exposed to seawater and algae mixtures contaminated with cadmium.
Separation of the two pathways of transfer identified the algae
as a principal source of accumulation in the aquaculture system,
while direct absorption of soluble cadmium was the cominant path-
way of accumulation by shellfish in natural waters. Absorption
via the direct pathway can be monitored by laminate discs con-
taining a chelate matrix sandwiched between membrane filters.
The discs act like artificial shellfish by integrating ambient
metal concentrations with time.
*TM
216
-------
A need exists for economical and reliable monitoring of heavy
metal concentrations in marine environments, particularly to control
the rate of exposure of organisms such as shellfish during aqua-
culture operations and to control rates of corrosion at a source.
Pringle et.al. (1968) found that soft shell clams accumulated
cadmium at a rate of 0.1 ug/g wet weight/day.
Kerfoot and Jacobs
(1976) studied the food-chain mechanics of accumulation of cadmium
and defined a linear regression between dissolved cadmium and the
rate of accumulation in shellfish.
Rossenburg (1967) employed the
natural concentrating ability of oysters to investigate copper
erosion and leaching from power plant condenser tubes.
The following
text compares the observed absorption mechanics of live shellfish
to the uptake of artificial oysters designed for monitoring.
Live organisms respond to background metal levels through
different mechanisms, reacting to particulate loadings in a manner
distinct from dissolved forms.
The mechanics of concentration
can be quantified for individuals and populations to provide a
valuable tool for measuring dosage.
However, the reliance upon
live organisms introduces several inherent difficulties into inter-
pretation of background metal concentrations (Brainard and Kerfoot
1975).
1.
Frequent problems are often due to:
The difficulty of maintaining healthy shellfish populations
when exposed to a variety of environmental and discharge
conditions.
217
-------
2.
Individual variability in uptake based upon physiological
conditions, age, and temperature.
3.
Seasonal variability in whole body metal concentration due
to spawning activities.
4.
5.
Weight loss of body fluids during thawing or cleaving.
The need for expensive chemical digestion and sample pre-
paration.
ABSORPTION KINETICS OF SHELLFISH.
The uptake of cadmium by shellfish was intensively investigated
in flowing aquaculture systems employed in a prototype tertiary
treatment-aquaculture system in operation at Woods Hole Oceanographic
Institution. (Kerfoot and Jacobs, 1976).
In the study, two species
of algae and two species of shellfish, under cultivation in the
treatment-aquaculture system, were exposed to cadmium.
One algae
culture was dominated by a green platymonad, Prasinocladus subsadsa,
the other by a mixture of diatoms, predominantly Phaeodactylum
tricornutum and Chaetocerus simples.
The diatoms are the normally
preferred food since they encourage rapid growth during culture.
The green algae, which are considered undersirable from a culture
standpoint, commonly coat the sides of culture pools .and replace the
diatoms unless the tanks are cleaned frequently.
The American oyster
(Crassostrea virginica) and the hard clam (Mercenaria mercenaria)
were the shellfish species employed in this study.
The oysters
were obtained from Long Island Oyster Farms, Inc., and the clams
removed from beds seaward of Chatham, Massachusetts.
218
-------
Phytoplankton was cultured by batch exposure in media specially
prepared from Guillard and Ryther's "f".
A started monoculture of
100 ml of algae was added to the media, and the mixture brought to
a final volume of 2 liters. In enrichment experiments, a 1000 ppm
standard of Cd2+ in doubly-distilled water was prepared from cadmium
iodide salt (CdI2) before dilution with seawater.
Then 5 ml of
cadmium stock solution, diluted to yeild the appropriate concentration,
was added to the solution.
Batched cultures of the algae were placed
under fluorescent lights and agitated continually by magnetic stirring
bars at 20°C.
Harvested phytoplankton was collected on acid-rinsed
membrane filters (3~ Nuclepore), rinsed with distilled water, dried,
wet-ashed, and analyzed for total content of cadmium.
For direct exposure of shellfish, the stock cadmium solution was
diluted by seawater up to 10.1.
The resulting cadmium solution was
then mixed at a rate of 7-300 mlfmin of seawater before flowing
into 40 x 60 cm fiberglass trays containing oysters and quahogs.
The controlled residence time in the tray was 22 minutes.
A control
tray received only seawater and phytophankton as food.
At each
sampling period, three shellfish were removed, allowed to void their
intestinal tracts by placing the animals in clean seawater for 1 hour,
and then frozen.
To determine the transfer through ingestion, phytoplankton exposed
to Cd was resuspended in uncontaminated seawater, fed to shellfish,
and then the shellfish were analyzed for accumulation.
Algae were
cultured in 10-1. carboys enriched with cadmium as previously described.
Samples were taken to measure carbon, nitrogen, and hydrogen composition
219
-------
After 5-day exposure, sufficient to establish equilibria, the algae
were removed from solution by continuous centrifuging and then
resuspended in 100 ml of uncontaminated seawater.
Microscopic
examination of a l-ml aliquot was made following centrifugation
to assure that cells were not damaged during removal and resuspension.
A second sample of 10 ml was removed for analysis of total cadmium
and concentration on a dry weight basis.
Shellfish were fed the contaminated algae by two methods:
the
resuspended algae were diluted to 10-1., placed in a 12-1. carboy,
and added continuously during 24 hours to a tray containing shell-
fish; or apportioned to 500 ml of seawater in 1-1. beakers holding
individual shellfish.
Periodic sampling of the water was performed
to monitor changes in the dissolved cadmium concentration.
After
a set time or, in the case of individual feeding, when the suspended
algae were removed from solution, the shellfish were placed in un-
contaminated flowing seawater to allow time to completely void their
tracts of ingested matter.
The specimens were then frozen prior to
digestion and analysis.
For wet ashing, the entire body of an oyster or clam was removed
from the shell, rinsed with distilled water, weighed, and transferred
to a aqua-regia washed l25-ml Erlenmeyer flasks.
Phytoplankton
was rinsed with distilled water, dried in a warming oven at 50°C
for 24 hours, weighed, and added to similar acid-rinsed flasks.
A detailed description of the digestion and analytic procedure
can be found in Kerfoot and Jacobs (1976).
All analyses were done
on a Jarrell-Ash Model 800 atomic absorption spectrometer, a
double-beam dual-channel instrument with recorder printout.
220
-------
Algae were ashed and analyzed following the same procedure as
shellfish.
PHYTOPLANKTON UPTAKE OF CADMIUM.
Figure 1 illustrates uptake observed in a 0.05~g/ml (ppm)
solutions of cadmium simulating the algal culture tanks.
Cadmium
was incorporated rather rapidly during the first few hours of exposure
and then at a progressively diminishing rate.
After 24 hours a
roughly constant level of cadmium concentration was reached in the
cultures.
Samples of batches removed 5 days following addition of cadmium
showed a proportional increase in the content of cells with increase
in concentration in seawater (Figure 2).
The green platymonad,
Prasinocladus subsalsa, showed a greater tendency to accumulate
cadmium than the mixed diatom culture of Phaeodactylum and Chaetoceros.
SHELLFISH UPTAKE OF CADMIUM FROM SEAWATER.
Both oysters and clams responded to cadmium enrichment of seawater
with a linear accumulation of metal in their tissues for the entire
duration of an experiment and over all concentration ranges studied
(Figure 3).
Originally, the oysters (Crassostrea virginica) and the
clams (Mercenaria mercenaria) contained background concentrations of
1.77 t 0.29 and 0.09 t 0.02~g/g (ppm) wet weight of tissue, respectively.
Each point in Figure 3 represents the mean of three individual shellfish
analyses.
The rate of accumulation varied with concentration, the
higher the level of cadmium in seawater the greater the rate of uptake.
The addition of 0.03mgjml (ppm) cadmium was continued for 67 days
221
-------
without any apparent departure from linearity.
No mortality of
shellfish that could be related to metal poisoning was recorded
with experimental animals at any concentration being studied.
After 17-day continuous exposure to seawater containing cadmium,
no further metal was added to the 0.05 ppm system.
The shellfish
were allowed to stand in running seawater for 25 days.
Analyses
of the oyster during this time showed no measurable decrease
in cadmium content of the tissue (Figure 3).
SHELLFISH UPTAKE VIA INGESTION OF DIATOMS.
Early in the investigations of phytoplankton uptake, algae
exposed to cadmium could be resuspended in uncontaminated seawater
and would retain their original cadmium content for a considerable
time.
The algae were removed from solution by continuous centri-
fuging and then resuspended in 100 ml of uncontaminated seawater.
A second sample of 10 ml was removed for analysis of cadmium con-
centration per dry weight of tissue and total content per ml of
algae.
Shellfish were then fed the contaminated algae by two
techniques: the resuspended algae were placed in a 10.1. carboy
with seawater and added daily to a tray containing shellfish; or
apportioned 10 or 20 ml resuspended algae to 500 ml seawater in
1-1. beakers holding individual oysters.
In general, the shellfish assimilated little of the cadmium
presented to them in the algal diet (Table 1).
The percentage of
cadmium persisting following feeding was calculated only when a
significant difference was detected between controls and experiments.
222
-------
Table 1. Uptake of Cadmium from Ingested Algae
Number of Mean Total ).lg Cd Final Cd
Irganism Individuals Weight Fed in Algae Content Significance % Uptake
(meat) (ppm wet weight)
Prasinoc1adus - Batch Exposure
Iys ter 4 3.29 1.1 1. 91 :t .25
5 3.41 67.5 2.63 :t .42 p < .025 7.3%
Prasinoc1adus - Continuous Exposure
Iyster 4 4.37 0 1. 77 :t .25
16 3.82 41. 6 3.25 :t .43 p < .02 14.3%
Clam 7 5.95 0 .08 :t .014
N 4 6.59 41.6 .48 :t .18 P < .01 7.0%
N
w
Phaeodactylum-Chaetoceros - Batch Exposure
Oyster 10 7.52 0 1.23:t .20
5 5.38 92.5 3.58:t .77 p < .01 13.6%
2 7.86 109.0 2.38 :t .38 p < .01 4.7%
Clam 11 8.63 0 .21 :t .04
4 10.40 10.4 .15 :t .02 ns
2 8.73 92.5 1.18 :t .31 p < .01 9.1%
-------
Crassostrea retained from 4.7 to 14.3% of the total cadmium fed in
the food, with hardly a noticeable difference between species of
algae.
Similarly, Mercenaria removed 7.0 and 9.1% of the cadmium
presented it in the separate diets of the green algal and diatom
species, respectively.
If the natural seawater is enriched with
cadmium, the greatest load of metal is obtained directly through
absorption.
To demonstrate the difference, in Figure 4, the expected rate
of increase in cadmium content of tissue is compared for 3-g oysters
and 5-g clams under natural coastal seawater conditions.
For
instance, a 3-g oyster commonly ingests 1.4 mg of carbon per day
derived from coastal seawater.
When feeding on prasinocladus, which
has a measured carbon content of 26.3% dry weight, the intake amounts
to 0.0053 g dry weight of algae per day.
Exposed to O. 10 JUg/m1
(ppm) cadmium in the seawater, the algae would contain 670JUg
cadmium/g dry weight.
Using the highest retention measured (14.3%),
each day a feeding oyster would ingest 3.55JUg of cadmium with only
0.5 JUg being retained.
Diffused throughout the 3-g weight of the
oyster, the projected increase in cadmium content of the tissue
would be 0.16JUg cadmium/g day from ingested algae (as indicated
by the line marked "OYSTERS--Ingestion" on the left hand of Figure 4).
Even considering the algae which absorb cadmium the highest and
using the greatest measured percent retention, we note ingestion of
contaminated algae (by the oysters) under natural seawater conditions
contributes only about 1/10 of that absorbed directly from solution.
224
-------
ARTIFICIAL SHELLFISH FOR MONITORING MARINE WATERS.
While posing inherent problems, shellfish do possess an
important ability to remove metallic ions from solution, integrate
time effects, and concentrate the ions internally to high levels,
reflecting ambient concentrations in background water.
The
difficulties created by employing live organisms may be overcome
by developing mechanical analogs which incorporate the desirable
attributes of shellfish while eliminating the detrimental character-
istics.
Environmental Devices Corporation has been developing an
artificial shellfish for the past 5 years.
was termed the METRO-DISC+ Type 140 sensor.
The first analog device
Design.
The fabricated shellfish includes a layer of an adsorptive
material sandwiched between a pair of porous membranes (Figure 5).
The adsorptive agent consists of ENDECO* Type 140 chelate exchange
matrix engineered for this specific application.
Hydrophilic
polycarbonate membranes are used and have a degree of porosity
selected to regulate the uptake of soluble metal by the adsorptive
matrix.
The two membranes are heat sealed to a spacer ring placed
around the inner circumference of the disc.
When the METRO DISC is placed into aqueous solution, metallic
ions diffuse through the membranes and are adsorbed linearly with
time to the chelate matrix (Figure 5).
The porous membrane barrier
reduces the usual rapid uptake found with the freely suspended
adsorptive matrix to below .4% of the total content in solution
*Reg.U.S.Pat.Off.
+TM
225
-------
per 24 hours, or with copper (Cu2+) to 4.0~g per 24 hour period
in a solution containing 1000JUg per liter.
Restricting adsorption
to a small percentage of the total solute avoids competitive inter-
actions among ions which would interfere with independent adsorption.
With 10Jug of adsorptive material, the adsorbed 4.0JUg of copper
represents a concentration by weight which is 400 times the back-
ground concentration of Cu (lOOOJUg/kg) in solu~ion.
The amount
of metal adsorbed is relatively independent of the weight of adsorp-
tive agent used (Figure 5), allowing the mass to be varied to
obtain the range of concentration desired on the adsorptive agent
for analysis by combustion.
For analysis by atomic emission a
minimum of 4~g is desirable, yielding a maximum concentration factor
for Cu2+ of 1000 times background concentration.
The uptake of metal by the METRO-DISC sensor can be described
by the formulation:
C = at Cb
m M
where: Cm = the concentration on the adsorptive matrix (~g/mg)
C = the concentration in solution ~g/liter)
M = the mass of adsorptive material (mg)
t = time (in hours)
a = the rate of uptake in hours ~g/hr)
b = slope of activity of adsorption
By combining the appropriate chelating agent with the correct
membrane, the METRO-DISC sensor can be designed to collect specific
metals at definite or definable rates.
226
-------
The sensitivity of uptake to temperature was also investigated.
The 24-hour adsorption of copper was obtained in distilled water
solution at temperature extremes of 3°C and 24°C.
The results are
plotted on log-log coordinates in Figure 5.
A combination of the
membrane porosity and chelation reaction significantly reduces
the sensitivity t~ temperature.
The Type 140 METRO-DISC sensor removed ions from solution by
passive diffusion and locked the capacity to record the precise
volume of water extracted and the particulate metal concentration
in the sampled water.
Most recently Environmental Devices Corporation
has developed the Type 1410 METRO-DISC ion filter which can be used
with prefilters for precision monitoring of particulate and dissolved
transition metals, particularly cadmium (Kerfoot and Crawford, 1977).
Seawater aliquots of 200 ml each were placed in 250-ml acid-
rinsed pyrex glass beakers and gently mixed by rotation.
Type 1410
METRO-DISC sensors were mounted in in-line filter holders sequentially
placed in a 5-sample vacuum manifold (ENDECO Type 886).
Simultaneous
multi-metal analyses were performed on a Jarrell-Ash Inductively-
Coupled Plasma Spectrometer Model 90-975 containing a built-in
computer-controlled system for data calibration and statistical mani-
pulation.
Reproducibility was also compared by determination by EPA
standard methods (EPA, 1974) on a Perkin-Elmer 306 Atomic Spectro-
photometer with an HGA 2100 graphite furnace.
The calibration series
used Eppendorf micropopettes of 1000, 500, 250, 100, 50, and 25
microliters with disposable tips.
227
-------
Doubly-distilled deionized water was used to wash out inter-
stitial seawater remaining in the METRO-DISC sensor before acid
elution.
Low metal "Ultrex" nitric acid (Baker) was diluted to
a 1% solution for elution of the METRO-DISC sensors.
The METRO-
DISC sensors were extracted a second time with another rinse of
1% HN03 to determine the remaining fraction of acid-leachable metal.
Figure 6 shows the concentration of cadmium found in 5 ml of acid
elute compared with the original concentration of cadmium added
to the background Vineyard Sound seawater.
A regression analysis
of the methods of additions indicated a detection limit of 0.1
~g/liter with 111% standard deviation at the lO)ug/l level.
DISCUSSION.
A developing oyster of about 3 grams wst weight will maintain
a daily pumping rat2 of ab~ut 10 to 30 liters, depending upon the
mass of algae present in the seawater and the ambient temperature.
A total intake of 1.3 mg per day is sufficient to maintain the young
shellfish (Ken Tenore, personal communication).
If 10 liters is
processed per day, a retention rate of .45% would be necessary to
provide the observed daily rate of cadmium increase of .15JUg/gm
wet weight of tissue in a 3-gram oyster.
The Type 140 METRO-DISC
sensor which adsorbs soluble cadmium passively from solution has
an inherent efficiency of extraction identical to thdt observed
from intermittently pumping natural oysters.
The rate of increase
of the Type 140 is about 10 times greater than the oyster because
of the high surface to volume relationship and adsorbtive capacity
of the interior matrix.
In comparison, when seawater ;s filtered
228
-------
through a 4 micron prefilter for particulates and passed through
the Type 1410 METRO-DISC sensor, an efficiency of extraction of
65% is obtained with an intermittent pumping of 1 liter/day
(.042 liters/hr at hourly intervals).
The added efficiency of
extraction and flow-through arrangement increases the rate of
accumulation of metal per unit mass to 1000 times that observed
with natural oysters.
The Type 1410 can, therefore, be used for
daily-monitoring of background natural cadmium.
229
-------
TABLE 2.
Observed Update of Natural Oysters (3 gm) and Artificial Shellfish Exposured
to a Cadmium Concentration of 10 ug/l - ppb in Seawater
Accumulation
Observed Oysters
METRO-DISC 140
METRO-DISC 1410
Weight
Intermittant Pumping
3 gm wet wt.
Continual Exposure
30 mg
Rate of Increase
ug/gm/day
.15
1.33
Intermittant
Pumpi ng (1 1 iter/
30 mg day)
220
Efficiency of
Extraction
.45%
.4%
65%
Particulate Filtering
mg/day
1.4
1.0
Concentrations, whereas both natural oysters and the Type 140 METRO-DISC
must be left in for at least 10 days to integrate sufficient cadmium to
provide a large enough signal to noise ratio for discriminating the daily
rate of increase.
230
-------
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Figure 7.
Figure Captions
Uptake of cadmium by phytoplankton during culturing.
Content of cadmium in tissue of algae removed after
average of 5 days culture.
Cadmium content of meat of shellfish removed at
different times during continual exposure to
contaminated seawater.
Rate of increase of cadmium in meat of shellfish as
a function of concentration in seawater and source
of contamination.
The artificial shellfish is composed of an
adsorptive matrix sandwiched between porous
membranes (A). The rate of adsorption of copper
by the Metro-disc 140 sensor is shown as a function
of concentration in solution (B). Using nickel as
an example, the concentration of adsorbed metal is
shown as a function of concentration in solution
and mass of adsorptive material (C). The influence
of temperature on 24-hour adsorption uptake of
copper (D).
Concentration of cadmium in acid elute from the
Metro-disc 1410 sensor as a function of initial
concentration of cadmium in seawater.
Removal of the .4 micron prefilter (a) and the
type 1410 Metro-disc (b) from plastic holders.
231
-------
N
W
N
250
Phaeodactylum tricornutum
+ Chaetocerus sp.
-
. /",,'-
/"
/
8/ .
..
.
./.
50 /
/
I
o
o
2
~
~
~
"
~ ~ 200
~ ~
....... .......
~ ~
la.J ~ 150
h.. ~
~ tt
C) t::)
~
~ ~ 100
~ "
........ ~
~~
~
~
~
.
.
.
.
.
.
- -- - ---
..- -
--
...-
.
.
.
4
24 72
TIME (hrs.)
.
.
120
168
216
-------
N
W
W
It.J
~
-.....J
~~
~ ~ 600
~~
~~
~ ~ 400
~Q::
~~
~ ~
~ ~ 200
~ ~
........
~~
C)
~
~
800
Prasinocladus subsalsa ~ ./
(Y " 6 7 42 x ) y:
1/ .
/: --~
A - ........
. t
/A
yf/&PhaeoctactYIUm tricornutum
. + Chaetocerus sp.
o
.02 .04 .06 .08 .10 .12
CADMIUM CONCENTRATION IN SEAWATER
(pg/mIJ
-------
-... 2 0
~ OYSTERS
~
C>i (CADMIUM DISCONTINUE ~
'..... 16 -------8--- 8--
<0 8 8 8 0 0
~ .
~
<0
~ 12
~
~ 8
~
~
4J 4
~
V)
V)
........
h. 0
~ CLA MS
C) 2.5
h.
~
~ 2.0
~
C) 0
~ 1.5
<:<~
~ :':><:<
~ 1.0 9 0
0 (.01 ppm .000 ppm CONTRO
........
~ 0
(:) .5 .006 ppm
~ .... A
A
0 .
10 20 30 40 50
TIME (DA YS)
234
-------
~
~
h:
~
~
~
~-...
~~
~~
~~
~G
~~
G~
~~
~~
V)
~ ~
Q:~
~ ~
,'-...::
~
C:J
~
~
1.0000
UPTAKE OF CADMIUM
FROM NATURAL
SEAWATER
.1000
.0100
.0001 .0010 .0100 .1000
CADMIUM CONCENTRATION
IN SEAWATER
(pg/ml)
235
-------
~EALED
-~ -.. ~ AREA
-, -0:: "
- C --.;'-7 - ~CTIVE
-- -:;- AREA
OF
POROUS ADSORPTION
MEMBRANE
c.-
0'1
E
o 16
"-
0'1
~
;:- 12
Z
~ 8
Z
o
U 4
~
~ 0
W 0
~
NICKEL
ADSORPTIVE
MATERIAL
10mg 0
20mg .
27mg 6
A.
100 200 30.0 400 500
MET AL ADDED IN SOLUTION
~g/I-ppb)
B. D.
---.
0'1
:::J... / ---. 100
'--'" COPPER
0 / 0'1
w .8 / :::J...
/ -- I
CO / 240 '/
/ 0
0::: / '/
o .6 //'- 50ppb W 10 '/
(f) 0::: I'
o / W I'
A / > 1
« ///// ~~~~-- 1
0 ~'- 30
0::: .2 U
W / ----- W ~
CL / --- 0::: f'
/ -----
0... 0 -- 0.1
0 0 6 12 18 24 I 10 100 1000
()
TIME (HOURS) SOLUTION (}Jg/I-ppb)
236
-------
10
,-..
-
"-
C1
E
.........
w
~
::::>
--1
w
o
-
()
<{
z
~ .10
-
~
«
a::
r-
2
W
U
Z
o
U .01
SEAWATER BACKGROUND SUBTRACTED
CADMIUM (Cd 2+)
x
'/..
/
o
o /
/
./
/
/
~
5
10
50
100
METAL
ADDED
237
(.ug /1)
-------
238
-------
References
Brainard, E. C. and W. B. Kerfoot, 1975. Artificial shellfish
for Ihe extraction and determination of transition
meta s in aqueous solution. Proc. Marine Technol. Soc.
IEEE Ocean, p. 901~905.
E.P.A, 1974. Methods for chemical analysis of water and
wastes. National Environmental Research Center, U.S.E.P.A.,
Cincinnati, Ohio.
Kerfoot, W. B. and R. Crawford, 1977. Rapid multielement
analysis of trace metals in seawater by a laminate
membrane adsorptive disc for inductively coupled plasma
atomic emission spectroscopy. ICP Inform~~ion Newsletter,
2(10):289.
Kerfoot, W. B. and S. A. Jacobs, 1976. Cadmium accrual in
combined wastewater treatment"aquaculture system.
Envir. Sci. and Technol., 10:662.
Pringle, B. M., P. E. Hissong, E. L. Katz, and S. T. Mulawka,
1968. Trace metal accumulation by estuarine mollusks.
.z~F'a!"rhb--&J:lg., 3: 455.
Rossenburg, W. H., 1969. Greening and copper accumulation in
the American oyster, Crassostreavirginica, in the vicinity
of a steam electric generating station. Ches. Sci..,
1 0 ( 7;) : 24 1 .
239
-------
Artificial Shellfish for MOnitoring Ambient Cadmium
Levels in Seawater
MR. WHITE: Martin White, Cadmium Association. I am impressed
with this very adequate technique. Could you comment on the methods
of analysis you used for cadmium in seawater since you are getting to
some extremely low levels?
Second, could you comment on the effects of pH and salinity on the
performance of your artificial oysters, because often these are used in
estuary conditions where there might be tremendous flucuations in
salinity over the course of a day?
MR. KERFOOT: On the first question, at that time, we were underway
at Wood's Hole Oceanographic with a standard seawater geosect program where
we used APDC followed by MIBK solvent extraction procedures to confirm
the cadmium concentrations for background levels in the flowing seawater
system. We used essentially a standard procedure developed by Derrick
Spencer and Peter Brewer at Wood's Hole Oceanographic, certainly in its
application to seawater.
In response to the second question, we do find a small decrease in
uptake due to salinity and some competition for the chelator sites. This
tends to vary, though, over a long exposure period when the principal
uptake is by the chelator system on the interior matrix.
This is far superior, in terms of absorptive characteristics because
it relies on a chelate-base substrate instead of an ion-exchange substrate.
As a result, you do not have the replacement to the extent that you have
seen on other products like those which involved Chelax-lOO on the surface
and deal with very short term ion-exchange reactions.
MR. JORC2YK: Ed Jorczyk, 3M Company. I have seen a lot of oysters
come out of the Hoosatonik River in Connecticut which is probably quite
heavily contaminated with metal, and I was wondering whether these
absorbed metals will color the flesh of the oyster.
MR. KERFOOT: Some metals will. Copper particularly, as noted by
Rosenberg, causes an aquamarine blue to occur in the protein structure
of the oyster itself.
240
-------
Alternative Materials and Processes
Session III
Wednesday Morning 10:05
UNIQUE CHARACTERISTICS OF
CADMIUM ELECTROPLATING
Albert R. Cook
International Lead Zinc Research Organization, Inc.
Manager, Electrochemistry
New York, New York 10017
Cadmium electroplating need nQt be a threat to the environment. Avail-
able technology can ensure complete safety in processing and in application.
The choice of carnnium plating can thus be based upon rational economic
and technical considerations.
The special characteristics of cadmium plating are described.
Case histories are presented to demonstrate
plating in specific applications, especially those
factors are of special importance.
the value of cadmium
where engineering safety
Government and industry specifications which involve cadmium plating
are cited and possible alternatives are discussed, together with the evalua-
tion procedures which must be followed to prove that substitution can safely
be made.
The special needs of the aircraft industry are taken into account.
241
-------
UNIQUE CHARACTERISTICS
OF CADMIUM ELECTROPLATING
by
Albert R. Cook
Manager, Electrochemistry
International Lead Zinc Research
Organization, Inc.
292 Madison Avenue
New York, New York 10017
Presented at the U.S. Government-Industry Workshop "Alternatives for Cadmium
Electroplating in Metal Finishing", October 4-6, 1977, National Bureau of
Standards, Gaithersburg, Maryland.
242
-------
Cadmium metal, a byproduct of zinc production, is of vital importance
to industry.
The end uses of cadmium for five major industrial nations* in 1974 are
shown in this pie chart in metric
1974 Total: 11444 metric tons
Others
(including alloys)
1317 tons
(11%)
Plating
3830 tons
(34%)
Batteries
1646 tons
(14%)
Stabilizers
1676 tons
(15%)
Pigments
2975 tons
(26%)
These 3,830 tons of cadmium used for electroplating would be sufficient
to provide corrosion protection for 700 million sq. ft. of steel.
* Germany F.R., Japan, United Kingdom, United States and France.
243
-------
That was the position in 1974, and it can be seen that electroplating
is an important application for cadmium.
This is a rapidly changing world,
but we must do what we can to ensure that any changes are made for the
better.
Changes hastily made and for the wrong reasons can have disastrous
consequences.
This workshop is entitled IIAlternatives to Cadmium Plating. II
The purpose of this paper is to point out some of the unique characteristics
of cadmium plating and to demonstrate that cadmium plating should retain
an important place as a unique cost effective protective coating for metals.
Preservation of the environment is a matter of the greatest concern to
us a 11 .
The metals-producing and electroplating industries have demonstrated
their ability to meet the increasingly stringent environmental controls now
bei ng imposed.
The cadmium plating industry is no exception.
The i nd us try
is meeting its obligations as regards effluent control and the cadmium
plating process is compatible with high standards for the environment.
We
can therefore confine ourselves to making a cost-benefit analysis to determine
what may be the result of using a particular alternative to cadmium plating.
Some of the benefits of using cadmium are not immediately obvious, and il1-
considered changes can be hazardous or costly.
What of the present uses of cadmium plating in the U.S.A.? The following
pie chart shows how an average annual consumption of 5,400,000 lbs. was
utilized in the U.S.A. from 1965-1974.
244
-------
fADMIUM L~AGE - PLATING IRON AND STEEL PRODUCTS FOR CORROSIO~
PRarECTION
2-11
Consumption of Cadmium in Electroplatinq By End Vse
Household -
Appliances 2.3%
Hardware (e.g.,
hinges) 3.1%
Ordnance
5.6%
Average Values for Consumption from 1965-1974
of 5,400,000 pounds
Taken from Cadmium Utilization Environmental Impact Mater~als and Process
Specifications and Substitutes by E. J. Dyckman, Naval Shlp Research and
D~velopment Center, June 26. 1975
245
-------
In order that you may have an appreciation of the diversity (and
essentiality) of the use of cadmium plating, here is a list of components
which are typically cadmium-plated.
Fasteners
Metal cutters
Nuts
Turbine engine blades
Bolts
Vanes and cases
$crews
Piano wire
Washers
Catapult hooks
Rivets
~1arine hardware
Nails
Pole line hardware
Fittings
Metal cutting machinery
Cast and Malleable iron
components
Tools
Electrical connectors
Rifl e barrel s
Low alloy steel heat treated
below 200 K psi
t~ortar Tubes
Actuator arms
Carburetor Parts
Be-Cu bushings and bearings
Magnet parts
Clutch throw out plungers
Compressor blades
Dissimilar metal faying surfaces
Aircraft undercarriage components
Gea rs
Titanium aircraft parts coated
with cadmium followed by
molybdenum disulphide*
Diode holders
Shafts
Splines
Shrouds
Voltage regulators
Electrical relays
Stainless steel bushings
Tools
Textile machinery
* Where the aircraft will meet extreme temperature conditions.
246
-------
Following are some of the U.S. specifications and standards calling for
the use of cadmi urn.
MATERIALS ANi PROCESSES SPECIFICATIONS AND
STANDARDS CALLING FOR THE USE OF CADMIUM
Military Specifications
~lIL-STD-171
t1I L -STD-454C
~lIL-STD-870
MIL-STD-889A
MIL-STD-1500 (CdTi)
MIS-S- 5002C
MIL-P- 23408A
QQ-P- 416C
~lIL-C- 8837
MIL-C- 81562
MIL-C- 0026482F (Navy)
MIL-C- 005015F (Navy) Contact plating
MS Sheet Forms including:
Bolts
MS-9882, 9881, 51968C, 51967D, 27040B
MS-9088-91, 9146-51,9441-48,9451-57, 9458A, 9459A,
9942,9926,9941,9927,9928,9946,9929,9947,9944,
9932, 9937, 9933-36, 9914-18, 9688, 9639, 9691, 9693,
9924, 9518-26, 9530-37, 9217, 9222, 9681, 9938, 9920,
9919, 9208-14, 9219, 9221, 9223, 9680, 9682, 9683,
9218, 35754B, 9400-02, 9397-99
Nuts
Washers MS-27183D
Screws
90728C, 90727D, 51095E, 18153C, 18154C, 51106C, 90725C,
90726B, 35458B, 35457B, 16998D, 16997C, 24667A, 24677A,
24678B, 21318A, 9449, 9940, 9939, 9930, 9931,9913, 9921
9527, 9516, 9517, 9216, 35206F, 35207F, 9215, 9206,
9207, 9528, 35190D, 35223B, 9184, 9183A, 51975A, 24629C.
Industrial Specifications
ASTM-A-165
M1S-2400M
AMS-2401
AMS-2416
AMS-2419
AMS-2426
247
-------
Let us now consider the special qualities of cadmium plating which led
to its use for these components and very widespread presence in military and
aircraft industry specifications.
Plateability
Cadmium plating requires only very simple control of plating solutions.
It is less demanding as regards surface preparation as compared to zinc.
Cast
and malleable iron components are easily plated with cadmium in barrel plating,
because cadmium electroplate offers unusual ability to bridge pores in the
basis metal, cadmium's hydrogen overvoltage favors the deposition of cadmium
rather than hydrogen.
Corrosion Resistance
More resistant to some corrosive environments than zinc, cadmium's
corrosion products are always less voluminous, reducing the possibility of
cracking bolted joints or binding sliding surfaces.
It shows greater resistance
to wet storage stain.
In bimetallic couples, the following table allows comparison of cadmium's
ro 1 e ( 2 ) .
Metals with a relatively large difference in electrode potential can
be effectively separated by cadmium.
The electrode potential of cadmium in
sea water is 0.43V; lying between aluminum, 0.52V; and mild steel, 0.34V.
That
of zinc is 0.76 volts.
Cadmium and zinc are the only two plating materials which can provide the
benefit of galvanic protection for steel.
The position of cadmium in the electro-
motive series means that it is able to provide galvanic protection to steel but
since the difference in potential is relatively small there is no tendency for
cadmium to "overwork.1I
Thus, while it will not cover a large expanse of bare
steel with its protection, it will provide long term protection, and without
248
-------
undue production of corrosion products.
Tin plated steel, when exposed to the
atmosphere, will rust overnight because tin is cathodic to steel and will induce
severe corrosion because a large area of tin (cathodic) is related to a small
area of steel.
Plating with cadmium before application of tin will prevent
this problem and provide a corrosion resistant bright finish.
Cadmium plating of copper alloys, stainless steel and aluminum provides a
long lasting finish because the galvanic couple does not stimulate aggressive
action from the cadmium.
In general, cadmium is the preferred galvanically active coating for use
in "factory" atmospheres.
Number
2
3
4
5
6
7
8
9
10
11
Effects of metallic contacts on atmospheric corrosion
Investigated metal
Carbon steel, cast iron
Stainless steel
Nickel and nickel alloys
Chromi urn
Copper and copper alloys
Aluminum and aluminum alloys
Zinc and zinc alloys
Cadmium
Magnesium and magnesium
a 11 oys
Lead, tin and their alloys
Silver, gold, platinum
(rhodium, palladium,
8smi urn, i ri di urn)
Affected metal
2 3 4 5 6 7 8 9 10 11
B B B B B A A A B B
A - A A A A A A A A A-B
A A - A B A A A A A A-B
A A A - A A A A A A A
A B B B - A A A A A B
B B B B C - A A B A C
C C B B C B - B B B C
B B B B B B A - A A B
C C C C C B B B C C
A B A B B A A A A B
A A A A A A A A A
A
Columns 1 to 11 correspond to the description on the row with the same number.
A: There is no effect of contact of the metals on the corrosion o~ the
investigated metal.
249
-------
B:
There is a small effect of contact of the metals on corrosion of the
investigated metal, but is is significant only in very aggressive
atmospheres.
Strong effects in outdoor exposures, and also exceptionally, in aggressive
indoor climates.
C:
One alternative to cadmium plating is zinc plating.
V. E. Carter of the
British Non-Ferrous Metals Research Association (now BNF Metals Technology
Centre) has compared the corrosion resistance of the two(3). Greater coating
thickness of zinc can be used on account of its lower cost but cadmium per-
forms better in contact with aluminum and in enclosed spaces in high
humidity(4. 5, 6, 7), especially at elevated temperatures (tropical con-
ditions) .
Where coating thickness must be kept to a minimum, say 5 pm,
cadmium performs better than zinc under marine and alkaline conditions(8).
It is 2 or 3 times more resistant to organic vapors from electrical
insulation(9) and is more resistant to the formic acid from paint films.
In the textile industry, zinc corrosion products can cause deterioration
of some fabrics whereas cadmium has no adverse effect.
In the weaving industry
in the U.K. cadmium plating is regarded as essential for protection of fasteners
and pins in water jet looms.
High humidity in the conventional shuttle loom
weaving shed can lead to corrosion which can jam machinery solid over a weekend.
Cadmium plating provides better protection and a necessary supplement to the
lubrication used.
Parts which are to be disassembled after service in a
corrosive environment should preferably be plated with cadmium.
Bolted
connections will not seize and electrical conductivity will be maintained.
When codeposited with nickel, a corrosion resistant coating of unusual
quality is created(lO). P. S. Willcox of ITT has commented that the inter-
metallic compound formed between nickel and cadmium seems quite unique as it
has a high melting point and is quite low on the electromotive series.
Ni-Cd
250
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diffused coatings are used for compressor parts in low alloy steel (max. U.T.S.
140 Kg/mm), 12-14% Cr, 18-8 Cr Ni steels and nickel based alloys.
These
materials are less susceptible to hydrogen embrittlement and permit the use
of dense cadmium deposits(ll).
Low-alloy steel parts which operate in jet engines at temperatures up
to 10000F have been protected from corrosion with 0.0003 in. (7.6 ~m) of
nickel plus 0.0001 in. (2.5 pm) of cadmium diffused at 6300F (3320C)(12) for
one hour.
This coating could withstand 100
hours salt spray without rusting
even after 23 hours at 7000F (3720C) and one hour at 10000F (5390C) prior to
exposure.
Three independent studies have shown that chromate-treated cadmium over
nickel offers the best conductive corrosion-resistant finish for aluminum.
Recent work by McDonnell-Douglas has shown that for aluminum a diffused
cadmium over nickel coating, proprietary to Stanford Applied Engineering(13),
meets conductivity requirements and successfully passed 816 hours of salt
spray exposure (salt spray tests to ASTM 8117-73).
of the R.W. Moeller technique(12, 14).
Jankowsky(15) found cadmium with chromate conversion coating over nickel
This may be a development
to be a superior coating for aluminum (6061 T6 panels) and advocated its use.
His testing involved 25 cycles, each cycle consisting of 16 hours at 2000C
(392°F) followed by 32 hours of salt spray exposure.
That is 800 hrs. salt
spray plus 400 hrs. elevated temperature exposure.
Willcox has shown that cadmium, with chromate conversion coating, over
nickel on a variety of aluminum alloys, 2024, 2011, 7075, die cast A380, and
6061, has successfully withstood 500 hours of salt spray exposure(16).
251
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Torque Resistance
Cadmium-plated components have an inherent lubricity and demonstrate
lower torque resistance than zinc plated components(17, 18) and exhibit a
more constant torque resistance than is the case with lubricants.
In some
cases, this will be a vital consideration.
A cadmium plated part will not
gall when in sliding contact.
On this account, if an assembly is to be subject
to corrosion and then dismantled for maintenance, it is necessary that cadmium
plating be used.
Formability
More ductile than zinc, cadmium plate allows easy forming after plating.
Electrical Resistance
Cadmium has a relatively low electrical resistance(7) even when provided
with a chromate conversion coating for additional corrosion protection.
Jamming
Cadmium corrosion products are closely adherent and not voluminous.
This reduces the danger of fouling switches and relays and makes cadmium
plating ideal for the return springs in automobile brakes and clutches and
for hydraulic rams used in the coal industry.
Solderability
Cadmium surfaces are excellent for soft soldering(7, 8, 17).
Appearance
Cadmium retains brightness for excellent decorative appeal.
~~drogen Embrittlement
After cadmium plating from cyanide solutions, high strength steel, such
as is used for aircraft landing gear, can be baked to eliminate hydrogen
embrittlement.
In general, hydrogen can be baked out through an initial
flash of cadmium of thickness about 2.5 microns (.00005 mils).
Because
252
-------
cadmium can be plated at approaching 100% efficiency, subsequent cadmium
plating can be carried out over this initial flash without danger of hydrogen
embrittlement(19) .
High Temperature Operation
Cadmium plated steel parts can operate under stress at temperatures up
to 9000F (4820C) provided that a nickel undercoat is applied before cadmium
plating followed by a diffusion baking operation.
Compatibility with Adhesives
Cadmium provides an excellent bond when adhesives are used, this is true
even for passivated coatings.
Problems may occur when passivated zinc coat-
ings art: u':.ed and expensbe adhesives may become obligatory.
A decal placed
over cadmium pla~ing will not be displaced by any corrosion products.
Conclusions
When considering whether an alternative for cadmium plating can be
justified, it is not only necessary to con3ider carefully what cost penalty
may be incurred, but to pay particular attention to some of the above vital
and beneficial characteristics which are not always apparent at first sight.
Cadmium electroplaters can comply with needed pollution control regu-
lations.
We, therefore, question the need to develop "Alternatives to
Cadmium Electroplating in Metal Finishing."
Cadmium electroplating need not be a threat to the environment and we
must be sure that we do not risk failure of life supporting components because
we have not given careful thought to the implications of finding alter~atives
to cadmium plating.
253
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REFERENCES
1.
"Cadmium - The Metal of Benign [Ileglect", R. L. Stubbs, Cadmium Association
London.
2.
Table 13 "Protection Against Atmospheric Corrosion" by Karel Barton,
translated by John R. Duncan, John Wiley & Sons, New York.
"The Choice Between Cadmium and Zinc Plating for the Protection of Steel",
by V. E. Carter, Metal Finishing Journal, October 1972, p. 304-306
3.
4.
P. T. Gilbert, BNF Metals Technology Center, Miscellaneous Publication
No. 457, 1954.
5.
P. T. Gilbert and S. E. Hadden, Journal of Electrodepositors Technical
Society, 1950,25,41.
F. Obgurn, Product Engineering, 1949, 20 (12), p. 135
6.
7.
S. J. Beyer, Plating, 1960,47 (12). 136l.
P. F. Norrish, Corrosion Prevention and Control, 1957, 4 (8), 51.
8.
9.
G. Kloetz, Galvotechnik, 1965, 56 (9), 514.
10.
Kudryavtsev N.T., IX Intern Kolloquim Tech, Hochschule Illmenau,
Galvanotechnik 9, 10 (1964).
11.
"Diffusion Characteristics of Heat Treated Electro-Deposited Nickel Cadmium
Coati ngs and thei r Effects on ~1i cro-Structure and Hardness of Cadmi um",
thesis by ~1. P. Malik, submitted to University of London, April 1975.
12.
"Diffused Nickel Cadmium as a Corrosion Preventive Plate for Jet Engine
Parts" by R. W. Moeller and W. A. Snell, Plating, 42, December 1955, p. 1537,
"Materials and Processes Design Data", Bulletin No. 10-02, Dept. E 457,
McDonnell-Douglas Astronautics, St. Louis (1975).
13.
14.
Aerospace Material Specification 2416, Society of Automotive Engineers,
New Your, 1968.
15.
E. J. Jankowsky, Report No. NADC-76274-30, Naval Air Development Center,
Warminster, Pennsylvania, 1976.
16.
P. S. Willcox, unpublished research 1976-7, ITT Cannon Electric, Santa Ana,
Ca 1 iforni a.
17.
18.
D. N. Layton, Trans I.M.F., 1965,43(4),153.
G. David, Corrosion (Paris) 1969, 17(7), 343.
19.
Private communication with L. Morin
254
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Unique Characteristics of Cadmium Electroplating
MR. GROBIN: Allen Grobin, IBM Corporation. I think you have
adequately demonstrated the place of cadmium in the electroplating
industry; however, do you think we have been using cadmium where it
wasn't necessary? Could we possibly reduce the environmental hazards by
using, say, zinc in many of the applications where today we specify
cadmium because of the reputation that cadmium has gained, justified or
not?
MR. COOK: I think that is possible; however, the considerably
increased cost of plating cadmium compared with zinc, for example,
should mean that those instances are really at a minimum; however,
I am quite sure that those instances will occur.
MR. DROSTEN: Fred Drosten, Army Aviation Research and Development
Command, St. Louis. I think you made an error on your tabulation showing
Cd plating on titanium. There have been some cadmium embrittlement
instances of the titanium definitely traced to cadmium plating.
MR. COOK:
was at fault.
Thank you for pointing that out. My reference apparently
I think we should make that change in the final paper.
MR. MEYER: I am Fred Meyer, Air Force Materials Lab. There are
many occasions where we find other materials have better corrosion
resistance than cadmium. I think we should not rely totally on saying,
'we have the good material. Let's not look for anything else."
Some of the materials we have looked at are definitely superior from
the service standpoint. Tomorrow, I will be giving a paper with actual
service tests. This is one thing we haven't seen quite yet. We have
laboratory salt spray tests which have a certain degree of value, but the
final criteria are how well does it perform a service?
In certain aircraft applications, we are advocating the use of other
coatings because they are superior from the corrosion standpoint.
I am also wondering whether, ultimately, a good bit of the cadmium
plating usage may be picked up in the rapidly developing battery areas.
There is probably a good chance they will be using more cadmium in
batteries in the future.
This meeting has been set up for the purpose of determining available
alternatives. We shouldn't totally abandon cadmium because it is an
environmental hazard, but probably the number of applications will diminish
because we do have alternatives.
MR. COOK: I think that the cadmium plating industry would be very
happy to bow out of any application where a cost-benefit analysis has
demonstrated some improved coating is available.
255
-------
I think we have to
There is no accelerated
will happen in service.
be careful of relying upon
test which will adequately
I say that unequivocably.
accelerated tests.
demonstrate what
You are faced with long-term testing of these materials. The
hygiene point of view is again being brought up. I think it should
not be brought up because our premise is that the cadmium plating
industry can operate within whatever controls may be set up. It is
up to the regulatory agencies to set up those controls, and let us
operate within those limits. Then let the economics decide where we
go from there.
MR. HEIDERSBACH: BoB Heidersbach from Ocean Technology Incorporated.
The one thing absent from your presentation, is the fact that while
cadmium has its problems during the plating process as far as the
elimination of hydrogen in the substrate metal is concerned, once the
cadmium has been applied after a proper bake-out procedure, it is a
very effective barrier to the further introduction of hydrogen into
the substrate.
This is at least one application where I am unaware of another
coating material that is as effective in a hydrogen or hydrogen sulfide
or hydrogen cyanide environment.
MR. COOK: Thank you very much. I should have made that stronger.
A zinc coating is impervious to hydrogen and will prevent hydrogen from
getting in and getting out.
MR. DROSTEN: Fred Drosten, Army Aviation Research and Development
Command. How is it you quote salt spray tests, accelerated tests, and
yet say they are not valid? I am looking for experience like Mr. Meyer
can supply.
MR. COOK: I think that is a point well taken. I think salt spray
tests are very useful in the laboratory for putting materials into some
descending order of corrosion resistance, if you like, with a tongue
in cheek, because in actual service, that order is going to be disturbed
anyway, and you haven't got anything else.
The fact that you haven't got anything else shouldn't lead you to
risk using some other coating on a life-supporting component. You
shouldn't just say, "In salt spray tests it was perfectly all right,
and it is just too bad that in practice it didn't do too well."
I think we heard that in previous papers.
MR. MUEHLBERGER: Don Muehlberger, McDonnell Douglas. From an
environmental standpoint, isnlt part of the problem not only how to
clean up the plating baths during the plating process, but what to do
with the cadmium that you have in fact cleaned up and now have some
place within the plating area? Also, what happens to the cadmium on
the plated part that now enters the environment?
256
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MR. COOK: Yes. I think regarding the cadmium in sludge, for
example, it is the responsibility of the cadmium industry to work out
recycling techniques.
We mentioned other applications for cadmium. I think
nickel-cadmium battery for a hybrid vehicle is a wonderful
which ought to be further pursued.
that the
application
Cadmium is used in the lead acid battery grid, for example, and
at one and a half percent in some grids. Gould Corporation, for example,
uses it, so there are other applications.
Regarding the use of cadmium electroplate and its effect on the
environment, so far as I know, the tests have not shown any problem.
Dr. Yost would be more qualified to talk in the environmental field
then I am.
MR. GROBIN: I am Allen Grobin, IBM Corporation, and a member of
ASTM Committee B-8, which isnow the jurisdiction of Committee G-I. The
salt spray test while initially developed as a corrosion test was very
quickly found not to be a corrosion test. Many of the metal plating
specifications disqualified the salt spray test as a corrosion test.
It is a comparative test for quality control and should not be used as
an evaluator of corrosion resistance. It should not be used to compare
the resistance of one type of plating against another.
All you can do is compare a single plating against itself.
are you producing it today the way you produced it yesterday?
That is,
257
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Alternative Materials and Processes
Session III
Wednesday Morning 10:40
THE PROPERTIES OF CADMIUM AND
TIN-ZINC ELECTRODEPOSITS
John M. Bih1
Tin Research Institute, Inc.
Columbus, Ohio 43201
Laboratory tests have established that tin-zinc alloys of suitable com-
position, 75-80% tin, provides corrosion resistant properties equivalent to
or be~ter than cadmium in certain environments. Tin and zinc, are widely
used as coatings for protection of steel against corrosion. Tin itself is
resistant to atmospheric corrosion, but since tin is cathodic to steel, rust
develops at pore sites. Zinc is anodic to steel and protects the base metal
through sacrifical action. However, an e1ectrodeposited compos it of tin
and zinc results in a compromise of reducing the porosity of the coating
and the rate of sacrifica1 attack of the zinc.
A comparison of the corrosion properties of tin-zinc alloy with cadmium
on steel shows the alloy to have slightly inferior corrosion properties in
marine atmospheres but superior to cadmium in industrial atmospheres. For
long term protection of steel coated with tin-zinc or eadmium in contact with
aluminum alloys, the tin-zinc proves to be the favored coating in both indus-
trial and marine environments.
As plated tin-zinc has a mat silver-white finish that can be polished
to a high luster, good anti-friction properties and solderability superior
to that of cadmium. The deposit is usually plated from an alkaline potassium
stannate zinc cyanide electrolyte, although non-cyanide electrolytes have
been shown to be practical. The stannate zinc cyanide electrolyte provides
excellent throwing power, far superior to the typical cadmium cyanide elec-
trolyte.
259
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THE PROPERTIES OF CADMIUM AND TIN-ZINC ELECTRODEPOSITS
John M. Bihl
Tin Research Institute, Inc.
483 West Sixth Avenue
Columbus, OH 43201
A number of electrodeposited metallic coatings are used for pro-
tection of steel, aluminum and other metals against various corrosive
conditions.
Tin, zinc and cadmium deposits are commonly used for
this purpose, each having its advantages as well as limitations.
A
satisfactory electrodeposit used solely to prevent the corrosion of steel,
for example, should furnish sacrificial (anodic) protection of the steel
base.
Zinc and cadmium are two protective metals capable of being
easily deposited from an aqueous electrolyte that furnish this anodic
protection to steel.
But, while providing good sacrificial protection,
zinc is itself consumed in the process which usually results in a white
corrosion product that not only deteriorates the aesthetics of the plated
parts, but renders them unsolderable and in certain cases can cause
interference with the electrical or mechanical operation of the plated
items.
In the case of cadmium, it is well known that this metal affords
good sacrificial protection to steel in humid and marine atmospheres,
but its prote cti ve value in an industrial atmosphere is limited.
Tn contrast
to zinc and cadmium, tin itself is resistant to atmospheric corrosion, but
under most conditions tin is cathodic to steel which results in the rusting
of the steel at pore sites.
260
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As an alternate to cadmium, zinc or tin, a tin-zinc alloy coating
of suitable composition, usually 70-80% tin.. provides excellent cor-
rosion protection with fewer limitations in many applications than
these pure metals.
Thetin-zinc alloy as-plated has a fine-grain
crystalline structure, a silvery-white color and a mat finish which
can be polished to a high luster (Fig. O.
The solderability of the
75-25 tin-zinc alloy is superior to cadmium or zinc, but inferior to
tin or a 50-50 tin-lead coating, in solderability tests indicating area
of spread (Fig. 2).
The plated alloy is ductile permitting forming and
deep drawing.
The 75-25 tin-zinc alloy provides a coating which is slightly anodic
to steel, a property that gives sacrificial protection to the steel at pore
sites or discontinuities in the coating, but at a sacrificial rate that is
less than that of a pure zinc deposit.
Further, the unsightly white cor-
rosion product commonly associated with zinc does not appear on the
surface of the tin-zinc plated items, even after long periods of service.
Tin and zinc can be co-deposited in all proportions from an electrolyte
containing sodium or potassium stannate, sodium hydroxide, zinc cyanide
and free hydroxide, either sodium or potassium (Fig. 3).
The use of the
potassium salts leads to an improvement in the conductivity of the electro-
lyte which permits the use of higher current densities.
Satisfactory
261
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operation of either the potassium or sodium bath requires the anodes to
be operated in the filmed condition to insure the dissolution of tin in the
stannate form.
The composition of the deposit is changed by variations
in the zinc and hydroxide content of the electrolyte while bath tempera-
ture, current density, tin content, and total cyanide do not have a
significant effect on the deposited tin-zinc ratio.
2
Davies and Angles made investigations into the deposition of tin-zinc
from cyanide-free alkaline solutions containing trisodium salt N-hydroxyethyl-
ethylenediamine triacetic acid, sodium hydroxide, sodium stannate and
zinc carbonate.
The electrolyte was found to be stable and the deposits
obtained were similar to those obtained from the convemional stannate-
cyanide electrolyte.
Satisfactory deposits from a fluoborate electrolyte
in the 70-30 tin-zinc range have also been obtained by Cohen3.
How-ever,
there has been no commercial use of either of these two formulations.
Alternately, tin-zinc can be deposited by a mechanical process developed
by the 3M Company.
In this process the powdered metals, in this case
tin and zinc, are cold welded to the base material in a rotating barrel
containing water, glass beads and ,proprietary promoter additives.
The
glass beads provide the peening action necessary for the cold weld process.
Mechanical plating has the advantages of reduced waste disposal problems
and lack of hydrogen embrittlement.
262
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Tin-zinc plate of any composition can be passivated to enhance its
protective value by treatment in a hot 2 percent chromic acid solution
or a solution of sodium dichromate containing 0.33 percent by weight of
sulphuric acid.
From the corrosion viewpoint, it is usually not necessary
to passivate tin -zinc but a chemical surface treatment will improve the
corrosion resistance, serve to reduce finger marking, and provide better
paint adhesion without impairing solderability significantly.
Figures 4 and
5 show the improved protection provided by chromic acid treatment of a
80-20 tin-zinc plate (lOOp-in.) on steel panels subjected to 192 hours in a
humidity chamber and to salt spray.
Since tin-zinc can be
plated in all proportions a program was under-
taken at the Tin Research Institute to determine the most suitable tin-zinc
ratio in terms of corrosion resistance.
Plated steel panels of tin, zinc,
cadmium and tin-zinc, ranging from a 92-8 to a 28-72 ratio, at thicknesses
of 300, 500 and 700f-in. , were subjected to 400 hours of salt spray and to
1,100 hours of humidity testing.
The results of the salt spray (Fig. 6) show heavy rusting on the tin
and cadmium samples at all thicknesses while the zinc coatings were almost
entirely converted to a whitish corrosion product which then allowed
massive rusting of the base steel.
Tin -zinc panels of 92 -8 composition
exhibited localized rusting due to the limited anodic protection afforded
263
-------
by the zinc while the 28-72 tin-zinc panels showed excessive amounts
of the white corrosion product from the zinc.
The alloys of the 86-14
and 78-22 tin-zinc ratios provided adequate protection and retained
good aesthetics at all thicknesses.
The relative corrosion resistance of similarly plated panels subjected
to humidity testing (Fig. 7) indicated pore site rusting where tin alone
was used as a protective coating.
Panels of plated tin-zinc in the 70-80
percent zinc range not only provided adequate protection but again retained
much of their aesthetic value.
Zinc provided the needed base metal
protection but the appearance of the panel deteriorated rapidly.
The
cadmium-plated panels performed well in the humidity tests.
Since it is important that a protective coating remain protective even
after the base metal is deformed, steel test panels of plated tin, zinc,
cadmium and the 78-22 tin-zinc alloy were exposed to humidity tests
after being deformed by cupping (Fig. 8) and by bending and reflattening
(Fig. 9).
In both cases the tin and cadmium. coatings were damaged and
rusting of the base steel occurred.
The tin-zinc like the pure-zinc-plated
panels were little affected by deformation.
The protective value of a coating in an industrial em'ironment becomes
another important area for investigation.
The results of 200 days outdoor
light industrial exposure of steel panels plated with 500fin. cadmium and
78-22 tin-zinc provided evidence that the tin-zinc was far superior to
cadmium in this case (Fig. 10).
264
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With the increasing us e of aluminum by the automotive and other
industries, the need to prevent galvanic corrosion between aluminum
and steel components is critical.
The extensive us e of steel fasteners
to secure aluminum alloy structures led the Tin Research Institute to
undertake a program to study methods of preventing this galvanic cor-
rosion.
Since tin-zinc has a galvanic potential near that of aluminum, it was
natural to try plating the steel fasteners with tin-zinc.
To study this complex problem, steel nuts and bolts coated with
cadmium, zinc and the 75-25 tin-zinc alloy were mounted in aluminum
plates and subjected to suburban and marine atmospheres, laboratory salt
spray and exposure to the sea at mid-tide level.
Tests indicated that the
corrosion protection afforded by both zinc and tin-zinc was superior to
that of cadmium after exposure to 974 days in a suburban atmosphere
(Fig. 11).
Exposure to a marine atmosphere for 684 days showed thE"
rather poor performance of zinc, while tin-zinc aTln DClumium provided
adequate protection (Fig. 12).
Eypvsure under the same conditions,
marine atmosphere
Ł0r nine years, 2 months, resulted in the cadmium
and zinc -plated bolts severely rusting and the surrounding aluminum
experienced heavy pitting.
The tin-zinc-plated bolts were still in good
condition with only minor pitting of the aluminum (Fig. 13),
265
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Laboratory tests also indicated etching of the aluminum after 326
days of salt spray in areas surrounding zinc-plated bolts.
Tin -zinc
and cadmium produced less severe galvanic corrosion in the salt
spray tests but the aluminum in both cases did exhibit some pitting
(Fig. 14).
The results obtained from exposure to the sea at middle tide level
for 650 days were again somewhat different than those of other tests.
Localized corrosion of the aluminum took place prior to the rusting of
the coated steel components.
This condition was most pronounced with
the zinc-plated bolts followed by tin-zinc and cadmium.
The cadmium-
plated bolts and the surrounding aluminum remained in relatively good
condition throughout the test (Fig. 15).
Although no protective coating is suitable for all applications, the
prop~rties of tin-zinc as a substitute coating for cadmium can find
numerous ~pplications.
With its ease of plating, good solderability,
excellent corrosion prottoQ-lion for steel in most environments and as a
viable coating to prevent galvanic corrosiorl ""0.tween aluminum and steel,
tin-zinc coatings have a place in industrial as well as con~"'rner applications.
266
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References
Tin Research Institute, Publication No. 202, (1963)
Davies, A. E., and Angles, R. M., The Electrodeposition of Tin-
Zinc Alloys from Stannate -Complexone Solutions, Trans. Inst. Met.
Finishing, 33, (1956)
Cohen, B., Plating, Sept. 1957, 963 - 8
Hedges, E. S., (editor), Tin and Its Alloys, Edward Arnold, Ltd.,
London, 1960, 131
Tin-Zinc Coatings, Tin and Its Uses, No.1 7, 5-8
Britton, S. C., and de Vere Stacpoole, R. W., Metallurgia. 52, 310,
64-70, (1955)
The Trend to Tin-Zinc Coatings, Tin and Its Uses, No. 59, 12-13
U. S. Patent No. 2,675,347
Britton, S. C., and Angles, R. M., Weathering Tests of Tin-Zinc
Alloy Coatings on Steel, Metallurgia, 44, 264, (1951)
267
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Fig. 1
Fig. 2
Fig. 3
Fig. 4
Fig. 5
Fig. 6
Fig. 7
Fig. 8
Fig. 9
Fig. 10
Fig. 11
Fig. 12
Fig. 13
Fig. 14
Fig. 15
Figures and Illustrations
Various tin-zinc-plated items
Solderability tests of various coatings
Composition and working conditions of tin-zinc alloy plating bath
Humidity chamber test of passivated and as-plated tin-zinc
Salt spray test of passivated and as-plated tin-zinc
Salt spray test of tin, zinc, cadmium and various tin-zinc alloys
Humidity chamber test of tin, zinc, cadmium and various
tin -z inc alloys
Humidity chamber test of tin,
tin-zinc after cupping
cadmium and 78/22
zinc,
Humidity chamber test of tin, zinc, cadmium and 78/22
tin-zinc after bending and reflattening
Outdoor exposure of 78/22 tin-zinc and cadmium
Tin-zln<:o-, zinc-, and cadmium-plated bolts in aluminum plate
exposed to SUburban <:!tmosphere
Tin-zinc-, zinc-, and cadmium-pl!:l.ted bolts in aluminum plate
exposed to marine atmosphere, 684 day~
Cadmium-, zinc-, and tin-zinc-plated bolts in aluminum plate
exposed to marine atmosphere, nine years, two months
Aluminum plate, corrosion products removed, after laboratory
salt spray
Tin-zinc-, zinc-, and cadmium-plated bolts in aluminum plate
after exposure to sea at middle tide level
268
-------
Figure 1.
Various tin-zinc plated items.
269
-------
Figure 2.
$C;"SR..31'ftM.O (iii 1J4RI1.~..
(,.0003 1'1. rdre>
Solderability tests of various coatings.
270
-------
Figure 3.
ALLOY PLATING
TIN-ZINC ALLOY
COMPOSITION Of BATH
SODIUM
oz.tGAL.
TIN 4
(As No or K STANNATE) (10)
ZINC 1/3
(M llNC CYANIOE) (0,6)
TOTAL CYANIDE (As No or K CYANIDE) 3.8
fREE HYDROX I DE (No or K ) 0.6 - 0.8
POTASSIUM
OZ./GAL.
5-7
113.5 -18.5)
0.6-1
(1.1-1.9)
5-7
0.65-1.1
WORKING CONDITIONS
TEMPERATURE 150 f! 5 -150 f! 5
VOLTAGE 3-1/2-4-1/2 4-5 V
CATHODE CURRENT DENSITY 1O-30A.S,f, 10-75 A.S.P.
ANODE CURRENT OENSITy 8-15A.S.P. 15-25A.S,f.
RATIO -ANODE AREA TO CATHODE AREA 2:1 - 1.5:1-2:1
PLATE COMPOSITION FOR MAXIMUM pROTEC'fJON 20-25% ZINC
ANODES " CAST-SAME AS PLATED
COMPOSITION
Composition and working conditions of tin-zinc alloy plating bath.
271
-------
Figure 4.
As
pia led
Filmed
HUMIDITY CHAMBER, 192 HOURS,
80/20 TIN-ZINC, 0.0001 INCH
Humidity chamber test of passivated and as~lated tin~inc.
272
-------
Figure 5.
SALT SPRAY, 192 HOURS,
80/20 TIN-ZINC, 0.0001 INCH
As
plated
Filme
Salt spray test of passivated and as-plated tin-zinc.
273
-------
. .~;~.. ,'cmil :.'=
Ti,!:8I1JC ,....k~
SALT SPRAY. 400 HOURS
. ~ .
-------
Figure 7.
0'0003.
thkk
0'000'.
thick
0-0007-
thid::
92,8
Ti".::""
M6'T4
Tm-zmŁ
7821
T"'-,u1ll:
70 )0
Tin-zm<
53 47
Tin.;,".:
HUMIDITY CHAMBER, 1,100 HOURS
Humidity chamber test of tin,
tin-zinc alloys.
275
2M 12
Tm-:i",
Z''b,-
zinc,
cadmium,
0'0003"
thick
o coos"
(hick
o 0007" I
ilikk I
CoJIIII"m
and various
-------
:Figure 8.
Till 0'0007"
78/22 Till-:;illc o. 0007"
Zillc 0'0007"
Cadmium 0'0007"
HUMIDITY CHAMBER, 1,430 HOURS,
DEFORMED IN THE ERICHSEN CUPPING
MACHINE AFTER PLATING
Humidity chamber test of tin,
after cupping.
cadmium, and 78/22 tin-zinc
zinc,
276
-------
Figure 9.
r-
Till 0'0007'
Cadmium o. 0007 .
HUMIDITY CHAMBER, 1,430 HOURS, DEFORMED BY
BENDING AND REFLATTENING AFTER PLATING
Humidity chamber test of tin, zinc, cadmium and 78/22 tin-zinc
after bending and reflattening.
277
-------
Figure 10.
OUTDOOR EXPOSURE, 200 DAYS
78/22
Till-zi,zc
0'0005"
rhicR
Cadmium
0'0005'
rhick
Outdoor exposure of 78/22 tin-zinc and cadmium.
278
-------
Figure 11.
.",-
.:,.".
, "
..~.,.."
,. ~
'""}'
~
SUBURBAN ATMOSPHERE, 974 DAYS,
UPPER TIN-ZINC, MIDDLE ZINC,
LOWER CADMIUM
Tin-zinc, zinc, and cadmium plated bolts in aluminum plate
exposed to suburban atmosphere.
279
-------
Figure 12.
','.."
~ ;~,..
:...-;
, :......
:;5~'
;.«:\,..~
C" '. .~?/ff
~~\ :;':
.
-------
Figure 13.
a
MARINE ATMOSPHERE, 9 YEARS, 2 MONTHS,
LEFT CADMIUM, CENTER ZINC, RIGHT TIN-ZINC
-- ------ - --- - - - ---- --
Cadmium, zinc, and tin~zinc plated bolts in aluminum plate
exposed to marine atmosphere, nine years and two months.
281
-------
Figure 14.
LABORATORY SALT SPRAY, 326 DAYS, RIGHT
CADMIUM, CENTER ZINC, LEFT TIN-ZINC
(CORROSION PRODUCTS REMOVED)
Aluminum plate, corrosion products removed, after laboratory
salt spray.
282
-------
Figure 15.
---- --
,"
--.......~ ~.
:. )\
~Y.\.
-.'
, . ...~
SEA AT MIDDLE TIDE LEVEL
660 DAYS. UPPER TIN-ZINC'
MIDDLE ZINC. LOWER CADMIUM
I
I
'oj
Tin-zinc, zinc, and cadmium plated bolts in aluminum plate
after exposure to sea at middle tide level.
283
-------
The Properties of Cadmium and Tin-Zinc Electrodeposits
MR. KOVELAN: John Kovelan, Diamond Shamrock. Yesterday in my
talk I made reference to Zincrometal, which is our proprietary coating
which is pre-coated sheet steel, formable, weldable, paintable, non-
corrosive and of course non-polluting, and it is used on 8,000,000
automobiles. I am just wondering in your objective reporting here why
you didn't include any panels of Zincrometal.
MR. BIHL: One of the panels that I did show was nine years and
two months old. Tin-zinc is not new. It is an alloy that is quite
old. As a matter of fact, it was developed in the early '50's when
there was a shortage or restriction on the use of cadmium, and it
was specifically developed by the Tin Research Institute as a substitute
for cadmium.
Of course, when there was plenty of cadmium metal, again with no
restrictions on its use, people went back to using the old stand-by,
cadmium. Only recently have we felt that there was some need to re-
introduce our original work on tin-zinc and the corrosion data on tin-
zinc as a possible substitute.
MR. GROBIN: Allen Grobin, IBM Corporation. I would like to point
out that a number of years ago, with the Bureau of Standards Research
Associate Program, Dr. Sidney Phillips of the IBM Corporation did a
study of a number of alloys for electrical contact. Tin-zinc was one
of thes=, and tin-zinc did very well for electrical contact material.
MR. TAYLOR: Ed Taylor, Standard Pressed Steel Company. I have
been involved in conducting a number of global exposure programs for
fasteners of many different alloys. We have coated a number of these
alloys with cadmium and other metals. We have exposed these allover
the world on the roofs of our various plants, on 98 cars in various
countries throughout Europe, the United States, and Puerto Rico. I
have never seen cadmium decompose as rapidly as you have shown, and I
wonder whether this is due to the job shop or the facility where your
fasteners were plated.
I am offering the facilities of Standard Pressed Steel Company for
any further investigations you might have. I am sure we can do a good
job and show you that Cd can be longer lasting than what you have shown.
MR. BIHL:
Which particular test?
MR. TAYLOR: In general I noticed that some of your atmospheric
results were very short.
MR. BIHL: We have found that cadmium is not really the best
coating in an industrial atmosphere.
MR. TAYLOR: Various references attribute this to the presence of
sulfur dioxide. Zinc is supposed to be much more resistant. I feel
that with all the salt currently in the atmosphere as an industrial
284
-------
pollutant, times have changed, and perhaps cadmium is a lot better
than it used to be.
MR. BIHL: This may very well be true. I will get back to my
statement. These tests were run a number of years ago, and it could
be that the industrial pollutants today are much different than what
they were 15 years ago.
MR. TAYLOR: I just want to reiterate that we have seen cadmium
plating from a number of different job shops and different companies,
and cadmium plating done on different days or by different people
gives completely different results.
MR. BIHL: I am sure if we continue with this study, we will take
you up on your offer.
MR. MAYER: Jim Mayer, 3M Company. I wonder what the thickness
was on the nut and bolt specimens you were showing.
MR. BIHL: All of them, including the cadmium, the tin-zinc, and
the aluminum were plated seven-tenths of a mil.
MR. MEYER: Fred Meyer, Air Force Materials Lab. Ed was talking
about atmospheric changes. Since we started removing particulate
matter, the atmosphere is much more acidic. In some of the European
countries, the rain has a pH of somewhere around three or four, due
mainly to the removal of the particulate matter from power plant exhausts
which would generally tend to neutralize the gases. The gases coming
off from power plants were relatively innocuous, but now they are
definitely acidic.
Like silver, cadmium is particularly susceptible to sulfur, sulfur
dioxide and hydrogen sulfide. In marine environments, cadmium performs
well in seawater, but doesn't perform quite as well on a carrier aircraft
as it would on an aircraft flown out of a coastal area because, on our
carriers, we have sulphur dioxide coming out of the stacks.
One of the big enemies of cadmium is sulphur in the atmosphere, and
we are probably getting more of this in the air now than we used to. It
is definitely more in the acidic end than on the alkaline end.
MR. BIHL: Yes, as a matter of fact we have done work with tin-Cd.
Tin-Cd in most instances was similar to the tin-zinc. In marine atmosphere
it tended to do quite well. Solderability was superior to pure cadmium.
Obviously it would have excellent lubricity because of the cadmium and
tin present.
MR. MEYER:
Was cadmium in short supply at the time of this work?
MR. BIHL: No, some of the work was done later. I suspect that
what you are asking is why I didn't present the tin-cadmium information
also. Obviously, the reason I didn't is because the title of this
seminar is "Alternatives to Cadmium," and I think we have an alternative
to cadmium, tin-zinc, without adding cadmium back into it.
285
-------
MR. MEYER: I don't think we are
can replace cadmium across the board.
that there really isn't a valid total
at each application individually.
going to find one material that
I think you made the statement
alternative, and we have to look
MR. BIHL: If you give me time enough to present three or four
more papers, I can probably give you other tin alloys that work quite
well.
MR. MEYER: Each one of these materials has its drawbacks, including
cadmium. Maybe the title of the conference should have been "Substitutes,"
rather than "Alternatives," because we aren't going to completely abandon
it.
Another topic not addressed by this conference is the various sources
of cadmium wastes. If we wash airplanes and vehicles at air and naval
bases and the waste water carries the metallic oxides into waste treatment
plants, and if we continue to use cadmium for these applications, are we
really separating it out of the end use environment, even though we are
controlling the plating effluent.
What was the cost of the tin-zinc compared to cadmium?
MR. BIHL: The metal cost, will be higher. For the total overall
process, I really cannot answer. We have not made a study of the
treating of the cadmium waste versus the waste that would come from the
tin-zinc plating bath. This is somewhat out of the realm of the Tin
Research Institute. The pollution control costs for the cadmium would
probably equalize the costs, or the two will be very close.
MR. MEYER:
Will the tin-zinc contribute to hydrogen embrittlement?
MR. BIHL: It undoubtedly will get hydrogen embrittlement, but not
extensively because zinc and tin aren't known for hydrogen embrittlement.
MS. ZILEK: I am Mrs. Carolyn Zilek from Ford Motor Company. In
testing protocol on the thickness of the metal applied, do you think that
it is important to check different mil thicknesses in relation to the
coating? In your case, y~u represented results for one specific thickness,
but how do these so-called alternatives stack up against cadmium when you
evaluate them at different mil thickness?
MR. BIHL: The thicknesses are going to make a difference. One prime
example of this would be the tin thickness. In every case here, tin showed
rusting pore sites because it is cathodic to steel. If we were to put a
one mil coating or a one and a half mil coating of tin on steel, the tin
would exceed all the other coatings in the tests that I showed here simply
because the steel would be entirely covered, and the tin itself is
extremely resistant to corrosion.
286
-------
Undoubtedly we are going to see variations like this with zinc,
for instance. If we put a very thick coating of zinc on a strip of
steel, it is going to give adequate corrosion protection to the steel
until all the zinc is used up sacrificially. I assume that this would
be true of cadmium and my tin-zinc also.
Our research programs tried to use something that was within the
realm of practicality that is plated in our shops for use. Most of the
tests were done at between one-half and seven-tenths of a mil which
represents typical coating thicknesses. To get a true evaluation, we
should test a whole gamut of thicknesses.
We have done considerably more tests than I have shown up here.
I don't recall that any of them happen to be of different thicknesses.
We have tested aluminum plates and various aluminum alloys. We did
some scratch testing on plated steel.
MR. GROBIN: Allen Grobin, IBM Corporation. I want to make two
comments, one on the degree of corrosion shown in your slide on cadmium.
I have also seen that type of corrosion in heavy industrial environments
here in the United States, and I think part of the problem is that
cadmium plates so well that many platers do not plate it on adequately
prepared substrates.
The other platings require more stringent preparation techniques
to achieve fewer pores and a more adherent coating.
MR. BIHL:
That is a point well taken.
MR. SIMMONS: Gene Simmons, Sermetel, Incorporated.
is the quality of the tin-zinc from source to source?
How reliable
MR. BIHL: In starting up any new plating line, there are going to
be some problems. In general, plating tin-zinc should not be difficult.
It is basically run like an alkaline tin bath, and there have been no
significant problems reported in running this bath. Since the operation
of these plating lines is similar, the quality from plater to plater should
be similar.
287
-------
Alternative Materials and Processes
Session III
Wednesday Morning 11:35
THE ADVANTAGES OF CHLORIDE ZINC PLATING
Edward R. Jorczyk
3M Company
Plating Systems Department
Saint Paul, Minnesota 55101
Pollution problems and the high cost of waste treatment of cyanide
zinc electroplating baths has prompted the development of chloride zinc
baths. Mirror bright deposits are readily attainable. The chloride bath
offers several advantages. Higher efficiencies, thereby liberating less
hydrogen at the cathode, enables the chloride bath to deposit more metal in
a shorter period resulting in greater production output. Energy savings
are realized by lower bath operating voltages. No chelating agents or
ammonium ions are present, as in some chloride zinc baths, which could
interfere with subsequent waste treatment of other metals in the effluent.
Zinc readily plates onto carbonitrided steel, cast and malleable iron out
of the chloride zinc bath, which previously required either a cadmium
cyanide strike or plated entirely with cadmium. Zinc in this case re-
places cadmium, which is more toxic and expensive.
289
-------
The Advantages of Chloride Zinc Plating
by
Edward R. Jorczyk
The 3M Company
St. Paul, Minnesota
If there is a voluntary or mandatory reduction in the
use of electroplated cadmium because of its toxicity, then
there should be suitable alternatives.
One of the obvious
substitutes is zinc, which is considerably less toxic, less
expensive, and readily available.
The situations in which
zinc may be substituted for cadmium will have to be determined
by design engineers and related laboratory evaluations.
Until the last ten years, bright electrodeposited zinc
has been primarily plated from cyanide type baths.
One can
choose from several cyanide zincl bath formulations depending
upon the application.
A typical 33.7 g/l zinc bath is given
in Table 1.
Pollution problems and the high cost of waste treatment
of cyanide zinc electroplating baths has prompted the development
of alkaline2, neutral chloride3, ammonium chloride4, and the
potassium chlorideS zinc baths.
Other types of baths have
found only limited acceptance because of poor deposit
characteristics, cost, and control problems.
Zinc Substituted For Cadmium
One of the outstanding features of the chloride type baths
are their capability of not only plating onto substrates normally
plated with cyanide zinc or cadmium, but also onto such substrates
as cast iron, malleable iron or carbo-nitrided steel.
290
-------
These substrates cannot
be directly plated with zinc from
a cyanide bath.
In order to plate zinc from a cyanide bath
onto cast iron, malleable iron, or carbo-nitrided steel, the
part is first given a thin strike coating of cadmium and then
zinc plated to the required thickness.
This results in a part
with a composite coating of cadmium and
zlnc.
The other choice
is to plate the part with cadmium to the specified thickness.
Probably at one time or another cadmium has been substituted
for zinc on difficult to plate substrates, since visually one
looks the same as the other.
Since most platers don't know the
end use of the parts being plated, the substitution of cadmium
for zinc could result in serious complications.
Also,
the use
of a cadmium strike prior to zinc plate usually results in the
cyanide zinc bath becoming contaminated with cadmium which
codeposits with zinc resulting in dull as well as contaminated
deposits.
Types of Chloride Baths
The neutral chloride bath was introduced in 19676 and it
had two shortcomings.
First it was expensive to operate, and
secondly, it contained chelating agents which presented problems
when they were mixed with waste effluents containing other metal
ions.
The chelated metals cannot be removed from effluents by
conventional means.
The ammonium chloride bath which followed appeared to solve
the cost and chelate problem.
However, it was quickly found
that the ammonium ion from the zinc bath would complex metal
ions, such as copper or nickel, if they were present in the
effluent, making their removal difficult.
291
-------
Many countries have restrictions on the amount of ammonium
in the effluent that can be discharged into the environment.
There are indications that tighter restrictions may be
imposed in the future.
The ammonium ion increases the nutrient
level in aquatic environments and depletes the oxygen supply.
In spite of these problems, the ammonium chloride zinc bath has
found wide acceptance.
The need of a non-cyanide, non-ammoniated and non-che1ated
zinc plating process which produces bright leveled deposits led
to the development of the potassium chloride bath.
It has all
the advantages with none of the disadvantages.
Advantages
The advantages of the potassium chloride zinc plating
process are:
1. Simplified and low cost waste treatment since ammonium
ions, che1ates, and cyanide are not present in the bath.
2. High efficiency (95-98%) which can result in energy
savings up to 60% with an increase in productivity up to 30%
when compared to alkaline processes.
3. Ductile, bright deposits whose appearance resembles
bright chromium.
4. Ease of bath control and maintenance.
5. Deposit less susceptible to staining.
6. Difficult to plate substrates readily plated.
7. Deposit readily chromated to impart additional corrosion
protection.
292
-------
composition And Operating Conditions
A typical composition of the potassium chloride bath is
given in Table II.
The operation conditions for this bath are shown in
Table III.
Process Cycle
Parts to be plated in the chloride
zlnc
bath generally
require better cleaning than is required when plating in a zinc
or cadmium cyanide bath.
The cyanide baths actually have some
cleaning ability to remove organic contaminants such as oil, but
this is a poor practice since a plating bath is short lived if
contaminated with oil and grease.
Pickling must also be adequate
because zinc plated from the chloride bath tends to plate over
scale.
These areas could ultimately blister.
A typical process cycle suitable for plating most ferrous
substrates is as follows:
1. Soak clean
2. Anodic electroclean
3. Water rinse
4. Hydrochloric acid pickle, 50% by volume
5. Water rinse
6. Chloride zinc plate
7. Water rinse
8. Chromate dip
9. Water rinse
10. Dry
293
-------
Two or more rinse tanks may be used between each
process tank, and cascading rinse tanks are commonly used to
conserve water.
Adequate rinsing of parts is very important
so that the solution from one process tank is not carried to
the next causing contamination.
Cleaner dragged into the acid
will shorten its life as well as contaminate it with oil or
grease.
Hydrochloric acid dragged into the plating bath will
lncrease the chloride level to a point where deposits become
streaked and pitted and the solution becomes cloudy due to
organic "kickout".
Iron Problem
A common problem to chloride zinc baths is that iron
increases in the bath and soon reaches a point (250 to 350 ppm)
where it acts as a contaminant.
The deposit becomes dark and
brittle.
Iron is introduced from parts being plated, parts
that falloff racks and are on the bottom of the tank, drag over
of used acid pickle, anodes and replenishment chemicals.
The iron can be kept under control so that it never reaches
a point where it is detrimental to the deposit.
Iron parts, chips,
and burrs that fall to the bottom of the tank should be removed
with a magnet on a daily basis; otherwise, they will corrode
and contaminate the bath with iron.
Daily additions of hydrogen
peroxide are made to the bath to precipitate the dissolved iron
as ferric hydroxide which is removed by filtration.
The hydrogen
peroxide (30%) is added each day at a rate of 10 ml of hydrogen
peroxide for each 100 liters (1.2 fl.oz. per 100 gallons) of
plating solution.
294
-------
The hydrogen peroxide should be diluted with 4 parts water
prior to adding.
A properly maintained bath should have iron
levels below 75 ppm.
Equipment
Equipment for the ammonium or potassium chloride zinc bath
differs from the zinc or cadmium cyanide bath in that corrosion
resistant equipment is required.
Since a monetary expenditure is required to purchase new
equipment or to convert existing equipment, there is reluctance
to change.
However, when the plater is faced with capital
expenditures to install cyanide waste treatment facilities and
the continued expense for chemicals required to treat the cyanide,
then costs to change to the chloride system become more attractive.
The cost of converting from a cyanide bath, which consists
of two 600 gallon plating tanks having eight stations with 18 by
36 inch barrels
7
has been estimated at $7,895.00.
Tanks - Suitable materials to contact the solution
are PVC, polypropylene, polyethylene, and
some grades of rubber and fiberglass reinforced
plastics.
Filter - Acid resistant components and no metal contact
with the solution.
Turn solution volume over once or twice per hour.
Capable of removing particles 15 micron size and
larger.
295
-------
Heating and Cooling - Materials of construction
may be Teflon* tubes, Teflon coated
copper tubing, Titanium coils that are
electrically isolated or graphite heat
exchangers.
Bus bars - Copper wrapped with vinyl tape or enclosed
1n PVC tube with contact points exposed for
anode or rack contact.
Anodes - Zinc balls or slab meeting ASTM B6-67 "Special
High Grade"
(zinc - 99.990%).
Racks - Conventional racks coated with insulating
coating and stainless steel tips.
Power source - Rack Plating:
6 volts, 5% Max., ripple
Barrel Plating: 12 volts, 5% Max., ripple
Waste Treatment
Effluent from chloride zinc rinse tanks containing 200 ppm
zlnc
can be reduced to at least 0.02 ppm by treating with sodium
hydroxide or hydrated lime to raise the pH of the effluent to a
range of 9.0 to 9.5.
At this pH, the zinc precipitates as a
hydroxide and can be removed by filtration, settling, or
decantation.
Current cost to treat one pound of zinc chloride is less
than $0.15, as compared to $1.10 to $1.50 to treat one pound of
zinc cyanide.
Cost depends on zinc concentration in the effluent
and method of treatment.
*Teflon is a registered trademark of DuPont de Nemours Co.,
Wilmington, Delaware.
296
-------
M. ROdenkirchen8 reported that the maximum
zinc
metal concentration found in production plating rinse tanks
is generally 200 mg/l; 400 mg/l indicated faulty rinsing
practice.
Summary
The potassium chloride bath produces bright ductile
z~nc
deposits economically.
It represents a new generation of
plating solutions that have minimum impact on the environment
because of pollution problems.
Energy savings are realized
by lower bath operating voltages.
Chloride zinc plates readily
onto surfaces that formerly required a cyanide cadmium strike
prior to cyanide zinc plating or that had to be plated entirely
with cadmium.
297
-------
References
1. E. Leroy Gabel, Plating, 50 (12) 1089 (1963)
2. J. H. Hajdu and J. S. Zehnder, Plating, 58 (5) 458 (1971)
3. "KENBRITE", Product of 3M Co., Pat. No. 3,730,855.
4. "KENLEVEL I", Product of 3M co., Pat No. 3,729,394
5. "KENLEVEL II", Product of 3M Co., Patent Pending
6. K. P. Bellinger, Plating, 56 (10) 1135 (1969)
7. Anon., Product Finishing, 41 (11) 70 (1977)
8. M. Rodenkirchen, Plating, 60 (7) 698 (1973
298
-------
TABLE I
Typical 33.7 g/l Zinc Bath Composition
Zn (CN)2
60.0 g/l
42.0 g/l
NaCN
NaOH
78.0 g/l
Brightener Additive
Required
299
-------
TABLE II
Composition of Potassium Chloride Bath*
Rack
Preferred Ran~
Barrel
Secondary Additive
30-34 g/l 18.8-22.5 g/l
128-143 g/l 121-128 g/l
26 - 30 g/l 25 - 28 g/l
30 ml/l 30 ml/l
1. 25 ml/l 1.25 ml/l
5.0 - 5.5 5.0 - 5.5
Zinc (as metal)
Chloride (as chloride)
Boric Acid
Primary Additive
pH, electrometric
*KENLEVEL II, Product of 3M Company, Patent Pending.
300
-------
TABLE III
Operating Conditions
pH (electrometric)
Temperature
Agitation
Filtration
Voltage
Cathode Current Density
Anode Current Density
301
4.7 - 5.5
21° to 32° C.
Cathode rod: 1 to 2 meters
per minute or gentle air for
rack plating only.
Continuous:
1 to 2 turnovers
per hour
Rack: 1 to 3 volts
Barrel: 4 to 12 volts
0.1 to 5
A/dm2
Not to exceed 2.5 A/dm2
-------
The Advantages of Chloride Zinc Plating
by
Edward R. Jo~czyk
The 3M Company
St. Paul, Minnesota
Typical 33.7 g/l Zinc Bath Composition
Zn {CN)2
60.0 g/l
42.0 g/l
NaCN
NaOH
78.0 g/l
Brightener Additive Required
Types of Bright Non Cyanide Zinc Baths
Alkaline
Neutral Chloride (chelated)
Ammonium chloride
Potassium chloride
Difficult to Plate Substrates
Cast Iron
Malleable Iron
Carbo-nitrided steel
Shortcomings of Chloride Baths
Neutral Chloride:
Expensive to operate
Contains chelating agents
Ammonium Chloride:
Ammonium complexed
Nickel and Copper in
Effluent
302
-------
Potassium Chloride Bath
No Cyanide
No Chelating Agents
No Ammonium
Advantages of Potassium Chloride Bath
1. Simplified and low cost waste treatment
2. High efficiency (95-98%)
Energy savings up to 60%
Productivity increase up to 30%
(Comparing to zinc cyanide bath)
3. Ductile bright deposits
4. Bath easy to control
5. Deposit resistant to staining
6. Difficult to plate substrates
readily plated
7. Deposit readily chromated
8. Bath easy to control and maintain
Composition of Potassium Chloride Bath*
Rack
Preferred Range
Barrel
Zinc (as metal)
Chloride (as chloride)
Boric Acid
Primary Additive
Secondary Additive
pH, electrometric
30-34 g/l
128-143 g/l
26-30 g/l
30 mIll
1. 25 mIll
5.0-5.5
18.8-22.5 g/l
121-128 g/l
25-28 g/l
30 mIll
1. 25 mIll
5.0-5.5
* KENLEVEL II, Product of 3M Company, Patent Pending.
303
-------
OPERATING CONDITIONS
pH (electrometric)
Temperature
Agitation
4.7 - 5.5
21° to 32° C.
Cathode rod: 1 to 2 meters
per minute or gentle air for
rack plating only.
Filtration
Continuous: 1 to 2 turnovers
per hour
Voltage
Rack: 1 to 3 volts
Barrel: 4 to 12 volts
Cathode Current Density
0.1 to 5 A/dm2
Not to exceed 2.5 A/dm2
Anode Current Density
Typical Process Cycle
1. Soak clean
2. Anodic electroclean
3. Water rinse
4. Hydrochloric acid pickle,
50% by volume
5. Water rinse
6. Chloride zinc plate
7. Water rinse
8. Chromate dip
9. Water rinse
10. Dry
Iron Contamination
Detrimental to Zinc Deposit
Source: Ferrous Alloy Parts,
Burrs and Chips
Anodes and Chemicals Used
Carryover from Acid Pickle
304
-------
Iron Removal
Oxidize Soluble Iron (Ferrous) to
Insoluble (Ferric) Form and Remove
by Filtration.
How:
Add 10 ml Hydrogen Peroxide
(30%) per 100 liters of Plating
Solution on a Daily Basis.
Equipment
Acid Resistant Equipment is Required,
which means Capital Expenditures to
Modify Existing Equipment or Purchase
New Equipment.
Waste Treatment
Treat effluent with sodium hydroxide
or hydrated lime to pH 9.5.
Remove precipitated zinc hydroxide.
Clear filtrate should contain less than
0.02 ppm zinc.
Summary
Potassium chloride zinc bath has minimal
impact on the environment.
Energy saving realized by lower bath
operating voltages.
Replaces cadmium on difficult to plate
substrates.
305
-------
The Advantages of Chloride Zinc Plating
MR. BAYNE: Mike Bayne, Battelle-Northwest. What is the source
of your information on that low concentration you find in the effluent?
MR. JORCZYK: That was from laboratory evaluation. Of course,
that will vary with industry. because a lot depends upon what else is
in the effluent.
MR. COLE: Frank Cole, Republic Steel.
the potassium chloride? Conductivity?
What is the function of
MR. JORCZYK: It will improve conductivity, of course, and it does
add to the grain requirement and overall brightness of the deposit.
MR. COLE:
How do you prevent sludging and zinc oxychloride?
MR. JORCZYK:
I didn't see any sludging.
SPEAKER: Could you use sodium chloride, or is there a specific
reason for potassium chloride?
MR. JORCZYK: It doesn't work as well as the potassium salt,
and it is not as conductive.
306
-------
Alternative Materials and Processes
Session III
Wednesday Morning 12:10
MANGANESE PRESSURE PHOSPHATE COATINGS
AS A SUBSTITUTE FOR CADMIUM COATINGS
Henry Crain
Engineering Directorate
Rock Island Arsenal
Department of the Army
Rock Island, Illinois 61201
Rock island arsenal has developed and tested a superior manganese phos-
phate coating produced under a positive pressure of steam. The pressure phos-
phate coating has demonstrated salt spray corrosion resistance in excess of
500 hours compared with conventional phosphate coatings having two to four
hours salt spray resistance. Pressure phosphate coatings have also exhibit-
ed heat resistance to 450.F while still maintaining excellent corrosion re-
sistance. As opposed to the conventional open tank phosphating process, the
pressure phosphating process takes place in a closed vessel where the solution
and parts are brought to a gage pressure of 1 psi and a temperature of 21S.F.
With their excellent corrosion protection, pressure phosphate coatings can
replace certain metallic coatings, e.g., zinc and cadmium which are not only
expensive but present environmental problems. The replacement of conventional
cadmium coating on ammunition shim stock by pressure phosphate coatings has
been presented as one feasible application of this new process.
307
-------
MANGANESE PRESSURE PHOSPHATE COATINGS
AS A SUBSTITUTE FOR CAIMIUM COATINGS
Henry Crain
Engineering Directorate
Rod: Island Arsenal
Department of the Arrrr:f
Rock Island, Illinois 61201
The development of a new and improved manganese phosphating
process at Rock Island ~'senal presents a possible alternative coating
for cadmium plate.
This improved manganese phosphate coating has
displayed corrosion resistance of several hundred hours salt spr~.
resistance, a dramatic hundred-fold increase over the salt spr~
resistance of conventional manganese phosphate coatings.
The coating
is produced with steam pressures of approximately 1 psi gage to reach
bath temperatures exceeding 212QF.
Additionally, large quantities of
manganese are present in the bath to yield the superior coating.
Pressure phosphate coatings have also exhibited heat resistance to
450'F while still maintaining their excellent corrosion resistance.
The applicability of this new coating process lies in the corrosion
resistance which is comparable to cadmium plate.
With cadmium being
being scrutinized for detrimental effects on the enviro~~nt, the
improved manganese coatings do offer a-possible alternative to cadmium
plating.
However, applications of this new coating would have to be
examined individuallJ- and alirect comparison made between the improved
manganese phosphate coating and cadmium. plate for any particular
application.
308
-------
The paper that follows discusses some of the research and devel-
opment that Y1as undertaken to de,'elop the process:
INTRODUCTION
Manganese phosphate coatings have been applied to ferrous articles for
more than sixty years.
The coatings are easy to apply and offer an excellent
base for supplementary oil or paint treatment.
Specification MIL-P-16232
requires these coatings, without any supplemental treatment, to withstand a
5% salt spray test for one and one half hours.
The conventional manganese phosphate bath contains manganese dihydrogen
phosphate L-Mn(H2P04)2J, ferrous iron (Fe -++), and phosphoric acid (H3P04).
The processing temperature range is usually 205°F-210°F.
In the process,
the basis metal is pickled by the acid at firs~and the insoluble manganese
phosphate is then precipitated on the metal as a coating.
In recent years, a new and improved manganese phosphate coating has
been produced in this laboratory.
This new coating is formed by the addition
of either manganese tartrate, manganese gluconate, or manganese citrate to
the conventional manganese phosphating bath and by processing a t temperatures
in excess of 212 of under steam pressure.
The coating is capable of resisting
corrosion for several hundred hours in a 5% salt spray test and displays
309
-------
even gl~ater corrosion resistance after being heated to 450°F for one hour.
Several problems have arisen, however, in attempting to control the
continuous production of the superior coatings.
In order to solve these pl'O-
blems, this effort was initj.a.ted to obtain a better understanding of the under-
lying phenomena and reaction mechanisms of the modified manganese phosphating
process.
A previous report* in this same effort has recorded that the primary
function of the manganese-organic compounds appears to be in enriching the
bath with manganese.
The present report details the investigation of the
specific concentrations of nanganese needed to obtain superior coatings.
Since the solubility of manganese compounds are in part determiiledby the
free acid content of the phosphating bath, a study has also been conducted to
determine the effect of free acid on baths with high manganese content.
PROCEDURE
An experiment was designed to measure the effect of manganese bath con-
cent rat ion on corrosion protection.
The experiment was approached using
two different methods to vary the manganese concentration.
One method used a new phosphating solution for each of seven experi-
)Ilental baths.
Each bath contained six liters of deionized water, ten milli-
liters of 85% phosphoric acid, and one of the following amounts of Mn(H2P04)2:'
30, 60, 90, 120, 150, 180, and 240 grams.
free acid value of the bath to 2.5 points.
The phosphoric acid corrected the
*Crain, H., "Improved Manganese Phosphate Coatings" GEN Thomas J. Rodman
Laboratory Technical Report R-RR-T-6-49-73, July 1973.
310
-------
The other method used the same six liter bath for all processing runs.
Initially the bath contained six liters of deionized water, ten milliliters
of 85% phosphoric acid, and 30 grams of Mn(H2P04)2. For each succeeding ron,
60 grams of additional Mn(H2P04)2 was added before lJrocessing. Manganese
carbonate or phosphoric acid were added after each processing period to
readjust the free acid value to 2.5 points.
Another experiment was designed to determine the effect of free acid
values on corrosion resistance.
A series of baths was used for this experi-
ment, each containing six liters of deionized water, 270 grams of Mn(H2P04)2,
and one of the following amounts of. 85% H3PO 4 :
o~ 5, 10, 20, and 30 milliliters.
The specimen panels measuring 2" x 3" X 1;16" were of SAE 1020 steel.
Panels were weighed to the nearest milligram before and after processing.
Coatings were stripped in chromic acid and the panels were weighed again.
These weights yielded the amount of iron etched and coating weights.
All
processing was done in a pressurized vessel for 30 minutes at 2l3°F.
The
gage pressure was always maintained at less than one pound per square inch.
Samples of solution were taken from the bath before and after processing.
Titrations with 0.1N NaOH were used to determine free and total acid values.
Atomic absorption analyses were used to obtain the manganese content.
RESULTS
Table I summarizes the parameters obtained when a series of baths,
varying only in Mn(H2P04)2 content, were used to study the effect of manga-
nese concentration on corrosion resistance.
The best coatings were obtained
with the largest additions of Mn:(~P04)2.
311
The coatings obtained with 30. ani
-------
TABLE I
Experimental Parameters For Individual Baths With Fixed Amount of Mn(H2P04)2 Added
Total Acid Coating Weight Salt Spray Iron Etched Manganese
Bath Mn( H~P04)2 in points* in milligrams Corrosion in grams Concen tration
J ad ed NaOH per square foot Resistance pe r panel In%
1 30 grams 9.6 2,580 1 hour 0.488 0.070
2 60 grams 14.8 1,300 1 hour 0.126
) 90 grams 18.2 1,480 2 hours 0.120 0.178
w 4 120 grams 22.8 2,470 2 hours 0.106 0.226
f--I
N
5 150 grams 27.6 4,940 8 hours 0.088 0.275
6 180 grams 31.4 7,260 56 hours 0.078 0.300
7 240 grams 40.2 8,340 31 days 0.070 0.)82
* One point equals one milliliter of O.lN NaOH per 10 milliliters of sample.
-------
60 grams of Mn(H2P04)2 were inferior, failing the 5% salt spray test in
less than one hour.
Coatings produced in baths having 90, 120, and 150
grams of Mn(H2P04)2 appeared similar to conventional manganese phosphate
coatings.
Figure 1 shows manganese content in weight percent versus salt spray
resistance in hours.
An inflection point is not ed in the curve at approxi-
mately 0.27% manganese.
Above this concentration, the coatings display
superior corrosion resis.tance.
Figure 2 shows coating weight versus salt spray resistance.
The curve
is similar to the one in Figure 1 and yields an inflection point at approxi-
mately 0.50 grams coating weight.
/iliove this point, the coating provides
superior corrosion resistance..
The data and plots obtained from the continuous bath experiment, in
which increments of Mn(H2P04)2 were added after every processing run, are
similar to the experiment just discussed.
An example of this similarity
is shown in Figure 3.
1~ this plot, the salt spray resistance versus man-
ganese content curve displays an inflection point at approximately 0.30%
manganese.
Table 11 summarizes the data obtained in the free acid experiment in
which varying amounts of 85% H3P04 were added to the phosphating baths.
The poorest coatings were produced with 30 milliliters of H3P04' while the
best coatings were produced with 5 and 10 milliliters of H3P04. In Table
II, note that the difference between the initial and final manganese bath
concentrations decreased as the amount of phosphoric acid w8sincreased.
313
-------
0.35
0.30
I-
:I:
(.!'
-
I.LI
31:
I-
z:
I.LI
L>
ex: 0.25
I.LI
0.
0.20
z:
-
FIGURE 1
z:
o
-
w l-
f-' ct:
.j:-. cr
I- 0.15
z:
I.LI
L>
z:
o
L>
I.LI
V')
I.LI
z:
ct:
(.!'
z:
<:
r
SALT SPRAY RESISTANCE VERSUS
MANGANESE BATH CONCENTRATION
0.10
0.05
10
20
30 40 50 60
SALT SPRAY RESISTANCE IN HOURS
POINT FOR 0.38%
OCCURS AT 434 HOURS
70
80
-------
7000
b
a
c...
~ 6000
t3
a
(J)
~ FIGURE 2
~
Po.
~ 5000 SALT SPRAY RESISTANCE VERSUS
COATING WEIGHT FOR INDIVIDUAL
\:..." BATH EXPERIMENT
H
H
H
VJ~
1-'
\J1Z
H
E--< 4000
(5
H
~
d
~
E--<
< 3000
a
u
2000
1000
10
20
50
60
30
40
SALT SPRAY RESISTA~E IN HOURS
70
80
90
-------
~
Z
H
Z
o
H
E--o
~
~
riI
~
o
,-,>U
1-'riI
"'~
<
(OJ
~
0.35
0.30
0.25
0.20
0.15
0.10
0.05
FIClJRE :3
S~LT SPRAY RESISTANCE VERSUS MANGANESE
COtl:ENTRATION FOR CONTINUOUS BATH EXPERIMENT
10
20
30
40
50
60
70
80
90
SALT SPRAY RESISTANCE IN HOURS
-------
TABLE II
Experimental Parameters For Free Acid Study.
Manganese Manganese
Amount of. Coating weight Salt spray content in % content in % Difference be-
Bath HJPO~ in milligrams Free acid co rros ion (before (after tween initial
# a de per square foot in points* resistance process~) process~) and final %
1 0 rol. 6,190 1.0 30 hours 0.47% 0.35% 0.12%
2 5 ml. 7,730 2.2 100 hours 0.45% 0.36% 0.09%
3 10 rol. 7,510 3.6 100 hours 0.46% 0.38% 0.08%
w 4 20 ml. 8,570 4.6 36 hours 0.47% 0.42% 0.05%
f-'
.......
5 30 ml. 4,270 6.5 4 hours 0.47% 0.45% 0.02%
* One point equal one milliliter of O.lN NaOH per 10 milliliters of sample.
-------
A plot of this difference is illustrated in Figure 4.
DISCUSSION
The experimental data, derived from studies of varying the manganese
bath concentration, clearly show the great importance of manganese content
in producing superior coatings.
The critical points in the plots of manga-
nese concentration versus salt spray resistance indicate the value at which
the coatings become better than conventional coatings.
Coatings having
several hundred hours of salt spray resistance can be produced with baths
having manganese concentrations slightly higher than the critical values.
In the experiments mentioned in this report, phosphating baths have
been enriched with manganese by adding additional Mn(H2P04)2'
In previous
testing, Wagner* of this laboratory has accomplished the manganese enrich:'"
ment by adding manganese organic compounds such as manganese tartrate,
gluconate, and citrate.
He added 10 grams per liter of these compounds
He thus succeeded in exceeding the critical manga-
to a conventional bath.
nese value and produced superior coatings.
The main function of these
compounds can be stated as manganese enrichment.
Any manganese compound
can be used for this purpose as lopg as the anionic part of the compound
is not detrimental to the bath.
The increase in manganese bath content is linked to heavier coatings.
Larger amounts of manganese result in larger amounts of Mn3(P04)2 being
formed and deposited as heavy crystalline coatings. The heavier coatings
*Wagner, L. H., unpublished technical report, GEN Thomas J. Rodman Laboratory.
318
-------
FIGURE 4
30
PLOT SHOWING TIlE DIFFERENCE BE'IWEEN
INITIAL AND FINAL MANGANESE CONTENT
FOR VARIOUS BATffi
25
o...:t
Il..
C""\
:r::
~ 20
o
K!
r3
~
H
:j
H 15
~
W
I-'
,\0
10
5
0.02%
0.04%
0.06%
O. 08%
0.10%
0.12%
0.14%
DIFFERENCE BETWEEN INITIAL AND FINAL Mn%
-------
result in less free pore area.
Consequently, the coatings withstand cor-
resion better.
Manganese solubility is determined to an extent by the acid condition
of the bath.
The experiment which used various free acid values demonstra-
tes that high free acid values result in less manganese being precipitated
from solution.
Thus, less Mn3(P04)2 is fonned, and thin coatings appear.
The best coatings are obtained with free acid values between 2.0 and 4.0.
320
-------
Manganese Pressure Phosphate Coatings as a Substitute
for Cadmium Coatings
MR. TUTTLE: Jim Tuttle, Rust Proofing and Metal Finishing
Corporation. In the specification you mentioned, MIL-P-16-232, you
were working with Type M, Class 1, which has one and a half hour salt
spray requirement. Under that same spec, Type M, Class 4 is a treatment
with an inorganic salt and the salt spray resistance is elevated to 24
hours. Have you tried treating this new phosphate with the inorganic
salt?
MR. CRAIN:
No, we haven It.
MR. TUTTLE:
I think that would be very interesting and worthwhile.
MR. CRAIN: Right. As a matter of fact, there are several areas
that we still can investigate. As I mentioned, this improved corrosion
resistance up to several thousand hours is without any supplemental
treatment at all. That does not include the chromate post-treatments.
It might extend up to 5,000 or 10,000 hours, but we have not looked at
that yet.
MR. TUTTLE: Treatment with this Class 4 inorganic salt improves
the heat resistance of the manganese phosphate a great deal so that it
will pass the requirements after being heated to 500 degrees fahrenheit.
This is not reflected in the spec.
MR. LAURILLIARD: John Laurilliard, Standard Pressed Steel. With
your high coating weights, 8,000 milligrams per square foot, what kind
of coating thickness do you get? What kind of build-up?
MR. CRAIN: Conventional manganese phosphate coatings usually have
two to six ten-thousandths of an inch coating thickness. This improved
phosphating process will give coatings approximately five times this, so
we are talking about one-thousandth of an inch.
MR. LAURILLIARD: During the processing, building up the heavy
coatings, is there any consumption or etching of the base metal?
MR. CRAIN: In one slide I have the amount of iron that was being
etched. The low coating weights that are comparable to conventional
manganese phosphating have more iron being etched, on the order of four
or five times more. With the heavy coating weights, we would have very
little iron being etched.
MR. LAURILLIARD: This could be detrimental to high strength fatigue'
rated materials; increased etching can reduce fatigue.
MR. CRAIN:
Well, we have reduced etching for the new process.
321
-------
MR. IAURILLIARD: How about hydrogen embr it t lement ?
coating weights cause more hydrogen embrittlement?
Do higher
MR. CRAIN: We have not run tests, and in
looked at, the new coating seems to have the
conventional manganese phosphate.
everything that we have
same properties of the
I would
There is a
to be used
expect the hydrogen embrittlement problem to be
baking treatment described by MIL P-l6-332 that
with this coating.
the same.
would have
MR. LAURILLIARD: On one of your last slides, your last data point
at 7,000 milligrams per square foot showed 60 or 70 hours.
MR. CRAIN: The last point on the graph could not be presented on
this slide. As I mentioned, it would be far out on the curve. The
7,000 milligrams per square foot was something like 56 hours.
MR. LAURILLIARD: Do you have any corrosion data on production pieces,
or only on test panels?
MR. CRAIN: We have only tested two by three inch panels of low
carbon 1020 steel. Recently we have been processing some fasteners, but
we don't have the results on these yet.
MR. IAURILLIARD:
Were these tumbled?
MR. CRAIN: No, they weren't tumbled. They were suspended.
system that the Army is going to try to set up, they are going
tumbling.
In a
to use
MR. LAURILLIARD: Do you get the same type of results on grit-blasted
parts as you do on those that aren't? The latest revision on the spec
doesn't make it mandatory that parts be grit-blasted.
MR. CRAIN: It has always been my experience that grit-blasting is
quite essential to the quality of the phosphate coating. I have noticed
when grit-blasting was not performed that the coatings were of a poor
quality.
The quality of this improved phosphate coating will be reduced if the
specimen is not properly grit-blasted.
MR. LAURILLIARD: Don't you think that there are more parts being
phosphated that are not grit-blasted?
MR. CRAIN: In our shop, we have a series of grit-blasting machines
varying the size of the grit. We get the best results when parts are
grit-blasted with number 80 grit. As a finer finish is required and
finer grit is used in the blast, the quality of the phosphate coating
seems to decrease.
322
-------
MR. LAURILLIARD:
like aluminum oxide?
Do you find any difference with the non-steel grit
MR. CRAIN: The steel grit is better than aluminum oxide. It imbeds
steel particles into the piece being plated that promote the deposition
of the manganese phosphate so that you get a better coating. The aluminum
oxide, of course, will not do this. The iron forms the bonding between
the coating and the specimen. If there is more aluminum oxide, you are
not going to obtain that bond or the same quality of the coating.
MR. BLESS: Mike Bless, Naval Air Engineering Center, Lakehurst.
you intend to produce a specification to cover the new process?
Do
MR. CRAIN: I don't know what plans are
I am not going to be involved. The people
currently in charge of this project, but I
would definitely have to be written.
being made for that. I know
at Picatinni Arsenal are
suppose a specification
MR. BLESS: Since we are not a manufacturer, the only access we could
have to it is by calling out a specification of some sort.
323
-------
Alternative Materials and Processes
Session IV
Wednesday Afternoon 1:45
EFFECTS OF CADMIUM ON FISH AND WILDLIFE
Calvin M. Menzie
Division of Habitat Preservation Research
Fish and Wildlife Service
Department of the Interior
Washington, D.C. 20240
Cadmium, produced as a metal refining by-product, passes into the
aquatic environment in effluents from pesticides and metal industries -
extraction, refining, machinint, electroplating and welding. Studies
have shown that this material can then be accumulated by some aquatic
organisms to a significantly higher level than occurs in the aquatic
environment. Analyses have also shown that levels of cadmium in muscle
of finfish is lower in deep-water fish then in fish taken in coastal
waters.
Bioassays have been used to determine acute toxicity of cadmium
compounds to various marine species. Exposure of successive generations
of brook trout to cadmium has shown that low concentrations can adversely
affect growth and reproduction.
Studies with Small mammals such as rabbits indicated that cadmium
exhibits a variety of physiological effects that include enlarged splepn
and heart and fatty degeneration of liver and kidneys as well as some
hematological effects.
325
-------
Effects at ~aumium in tne ~nvironment
~alvin M. Menzie
Fish ana wi lal ife
uepbrtment of the
~iasn i n::iton, u.~.
::>ervice
Interior
LUL4u
~aumium is an uoiyuiTOUS chemical tTauias 1-0) in a~uatic and
terrestrial ecosystems tAnderson et al., 1~74, DlaylocK eT 01.,
I~h; dondietti et 01.,1::17.:»).
A I tnou~i) some mar i ne sfJec i es flave
the abi I ity to concentrate caumium aoove very low levels, tnere
aoes not apfJear to De eviuence ot caamiurn concentraTion in marine
tood cnains.
Tne ~oTentjal, nowever, aoes exist. ~aamium concentrations
appear to De tli~ne~t in snorel ine sections of contaminatea areas.
ueep sea seu i rnents of tn6 I~orth At I ant i c avera~ea on I y about u. L. ripm
tAston eT a I., I Si7.d.
In Tne IViississit-ipi-l>iissouri I-
-------
TABLE I.
Samples collected in vicinity of a deep water dump site
in the Middle Atlantic Bight*.
Muscle
(ppm, wet wt)
Liver Whole Animal
Gi lis
Antimora rostrata <0.12 0.33
Nematonuras armatus O. II 1.27
Halosauropsis macrochir <0.12
Synaphobranchus kaupi 0.12
Geryon quinquedens <0. 10 0.81
Seriola sp. <0. 10 0.24
Hygophum sp. 0.09
Stephanolepsis hispidus 0.13
*Sediments also taken from deep water dumpsite in New York Bight--
analyses of 9 samples each taken on a different date or at a different
location.
Cd =
I .25 ppm (dry wt) for a 1 I nine (Gre i 9 et a I ., 1976).
327
-------
TABLE 2. Concentration of cadmium in fish tissues (ppm wet wt)
(Northumberland Coast of England)
Tissue
Axial Stomach
Species Gi II Skeleton Skin Wall Liver Fat I(idney Muscle Gonad
Lumpsucker 1.7 0.6 1.08 0.82 1.83 0.12
Sprat 0.8 0.24
Coal Fish 3.2 1.3 3. I 2. I 4.2 0.64
Plaice 0.8 1.3 3.9 2.9 1.4
w
N Young Cod 1.2 1.3 3.5 0.6 1.7 I .3
00
Viviparous
Blenny 0.8 1.9 I .0 0.4 0.3 I .6
Dab 0.47 0.26 0.36 1.38 0.2 0.18 0.09
Cod
0.25
0.4
0.1
0.06
0.17
0.99
0.1
0.09
(Wright, 1976)
-------
TABLE 3.
Cadmium in dressed Canadian fish (ppm wet wt)
Source Concn.
Moose L. 0.05
L. Ontario 0.05
Moose L. 0.05
L. St. Pierre 0.05
L. Erie 0.05
L. Erie 0.06
L. Erie 0.05
CUthe and 81 i gh, 1971)
Species
Lake white fish (Coregonus clupeaformis)
Northern pike (Esox lucius)
Rainbow smelt (Osmerus mordax)
Yel low perch (Perea flavescens)
TABLE 4.
Cadmium in Great Lakes fish (ppm wet wt)
Species
Liver
Herring
Bloater
Whitefish
Round whitefish
Lake trout
Smelt
Goldfish
Wh i te bass
Yellow perch
Wall eye
1.6
0.09 & 0.3
0.4 & 0.7
0.4
0.07&::3
0.07
1.4
0.2
0.54
0.2
Grand Average
0.4
(Lucas et a I ., 1970)
329
-------
TABLE 5.
Cadmium in organisms from the Irish Sea (ppm dry wt)
Coelenterates
Teal ia fel ina
Alcyonium digitatum
0.66
4. I
Echinoderms
3.7
Asteria rubens
Solaster papposus
Porania pulvi I Ius
Henricia sanguinolenta
5.3
4.5
9.4
3.5
(Ri ley and Segar, 1970)
TABLE 6.
Cadmium distribution in water from Florida Everglades
g/ I ! ter water
Source
South Florida Canal - Undeveloped Area
Developed Area
0.4
2.8
Everglade estuaries
Lostman's Bay
Chokoloskee Bay
1.4
4.2
Highest concentration cadmium in Barron River canal occurred in
the portion of canal adjacent to cultivated areas.
Chokoloskee Bay receives direct discharge from the canal.
Lostman's Bay has a natural drainage without an obvious artificial
source for heavy metals.
(Horvath et al., 1972)
330
-------
TABLE 7.
Cadmium in marine animals from Bristol Channel samples (ppm)
Species
Range
Fucus veslculosus
2 to 75
Pate I I a vulgata
Mytilus edu I Is
Nuce I I a I ap I II us
9 to 500
4 to 60
3 I to 725
Llttorlna Iittorea
8 to 75
(Nickless et al., 1972)
331
-------
TABLE 8.
Cadmium in marine organisms from Somerset
coast of England
Species
Cone. (ppm wet wt)
Range Av.
Limpet (Patella vulgata)
controls
10.3 to 118.5
0.9 to 13.9
6.4
Crab (Carcinus maenas)
14.3
to
33. I
22.4
(Cancer pagurus)
5.0
Lesser Blackbacked gul I eggs
0.06
Cod
(3 yrs old)
(2 yrs old)
0.03 to 0.06
16.3 to 39.0 24.0
2.2
0.26
0.12
0.07 to 0.59
0.68 to 1.67
0.08
0.46
0.06
0.47
0.09
O. 10
0.29
0.39
(Peden et al., 1973)
Herring gul I eggs
Dog whelk
(contra I )
Dogfish
Flounder
Grey Mu I let
Poll ack
Rock ling
Skate
Whiting
Thronback Ray
Shrimp - cooked
- raw
332
-------
that receivea caamium chloride for b to 7 montns by sUDcutaneous
injection (Piscator and Axelsson, 197u).
rlistolo~ical examination
snowed si~ns of damage to renal tubules ana blood tests revealed
hemolytic anemia ana plasma protein cnanges (Axelsson ana Piscator,
IY66a and OJ Axelsson et al., I~bo).
In other studies, tissues
of hypertensive raDDits haa si~nificantly hi8ner caamium levels
than was present in tissues from control animals.
Iii tn i n tne
hypertensive group, Kiuney ana liver containeo the greatest caomium
level, fol lowed by mesenteric artery, aorta and heart in that
order.
1.0 significant uifference in water content Detween hypertensive
ana normal tissues was observed (Fischer ana Tninu, IS!]I).
usin9
aortic strips frorn normal rabbits, it was observeo tnat caumium
producea a case-related but reversible innibition of epinepnrine,
norepinepnrine ana an8iotensin responses (rhino et al., I~/v).
In vitro stuaies indicateo that steroid biosyntneses ~ere alterea
--
in the :dray seal (I-Ial icnoerus 8rypusJ (Fr8emana ana ::Jan8alan::J, 1':177).
diras
Ivla II aro aucKs (Anas pi dtyrhyncnos) were feu amounts of caom i urn
varying from ap~roximdtely 2 ppm to LUU ppm.
At Lana LU p~m caomiurn,
no appreciable renal uama8e was oDSerVeOj at LVU pprn, after au ana
':JU oays of treatment, interstitial naphriti~, tubular u~~eneration,
ana tUDular necrosis was seen.
Kioney wei~ht~ also increaseu si~nif-
icantly.
At Lu ppm, tnere was inuuction of some alterations in
testes of biros.
~evere lesions were proouceu at LUU ppmj testes
333
-------
nad atro~hiea after ~v aays treatment and tt1e 5permat0genic ~rocess
ceasea (Wh i te et a I ., in foiress).
Ja~anese 4uai I (Coturnix coturnix) were fea aiets containing 7j
m8/K~ caumium for 4 weeKS.
In audition to severe anemia, low iron
ana hi8h caamium levels in I iver, some retardation of 8rowto also
occurreo.
Addition of ascorDic acia to the aiet decrease a tne toxic
effects of cadmium (Fox and Fry, IY7u).
when sparrows were fea l09Co-tagged seed, toe amount of Ladmium
assimi latea wa5 about op of tnat avai laDle and was not concentrated
above the fOOd source level.
Toe naif-life was relatively lon~
and b4~ of tne boay Duraen ~not incluoin9 tne gut) was founa in
tne Kianey and I iver (Fassett, 1~75).
Ay0ATI~ URbANI~~~
Fist!
Zebra fisn (dracnyoanio rerio) were fea fish fooo containin~ 10 ~pm
~aomium as cadmium acetate.
u~taKe plateaued at aDout Ij ~g/~ (ary
wt) in females after aDout 4 montns ana at about , ~~/~ (ory wt)
in males after about L.' montns.
The monthly total number of e8~S
produced Degan to decl ine after tne first month ~Renwolat and
Karimian-Tenerani, 1~76).
Livers from ki I I ifish ~Funaulus oeterocl itus) were used to assess toe
effects of caamium on five enzymes (Table 9) (JacKim et al., IY7u).
334
-------
T AdL I: 9.
Percentage enzyme inhibition by cadmium
Enzyme
Molar concn
p Innibition
AIKal ine pnosphatase
IV-7
10-6
27
IU-5
72
Ilr4
dU
Acid phosphatase
IU-2
11.5
Xanthine oxidase
Il;-4
I~.t .
Catalase
IV-4
IU-3
u
kl~Aase
10-4
12.6
Goldfish (Crassi~s auratus), when ex~osea to )60 ~g Call for )U aays,
exhibited deviations in plasma sooium and chloride levels ana in
sOdium, potassium, chloride ana water content of tissues (McCarty
and Houston, 1976).
Adult bluegi I I (Lepomis macrochirus) were exposed to cadmium for
II montns.
Hignest tissue resioues were founa in I {ver, intestine
and caecum, and kidney.
At ~I ~9/1 no adverse effects were ODservea.
At dU ~g/I cnronic effects occurred.
Mortal ity was relateo to
concentration.
At L)~ ~~/I, onset was the same as at dU ~9/1 but
subsequent mortal ity was nigher at the 2)9 ~9 level.
Spawn i ng was
erratic.
Oevelopment of embryos appeared normal at the lowest level
tested.
At 00 ~g/l, some embryos developea severe aDnormal ities.
At
335
-------
the higher levels of exposure, nearly al I embryos developed
abnormalities, including pericardial and abdominal edema, delayed
yolk sorption, shortened and deformed caudal fin and peduncle,
microcephal ia and lordosis dorsally of more than 90 from normal
-------
TABLE I I.
Biomagnification of cadmium in catfish
Exposure
level (ppm)
Biomagnification
by liver
Biomagnification
by kidney
o
50
12 x 41 x
6 15
4 15
3 6
2 5
100
200
400
800
In order to evaluate the possible changes in toxicity of cadmium, eggs
of autumn spawning Baltic herring (Clupea harengus) were incubated
in contaminated waters at varying sa I inity.
Embryonic survival was
dependent on the sal inity and deleterious effects were more evident
in brackish water than in sea water.
Activity of the embryos
decreased with decreasing sal inity.
Embryo survival was greater at
high sal inity than at low sal inities.
Hatching rates were good at
all cadmium-sal inity combinations, but incubation time shortened with
increasing cadmium concentration.
Viable hatch was unaffected at
sal inities of 16 0/00 to 32 0/00 and cadmium concentrations up to
0.5 ppm.
At 0.5 ppm cadmium and 5 0/00 sal inity, there was only 1%
viable hatch.
At 5ppm cadmium, there were no viable larvae.
With
increasing cadmium concentration, length of newly hatched larvae
decreased and yolk sac volumes increased.
Cadmium content of eggs was
higher in lower sal inities (Table 12) (von Westernhagen et ai, 1974).
337
-------
TABLE 12. Effect of cadmium and sal inity on herring eggs
Embryonic survival 50% Hatching, % Viable
unti I hatching, % days hatch
Sa I inity, 0/00 5 16 25 32 5 16 25 32 5 16 25 32
Cd, ppm
0 13 13 13 12
o. I 95 92 95 67 12 13 13 13 88 97 98 96
0.5 85 92 95 67 12 12 13 12 0 96 98 98
1.0 90 90 99 58 12 II II 12 0 60 97 97
5.0 21.7 32.8 54.9 51.0 14 12 12 10 0 0 0 0
When 3 generations of brook trout (Salvel inus fontinal is) were exposed
to cadmium, a significant number of first and second generation adult
males died at 3.4 ~g/I during spawning.
Growth of second and third
generation offspring was significantly retarded.
As in other fish
exposed to cadmium, kidney, 1 iver and gi I I tissue accumulated the
greatest amounts of cadmium (Benoit et al., 1976; Rowe and Massaro,
1974; Kumada et a I., 1973).
When exposed to cadmium levels of one to 25 ppb, 3-4 year-old brook
trout exhibited testicular injury and changes in androgen synthesis.
At 25 ppb, testis of fish showed marked discoloration with dark
purple-brown patches randomly scattered.
At 10 ppb of cadmium,
abnormally vascularized discolored testis were seen in seven of
338
-------
eight fish.
Histological examination also revealed extensive
hemorrhagic necrosis.
Histochemical studies indicated a reduction
of lip i d mater i a I in the I obu Ie-boundary ce II s of damaged testes
and no regeneration of Leydig cel Is, the probable site of steroid
production in brook trout.
In vitro studies with tissues from mid-
--
testes of control fish and fish exposed to 25 ppb cadmium showed
synthesis of I I-ketotestorone (I I-KT) from 4-14C-pregnenolone in
control but not in Cd-damaged tissues.
Altered biosynthesis of
other unidentified compounds was also indicated by X-ray auto-
radiography of chromatograms (Sangalang and O'Hal loran, 1972).
Rainbow trout (Salmo gairdnerii) respond slowly to cadmium poisoning.
In a continuous flow system, with 290 mg/I CaCa
and ambient tempera-
ture I 1.0-12.5C, data suggested a 7-day TLm between 0.008 to 0.01
mg Cd/ I .
Prel iminary tests in soft water indicated a 7-day TLm
of about 0.01 mg Cd/I (Ball, 1967).
Fathead minnow (Pimephalas promelas) were exposed to varying concen-
trations of cadmium.
The data indicated that 57 ~g Cd/I decreased
survival of developing embryos and that mortal ity occurred during
the last three days of incubation.
Many of the hatched fish were
inactive and deformed.
In some the heart was beating but RBC was
not circulating.
In others, there were many blood clots throughout
the vascular system.
At 4.5 to 37 ~g Cd/I, no adverse effects on
survival, growth or reproduction was observed (Pickering and Gast,
1972) .
339
-------
The common mummichog (Funaulus herterocl itus), when exposed to 50 ppm
cadmium (jO 0/00 salinity, pH 7.8, LOC, and 7 mg U /1), showed changes
in the intestinal tract, in the kidney, and in the blood.
Eosenopn i Is
rose from 3p (In controls) to an average of 43~ (In exposed fish).
Intestinal lesions occurred after one hour of exposure; kianey
lesions, after d hours (Gardner and Yevich, 1969).
Mixtures of cadmium, copper and zinc salts were more toxic than
expected on the basis of individual salts.
Cadmium, at concen-
trations not usually lethal, aecreased survival of mummicnogs that
had been intoxicated by salts of copper, zinc or both.
Residues In
survivors held in cadmium-containing mixtures did not conform to
patterns of single elements (Eisler and Gardner, 197j).
When mum-
michoys were exposed to 50 ppm cadmium alone, pathological changes
attributable to cadmium poisoning were observea in the intestinal
tract, tne Kidney and gi I Is.
The observed effects resemble patho-
logical changes demonstrated experimentally in animals ana cl inical Iy.
Changes among eosinopni I ic cel Is were also indicated (Gardner and
Yevich, 1970).
Exposure of the cunner (Tautogolabrus adspersus) to varying cadmium
concentrations affected blood serum osmolal ity and 9i I I tissue oxygen
consumption.
At a level of 48 ppm, abnormally high serum osmolal ity
occurred; at a level as low as 3 ppm, the normal rate of oxygen
consumption was reduced (Thurberg and Uawson, 1974).
Histopatho-
logical effects, after acute exposure (4~ ppm and 96 h) to caamium
340
-------
Species
upossum shrimp
Amphipod
Freshwater shrlm~
St ick I eback
Hermit crab
Sand snrimp
Grass shrimp
Common starfish
Juveni Ie bay scallop
~ommon soft-she I I clam
Pink shrimp
w
~
i-'
Green crab
Mud crab
Atlantic oyster dri I I
t. mud snal I
Sandworm
Yel low-eye mul let
~mal I-mouthea hardyhead
Str i ped k I I 1 If i sn
81 ue musse I
Sheepshead minnow
Mummichog
1 29 days
2 .)U days
3120 h
4 5d h
5166 h
T AdL t:: I 3 .
Toxicity of caamium to marine species
LC
(].19/1 )
96 h
(Mysidopsis bahla)
(Austrochi Itonia subtenius)
(Paratya tasmaniensus)
(Gasterosteus aculeatus)
(Pagurus longlcarpus)
(~ran90n septemsplnosa)
(Palaemonetes vulyarls)
I?
4u
6u
2uu
52u
32u
42u
760 ILUI
82u
14dU
L2uu
,):>uu 71d2
41UU
4Siuu
6bUu
IU:,uu
II uuv
14juu3
15?UU4
146uU5
l.luuu
2jUuu
5uuuu
:>5000
(Asterlas forbesi)
(Argopecten Irradlans)
(Mya arenaria)
(Plnaeus auorarum)
(Carcinus maenus)
(turypanopeus depressus)
(urosalpinx cinerea)
(Nassar ius obsoletus)
(Nereis virens)
(Aldrichetta forsteri)
(Atherinasoma microstoma)
(F u n d u 1 us ma.J a I Is)
(Mytilis edulis)
(Cyprinodon varlegatus)
(Fundulus neterocl Itus)
Reference
I~ i mmo et a I, i n
Thorp and LaKe,
Throp and Lake,
Jones, 1959
tis I er, I ~7 1
press
1974
1974
,.
Ii
il
"
bahner and Nimmo, 197'
Nimmo ana bahner, in press
Eisler,197/
Nelson et al., 1~7b
cis I er, 197 I
dahner and l\jimmo, 1~7'
Nimmo and 8ahner, in press
t. is I er, 197 I
~o I I i er et a I ., I ~ 7 .)
cis I er, hI] I
.j
"
Ii
"
Ne::;ilsKi, 1~76
It
I.
E I s I er, I 97 I
"
"
i.
II
II
-------
TABLE 14.
Toxicity of cadmium to aquatic insects
Diptera
Atherix variegata
Hexatoma sp.
Holorusia sp.
Ephemeroptera
Ephemeopteran nymph
Ephemerel la grandis
Ephemerel la grandis
grandis
grandis
Plecoptera
Acroneuria pacifica
Arcynopteryx signata
pteronarcel la badia
pteronarcel la badia
pteronarcys cal ifornica
Tricoptera
Tricopteran larva (leptoceridae)
Brachycentrus americanus
Zygopteran nymph
Daphnia magna
(in lake Superior water)
~g/I
10,000
10,000
42,500
84
42,500
28,000
17,500
17,500
42,500
18,000
14,000
2,000
42,500
250
100
650
Days
21
21
7
4
7
4
21
21
7
4
14
4
7
4
( 1 )
( 1 )
% Survival
100
80
50
50
o
50
10
10
o
50
100
50
100
50
50
50
(1) Time not specified
342
(Clubb et al., 1975)
-------
chloride, were manifested in kianey intestine, 9il I, epidermis, and
hemopoietic tissue (Newman and ~acLean, IY74).
Invertebrates
tarthworms appear to be able to concentrate cadmium.
CricKets, feeding
on l09Cd-labeled vegetation rapidly accumulatea cadmium but not aoove
the level of concentration of tne fooa source.
S~iders feeaing on these
crickets accumulated and excreted cadmium slowly but, simi larly, did
not concentrate it above the level in the fooa source (Fassett, 1975).
PinK shrimp were ex~osed for 5U days to varying concentrations of
cadm i um.
Accumulation is summarized in Table 15.
TABLE 15.
Cadmium accumulation by pink snrimp
Cd (mg/l)
Concentration Factor
u.079
48
u. I c>2
,:>7
u.307
5?
v.5d6
53
U.d66
j4
I . Lc>5
23
(L5 C, sal inity LU 0100)
(I'iirnmo et al., IY77)
After 96 h exposure of pinK shrimp lPinaeus duorarum) to cadmium (as
CaCI2)' it was found that the tissue concentration was proportional
343
-------
to water concentration with concentration factors of L) to 57 and
cadmium concentrations differed by ~ orders of ma8nltude among tissues
analyzed:
nepatopancreas > exoskeleton> muscle> serum.
The shrimp
were then placed in caamium-free flowin9 seawater ana held for 7 days.
unly in tne muscle and serum were cnanges noted:
a slfJniticant
decrease in tne serum and a significant increase in muscle.
PinK
snrimp excreted about ?Vp ot tne cadmium in 7-lv oays (I~immo et al.,
1977 ),
In other studies, Meganyctipnanes norvigica excreted 97)
after 96 days (benayoun et al., IY74).
Acute and sUDacute exposure ot pinK snrlmp to caamlum proauced
blaCKened toci or melanizea lamellae. In acute exposure, shrimp
exposed to cadm i um aeve I opea "b 1 acK 9 i I I s jj (N i mmo et a I ., I 977 ) .
When pinK shrimp (Penaeus auorarum) was exposed to cadmium (76j
~y/l) tor 15 days, tne gi I Is became necrotic.
Local and extensive
areas of cel I aeath were observed in the distal ~i I I ti laments.
Sucn aestruction of cel Is coula cause osmoregulatory, respiratory
ana detoxifying aysfunctions (CouCh, 1977).
Pink Shrimp and grass snrim~ (~. vulgaris) bioaccumulated cadmium
trom water even at concentrations.
Gi I I lamellae of ~. vulgaris
were also blackenea, necrotic and distended aue to con8estlon
with large numbers ot nemocytes after exposure to 75 ~g Gall for
10 days.
Brine shrimp (Artemla) containing cadmium were usea as
fOOd for grass shrimp.
8ioaccumulatlon was poor ana the transfer
344
-------
of cadmium from brine shrim~ to grass shrimp was mucn lower than
from the water (Nimmo et al., 1977).
Pink shrimp were exposed to cadmium, methoxycnlor and P~DS, singly
and in combination.
I~ethoxychlor influencea the accumulation
and loss of cadmium from shrimp.
Less cadmium was found in the
muscle of shrimp exposed to the combination than in the aosence
of methoxychlor (Table 16) (Nimmo and Bahner, 1~76).
T A8U:: 16. Accumulation of caomium in shrimp
exposeo to multi~le compoundsl
t.xposure p~D2 l'"1ethoxych lor
Level ( tlQI I ) ( tlgl I) ~oncentration Factor
640 L4
774 I. I 15
746 u.9 19
t>:L9 u.9 O.t> 20
(J'-jimmo and dahner, 1'::176)
llu-day flowing water bioassaysi 20 0100, 25 C
2Aroc I or 1254
Marine and estuarine species of isopoas (Crustacea) were exposed
to varying sal inity and temperature in the presence and absence of
caamium (jCa~U4dH2U).
In 100) sea water, mortal ity was low in the
presence of IU ana 20 ppm cadmium.
When the sal inity was aecreased,
mortal ity increased.
Temperature increases also increased toxicity
345
-------
of cadmium (Table 17).
In Jaera alDifrons sensu stricto, caamium
also altered osmoregulatory abil ity (Jones, 1975).
TA8Lt: 17.
Lethal time of cadmium x sal inity to isopoas
10
LTSD
time sea water
(h) (p)
12u IUU
34 4U
67 IUU
56 8u
3b 6U
<24 4u
95 IUu
86 bu
64 60
26 4u
IVb Ivu
61 bli
52 60
26 4u
>ILU Iuu
46 I
>120 IU0
29 I
Temp.
(DC)
Species
Cd concn.
(ppm)
lodotea baltica
IU
LO
loaotea neglecta
5
10
IU
Jaera alDitrons
sensu stricto
10
5
10
10
346
-------
After eating food containing 13-15 ~g/g, people have become il I.
Because seafood constitute a source of cadmium in the human diet and
the known abi I ity of shellfish to accumulate trace metals, American
oyster (Crassostrea virginica) was exposed to 0.005 ppm cadmium.
Within 40 weeks, the cadmium concentration in oyster tissues had
increased from a background of about 3 ~g/g to more than 13 ~g/g
(dry wt).
This level could pose a potential health hazard when
oysters constitute a major diet item (Zaroogian and Cheer, 1976).
At 0.010 ppm cadmium in flowing sea water, residues in American oysters
quickly exceeded 13 ~g/g; at 0.025 ppm and 0.100 ppm, this level
was surpassed in 5 and 2 weeks, respectively (Shuster and Pringle,
1969) .
Analyses of the Pacific oyster (Crassostrea ~) from the
Tamar River, Tasmania, showed cadmium residue levels of 63 ppm.
Oysters
from one site have caused vomiting but no cases of cadmium poisoning
were diagnosed (Thrower and Eustace, 1973a, b; Ratkowsky et al., 1974).
The Pacific oyster accumulated cadmium to 25 ppm from a level of about
I ppm in the mud of their bed (Ayl ing, 1974).
Cadmium exposed oysters Crassostrea virginica exhibited very little
shel I growth, emaciation, loss of pigmentation of the mantle edge,
and coloration of the digestive diverticulae.
At the levels studied,
0.1 and 0.2 ppm, mortal ity was 84% (126/150) and 100% (150/150).
respect i ve I y.
Residue levels exceeded 100 ppm at both exposure
levels before 20 weeks exposure (Shuster and Pringle, 1969).
3.8 ppm cadmium was toxic to 50 % of exposed oyster embryos with
At
48 h (26C)
-------
TABLE 18.
Heavy metal toxicity to oyster embryos
(48 h at 26C !I C)
LCSO( ppm)
Salt
Mercuric chloride 0.0056
S i I ver nitrate 0.0058
Cupric chloride o. 103
Zinc chloride 0.31
Nickel chloride I . 18
Lead nitrate 2.45
+ Cadmium chloride 3.80
Sodium arsenite 7.50
Chromium chloride 10.3
Manganese chloride 16.0
Crabs are capable of autotomizing injured appendages and regenerating
them.
When fiddler crabs (Uca pugi lator) were exposed to o. I mg/I of
cadmium, some retarding of regeneration occurred (Weis, 1976).
When exposed to cadmium, accumulation by fiddler crabs was maximal
at high termperature and low sal inity (O'Hara, 1973a).
In other studies,
the lethal ity of cadmium to fiddler crabs was found to be sal inity and
temperature dependent (Table 19).
Lethal ity also was greatest at high
temperature and low sal inity (O'Hara, 1973b).
348
-------
TABLE 19. Cadmium toxicity to fiddler crabs
Temperature, C Time, h Sal inity, 0/00 TLm
Cd, ppm
10 144 10 51.0
192 28.5
240 15.7
192 20 52.0
240 42.0
240 47.0
20 96 10 32.2
144 21.3
192 18.0
240 11.8
96 20 46.6
144 23.0
192 16.5
240 9.5
96 30 37.0
144 29.6
192 21.0
240 17.9
30 48 10 11.0
96 6.8
144 4.0
192 3.0
240 2.9
'. 48 20 28.0
.;
96 10.4
144 5.2
192 3.7
240 3.5
48 30 33.3
96 23.3
144 7.6
192 6.5
240 5.7
Mature and immature snai Is (Physa gyrina)
were exposed to Cd+2.
The LCso was 1.37 ppm and 0.43 ppm, respectively.
The rate of uptake,
0.550 ppm/h, was twice the rate of depuration, 0.229 ppm/h.
This
al lowed accumulation of Cd+2 in the snai I (Wier and Walter, 1976).
349
-------
Bay seal lops exposed to levels of Cd++ ranging from 0.75 ppm to 2.0 ppm
accumulated up to about 60 ppm of cadmium (Nelson et al., 1976).
TABLE 20.
Cadmium uptake by seal lops
0.75
Uptake (ppm)
49.4 :t 4.1
Biomagnification
factor
Exposure level (ppm)
1.0
54. I :t 2. 2
54
1.25
55.8 :t 1.9
44
1.5
58 . 9 :t I. 9
39
1.75
57.4 :t4.0
32
2.0
60 . 8 :t 5. I
30
Zooplankton is the main source of food for some species of fish and
destruction of this fish food source could result in the disappearance
of some fish.
Three representat.ive species of freshwater zooplankton
were co I lected and exposed to cadmium.
The 48 h-LCso was determined
for the three species and is summarized in Table 21 (Baudouin and
Scoppa, 1974).
TABLE 21.
Toxicity of cadmium to aquatic organisms
Cyclops abyssorum
48 h-LCso ()191 I )
3,800
Eudiaptomus padanus
550
Daphnia hyal ina
55
350
-------
Daphnia magna were exposed to Cd+2.
At 0.17 ~g/I there was a 16%
reproductive impairment after 3 weeks.
In Lake Superior water, the
LCsO was 65 ~g/I in the absence of food.
LCso was 5 ~g/I with a range of 4.0-6.2.
The chronic (3-week)
A 50% reproductive impair-
ment occurred at 0.7 ~g/I (Biesinger and Christensen, 1972).
The
threshold concentration of cadmium chloride on Lake Erie water for
immobil ization of Daphnia magna was found to be less than 2.6 ppb
(Anderson, 1948).
Exposure of adult Artemia sal ina (L.) and Ophryotrocha labronica
(LaGreca and Bacci) to 1.0 ppm CdS04 resulted in 50% mortal ity in
240 and 410 h, respectively (Brown and Ahsanul lah, 1971).
Aquatic Plants
Concentrations of cadmium as low as 6.1 ppb significantly inhibited
growth of the alga Scenedesmus quadracauda; 61 ppb and higher severely
inhibited growth (Klass et al., 1974).
The southern naiad (Najas quadulepensis), a pond weed, was exposed
to cadmium.
Toxic reactions and accumulation of cadmium increased
as exposure levels increased.
At an exposure level of 0.83 mg/I,
cadmium accumulation exceeded 5000 ~g/g ash.
Studies with this aquatic
plant indicated that there was a potential for introduction of
potentially toxic quantities of cadmium into the food chain of higher
organisms such as sunfish and waterfowl (Cearley and Coleman, 1973).
351
-------
Terrestrial Plants
Plant caamium is influencea by a complexity of interrelationships of
elements witnin ~Iants.
uirect and indirect influence may be influenced
by avai labi I ity of nutrients and other elements.
Tissue concentration,
uptaKe ana translocation of cadmium to tne tops of hyaroponical Iy-~rown
oats ana lettuce was reduced by increasing K supply or pH of the
solution.
Adoition of Ga, In, or AI reduced cadmium in a specific
tissue or crop (John, 1976).
~ome evidence indicated tnat cadmium uptaKe
ana translocation are genetically control led (John and van Laerhoven,
1970).
Summary
Cadmium is ubi~uitous and finas its way into the environment from
pesticiaes containing cadmium, from mine drainage, from burning fossi I
fuels, and from cadmium ~latin8 and other inaustrial effluents.
tffects
on mammals, birds, fish ana invertebrates have been observed.
In mammals,
studies have shown tnat caamium ingestion may cause nypertension and
adversely affect syntheses of steroid hormones.
As in humans, heaviest
deposition occurs in Kianey and liver.
InniDition of vasopressor
responses were also observed.
In birds, Kidney ana testicular necrosis
was observed.
Cnronic exposure also produced severe anemia and some
growth retardation.
A study of cadmium in a stream ecosystem showed distribution throughout
al I components.
Resiaues in fish and seaiment were simi lar but higher
352
-------
tnan in the water.
Highest concentrations were found in aquatic insects
(Table ~I) (Łnk ana Mathis, 1977).
Cnron1c ex~osure at lu ppm cadmium caused egg production of zebra fish
to decl ine; increasing sal inity, in the presence of caamium, adversely
affected herring reproduction; and exposure of fatheao minnow embryos
to less than 1 ppm caamium decreased survival.
Increased terata were
observed in bluegi I I fish at less than I ppm.
Golafish tissue ana
plasma exhibited deviations in levels of sodium and cnloriae.
Testicular
necrosis and altered steroid syntheses were observea in brook trout.
8ioconcentration was also observed in fish.
~hrimp ana other invertebrates were also aoversely affected by caamium
exposure.
Shrimp 9i I Is became necrotic.
Mortal ity in al I species
was dose related.
uecreased sal inity, at a constant cadmium exposure
level, caused increased shrimp mortal ity.
uysters were shown to be
capable of concentrating caomium to a level that could pose a potential
health hazard.
At an ex~osure level of I p~m, oyster mortal ity
was
d4p.
At 3.~ ppm, 5U~ of exposed oyster embryos oiea within 4b hours.
At V.I ppm, retaraation of regeneration by fiddler crabs occurreo.
8ioaccumulation of cadmium seems almost universal in the aquatic
environment.
Studies with a pond weed, tne southern naiaa, showed
that it was capable of accumulating cadmium and that nere was an
avenue to introduce potentially toxic amounts of cadmium into the
food chain of higher organisms.
353
-------
Source
Mayf lies
Uamse 1 f 1 i es
Caddisfl ies
River carpsucker
Fantail darter
Sma II mouth bass
Sediment
Water
TABLE 21.
Cadmium distribution in a stream
Range, Dpm
( I sonych i a sp.)
(Agrion sp.)
0.79 - 1.71
I . 00 - I. 9d
(Cheumatopsyche sp.)
0.73 - 0.99
(Hyaropsyche sp.)
0.22 - 0.85
0.06 - U.09
0.06 - 0.32
0.U5 - 0.19
O.Od - 0.23
<0.02
354
-------
BI8LIUGRAPHY
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1977. A study of the effects of methyl mercury, cadmium, arsenic,
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Gardner, G.R. and P.P. Yevlch
1970. Histological and Hematological Responses of an Estuarine
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1976. Distribution and Abundance of Heavy Metals in Finf,sh,
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Horvatn, G.J., R.C. Harriss, and H.C. Mattraw
1972. Land Development and Heavy Metal Distribution in the Florida
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John, M.K.
1976. Interrelationships Between Plant Cadmium and Uptake of Some
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John, M.K. and C.J. van Laerhoven
1976. Differential Effects of Cadmium on Lettuce Varieties.
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19)9. The Relation ~etween the Electrolytic ~olution Pressures
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1975. Synergistic Effects of Salinity, Temperature and Heavy
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1976. Acute Toxicity of Zinc, Cadmium and Chromium to the Marine
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1976. Effects of Mercury, Caamium, and lead Salts on Regeneration ana
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361
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EFFECTS OF CADMIUM ON FISH AND WILDLIFE
MR. JORCZYK: Ed Jorczyk, 3M Company. Most of the cadmium that
enters the environment from plating operations probably is in the
form of cadmium cyanide. I imagine your studies didn't use cadmium
cyanide as such. Which would be more toxic, cadmium or cyanide?
MR. MENZIE: I would suspect that cyanide would be quite
the mammals. It operates at a low, basic level and ties up
enzymes.
toxic to
many
Cyanide compounds have not been used to test the toxicity of cadmium
in order to eliminate as many of the variables as possible. The toxicity
of the different cadmium salts, chloride, acetate and so forth, are
approximately the same, and so these are the ones that are used in such
studies.
MR. WHITE: Marty White, Cadmium Association. Can you comment on
the relative toxicity to freshwater and marine fish of cadmium compared
with zinc, copper, nickel and ch~omium? I believe zinc is also highly
toxic to these particular fish.
Our main interest is the way that cadmium can get into the food chain.
What about the off-shore fish, the major foods? Compared with cadmium
levels in the ocean, do these food fish accumulate cadmium? What levels
of cadmium do you find on your fishmongers' slab?
MR. MENZIE: I am not sure I can remember all the parts of the question,
but I will try. The first slide projections that I showed indicated
differences in accumulation in some commercial species of fish. Young cod
were examined with somewhat different levels in different tissues. The
levels of cadmium seem to be more related to the proximity to industrial
areas, higher levels being reflected in areas close in shore.
Samples collected in the vicinity of a deepwater dump site in the
middle Atlantic bite when compared to samples taken from the dump site
in the New York bite indicate that the muscle levels were quite low,
being in the order of a tenth of a part per million on a wet-weight basis,
from the deepwater area. A series of samples from the dump site in the
New York bite were found to contain over one part per million. If you
will repeat your other questions, I will be glad to answer them.
MR. WHITE: Everyone agrees that cadmium is toxic to fish. I am
trying to get an idea of the toxicity of the other plating chemicals
such as zinc, chromium and nickel.
MR. MENZIE: All right. In one of the overhead slides, I had a
comparison of the toxicity of a number of salts to oyster embryos.
If I can refer to that, in the order, mercury, silver, copper, zinc,
nickel, lead, cadmium, sodium arsenite, and chromium chloride. Chromium
chloride is about three times as toxic as chromium, and about four times
as toxic as manganese.
362
-------
These are chlorides, copper being quite toxic, on the order of
about 30 times as toxic as cadmium; zinc being about an order of 10;
nickel about three times as toxic.
MR. WHITE: So basically, we have got a problem with all the metal
finishing metals, not just cadmium.
MR. MENZIE:
organisms.
Heavy metals in general are a problem for aquatic
MR. GROBIN: Allen Grobin, IBM Corporation. Is pollution from
electroplating the most serious cause of the problem for the aquatic
life? Or is it the corrosion of the plated metals in place? Which
of these things plays the greatest role? Is there any differentiation
at all?
MR. MENZIE: I haven't differentiated.
I can differentiate the sources. We have
is coming from. Some publications report
of cadmium in the environment is probably
electroplating.
I am not sure to what extent
a general idea where cadmium
that the biggest single source
industrial, and that includes
I am not in a position to quantify this. I really don't know which
is the major source of pollution. Certainly the effluents that come
from industrial sources playa tremendous part.
MR. GROBIN: I think one of the comments this morning
the gentlemen from the Air Force was that when they wash
aren't they indeed putting cadmium into the environment?
made by one of
their planes,
MR. MENZIE: There are a number of non-point sources, but the
relationship between cadmium residue levels and proximity to
industrialized areas implicates industry as being the major contributor.
363
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Alternative Materials and Processes
Session IV
Wednesday Afternoon 2:20
A NEW NON-CYANIDE ELECTROPLATING BATH
Edward R. Jorczyk
3M Company
Plating Systems Department
Saint Paul, Minnesota 55101
Cadmium metal has been electroplated almost exclusively from a
cyanide type solution for a least 45 years. Development on other systems
lagged because overall characteristics of the cyanide bath could not be
improved upon. The enactment of laws prohibiting the discharge of cadmium
and cyanide containing wastes into waterway3 and sewer systems prompted new
investigations. An acid sulfate cadmium bath has been developed which plates
a bright deposit equivalent to that obtained from a cyanide bath. It is
easily controlled. The metal content is kept within limits by the use of
both cadmium and insoluble carbon anodes. The metal content is 2 oz./gal.,
compared to 2.6 to 4.5 oz./gal. for cyanide baths. Therefore, less metal
is dragged out into the waste water effluent. The acid sulfate cadmium
bath eliminates the use of toxic sodium cyanide, which ranges in concen-
trations from 10 to 21 oz./gal., depending upon the type of parts being
plated. Savings are realized since cyanide waste treatment costs are
elbninated. Cadmium concentration parameters in the discharge effluent
are readily attained by raising the pH of the acid sulfate cadmium solu-
tion or effluent to a pH of 10.5 and removing the precipitated cadmium
hydroxide by conventional means.
365
-------
A NEW NON CYANIDE CADMIUM ELECTROPLATING BATH
Edward R. Jorczyk
3M Company
3M Center
St. Paul, Mn.
55101
Cadmium has been plated commercially from the cyanide
bath for at least fifty years.
Over the years, considerable
work has been done to optimize bath compositions.
Today's
organic additives are exceptionally stable.
Cadmium deposits
are uniform, fine grained, and bright.
The bath has a wide
current density plating range, good throwing power and is easy
to control.
There are various cadmium cyanide plating bath compositionsl
that may be used depending on whether parts are plated in a
barrel or on a rack and whether a high throw formulation is
required.
Other variab~es also have to be considered.
Most baths
will fall into composition ranges as given in Table I.
When one considers the environment, cadmium cyanide plating
solutions present a twofold problem.
Both cadmium and cyanide
are very toxic substances.
Before plating effluent containing
cadmium and cyanide can be discharged, it must be treated to
reduce these substances to a concentration level that meets local
requirements as well as EPA guidelines.
It was apparent in the late 1960's that toxic substances
should not be discharged into the environment if their concentrations
were above those specified by regulatory agencies.
It was
also apparent, as has happened, that stricter discharge limits
could be anticipated, with talk of zero discharge on some chemicals.
366
-------
During recent years, there were crash programs by
suppliers of proprietary plating and chemical products to
develop new products that contained non polluting chemicals
and that were easily treated in order to remove undersirable
constituents prior to their discharge to the environment.
One of the first major changes that came about in the
electroplating field was bright zinc plating from other than
cyanide type baths. In 1967 a neutral zinc chloride bath2
containing no cyanide was introduced.
Today, after a few years,
there have evolved non cyanide alkaline baths, ammonium chloride3
and potassium chloride baths which have replaced many cyanide
type baths.
The development of non cyanide cadmium plating baths has
not kept pace with the changes that took place in zinc plating
baths.
The reasons are .obvious.
The total zinc gallonage is
estimated to be ten to twenty times that of cadmium.
Also the
possibility of limitations and restrictions on the use of
cadmium plate resulted in a wait and see attitude.
Therefore
most research dollars were channeled into zinc plating rather
than cadmium plating.
The new non cyanide cadmium bath can be termed an acid
sulfate bath.
In the past, other acid baths have been introduced,
but deposits were not bright or fine grained.
Control was also
difficult.
This new bath plates deposits which are bright and
fine grained.
The deposit may be clear or iridescent chromated
to impart further corrosion protection.
367
-------
The bath is suitable for both rack and barrel plating.
Throwing power is considered adequate.
A high throw formulation
is available for parts with deep recesses.
Substrates such as steel, copper, brass, malleable and
cast iron, and carbo-nitrided surfaces usually plated in the
cyanide bath may also be plated in the acid sulfate bath.
addition, stainless steel can also be plated in the acid sulfate
In
bath without using a nickel strike.
The bath make up is given
in Table II.
The solution has a composition as follows:
Cadmium metal 15 g/l (2.0 oz./ga1.)
Free Sulfuric Acid, Sp.Gr. 1.84 23.4 m1/l (3.0 f1.oz./ga1.).
The bath has a fairly wide operating range as given in Table III.
Advantages and Disadvantages
Acid resistant equipment- is required.
Since the alkaline cadmium
cyanide baths may be contained in bare steel, there is some
reluctance to change because a monetary expenditure is required
for either equipment modification or new equipment.
However, when
faced with a capital expenditure for cyanide treatment equipment
and continuing cost of treatment chemicals, the alternative to
change to the acid sulfate bath becomes more attractive.
The
plater who has no cyanide type baths in his plant may now add the
acid sulfate cadmium bath.
When platers switched from cyanide zinc to the chloride zincs,
more thorough cleaning procedures were commonly adopted.
The
same procedures should be used with the acid sulfate bath.
368
-------
Chromating solutions used for deposits plated from
alkaline or cyanide baths are not always suitable for acid
sulfate deposits, and special chromating solutions are available.
Cathode efficiency of the acid sulfate bath is less than
the cyanide baths; however, a bath composition utilizing both
sulfuric and fluoboric acid results in efficiencies slightly
higher than those found in cyanide baths.
The sulfate-fluoborate
bath will not be covered in this paper.
Since cyanide, ammonium ions, chelating, or complexing
agents are not present in the bath, waste treatment is simple
and economical.
Less cadmium is dragged out resulting in potential savlngs.
No carbonate is formed as in the cyanide bath; therefore no
down time for its removal is required.
Equipment
Equipment requirements are listed in Table IV.
Anodes
Carbon anodes are used in conjunction with slab cadmium
anodes because cathode efficiency is less than 100~~, which means
some of the current that would be used to deposit metal is used to
deposit hydrogen.
Cathode efficiencies can vary from nearly 100%
at 5 A.S.F. to 70% at 20 A.S.F.
Since the cadmium anode efficiency is nearly 100%, the metal
content of the bath would continue to increase to a point where
the metal concentration is above the recommended range.
369
-------
To offset this, a ratio of approximately 2 carbon anodes
to 1 cadmium anode is used.
Some trial and error may
initially be required to balance the amount of cadmium plated
out and lost by drag out to that put back into the solution
from anodes.
Analysis and Control
Cadmium and sulfuric acid content are determined by simple
analytical procedures.
CADVERT No. 375 is added at the rate
of 120 to 240 ml (4 to 8 fl.oz.) per 1000 ampere hours of
operation.
CADVERT No. 374 is added to replace loss by drag-
out at the rate of 10% by volume of the amount of sulfuric acid
added.
Further control may be had using a Hull cell test.
Waste Treatment
The cadmium metal may be precipitated from the rinse water
by raising the pH to 10.5 with either sodium hydroxide or hydrated
lime.
The precipitated cadmium may be removed by filtration,
settling or decantation.
Th" filtrate should have a cadmium
concentration of less than 0.5 ppm.
370
-------
REFERENCES
1. 45th Guidebook Directory for Metal Finishing, Metals
and Plastics Publications, Inc., New Jersey, 1977,
pg. 180.
2. J. G. Poor, Somers, and G. B. Rynne, U. S. Patent
3,730,855.
3. G. F. Hsu and M. M. Beckwith U. S. Patent 3,729,394.
371
-------
TABLE
Cadmium (as metal)
Sodium cyanide
Sodium hydroxide
Sodium carbonate
Addition agent
372
I
2.6 to 4.8 oz./gal.
10.4 to 21.6 oz./gal.
1.8 to 8.0 oz./gal.
4 to 6 oz./gal.
Required
-------
TABLE II
CADVERT* Acid Sulfate Cadmium Plating Bath
1 Liter 1 Gallon
Cadmium Oxide 17 g 2.25 oz.
Sulfuric Acid, Sp.Gr. 1.84 31 ml 4 f1. oz.
CADVERT No. 374 30 ml 4 fl. oz.
CADVERT No. 375 3 ml 0.4 fl .oz.
Water to make 1 liter 1 gallon
*Product of 3M Co., Pat. No. 3,998,707
Pat. No. 4,045,305
373
-------
TABLE III
Operating Conditions
Cadmium Metal
Free Sulfuric Acid,
Sp. Gr. 1. 84
Temperature
Cathode Current Density
Voltage
Agitation
374
Range
11.25 to 18.75 g/l
(1.5 to 2.5 oz./ga1.)
23.4 to 31.2 ml/l
(3.0 to 4 fl. oz./gal.)
18 to 2 7 0 C. ( 6 5 to 8 0 0 F.) *
*Lower acid and temperature
are favored for plating on
carbo-nitrided steel and
cast iron.
Rack: 0.5 to 2.5 A/dm2
(5 to 25 A/ft.2)
Barrel: 0.2 to 1.5 A/dm2
(2 to 15 A/ft.2),
calculated on the basis of
the total area of the load.
Rack Plating: 6 to 12 volts
Barrel Platin~: 4 to 18 voltf
Cathode rod agitation (rack
plating) - 1 to 2 meters
(3 to 2 meters (2 to 6 feet)
per minute.
-------
TABLE IV
Equipment Requirements
Plating Tank
Steel, lined with PVC or
rubber. Polyethylene or
polypropylene.
Anodes
Cadmium slab anodes in
combination with carbon anodes.
Cooling Coil
Teflon tube, teflon coated
copper, titanium coil, external
heat exchanger of glass or graphite.
Filter
One or two turnovers per hour
desirable. Acid resistant
components.
Rectifier
Rack:
To 12 volts, 5% maximum ripple
Barrel: -
To 18 volts, 5% maximum ripple
375
-------
Composition Range of Cyanide Baths
Cadmium (as metal)
Sodium cyanide
Sodium hyroxide
Sodium carbonate
Addition Agent
2.6 to 4.8 oz./gal.
10.4 to 21.6 oz./gal.
1.8 to 8.0 oz./gal.
4 to 6 oz./gal.
Required
CADVERT*
Acid Sulfate Cad~ium Plating Bath
Cadmium Oxide
Sulfuric Acid
Sp . Gr. 1. 84
CADVERT No.3 7 4
CADVERT No. 375
Water to make
1 Liter
17 9
31 ml
1 Gallon
2.25 oz.
4 fl. oz.
30 ml
3 ml
1 liter
4 fl. oz.
0.4 f1. oz.
1 gallon
* Product of 3M Company, Pat. No. 3,998,707
Pat. No. 4,045,305
Bath Composition
Cadmium metal 15 g/l (2.0 oz./gal.)
Free Sulfuric Acid, Sp.Gr. 1.84 23.4 ml/l (3.0 fl.oz./gal.)
plus organic additives
Operating Conditions
Range
Cadmium Metal
11.25 to 18.75 g/1(1.5 to 2.5 oz./gal.)
23.4 to 31.2 ml/l(3.0 to 4 fl.oz./gal.)
Free Sulfuric Acid,
Sp. Gr. 1. 84
Temperature
18 to 27° C (65 to 80° F.)*
*Lower acid and temperature are
favored for plating on carbo-nitrided
steel and cast iron.
376
-------
Cathode Current Denisty
Rack: 0.5 to 3.0 A/dm2
(5 to 30 A/ft. 2)
Barrel: 0.2 to 1.5 A/dm2
-------(2 to 15 A/ft.2), calculated
on the basis of the total
area of the load.
Voltage
Rack Platinq:
to 9 volts
~arrel Plating: to 18 volts
Agitation
Cathode rod agitation (rack plating)
1 to 2 meters (3 to 6 feet) per
minute
Advantages and Disadvantages
pisadvantages
1. Acid resistant equipment required.
2. May require special chromating solutions.
Cathode efficiency slightly lower than
cyanide bath.
3. Less throwing power.
~_,:!,ant:age~
1. Simple economical waste treatment:
No cyanide
No ammonium ions
No chela tors
No complexing agents
2. Less dragout of cadmium metal.
3. No carbonate formation.
4. Nickel strike not required on stainless
steel.
377
-------
Equipment Requirements
Plating Tank
Anodes
Cooling Coil
Filter
Rectifier
Rack:
Barrel:
Steel, lined with PVC or
rubber. Polyethylene or
polypropylene.
Cadmium slab anodes in
combination with carbon anodes.
Teflon tube, teflon coated copper,
titanium coil, external heat
exchanger of glass or graphite.
One or two turnovers per hour
desirable. Acid resistant
components.
To 9 volt
15 volt for plating mild steel
18 volt for plating case hardened
carbonitrided or cast iron parts.
~nalysis and Control
Cadmium -
Sulfur ic acid -
\lolurnetr:i c analysis
Volumetric analysis
CADVERT No. 375 -
CADVERT No. 374 -
120 to 240 ml (4 to 8 fl.oz.)
per 1000 amperes of operation
Add at rate of 10% by volume
of sulfuric acid added
Hull cell test provides additional control.
Waste Treatment
Raise pH of effluent to 10.5 - 1] .()
Use sodium hydroxide or hydrated lime
Remove precipi.tated cadmium by filtration,
settlin0 or decantation.
Filtrate cadmium concentration less than 0.5 ppm
378
-------
A New Non-Cyanide Electroplating Bath
MR. GUIO: Ralph Guio from Amphenol Connector Operations.
try pulse plating with the acid-type cadmium?
Did you
MR. JORCZYK:
No, we did nit.
MR. GUIO: We have done some work with this particular type of
bath. We found that the acid-type cadmium bath is readily adaptable.
Pulse plating gives a finer grain and preferential deposition compared
with the cyanide-type bath.
MR. JORCZYK: The bath we have produces a bright deposit which is
fine grained, but we will keep your point in mind. Thank you.
MR. VAALER: Luther Vaaler, Battelle, Columbus.
chloride cadmium bath? If you don't, why not?
Do you have a
MR. JORCZYK: Not at this time. Perhaps in the future some work
will be done with that. Chlorides using insoluble anodes would evolve
chlorine gas, which would not be desirable.
MR. BOOKER: Jonathan Booker from Brush Wellman in Cleveland, Ohio.
I noticed that many speakers today have talked about both rack plating
and barrel plating. Would this bath be sufficient for continuous strip
plating?
MR. JORCZYK: It probably could be developed to that, but most of
our efforts have been in steel and in barrel plating. But as time
allows, we certainly will look at that area.
379
-------
Alternative Materials and Processes
Session IV
Wednesday Afternoon 2:55
BONDED SOLID FILM DRY LUBRICANTS AS AN
ALTERNATIVE TO CADMIUM ELECTROPLATING
Theodore M. Pochily
Benet Weapons Laboratory
Watervliet Arsenal
Department of the Army
Watervliet, New York 12189
Bonded solid film dry lubricants have gained wide acceptance in recent
years. These materials are used in many areas of military w~a?ons development
and production. The Evolution of dry lubricants from a rather a minor role
to a key ~ubricant in critical application has been rather startling. This
increase in application can be directly related to an improved performance
in the area of corrosion protection.
Their use as a corrosion barrier with the benefit of good lubricity
increased the scope of application for the ordnance engineer. Studies resulting
from these early findings indicated the possibility of replacing some of our
metallic coatings with a dry film lubricant. Carbon steel panels were plated
with .002 inches of nickel, electroless nickel, cadmium and chromium. Addi-
tional panels were coated with less thatn .001 inches of DFL after a base coat-
ing of zinc phosphate. Results of salt spray tests proved the dry film coat-
ing superior to the nickel chromium and electroless nickel coatings and at
least equal to cadmium after 960 hours exposure. Selective components pre-
viously coated with nickel and chromium are now sprayed with a DFL with ex-
cellent results. Equal results could be expected in the case of cadmium plat-
ing.
The replacement of cadmium by a DFL has merit when several areas are
considered. The elimination of hydrogen embrittlement associated with cadmium
plating, will be a direct benefit. The disposal of toxic chemicals and vapors
such as cadmium, cyanide and chromates will Dot be necessary and the costly
pollution control apparatus would not be required. Additional economic benefits
can be realized when the need for expensive plating equipment and the energy
required to heat the processing equipment is eliminated.
381
-------
BONDED SOLID DRY FILM LUBRICANTS AS AN
ALTERNATIVE TO CADMI~1 ELECTROPLATING
Theodore M. Pochily
Watervliet Arsenal
Department of the Army
382
-------
Solid bonded dry film lubricant~ (OFL) have gained wide acceptance in
recent years.
They are used on many principal systems and components tha~
comprise the Army's conventional weapons inventory.
These materials have
emerged from a limited role several years ago to a prominent function in
providing lubricating in many critical applications.
The properties of dry
film lubricants are unique in that they have the ability to function at
temperatures, pressures and aggressive environment beyond that of conventional
lubricants.
The advantages of a solid dry film material with respect to a
low frictional - possibly long life oil or grease can be states as follows:
1.
Solid dry films may be used effectively at higher and lower
temperatures.
2.
May be used in environments and atmospheres that would contaminate
or degrade an oil or grease.
3.
A dry film will suffice and reduce the requirement for oil feed systems
and associated equipment if bearings do not require cooling.
4.
It has the ability to be put on as an adherent film
will not
be displaced by excessive pressures.
s.
Has a good resistance to abrasive forces.
6.
Has the ability to impart a corrosion barrier to the substrate.
Disadvantages such as the following are recognized:
Because of the solid contact - wear of the coating is noted.
1.
2.
Solids cannot act as coolants.
3.
Coefficients of friction generally are higher than that obtained
with the conventional lubricants.
383
-------
4.
There is a finite life of the coating but normally this life
will exceed the life requirement.
Considering the advantages of these materials in providing lubrication
to reduce friction and wear, several areas of applications should be
recognizable.
Some examples might be:
1.
Light and moderately heavy bearings.
2.
Sliding motion under moderate to heavy loads.
3.
Temperature range - 300°F to 500°F.
4.
Mechanism lubricated for life.
5.
Mechanisms exposed to a range of climatic condtions varying
from dust to snow and ice, salt laden atmospheres, corrosive chemical
environments.
6.
Components stored for long periods of time.
7.
Parts exposed to high temperatures, with periodic disassembly
required.
8.
Mechanism that will malfunction when contamination of fluids
or greases occur.
From the vie~oint of the military and the personnel responsible for
the continuous operation of vehicles and weapons, these dry film lubricants
have the ability to resolve many problems concerning wear, lubrication and
corrosion.
It is the objective of this presentation to briefly outline the
successful application of DFL, principally those compounded with thermo-
setting, resins conforming to Mil-L-460l0.
The makeup of these compounds
follow a general compositions; an organic resin normally epoxy and/or
384
-------
phenolic. lubricating inorganic fillers such as molybdenum disulphide and
graphite and acid neutralizers.
These materials are blended with a suit- '
able solvent that allows for a consistency compatible with whatever method
of application is desirable.
It must be noted, that these materials have not nor will they replace
conventional lubricants in many applications.
What is important, however,
is to recognize that the dry film lubricants extends the range of
lubrication technology as well as the range of operation in aggressive
environments.
The ability to function in environments that normally corrode the
basis metal can, to a large extent, be attributed to a barrier resulting
from the organic resin.
It was this ability, a means of providing a corrOSlon
barrier with no sacrifice of lubricating properties that intrigued the weapons
design engineer.
The problem of corrosion is and has been of significant
importance to the military services.
The effectiveness and functionality
of weapons and systems have been deleteriously effected as a result of improper
or minimal corrosion protection.
During the early period of D.F.L. investigation at the Watervliet Arsenal,
the attitude of the engineers were concerned only with the replacement of
one form of lubrication with another.
This was a normal assumption and in
most cases these D.F.L. materials performed admirably.
Included in these
applications were two major components, the l20mm breech block assembly (#1)
and at the T206 firing lock (#2).
Both components were completely coated
and resulted in a decrease in the force required to actuate them.
385
-------
The next component (slide #3) a 20mm feed mechanism functioned well
under all environmental conditions.
However, the corrosion noted here
occurred during normal storage and presented an unacceptable situation
to the ordnance engineer.
Also revealed at this time by several other
agencies, was the fact that corrosion products have been found on surfaces
coated with dry film lubricants.
This knowledge stimulated investigations
at several manufacturers and user laboratories with the result that the
major contributor to the corrosion problem was isolated.
The commercial
product used by Watervliet during this period was known to have a high
percentage of graphite.
It was known that graphite relies on the moisture
in the atmosphere for assistance in lubrication.
It was also known that
when graphite was tested under vacuum, the lubricating properties of the
material no longer existed but become damagingly abrasive.
Consequently;
it was concluded that the D.F.L. compound in addition to lubricating also
promoted corrosion to the base metal.
Several lubricants both conventional and bonded solid dry film were
evaluated for wear life and corrosion protection.
The Falex Wear Tester
using a 1000 lb gauge load and a salt spray chamber with an atmosphere of
5% NaCl at 95°F were used for these determinations.
The results shown in
slide #4 are self explanatory indicating excellent performance in bath
catagories for the .0005" inches (.5 mil) DFL coating.
The efforts of the personnel in the dry film field were directed toward
386
-------
a resolution of this problem.
The results of these efforts were successful
to a point that the entire philosophy cf dry film lubrication was changed.'
Now, it was realized that, in addition to providing lubrication, these
compounds would be required to protect the base metal from corrosive forces.
A comparative evaluation of available D.F.L. material conforming to
specification Mil-L-8937 and Mil-L-460l0 appeared to be desirable at this
time.
The basic difference in the two specifications is concerned with
graphite as a lubricant.
Mil-L-460l0 prohibits the use of graphite while
the other does not.
The data in slide #S reflects the superior wear and
corrosion resistance of the graphite free DFL.
The perfect merger of these properties was expected to increase the
field of application.
The possibility of providing a barrier to corrosion
and to lubricate moving components with a coating less than .001 inches
thick was intriguing, and the elimination of comparatively heavy electro-
deposits, used as corrosion and wear protection, was an advantage that had
to be considered.
The validity of this pronouncement is quite evident today
by the extensive acceptance of dry film lubricants as a corrosion barrier
coating with a lubricant.
With this type of information, it was more easy
to convince the design engineer of the value of these materials.
During this
period, a severe corrosion problem was found in the storage and field use
of the lOSmm Ml03 (Slide 6).
Extensive corrosive attack was evident on
the recoil slide surface of this weapon despite normal field maintenance.
387
-------
This surface in several earlier gun models, was chrome plated for wear and
corrosion protection and lubricated with conventional lubricants.
The
susceptibility of chromium electrodeposits of .005 inches thick to corrosion
is illustrated in the next slide, slide #7.
Two badly corroded areas are noted on the recoil slide surface of this
90mm M4l weapon.
Concurrent studies relating to the above problems and to the lubricati9n
of the new l55mm M126 were in progress.
The new weapon was autofrettaged
throughout the bore and due to the presence of tensile residual stresses at
the a.D. induced through the autofrettaged process, no chemical acid treatment
of the tube was permitted on the outside surface.
The use of a bonded solid
film lubricant to the recoil slide surface presented a viable solution to the
lubricating problem of this weapon.
After 2000 rounds and six month outdoor
exposure to the varying climatic conditions of the Great Lakes area, no
evidence of wear or corrosion was noted.
This is illustrated in the next
slide where the expected burnished surface is noted (Slide #8).
With one
problem solved others were generated during extended firing sequence.
The muzzle end of a gun that is mounted on either a tank or enclosed
self propelled vehicle contains two necessary components.
The muzzle
break which is used to reduce the recoil forces when the gun is fired
and the bore evacuator which is necessary to evaluate the noxious
propellent gases from the tube during firing.
A deposit of propellent
residue, carbon and corrosive gases create a corrosion problem between
388
-------
these components and the mating threads or the weapon.
The application
of a dry film lubricant resolved this problem and reduced the dissassemb1y
of time by approximately four hours.
The subject areas are shown in this
slide (#9) a comparison of a corroded area and the D.F.L. coated area are
obvious.
Slide #10 shows the bore evacuator in place and Slide #11 illustrates
the extent of dry film coating on 3 lSSmm tubes.
The acceptance of the D.F.L. coating as a corrosion barrier was
further demonstrated when an experimental 10Smm when all mating surfaces,
all internal components such as springs, cams, extractor, etc. were
processed with a dry film lubricant.
The entire weapon assembly was towed
through the ocean surf and further exposed to the salt laden environment
for a two week period.
This exposure would normally corrode the weapon
whereby activation of the system would be difficult if not impossible.
This was not the case, and this howitzer continues to function with a minimum
of maintenace.
Slide #12 shows the weapon prior to acceptance by the Marine
Corps.
It must be recognized that corrosion control is a prerequisite to
proper lubrication since corrosion destroys both the surface and the
lubrication of that surface.
The encouraging results of these applications were at a level that
the anxieties created by the previous failures due to excessive corrosion
were quickly forgotten to the point that the D.F.L. coatings were looked
on with favor when a corrosion problem was evident.
389
-------
At this point in time the application of D.F.L. materials was
primarily a substitute for conventional lubricants.
However, the replac~-
ment of anodic and conversion coatings as well as black oxide treatment was
accompiished during this period.
The excellent performance with respect
to wear corrosion and lubrication led to a reevaluation of some of our
metallic coatings in our metal finishing system.
Results of this
reappraisal led to the replacement of several electrodeposited metallic
coatings.
As an example, the D.F~L. coatings replaced a .002" nickel coat-
ing on the extender tube of the Marine Drive Assembly.
This unit is
used to propel bridge components through water whenever the need for a
portable bridge is required.
Chromium deposits which used as a wear and
corrosion resistant coating have been either replaced or augmented with
a dry film lubricant (Slide #13).
The last slide (Slide #14) indicates the excellent corrosion resistance
of the D.F.L. material used at the Watervliet Arsenal.
The salt spray
resistance as compared to the deposited .002" coatings of chromium, nickel,
electroless nickel is considerably better.
The performance against the
chromated treated cadmium deposit is comparable at 960 hours.
To summarize what has been presented; the DFL coatings has given the
design engineer an alternative to several metal finishing systems.
At the
Watervliet Arsenal, after a comprehensive comparative evaluation of selected
components and systems the following changes have occurred.
The DFL covered
390
-------
under Specification Mil-L-46010 has replaced in many instances:
1.
Conventional lubricants
2.
Phosphate conversion coatings
3.
Black oxide coatings
4.
Chromate conversion coatings
5.
Anodic coatings on aluminum, magnesium and titanium
6.
Enamel and lacquer paint systems
7.
Copper deposits when used as a lubricant
8.
Lead deposits when used as a lubricant
9.
Nickel coating when used as a corrosion barrier
10.
Electroless nickel when used as a corrosion barrier
11.
Chromium deposits when used as a lubricant and .corrosion barrier
Several benefits of this system are quite apparent.
The ease of
application, simplification of processing equipment, absence of effluent
pollutants and a minimum of exposure to noxious and toxic fumes to the
operator.
Other benefits not obviously as apparent are concerned with the
mechanical and physical properties of the basis metal.
Included would be
phenomena such as hydrogen embrittlement from chromium and cadmium plating,
the intermetallic alloying of tin due to the diffusion of the liquidified
coating, intergranular corrosion when lead is used as a l~bricant under
high pressures and the concern for galvanic corrosion would not be a factor
when dissimiliar metals are coupled.
391
-------
The information shown on the last slide clearly indicates the excellent
salt spray resistance of the DFL material and was used as a basis for the
replacement of some of our metallic coatings.
It is, at the present time
the basis of a submitted Arsenal program relating to the elimination of our
cadmium plating facility.
The DFL coatings may not suffice in all instances
but a review of the requirements of each component and its relationship to
the over all weapons system, will find these materials more than acceptable.
It is the intent of this paper to present those areas where a successful
application has been realized and to introduce the DFL materials as a viable
replacement for electrodeposited coatings such as nickel, chromium and
cadmium.
392
-------
\
-
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, ~~~~
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SLIDE III
DRY. FiLM COATED 120MM BREECH MECH
-------
r;r~~ .. ~<,... - :~~~~;l:'
-:;.":0"'..-:
-~
~
0\
C"')
..
SLIDtE ~2
DRY FILM COATED T206. FIRING LOCt\
-------
. .
. ~LTD
FEED MECHAN ISM 20MM M2E7
1..:')
Ci
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-------
SPC 10)
SLIDE r!~
EFFICIENCY OF LUBRICANTS
(WHEN APPLIED TO PHOSPHATIZED STEEL)
WEAR LIFE
(FAUX TEST)
(AT APPROX H.'" 1'51)
200 300
MINUTES TO FAILURE
400
TY PE OF
LUBRICANTS
NO
LUBRICANT
SAE 30 I
ENGINE OIL
Mll-G-10924B I
GREASE
w
\0
(j\ EXTREME
PRESSURE I
GREASE
MIL - L -2105 -
GEAR Oil
HIL-L-8937
DRY
lUBRICANT
/.IIL-L-46010
DRY
lUBRICANT
0 100
CORROSION PROTECTION
(SALT SPRAY TEST)
I
-
I
I
500
~~o
HOURS TO FAilURE
-------
COMPARATIVE TEST DATA
SOLID FILM LUBRICANTS
SLIDE lis
SALT FOG: FALEX FALEX E.P.
(HOURS TO WEAR LIFE FAILURE
PRODUCT MANUFACTURER FAILURE) (MINUTES) (LOAD LBS.)
A S 850 680 2750
(Meets MIL-L-46010)
* D A ~ 80 3250
* S D 16 240 3250
w
'-0 (4
-....J * M A 230 3250
* l E 65 60 2750
* 6 E 4 136 3125
* H H 67 90 2875
. S H <4 168 3125
. N N 2 84 3250
. P P 4 210 3375
* MIL-L-8937 (ASG) Qualified Products
Surface Preparation: Grit Blasted & Zinc Phospated
Film Thickness: .()()a) + .0001 inches
-------
,,'
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CORRODED AREA UNDER 'BOREEV ACUATOR 15~MM
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SLIDE 1112
-------
SLIDE 1113
405
-------
COMPARISON: DRY FILM LUBRICANT TO VARIOUS
PLATINGS AFTER 960 HRS. IN 50/0 SALT SPRAY
SLIDE 1114
.
D.F.L - SANDSTROM 9A - 1/2 mil.
',S~O'M'IUM PLATE -'2 ",iI5. . .
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-------
Bonded Solid Film Dry Lubricants as an Alternative to
Cadmium Electroplating
MR. HRATKO: Bill Hratko, Sunstrand. In the elimination of
chromates, anodizing, and phosphating, how do you prepare various
substrates like steel?
MR. POCHILY: A lot of the weapons that we work with are
autofatigued. That means they are stressed to improve the fatigue
and the weld life.
In preference to using a zinc phosphate coating, we just vapor
hone.
The 155's are vapor honed, and there is no zinc phosphate underneath
those. If you want a longer corrosion time, you can use a zinc phosphate
plus this dry film, but we vapor hone most of these before we put the
dry film on.
MR. SEYMOUR: Daniel Seymour, Air Force, Sacramento.
apply the coating? Brush?
How do you
MR. POCHILY: It can be applied through brush, dip, or spray. We
at the arsenal are using electrostatic spraying. We find it is very
efficient and it is very effective. We have cut consumption down
about half.
407
-------
Alternative Materials and Processes
Session IV
Wednesday Afternoon 3:45
ALTERNATIVES FOR CADMIUM METAL DEPOSITION
IN THE FIELD OF MECHP~ICAL PLATING
Edward A. Davis
3M Company
Plating Systems Department
Saint Paul, Minnesota 55101
Methodology is not sufficiently ~meliorated for total elimination of
cadmium plating from some applications while sustaining its beneficial charac-
teristics. However, by incorporating other metal powders with cadmium and de-
positing an alloy or co-deposit finish, inroads have been made which si~nifi-
cantly reduce the consumption of cadmium and. continue to maintain the integ-
rity of the protective coating.
Two metal powders that have provided remarkable peLforrnance similarities
to straight cadmium coatings when mixed with cadmium are tin and zinc. By re-
moving half the amount of cadmium metal powder from a given mechanical plating
procedure and replacing an equal amount of tin metal powder, a co-deposit coat-
ing is formed which meets and in some cases exceeds established specifications
and test requirements. A 50% reduction in cadmium consumption is realized
without any irihibiting or deteriorating product end use effects.
Zinc metal powder is employed in much the same manner. Successful results
have been attained by furt~er reducing the amount of the cadmium deposit. 75%
zinc/25% cadmium combination coatings are curently being evaluated -- thus far,
all results are positive. In many instances the cadmium/zinc combination coat-
ings are receiving approved acceptance due to the following advantages:
1)
2)
3)
4)
5)
Lower plating costs than straight cadmium or cadmium/tin combinations.
75% reduction in the usage of cadmium.
Excellent corrosion protection.
Reliability of reproducing the finish.
Satisfactory torque tension drive characteristics.
Straight zinc, tin, and tin/zinc combinations do not sa~i~factoril~ re-
place all cadmium coatings because they fail to meet many speclflc corrOSlon
requirements. These coatings, unless specially lubricated or waxed, also fail
to qualify for various torque tension requirements called out in fastener drive
specifications.
409
-------
AL TERNATIVES FOR CADMIUM METAL DEPOSITION
IN THE FIELD OF MECHANICAL PLATING
Submitted by
E. A. DAVIS
3M Company
23923 Research Drive
Farmington, Mich. 48024
410
-------
ALTERNATIVES FOR CADMIUM METAL DEPOSITION
IN THE FIELD OF MECHANICAL PLATING
Abs tract
t1etal finishing technology today has not as yet reached the point
where industry can eliminate Cadmium and its reported negative features
and still obtain Cadmium's beneficial finishing characteristics.
However, by incorporating other metal powders with Cadmium and de-
positing an alloy or co-deposit finish, the quantity of Cadmium in use
has been reduced while the integrity of the protective coating itself
is still maintained.
Two metal powders that have provided remarkable performance similarities
to straight Cadmium coatings when mixed with Cadmium are Tin and Zinc. By
removing half the amount of Cadmium metal powder from a given Mechanical
Plating procedure and replacing it with an equal amount of Tin metal powder, a
co-deposit coating is formed which meets, and in some cases exceeds, established
specifications and test requirements. A 50% reduction in Cadmium consumption
is realized without any inhibiting or deteriorating product end use effects.
Zinc metal powder is employed in mych the same manner. Successful
results have been attained by further reducinq the amount of the Cadmium
deposit. 75% Zinc/25% Cadmium combination coatinqs are currently being
evaluated -- thus far, all results are positive. In many instances the
Cadmium/Zinc combination coatings are receiving approved acceptance due
to the following advantages:
1)
Lower plating costs than straight Cadmium or Cadmium/Tin
combinations.
75% reduction in the usage of Cadmium.
2)
3)
4)
5)
Excellent corrosion protection.
Reliability of reproducing the finish.
Satisfactory torque tension drive characteristics.
Straight Zinc, Tin, and Tin/Zinc combin~tions do not satisf~c~orily
replace all Cadmium coatings because they fall to me~t many sp~clflC
corrosion requirements. These coatings, unless spe~lally l~brlcated or
waxed, also fail to qualify for various torque/tenslon requlrements called
out in fastener drive specifications.
411
-------
Preface
WHAT IS MECHANICAL PLATING?
~~chanical Plating is the cold welding of a ductile metal onto a
metal substrate by the use of mechanical energy. The process is based
on the fact that if an oxide free metal is placed in contact with another
oxide free metal, metallic bonding can take place because of the free
exchange of electrons.
Introduction
HOW DOES MECHANICAL PLATING WORK?
There are six basic items necessary to perform the process:
1)
2)
3)
4)
5)
6)
Multi-sided, lined barrel.
Metal powder.
Glass bead impact media.
Oil free parts.
Proprietary chemistry.
Room temperature water.
In the Mechanical Plating process, finely divided metal powder is
charged into a multi-sided, lined barrel with glass bead impact media,
oil free parts, proprietary chemistry, and a small amount of water. Th'2
barrel is rotated at various speeds dependent on part size and configuration.
Rotational energy generated by the turning barrel is transferred to the parts
through the sliding/ tumbling action of the glass bead impact mE:'dia. The
proprietary chemistry produces and maintains oxide free surfaces of the
substrate and also of the metal powder to be plated. The impact media
ensures good contact betHeen the metal powder and parts to be plated and
facilitates plating of inner recesses of various part configuriitions. It
is the glass bead media that actually peens the metal powder onto the
substrate to form the sacrificial coating.
WHAT METAL POI..JDERS CAN BE PLATED BY THE PROCESS?
Typically, metals that are Mechanically Plated are ductile - thE
most common are Cadmium, Tin, and Zinc as ,well as various combinations
of these powders. Other metals that have been Mechanically Plated ar,
Lead, Indium, Silver, Copper, Brass and Tin/Lead solder. However, the
demand for plating the last group of metal powders has nc.t been large.
412
-------
WHAT METALS CAN BE PROTECTED BY MECHANICAL PLATING?
Mechanical Plating is typically applied to a large and varied
group of substrates including:
1)
2)
3)
4)
5)
6)
7)
8)
9)
10)
11 )
12)
13)
14)
15)
16)
low ca rbon s tee 1
cold rolled steel
high carbon heat-treated steel
various tool steels
high strength alloys
some stainless steels
free machining steels (including leaded steels)
nitrided steels
sintered iron (powder metallurgy)
some malleable iron and nodular iron
cast iron
copper
brass
bronze
lead
zinc diecastings
Mechanical Plating is a process for parts that are normallv and
typically batch handled, having no greater dimension than 6 in. (15~.4 nun)
in length and weighing less that 1/2 lb. (.227 kg) e3ch. Signific~nt
strides have been made toward pl3ting and handling of l~rger and
heavier part types; however, die majority of parts curr~ntly b~ing
Mechanically Plated are of the smaller v~riety.
Plating Procedures
PROCESS STEPS:
1)
Parts are thoroughly degreased and rinsed.
2)
Parts and impact media are loaded into plating barrel.
3)
Water level and temperature are adjusted
of room temperature water to app~ar just
load.
to alluw a sm3l1 pool
ahead of the tumbling
4)
Barrel rotational speed is set.
L<13
-------
PROCESS STEPS:
5)
First surface conditioaer for oxide, scale and rust removal
is added.
6)
Second surface conditioner is added for coppering step.
A4 pllev,<,oU1lly ~c.U1I.6ed, rran.y di.66ellen:t typu 06 &ub.6tJr1:ltu
aJte c.cated. VaJtioL!.6 t1JP~ 06 metat &ub~tlLa.tu w.iU Jtec.e.ive
pla-t.utg at diQ6ellent llatU. By adding a c.oppeJL ~:tJUke, :the
metat ,.:'owde/l dou not 6ee .the ~ub.6t1late - onty the c.oppelt -
and the Ju:tte 06 depo.6.Ui.oH can be mOlle c.lo.6dy cotttltoUed.
Sub.6eQucnt coa.ting adhe..6.ion -iA al60 e.nhilnced.
7)
Plating promoter is added. Th-iA chemical -iA added to ~UIle
comple.te. and even meA:ai powde.ll furubu.ti.on to ill .6Wtcacu
w.d1wt a g{ ven tUne ctjc.ie and to pile-vent lumpy OIL th.in c.o(LtA.ng~
( pa'l-t tc' pa.'tt vaJUat.io n! .
8)
'Flash' metal is added. A -6maiŁ. amourr.-t 06 me.tai powde.ll
!1to 3 iJuncU peA 100 .6q. nt. OIL 28 to 85 gJuVn6 peJt 9.3
-6Q. mtJL. OJ) -6U1t6ace Mea! i.6 added to IYlOduc.e a .dUn
coalillg complUe1y cove~i.l1g eacJl poJtt. 1 t 11M been
due/emined that ttU-6 '6Ł.Mh' c.oat.Utg W bene6{.Uali.H
pltl'V-i.di.Hg a .ti..ght, adheJLe.nt bond be-tween :the -6ub!.l:tJtatc
and the p~otec.ttve plating me.taŁ..
9)
Plating metal is added. Pl.a..ti..ng me.:tal .i-6 added {;'l o.~c 0'1. aIJo
-i.nc.llC17Je.Hu depeYldi.ng on du.i1te.d tJUcQne!.l.6 and ptnt CUHS-tguJr:.at-i.OH.
10)
Parts, media and spent plating chemicals are discharged. After
discharge, the plater barrel is re-charged and tile next load
started. Parts and media are either screen or magnetically
separated, and the media is rinsed and put in stand-by for the
following run. The parts are post plate treated, dried, and
packaged for shipment. Spent plating chemicals are pumped to
a holding reservoir fur subsequent waste treatment. Time
sequence for a complete plating cycle runs betwet'n 40 :lnd 55
minutes.
Advantages and Benefits
~!ECHANICAL PLATING PROVIDES:
1)
Assured product reliability through elimination of hydrogen
414
-------
~lliCHANICAL PLATING PROVIDES:
1 )
ernbrittlement. A Publ1'sh d h.
. e tec nlcal report titled "A Study
of Hydrogen"E~brlttlement and Hydrogen Content of Hardened.
Steel Parts 1S available upon request.
2)
X~cha~ical cleaning action from the media which definitely
alds 1n scale removal and shortens the time of the preplate
cycle.
3)
Ability to plate tangling
evenly. The impact media
flat parts which normally
others, allowing complete
and flat parts completely and
tends to keep tangling parts and
mask from making contact with
plating deposition.
4)
A system that consumes all chemistry during each process
cycle eliminating bath maintenance.
5)
Abilitv to change metal coatings from batch to batch in the
same equipment.
h)
Non-complex wdste treatment procedures; no cyanides or chelating
agents are used in the process.
7)
Ability to plate powder metallurgy without imprcgnat~on. A
technicAl bulletin titled "Mechanical T'l.ltin", of Powder
Metallurgy" has been published and is Zlva ilable upon reques t.
8)
Attractive economics especially for coatings in the 0.00U3"
(0.0076mm) and higher range.
9)
Good adhesion and uniformity of coating lm interior and
exterior of part.
10)
Ability to deposit heavy coatings in the 0.002" to 0.003"
(0.05 to 0.0 76nun) range. This process is called ~lechanical
Galvanizing and has application in mdny industries wher~
heavier coatings are specified. The difference between
Mechanical Plating and Mechanical Galvanizing is basic:
,\lecJw/J,,-lcal r fut-lHg depo,~ J:~ (( PlWtC-Ct{.vc metal coa.tu19 c' Yttl'
a ~u.bfJtkG.-ltL {It a th{dm~~,~ MYlgC. 6'l,om 0.0007 ti' 0.0007 -U1C.!,
(0.00245 tc' 0.0777mmJ. ~!ec.ltaH{.cai Ga.[VCUU2-lHg !Jw1:e!J !Ju.b~t'U.1~e!J
{.Jl tll{Cr.:H066 !WngM 6Jtom 0.0007S'to 0.003 tHcll (0.019 tc' 0 .0762~1Jn)
The cJ1CJrU.-fJ tJtlj (U1d pJtoceduJLe Li.1J ed 6c1Jt tile Mec.fmMcai Gaevcuu ={.)~9
M~~h t6 ,~tmUft'l to ~1c.chaMcai Pta.UYlgi howcve,'l, pta.ttHg OjcJ.c
,umM (l'i.e 15 to 30 m{.i1ute..6 .toYlgeJt ))(lj'L 'LWl bCCCL~!Je mctat 1-1()IA'd'<2.'l
depo,!Jd~ a/tc. up to 70 t.unM heav-<-eittJh1H nofU71c:Ł c.oatulJ!J.. Tile.
heav~e'1. depo!)-<--tfJ ne.ccM,date a to!1gC'1. ctjue tune. to aclL{,c.\.'c ,
comp.f.ue. p..Ł.a-ttng co rt6 0 udat.{o n. The. advantag e6 C' 6 Mc-chwu CClt
415
-------
PROCESS STEPS:
5)
First surface conditioaer for oxide, scale and rust removal
is added.
6)
Second surface conditioner is added for coppering step.
A~ pfte v{.o U1J ly fu c.U.M ed, m1n.y d{ 66 eftent ttjP~ 0 & 6 ub-6 tJta:te6
Me c.(!ated. VMtOM tlJP~~ 0 e me:tCtt -6 ub-6:tJtette6 will ftec.uve
pL:tt-Ul!] at die eefteVtt fta.:t~. By adMVtg a c.oppeft -6:tute, the
metat rfowde:l dOe6 not 6ee the -6u..b-6tftate - oVtly :the c.oppeft -
an.d the ftCttc 06 depO-6,i;t[oH MVt be mO,'le &O-6ely contJwlled.
Sub-6equent coiLtU1g adh~~on. ~6 wo en.hanced.
7)
Plating promoter is added. T~ dlCJnic.al ~ added :to in..6 Me
c.omrletc, aild even. meW powdefL di-6wbution. to all -6UJt6ace6
w,LtJun a gi ven time c.~!c1.e an.d to pftevent lumpy Oft fun c.oaun.g-6
(pau tC' pau va,ua.uon.) .
8)
'Flash' metal is added. A -6ma.il CUYlOu.n.A: 06 metal powdefL
(1 tD 3 OUHc.e,~ pefL 100 ,6 q. Ct. Oft 2& tD 85 gJtam6 pefL 9.3
-6q. 1'YItft. ofJ -6UJt6ac.e Mea) .(6 added to pftoduc.e a ,tJU.n
c.oating c.ompletely c.o ve'ltYl.g each rJa./lt. I t 11M been
dete,vntn.ed tha.t ~ ' &lMh r c.oattn.g t-6 ben.eMeiaŁ tit
pftOV,td{ll.g a tight, adheJr.eVt:t bon.d between the -6ub,6:tJz.a:tC
an.d the p'Lotec.Uve plaun.g mWLt.
9)
Plating metal is added. Pfattng me;taf ~ added in Oi~e. Oft aDO
in.c.ftemen t6 depen.dtng 0 n. de6 ifted fuc.lmeM and pa'lt c.o H 6,tgUJULt{.0 H.
10)
Parts, media and spent plating chemicals are discharged. After
discharge, the plater barrel is re-charged and tIle next load
started. Parts and media are either screen or magnetically
separated, and the media is rinsed and put in stand-by for the
following run. The parts are post plate treated, dried, and
packaged for shipment. Spent plating chemicals are pumped to
a holding reservoir fur subsequent waste treatment. Time
sequence for a complete plating cycle runs betwel'n 40 and 55
minutes.
Advantages and Benefits
~ffiCfu\NICAL PLATING PROVIDES:
1)
Assured product reliability through elimination of hydrogen
416
-------
10)
J)
t-mCHANICAL PLATING PROVIDES:
Ga1.~arUul1g 6oUow ~o1e1.y tho~e 06 Mechanic.al Pfat{ng; the
meJr.,{;t5 06 the Mecharu.c.al Gaivaniul1g p!toc.~-6 Me M 60Uow-~:
A)
Batch-to-batch and part-to-part uniformity.
Simple and easy control of plating thickness.
B)
C)
Freedom from hydrogen embrittlement.
D)
Room temperature process - no molten metal baths or
noxious ftUnes.
E)
Elimina tion of's tickers'. I n the moUen meW /hot
Iii)) pM c.~ -6, patr.;t6 0 Men -6 ti..c.h to 9 eth eft Jteq t.LUUng
({,n~ome c.M~J 100 pe.Jtc.ent -<.n-6pec.:t{.on a6;teft pMc.~-6-<.ng.
F)
Simple waste treatment.
G)
No re-tap after plating. In the motten-metaŁ cUp pftOC.~6,
i..ntc'Lllal th'teaded c.omponenU mU6t Uthe.ft be. plated and
'te-tapped to c.leart out thJte.ad two t6, Oft pŁ.Ll,te.d a6 bwnb and
then thfte.ad tapped. NU-the.ft method pftov-<.dcs c.U'r./W6-tN1
.'Y'LOtec.ti.on 60ft thfr.(!.adcd aJtea6. W--i;th the ,\kc.hani..c.a1' ('";aŁ.vaH-<.:i.Ylg
pftO C. eM , noftmaŁ.llj ovefr.-tapped -<.nteftnal tiUte.aded c.(!mp<'ltcnt~ a 'cc
plated pe't -6tanda/r.d pftoc.edU/Le... P la:ting pfr.otec. t-lo ,1 .{.,s ptr.o voided
i.n a1t '1.ec.e..Med MeM, and the.fte.. aJte no pftuble..rn6 will ea6e, 06
aMe.mblil Of[ :tfl./r.ead ~t.
H)
Low energy requirements/attractive economics.
1)
Ability to deposit multi-metal or Qlloy coatings for increased
corrosion protection. In 6att 6pfr.aLj te.6 ung -the add-i.:tA.oH (/6
25 pC'LC.c.ILt WI meta€. powde'1. to :the Ileal'~! zinc. c.ua.t~n9 (0.021 -In.
0'1. O.053mm) pftOv-<.de5 up tc' 400 add{.:t-i.onal hol.1}U) 06 c.oJt,'r.osion
p'1.(/tc c.ti..o n.
Smoother and improved appearance over the molten metal dip
coating application.
Vsers and Specifiers
Because Mechanical Plating is a unique process for applying currosion-
protective coatings, the list of its users is q~ite ~xtensive. Primlrv
users of the process are indus tries concerned Wl th tl1ese factors:
1) Hydrogen embrittlement.
2) Alloy coatings.
417
-------
3)
4)
5)
Torque drive relationships.
Powder metallurgy.
Heavy Coatings.
The performance of Mechani~al Plating in areas of corrosion protection
can be specifically tailored to end-user requirements. Salt-spray data are
available which details various finishes lasting from 24 to 20,000 hours of
exposure time. The performance of Mechanical Plating in areas of torque
drive relationships can also be tailored to meet specific requirements.
Results and Discussion
The Mechanical Plating process has the unique capability of producing
multi-metal finishes by co-depositing a mixture of metal powders. Many
factors must be put into perspective when selecting a finish for a given
application. To meet end user needs, requirements, and demands in areas
of product reliability, corrosion protection, torque drive relationships,
and economics, a considerable amount of time and effort has been devoted to
developing multiple metal coatings. Examples are the Cadmium/Tin coatings
used widely throughout the Automotive and Marine industry. They were
initially developed as alternatives to straight Cadmium coatings, and have
several inherent and desirable characteristics. Straight Cadmium coatings,
when given a post-plate chromate for inl~reased corrosion protection, take on
an iridescent or straw-colored appearance. However, Cadmium/Tin coatings,
when given the same iridescent chromate treatment, remain silver-colored
but take on the corrosion protection prnvided by the post-plate treatment.
The Tin does not accept the iridescent color but the overall co~ting does
exhibit increased corrosion protection. Results reveal a finish that has
the corrosion protection equal to or better than straight Cadmium, that remains
silver where brighter coatings are called for, has similar torqu~ drive
relationships to straight Cadmium, and is cheaper than straight Cadmium to
produce. Market prices of metal powders fluctuate at a very uncertain and
unpredictable rate. The cost of Mechanical Plating is directly attri~utable
to the ups and downs of metal powder prices.
An additional and very important benefit is a 50 percent reduction in
Cadmium consumption. \{hile continuing to maintain the integrity of the
protective finish the overall Cadmium usage has been significantly reduced,
the end user does not suffer product deficiency, and the loss of Cadmil~
into the environment is minimized.
Cadmium/Zinc is yet another co-deposit coating that is proving very
promising in the metal finishing field. This finish; still undergoing
rigid testing, was primarily developed as a high performance cnating for
components that fasten dissimilar or bimetallic surfaces. The trenchant
posture of this coating is the fact that up to 75 percent of Cadmiun can
be eliminated from a given procedure with no deterioration in end use affects.
418
-------
Fasteners coated with the 75 percent Zinc/25 percent Cadmium combination
coating, when tested in salt-spray environment against aluminum, fCJ.r
surpassed similar thickness coatings of straight Zinc, straight Cadmium,
Cadmium/Tin, and Lead/Tin/Zinc combination coatings. The advantages of
the Cadmium/Zinc combination coatings are as follows:
1)
Up to a 75 percent reduction in the consumption or usage of
Cadmium.
2)
Lower plating costs than straight Cadmium or Cadmium/Tin
combinations.
3)
Excellent corrosion protection.
4)
Reliability of reproducing the finish.
5)
Satisfactory torque tension drive characteristics.
~lechanically Plated Cadmium/Zinc coatings in the 0.00025 in. (0.0063mm)
thickness range (in contact with plain aluminum) have been tested for 1500
hours in salt spray environment without red rust corrosion damage to the
fasteners or exfoliation corrosion damage to the aluminum. All initial
t\sting was done in a 5 percent neutral salt spray cabinet (,\STM Bll7); now,
outdoor exposure tes t ing is underway along wi th .'lct ual roau tes ting in
assembled apt'lications. Plating costs to produce the Cadmium/Zinc coatinhs
are some\.,rhat less than s traigh t Cadmium or Ctdmium/Tin COil t ing~. ~1aterial
costs only for the three finishes are as follows:
Cadmium/Tin
$12.58/100 lbs.
(45.3kg)
Straight Cadmium
$12.56/100 lbs.
(45.3kg)
Cadmium/linc
$ 6 . 2 7/ 100 1 b s .
(45.3kg)
CD!>U ~{9Wtc.d &0'1 U-CCi.p 6a.!>.tenc-'(.,!> a.t 64 w)./c.ubi.c- 600t (28.191.~910.028cu..m)
votume. LU-tth a)UJLrJ,lc.e a.ttc.a 06 150!>q.St./100 tb).(13.95 6C{.m./J5.3Icg)
Summary
Hechanical Plating utilizes W'chanical energy to providL' peirts
that can be batch-handled with various protective finishes. The part
types, along with selected glass bead impact media and finely divided
metal powder, are barrel-tumbled in a chemical1\' contn:JllE'd .1queous
environment. The metal powder added is cold-welded to the part types
which provides the parts with an adherent, sacrificially protective
metallic coating.
419
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Mechanical Plating has the unique capability of enabling deposition
of multiple metals without inherent process deterrents. It is currently
being utilized in replacement of a percentage of Cadmium by alternative
metals having their own special advantages. This enables retention of
the Cadmium characteristics which have proven advantageous while at
the same time reducing the total amount of Cadmium consumed for any
given quantity of parts plated.
Mechanical Plating provides the end-user with product reliability.
freedom from hydrogen eIThrittlzillznt, consistent corrosion protection.
uniform controlled coatings, proper torque drive relationships. tailor-
made coatings fer specific corrosion and bimetallic fastening situations,
and competitive economics.
420
-------
Alternatives for Cadmium Metal Deposition in the Field
of Mechanical Plating
MR: ISLER: Will~am Isler, Harry Diamond Laboratories. Has this
techn~qu: been appl~ed to coating insulators; for example, if you
were try~ng to prov~de an RF shield to a circuit that has been
encapsulated, say, in epoxy. Will it stick to an insulator? Do you
have to coat one metal onto another metal for this process?
MR. DAVIS: We don't put deposition onto a plastic cr a resin.
The process is for steel or metal.
MR. GORDON: Philip Gordon, Cutler-Hammer. After you have applied
your coating, if you make a metallographic cross-section, do you see a
copper layer and a metal strike layer and then your final metal built-
up layer?
MR. DAVIS:
You can definitely see the copper layer in a microsection.
MR. BOOKER: Jonathan Booker, Brush Wellman. How do you avoid
incorporating the glass bead impact media into the coating?
Do you see any glass in there?
MR. DAVIS: We have on the plating of heavier part types. I didn't
get into any of the disadvantages of mechanical plating. In the plating
of very heavy part types, we sometimes pulverize the glass beads and
then some of the pulverized glass is included in the coating.
We have run torque drive relationship with these coatings
salt spray to see if the effect of the powdered glass in the
would be damaging. We really haven't found it damaging.
and also
coating
There are two other disadvantages. One is that we cannot apply a
very finite micro-inch finish, and we don't have a finish that has a
high luster. That is because we are peening down a metal powder and
then another metal powder on top of it. As a result, we have a matte
finish or an orange peel effect.
The third disadvantage we find is that we cannot handle all the
larger part types that we are asked to plate. A case in point is when
one of the highway commissions asked us if we could plate bars in 18 to
42 foot lengths. We don't have a barrel big enough to tumble those.
MR. KANN:
solderable?
Sam Kann, TRW.
Are the coatings conductive and are they
MR. DAVIS: We do have some conductive coatings. With an acid flux,
we can get solderability on some of the tin coatings. However, acid
flux is a no-no in some electrical applications.
421
-------
MR. KANN: Is the
coating for galvanic
aluminum, or steel?
tin cast, 50:50, an electrically conductive
action against dissimilar metals such as copper,
MR. DAVIS:
aluminum.
We don't have a process at this point to plate onto
MR. KANN: Suppose it were a steel screw that went onto a threaded
brass nut in a salt spray application or a marine atmosphere.
MR. DAVIS: In the marine atmosphere, the tin-Cd coatings work very
well in conjunction against brass or copper. We have several specifica-
tions written for that, so the answer to your question is yes.
MR. WHITE: Marty White, Cadmium Association. When you are talking
about recesses or the inside of tubes, you are saying that you can
plate as long as the glass beads can get inside. Surely the require-
ment is that you get inside and move rather than just get inside.
MR. DAVIS:
Yes.
MR. WHITE:
for example?
You wouldn't get a plate like that in the tip of a cone,
MR. DAVIS: Yes. The right copper part to media ratio in the
tumbling barrel must be used. If we have two volumes of media and one
volume of parts, the media can hold the metal powder away from the
parts. If you get the right mixture of media to the parts, we flow
in and out of the recess area, and that facilitates the plating.
MR. WHITE:
Do you have a range of glass bead sizes?
MR. DAVIS: We have ten different sizes ranging from six thousandths
all the way up to 250 thousandths.
MR. HANNA: Ed Hanna, Red River Army Depot. When you were talking
about degreasing, you did not say anything about solvent degreasing.
MR. DAVIS: I didn't bring that up because we don't like vapor
degreasing unless the vapor degreaser is kept very clean. The blanket
of vapor that forms over the parts will hold oil particles in suspension,
and when the parts are brought out of the vapor degreaser, the oil
redeposits itself on the surface. It doesn't take very much oil to
coat each little four-micron zinc particle and not allow it to go on
the surface with good deposition. So we tend to stay away from vapor
degreasing wherever possible.
MR. HANNA:
plating?
What if the part has been blast-cleaned or painted before
MR. DAVIS: There is no problem in doing that.
done on a daily basis.
In fact, that gets
422
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Alternative Materials and Processes
Session IV
Wednesday Afternoon 4:20
STATE OF THE ART FOR HIGH RATE SPUTTER DEPOSITION
J. W. Patten
E.D. McClanahan, R.A. Busch, R.W. Moss,
M.A. Bayne and E. N. Greenwell
Battelle
Pacific Northwest Laboratories
Materials & Process Engineering Section
Richland, Washington 99352
A brief description of the principles of the sputtering process
and of advanced sputtering systems is provided along with a description
of a typical experimental procedure referenced to one of these advanced
systems. Features of this technology include the abilicy to depos~t high
integrity materials and complex alloys at rates of 1 to 10 mils thickness
per hour for use as coatings or free standing hardware. The coatings are
typically free of growth defects. Further, metallic materials may be de-
posited on areas of several square feet to a thickness uniformity of + 10%.
Ceramic materials may be deposited at rates on the order of l mil thi~kness
per hour. Free standing parts may also be produced from uniq~e combinations
of materials to obtain lamellar composites and precipitation and dispersion
hardened alloys. Compositions ~~y be graded over a range of deposit thick-
ness to obtain coating-substrate material combinations normally impossible
to achieve because of debonding via thermal expansion or chemical incompat-
ibilities. Deposit-substrate bond strengths at least equal to the strength
of the lowest strength material of the pair are to be expected. Examples
of material and deposit geometries to which this technology have been
applied are discussed.
423
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STATE OF THE ART FOR HIGH RATE SPUTTER DEPOSITION
E.D. McClanahan, R.W. Moss, N. Laegreid, J.W. Patten,
R.A. Busch, M. A. Bayne, E.N. Greenwell
Materials and Process Engineering
Battelle Pacific Northwest Laboratories
P.O. Box 999
Richland, Washington 99352
Abstract
A brief description of the sputtering process and of advanced sputtering
systems is provided along with a description of a typical experimental procedure
referenced to one of these advanced systems. These systems are able to deposit
metals and alloys at rates of 1 to 10 mils thickness per hour for use in coatings
or free standing hardware. The metallic coatings are typically free of growth
defects, and may be deposited on areas of several square feet while maintaining
a thickness uniformity of ~ 10%. Ceramic materials may be deposited at rates on
the order of 1 mil thickness per hour. Free standing parts may also be produced
by combining materials to obtain lamellar composites and precipitation and dis-
persion hardened alloys. Compositions may be graded over a range of deposit
thicknesses to obtain coating-substrate material combinations normally impossihle
to achieve because of debonding via thermal expansion or chemical incompatibil-
ities. Deposit-substrate bond strengths at least equal to the strength of the
lowest strength material of the pair are to be expected. Examples of material and
deposit geometries to which this technology have been applied are discussed.
Introduction
This paper describes the sputter deposition process in general and some of
the characteristics of the high rate sputter deposition techniques and equipment
currently used at Battelle-Northwest Laboratories (BNW). The objective of this
discussion is to identify high rate sputter deposition as an alternative to other
coating techniques and to indicate unique coating capabilities and coating material
properties that could be beneficial in specific applications. Of immediate interest
to this conference is the observation that, in general, sputtering would not be
considered as a reasonable alternative to conventional cadmium plating
because of its comparatively high cost and the large volume throughput which
many cadmium plating applications require. However, the emergence of more sophisti-
cated treatment processes, the great reduction in the use of cadmium which may be
'424
-------
imposed in the future to reduce cadmium contamination of the environment, and the
high intrinsic value of many parts requiring a coating means that each application
or proposed application of the present cadmium electroplating process must be re-
viewed individually to determine the suitability of other coating materials and/or
coating processes. High rate sputter deposition technology can provide high quality
coatings of many different materials with a wide range of properties on almost
any substrate so that consideration of this technology should be included in any
extensive review of a critical coating requirement. After a brief discussion of
the sputtering process itself, and aspects of an advanced sputter deposition
technique, some of the unique properties of sputtered materials will be discussed,
along with some of the applications to which high rate sputtering has been applied.
Some observations have been made in the literature and are general to most sputter
deposition laboratories. Others, which will be noted, are particular to Battelle-
Northwest and have not been widely discussed.
Discussion of the Sputtering Process
1. The Sputtering Phenomena
Evidence indicates that sputtering is a momentum transfer process. (1,2)
A simple model illustrating momentum transfer through binary collisions is shown
in Fig. 1. Positively-charged ions are accelerated to the surface of the target,
which provides the material for coating. Sufficient energy can thus be transferred
to the target atoms to overcome their binding energy in the lattice. The impact
of a single ion on the target can cause the ejection or "sputtering" of many target
atoms. The ratio of ejected atoms to incident ions is called the sputtering yield.
Sputtering yields are dependent on the binding energy of atoms in the target and
the mass and energy of the bombarding ions.
2.
Principle of Operation of a Triode Sputtering System
The use of sputtering as a practical deposition process depends on achieving
a large current of high energy ions at the surface of a target of the desired
geometry and coating material. As illustrated in Fig. 2, this may be done by
immersing the target in a dense plasma generated between a thermionic cathode
and an anode in an evacuab1e chamber containing inert gas, The ions are formed
by collisions between electrons and inert gas atoms, and are accelerated into the
target surface by a large negative applied voltage. The sputtered target atoms
leave the surface with approximately a cosine spatial distribution. By properly
, 1. h' (3) .f
designing the target/substrate and shield geometrlcal re atlons lP, a unl orm
thickness distribution may be obtained. This is accomplished with sputtering
chamber hardware, Fig. 3, that has been designed with the built in flexibility
425
-------
to accommodate a variety of target/substrate configurations, without extensive
modifications. In most cases, one configuration can be removed and replaced
with another in a matter of minutes. To eliminate pinhole type defects and other
growth defects, BNW uses special arc suppressing circuitry. Computerized process
control techniques enhance deposition-to-deposition repeatibility, required for
production applications. To insure deposit quality, a residual gas analysis
system is used to continuously monitor the sputtering chamber atmosphere during
deposition.
In theory, any material with a reasonably low vapor pressure may be sputtered.
Therefore, in theory, great freedom exists to apply sputtering to the formation
of both existing and new materials with unique properties. This freedom has been
exercised at BNW to form coatings not obtainable in other ways for over ten years.
Special material property effects for a particular apnlication are obtained
by varying the composition of the target material; varying deposition parameters,
such as electrode voltages and current densities; varying substrate temperature
and surface condition; and by altering the geometrical configuration of the sput-
tering system itself. The measurement and evaluation of resultant coating
properties provides information permitting accurate prediction of the results
of future depositions. Enhancing this iterative process is the computer logging
of data and computer control over selected parameters which insures deposition-
to-deposition reproducibility. Over 40 variables are continuously monitored
during sputtering by computer programs especially developed for this purpose.
In the case of deposit thickness, for example, thickness measurements from initial
deposition provide data permitting selection of deposition parameters necessary
to obtain a specific coating thickness.
3.
Typical Deposition Procedure
Complex shapes may be deposited in existing apparatus similar to the one
depicted, Fig. 4. The apparatus is enclosed in a water-cooled stainless steel
vacuum chamber which is evacuated by a liquid nitrogen trapped oil diffusion
pump to base pressures of about 10 -7 Torr without baking. The power supplies
for the discharge current, sputtering target, and substrate etching or bias,
are equipped with current limiting and cutback circuits which limit overcurrents
during arcs and reduce the power supply output to zero within 5-10 ~ sec. The
target to substrate spacing is nominally l-l~ inches and the target is up to 9
in. in diameter and water cooled on the back surface. Substrates could be any
device up to 6 in. long and 5 in. major diameter. All surfaces upon which a
coating is desired must have line of sight to some portion of the target for some
portion of the deposition. This eliminates sharply convoluted surfaces and holes
with small aspect ratios from being coated in this apparatus. Dependinq upon
426
-------
the desired result, the substrate may be water-cooled (15-25°C), air-cooled
(~300UC) or heated (up to 1000°). Each type of substrate has its own pro-
cedure for cleaning prior to deposition.
Prior to assembly of the apparatus, all internal surfaces are vapor degreased
and ultrasonically cleaned.After assembly, the system is evacuated and helium leak
checked. At this time the electrical resistance of each electrode is also checked
to eliminate the possibility of internal short circuits. After a four hour (minimum)
pumpdown, the outgassing rate of the system is measured and if satisfactory, a
dynamic atmosphere of krypton is established at a pressure of about .003 Torr.
Then a termionic discharge is ignited between the cathode and anode, and increased
in power over a 15-30 minute period. The substrate is then ion etched, typically
for 5-10 minutes at -100 volts, 5 ma/cm2 ion current density. Finally the target
power is increased over an additional 15-60 minute period to typical values of
1500-2500 volts and 5-20 m~/cm2. This power ramping produces smoother ( i.e.
fewer arcs) depositions.
Target power is maintained until the desired coating thickness is obtained
on the substrate. After the deposition a cooldown period is required prior to
disassembly if some electrodes, or the substrate are designed to be hot during
the deposition. Post-deposition heat treating or final machining m8Y be required
for some types of coatings but many are ready for immediate use upon removal
from the sputtering chamber.
Technological Capabilities and Application Examples
To obtain an advanced technological position in high rate sputtering, one
must possess certain capabilities. Some of these capabilities are identified
and examples using the capability are presented. References for these examples
and other work performed at BNW are listed in the appendix.
. Deposit theoretically dense, high integrity metals and complex alloys at
rates of 1- to la-mils thickness per hour (depending on material) for use
as coatings or free-standing hardware. Sputtered deposits have been made
on a wide variety of substrate geometries such as flat plates (Fig.5 ),
inside surfaces of cylinders (Fig. 6.7), and complex shapes with both
concave and convex areas (Fig. 8, 9, 10). Deposits with thicknesses rang-
ing up to ~ 1/2 inch and weighing up to 12 pounds have also been made
(Fig. 11).
. Deposit metallic materials on areas of several square feet to a thickness
uniformity of + 10% at rates of mils per hour. In specific applications,
where required~ thickness uniformities down to + 2% are obtainable (Fig.
12, 13).
427
-------
. Expand sputtering process capability in terms of deposition rate, object
size, production rate, etc. This ability to scale-up a laboratory process
to a full production system was a key factor in the development and trans-
fer of technology to Rockwell International Company (Rocky Flats Plant)
of the first production application of semi automated high-rate sputtering.
With this background, and the continuing development of sputtering tech-
nology at Battelle-Northwest, our ability to develop and demonstrate produc-
tion prototype sputter-deposition equipment with subsequent transfer of
technology to industry for production is well established.
. Form "bulk" and/or free-standing parts from unique combinations of materials
to obtain lamellar (layered) composites, and precipitation and dispersion
hardened alloys, (Fig. 14,15,16,17,18).
. Grade in composition and/or properties over a range of deposit thickness
to obtain coating-substrate material combinations normally impossible to
achieve because of debonding via thermal expansion or chemical incompati-
bilities, (Fig. 19, 20). This technique may also be used with free-standing
materials.
. Obtain deposit-substrate bond strengths at least equal to the strength of
the lowest strength member of the pair. In most cases fracture during test-
ing does not occur at the bond but in the lowest strength member, (Fig. 21).
. Deposit ceramic materials at rates on the order of 1-mi1 thickness per
hour.
. Control the structure and composition of semiconductor and insulator films
and tailor their electrical and optical properties for specific applications.
. Control the incorporation of sputtering gas into the deposit from <1 appm
to >104 appm.
Properties of Sputtered Deposits
A wide variety of materials, including most pure metals amenable to sputtering
and a number of commercially available alloys, have been sputter-deposited under
various contracts at Battelle-Northwest, Table 1. Selected properties of these
materials which may be influenced by the sputtering process are discussed below.
. Oxidation Resistance - Our studies of the effect of sputter-deposition on
the elevated temperature oxidation resistance of iron-base and nickel-base
alloys have shown that sputter-deposited alloys can be made significantly
more oxidation resistant than non-sputtered material of the same composi-
tion. This is illustrated, Figure 22, for AISI Type 304 stainless steel
oxidized in air at 1200°C for 16 hours. The oxidation rate for the
428
-------
.
sputtered stainless steel was less than a tenth the rate for the wrought
control material. Furthermore, the oxide layer that formed on the
sputter-deposit was more adherent and had a higher chromium content than
the oxide layer on the non-sputtered stainless steel of the same composi-
tion. A similar improvement in oxidation resistance is illustrated
for 304 stainless steel deposited at 700°C on a substrate of
wrought 304 stainless steel and oxidized in air at 1000°C for 60 hours.
In both cases the sputtered stainless steel retained the fine-grain size
characteristic of as-deposited material even after long-term testing at
elevated temperatures.
In an extension of this work, the oxidation resistance of Ni-20 Cr
alloy was increased significantly by producing sputter-deposits containing
5 vol% alumina to stabilize the fine-grained, as-deposited material. The
average oxidation rate for the sputtered alloy was one-fourth the rate
for the non-sputtered control material after 1000 hours at 1100, Fig.23.
These results demonstrate that sputter-deposition can be used to
produce alloys with a high degree of microstructural stability and with
significantly improved resistance to high-temperature oxidation. One
application of these findings would be to use sputter-deposition to coat
high-temperature alloys with material of essentially the same composition
to minimize normal coating incompatibility and interdiffusion problems
while providing the enhanced oxidation resistance required for long-term,
elevated-temperature service.
Corrosion Resistance - A major problem in adapting gas turbine engines
for marine use is the hot-section materials used in the aircraft engine
are susceptible to sulfidation corrosion. The hot corrosion and sulfi-
dation resistance of marine gas turbine blades and vanes has been improved
markedly through the use of sputter-deposited platinum and cobalt-
chromium-aluminum-yttrium(CoCrA1Y) alloy coatings. Platinum may be
deposited on production physical-vapor-deposited (PVD) CoCrA1Y coatings,
Figure 24, to increase the production coatings hot-corrosion resistance.
It is believed the pt retains Al near the free surface by forming stable
Pt-Al compounds, Figure 25. During service, these compounds release
Al to form oxides and provide increased corrosion resistance.
In addition to improving the present PVD production coating with
the platinum, sputter-deposition offers a means of improving the CoCrA1Y
coating itself. Sputtered CoCrAly has been deposited over a production
PVD coating and representative metatography of one blade is given in
Figure 26. The sputtered CoCrA1Y consists of two layers with different
42~
-------
Al contents. These were obtained by using different voltages on the
aluminum target, Fig. 4. This metallagraphy shows the high integrity,
leader-free, fine-grained microstructure that can be obtained. The
improvement in performance of the sputtered coating was proven during
at-sea tests and may be attributed to the improved microstructure, which
severely limits the sites available for base-metal attack.
Mechanical Strength - Copper, with its high thermal conductivity was an
essential construction material for a special pressure vessel, but it
lacked the required mechanical strength. Fig.27 shows the effects of
small additions of alloying elements to form dispersion hardened alloys
and the effects of deposition temperature on the tensile strength of the
material. This program allowed the selection of a material with the
required mechanical strength without significantly reducing the thermal
conductivity of the copper.
Electrical Resistivity - Figure 28 shows the influence of substrate
temperature during deposition on the resistivity of sputter-deposited
CdS. The resistivity can be controllably varied over eight orders of
magnitude by depositing at selected substrate temperatures between 20
and 300°C. Thus, for example, the low-resistivity CdS required for
use in photovoltaic devices ( ~lOn.cm) can be easily obtained by depositing
at substrate temperatures near 70°C. The variation of the resistivity
is due to a slight deviation from stoichiometry, always in the direction
of excess Cd, which occurs at the lower substrate temperatures. The
deposits made near 300°C are very nearly stoichiometric. Those made near
room temperature contain an excess of Cd,or a deficiency of S,of~O. 1
at %. The substrate temperature controls the sticking coefficient of
the highly volatile sulfur, which re-evaporates from the substrate
unless it reacts quickly with Cd to form the compound.
Summary
Because of restraints which may be imposed on the cadmium plating industry,
alternatives must be sought which mitigate the adverse impact of cadmium on the
environment. High rate sputter deposition is a viable alternative coating
process if the restraints become very severe or the parts to be coated have
high intrinsic value. Sputtering is a momentum transfer process that requires
a clean vacuum environment and fairly stringent deposition procedures. Wide
ranges in structural, chemical and physical properties may be obtained by
430
-------
varying deposition parameters and coating material. As examples, the improved
oxidation resistance of sputtered stainless steel, the improved adhesion and
sulfidation resistance of sputtered CoCrA1Y, the improved strength of sputtered,
dispersion hardened copper and the controlability of the resistivity of
sputtered CdS were discussed. Some other features of high rate sputtering that
are also important to consider are the hi9h rate (1-10 mils/hour) deposition
of theoretically dense adherent material, the ability to scale-up to production
size, and the versatility in coating material selection that the sputtering
process a 11 ows.
References
1 .
Wright, A.K., American Journal Science Arts, 13, 49 (1877)
2.
Hyman, P., "Ionic Bombardment Theory and Application,"
J.J. Trillot, ed., Gordon and Breach, New York, 1964.
Moss, RW, McClanahan, E.D. Laegreid, N.
US Patent 9,038,171, July 26,1977.
3.
431
-------
TABLE I.
Materials Deposited by High-Rate Sputtering
Extended Solubility in Eutectic and Immiscible Systems
Silver - cobalt, copper, nickel
Copper - tantalum
Dispersion Hardened Systems
Aluminum - beryllium, silicon
Copper - alumina, silicon carbide, tantalum carbide
Cobalt - titanium carbide
Titanium - yttria, tungsten
Nichrome - alumina
Iron chrome cobalt - alumina, thoria
Graded Composition Layers
Ni - Zr02
Ni, Cr - Zr02
Semiconductors
Cadmium sulfide
Cadmium telluride
Indium tin oxide
Silicon
Hydrogenated (amorphous)
silicon
Nonequilibrium Phases
Beryllium - nickel
Boron - silicon
Compounds
Rare earth cobalt magnets
Niobium-tin and niobium-aluminum-germanium
Alumina, yttria, zirconia, titania, silica
superconductors
Pure Metals and Conventional Alloys
Unique properties and behavior
Protective Coatings
Platinum, CoCrA1Y and zirconia for turbine blades
Chromium and tungsten for small arm receivers and barrels
Chromium, titanium and niobium for fissile oxide fuel pellets
Copper and silver to minimize laser absorption
Nickel, vanadium and titanium for titanium alloy corrosion
Titanium and tungsten carbides for wear of sintered tool bits
Titanium for mechanical protection and bonding of A1203 fibers
Copper and aluminum for light and x-ray telescope optics
432
-------
~
-!:'-
W
v'
FIGURE 1.
Basic Sputtering Mechanism. Ions of inert gases like argon,.
krypton or xenon strike the surface of the target, transferrlng
momentum to the target atoms. When the target atom has enough
velocity to overcome its binding energy it leaves the surface
of the target.
-------
TARGET
+ A A + e
e A
w
0
0 e
z
4(
e
+
..,..
w
~ TARGET
POWER SUPPLY SUBSTRATE
0.2 KV DC
,/' DEPOSIT
CLEAN
SPUTTERED ATOM
A KRYPTON ATOM
A + KRYPTON ION
e ELECTRON
""",,,,,,-,~.,,,,,,,,,-,"",,,""""""""""-
e
1
TUNGSTEN j
FilAMENT j
\
e
e
e
""..""."..",-'".-.' ''''.- "~,.,,.~ "'-""''''''''"
c
PLASMA POWER SUPPLY 0-50 VOC
Triode Sputtering Components. A plasma of electrons and ions
is created between a hot tungsten filament and an anode. When
the negative voltage of electrons and ions is applied to the
target. ions are accelerated towards it. These cause the ejection
(sputtering) of target atoms. which subsequently land on the
substrate. building up as a deposit.
FIGURE 2.
VACUUM CHAMBER
(PRESSURE -5 MILUTORR)
'/
FILAMENT
POWER SUPPLY
Q-IOVAC
-------
,..
l
- -
~ ~
. .
II
i
.
l
FIGURE 3.
BNW Dual-Head Sputtering Apparatus. Whi1e a deposition is being
performed on one end, the other is being prepared. Note the oil
diffusion pump, cold trap, dual gate va1ves, ports for an RGA and
cooling water manifold. The deposit being held is copper foil
whose substrate was a pyrex pipe.
435
-------
INSULATOR
SHIELD
ROTATlIoJG SHAFT
IWD SEAL
Ni FOIL TIP "-
ROOT MASKS
TARGET SHIELD
FIGURE 4.
Representative High-Rate Sputtering Apparatus for Complex Substrate
Shapes. This example shows a marine gas turbine vane in position
to be coated with CoCrA1Y that may be made rich in aluminum with a
supplementary target. The hot tungsten filament is not shown.
436
-------
~
VJ
.......
IN5ULilTOR
TARGET
SUBSTRATE
SHIELDS
CHAMBER
FIGURE 5.
Flat-Plate Target-Substrate Sputtering Geometry. The substrate
generally has a smaller diameter than the target in this mode to give
a better thickness distribution at the substrate because the tarqet
atoms are ejected with approximately a cosine spatial distribution.
-------
ANODE
NA SA SPOOL PIECE
(w.4 TER. COOLED)
SURJ4CE TO
I3E COATED
r.5PUTTER.lIJG TAR.GET
:~:
IN5VLA 10/(5
I-
~
TARGET
SHIELD
FIGURE 6. Coaxial Cylinders Sputtering Geometry. The target is longer than
the substrate to improve the deposit thickness distribution.
438
-------
.p-
I...,)
,'-0
SHIELDS
FIGURE 7. Coaxial Cylinders Sputtering Geometry. The target may be designed
to yield a specific thickness distribution.
INSULATOR
AMZ I RC TARGET
FATIGUE 5PECIM[A) SU8STRATE
THERMOCOuPLE
IAJ5ULA TOR
51-11ELD
-------
.j::-
.j::-
o
ZIRCONIA TARG~T (RF)
WEDGE SPECI/V/ŁNS
NICKEL TARGET (DC)
SHIELDS
CHAMBER
FIGURE 8. Flat-Plate Target-Rotating Pin Substrate Sputtering Geometry.
Graded deposits may be made in this apparatus by continuously
changing the voltages on the targets.
-------
SI-IIELD
FIGURE 9. Concentric Cylindrical Targets for Complex Substrate Shapes.
This apparatus has a high throughput and is used primarily for
depositing thin layers that must be heat treated prior to use.
441
COOiANTJ-
AN 0 OE
NI FOIL ROOT Mil SI(
FT 4 VANE
0/5 Pi A T'NUM
TARGtTS
NI ~Oli TIP MIISK
-------
FIGURE 10. Flat-Plate Target-Complex Substrate Sputtering Geometry.
442
IIJ5ULATOR
TARGET
Sf/IELDS
INSULATOR
ANODE
-------
.
MASSIVE
DEPOSIT OF Cu 0.1 Wt % Zr ALLOY
.p-
.p-
I",.)
OUTSIDE
.
~ THICK
-
~A
5.5 kg
SECTION A-A
FIGURE 11.
Thick Deposit for Bulk Property Testing. This material was made
in four depositions, lasting 34.5, 35.5, 40 and 8 hours. The
target loss was 6.3 kg and substrate gain was 5.5 kg for a net
transfer efficiency of 87%. Deposition rate is about 4 mils per
hour.
.
INSIDE
~
GROWTH DIRECTION
-------
r-~~
, '.- .
.~...
. be.
~ . ~.
',~'.D
~LY-'
~
FIGURE 12. Dual-Head Sputtering Apparatus with 6.5 ft2 Substrate Installed.
Note the automatic pressure controller, by-pass valve and
roughing valve.
444
-------
A~
.p-
.j>.
Ln
I-
I
/
/
,;
",
",
....
I
A~
J.I.~~ WAY 8ETWUN
TIP AND R.OOT
,() ()fJ 4.
S fCT/ON A ~A
TIP END Or: FT4 TURJ31NE f3lAOE
FIGURE 13. Thickness Distribution of Sputtered Coating on Turbine Blade.
Coating thickness on this section varied from 0.0039 to 0.0057
inch.
-------
.j
FIGURE 14. Free-Standing Sputtered Copper Cylinder. This deposit, which is
over 1/8" thick was removed from its substrate by machining, producing
a high-strength cylinder.
446
-------
.:: :.l:,:~t: .
",- - ---...
__1"'- --:.:::........
l
CD SECTION AI RFOI L
ACID
4
@ DISSOLVE
MANDREL
~
@ INSPECT ITEST
G) BRAZE AIRFOIL
MAND REL TO ROOT
J
r><; Q
r> :. ;' Q
@ DEPOS IT I BOND
AIRFOIL
FIGURE 15. Free-Standing Turbine Blade Fabrication Sequence (soluble mandrel
method). The significant improvements this process could provide are
lighter mass blades with approximately the same strength.
447
-------
. r ~-I
-,.. 7: .; .,..
,.
"
~1~ ':~;
. . ~.-,..z'
FIGURE 16. Turbine Blades Fabricated by the Soluble Mandrel Method Shown in
Figure 15.
448
-------
ROTARY SEAL
INSULATOR
TARGET
COPPER
WATER COOLED
SUBSTRATE flOLDER
Sf-IIELD
THERMOCOUPLE
TARGET
MOL YBDENUfv1
SUBS TRA TE
ANODE
SHIELDS
FIGURE 17. Dual Half-Cylinder Targets - Rotating Coaxial Cylindrical Substrate
Sputtering Geometry for Lamellar Deposition. Layer thicknesses are
controlled by the target voltages and substrate rotation speed.
449-
-------
FIGURE 18. Lamellar Sputtered Deposit Micrograph.c This deposit is alternate
layers of Cu and Mo, approximately 80 A in thickness. (lOO,OOOX)
//
Zirconium ----
/
Nickel
~
FIGURE 19.
Coating
64 llm
Microstructure and Composition of Graded Ni-Zr02 Sputtered Deposit.
The deposit is graded in composition to improve adherence and to
reduce the thermal expansion mismatch between the copper substrate
and ceramic outer layer. Scanning Electron Micrograph (120DX)
450
\
substrateJ I~
.1
-------
FIGURE 20. Rocket Thrust Chamber Simulator with Graded Ni-Al 0 Sputtered
Deposit. The deposit was adherent, smooth-surfac~d3and grey-black
in color. This deposit just approached pure ceramic.
FIGURE 21.
Demonstration of Deposit-Substrate Bond Strength. A titanium
bond coat « 0.001" thick) was sputter deposited onto a
ceramic substrate, followed with about 0.015" of copper. The
stress induced separation did not occur at either the copper-
titanium interface or titanium-ceramic interface. Rather,
the fracture occurred about::: 0.08" inside the ceramic substrate.
Shown is the fractured ceramic substrate (right) and the
back side of the deposit (left) with the layer of ceramic
material attached.
451
-------
Wrought 304 stainless steel oxidized in air at
22000J' tor 16 hr. The normal temperature limit
ot resistance to progressive scaling in air tor
304 stainless steel is 17000J'. Magnitication
30 times.
Deposit
. .
Substrate
f-.
".
304 stainless steel sputter-deposit on
a wrought 304 stainless steel substrate.
Oxidized in air at 18500p' tor Go hr. The
tine-grained sputter-deposit vas signi-
ticantly more oxidization resistant than
the coarse-grained substrate. Magnitica-
tion 100 times.
Sputtered 304 stainless steel oxidized in air
at 22000J' tor 16 hr. Although the ccmposi tion
is the same, the sputter-deposit oxidized
much less than the wrought specimen (1.6 mils
vs 23 mils). Magnitication 30 times.
Higher magnitication (500X) micrograph ot
the sputter-deposit oxidized at 22000J'
tor 16 hr. shoving the oxide l~er and the
oxide/metal intertace. The oxide on the
sputter-deposit vas more adherent and had
a higher Cr content than the oxide on the
wrought specimen. Note also that the
sputter-deposit is still tine-grained.
FIGURE 22. Effect of Sputter-Deposition on the Oxidation Resistance of Theramally-
Cycled 304 Stainless Steel.
452
-------
SPUTIER-DEPOSITED Ni-2OCr
CONTAINING 5 VOL% ALUMINA.
OXIDIZED IN AIR AT llOO'C FOR
48 HR. NOTE THE ADHERENT OX I DE
LAYER AND THE ABSENCE OF GROSS
I NTERNAL OX I DATION. um<
SPUTTER-DEPOSITED Ni-2OCr
CONTAI NI NG 5 VOL" ALUMI NA.
ANNEALED AT llOO'C FOR 15 MI N.
NOTE THE FINE, EQUIAXED GRAIN
STRUCTURE. l000x
.
.
, J ", -~ .. - .
..
'.
I
--
WROUGHT Ni-2OCr. OXIDIZED IN
AIR AT llOO'C FOR 48 HR. NOTE
THE NONADHERENT OXIDE SCALE
AND THE GROSS INTERNAL
OXIDATION. um<
. ,#.....,. ~..' ,,"',;-fo{" ,r" "'r! ,',.'
'.1% r;..;r.';,,: ~~. (1:~..;),:f,1~"'i).,~:i.::~:'"'
'\.,. '~ ftM' 'f" . Il~' . ,t,...i~ ~. (
';~:~. ~.u" ,-:4o;;'f ;~.~~ "~".~/~~~"'.!~i': ii:
~.i.~. ~.... ~.:\.t.'.~,;'1 'I" "~ :~,; t ~/.; ~;--:1
':,.,~~:y )."-P:~~'~j":ti.(.;~,'1..,,-f. .i;!...,
~. .,.... '~"'~.".t"':\"'-'1J:..~"~~'''~. .
:_"..'" "'<~"'A .. fiI..,...y...I.r~..."':~'\ ,..:"
,,", ... ""~"'...".a" .t:::""... .,..' .On '.:fo.. ~~~.~.
.~.. -..... .,; ./!.ff.;~~:...J~'.1'~".~"'.1"".",
,.'" ~.,...,Ą:,...\......"....h~i'J,"J,..... ~.....
"'~:"'''.'r' .~.~" ''''-....:'!.'::r''.r,.,;".:.: .--, ai~. ~.~ ";"(
1;'~:'~"~' ;'1;'t;'::.:t::-i~rci..~r. '~~\i~i. :~':~;
., ,"...I..~~....,.. ..~..... ~- .,~.......(....~..~,;...:~. ft.
.._,-,...--;.~," .. .~.. ."'''~':..''-''",''-c-''''.., ",~'.'~f'''''~~
; V"\; f!' ..., ,,:,-,,,,~t'l"'-.;"~; r. "'~"':!'6;(~ ~,~ ,:,., \;,
~~ii..,:'1~4 ~...,.r;....~~-.:.":o(~~~,,~~"',,;.?~,' ~~~.
~~5. ~.':\) "~- .I:..~,....~ "t;.:""f!~~...~'''':~ ,.{~,..~....--
'; .-;i." ",'. "J" ""t~ -":"',- .~, :-'., ..;."I.';'.:,,:~ .
~ f -~~.: I.t . -~. ~~.,~!";// ~." ~.'" .....~~\. ..~T.:l ~\~~~.ft:~.:t.'"
. 'f-f~ "~}~'.~"X.' 'l~~i':,'J~:t#'f;itl!; "'''f'~!'''!>1
"""'.'''{,''~.I',j...... .-:'T.'"':''' ',\;..ar.:~'(~''''' * 'i'
".' ...'-;'.~." ""..s.;". ~ '.. ..'f ..~,....: ... .yu:: ~")
SPumR-DEPOSITED Ni-2OCr
CONTAINING 5 VOL" ALUMINA.
ANNEALED AT llOO'C FOR 48 HR.
NOTE THE MICROSTRUCTURAL
STAB I LlTY OF THE SPUTTER-
DEPOSITED MATERIAL HID<
FIGURE 23. Oxidation Resistance and Microstructure of Sputter-Deposited Ni-20Cr
Containing Alumina.
453
-------
---
I
J L-
, I,.
t'~-
If
8. '.'. ',-,',', '.. .8. 8. 8. '. '.-... -, _,-.8... . ",',','
c
", ."
'\
"
!- -i
-
.....". ~
,
.,. L '--..-.
". '...~ '''' ..-~., ~ .
- -:._~.- \.
: ...--:" -.~~::
I ,
. '--'
-'~'~~~':-~
"- - ---'
-j.' I
~
r- .
, '\ . .,
,\]
--
---
VANE # TOP VIEW
I ",
I )', (i':\';'
, : I
, ,
, . " I ' '"
,\ ,I I. ;\ '
(' . . I .,', .
" ,J . I,
,
( ") \' " ) ' ,
,I \ ,',' \
'\' '.' -' /
,
I I
J
VANE # 1-6 (TOP)
250X
! r
,
, ,I
I'
, .' \
\
, I
. '/~':"'''' -'
,/:: .
';.'-
"'--
. I
( ,i:~1
'. J-': t '
"?\ "
t~\ .
~ '
...., .~-_....~. '..
/
-
,
~~ . . '." .
. , ../ .
. . --:. .
, \,
, \," '
\
, 1,
"., S.
"
, '
"
r
\
/
VANE #1-6 (BOTTOM)
250X
VANE #1-6 (BOTTOM-END)
250X
FIGURE 24.
Platinum Sputtered Overlayer on Vapor-Deposited CoCrA1Y. Coating is
on vapor deposited CoCrA1Y. Coating is on an FT-4 Turbine Vane.
Micrographs are from Zone 6 (top left) and show the platinum coverage
around the trailing edge.
454
-------
.
'--\
""
,
, .;~~~l!~t~~::~'.~-::
~,:' I,' .c, , .;.: : ~. .
:'.'; Ii/. ;,' /',:' '-: il{i If .If
:' : ~,- 'l'iL?.:'! 1,1
." . OJ . ..o f,:. '; ...
: ,/:~:: ~I ,//' -:'
.. ,"'':,',''( ':./ I' ,;:
:.-' , ,I' !, ': 'f'
to" ',~,. . :'l . . I
~a ' of i.. '."
}~ Ii ~ ..\-; -9
.. J , "
....
~"t, ~ ~'r:
\
.....
-..
VANE #34-2
(TOP-AS POLISHED BEFORE H. T.)
425X
.'
"
, I I '
! I
I I I I
I .
I
I
.
"'.; .
, .
. ,
, ,
, :
I
t::.-
\.....
'-,
"'-
.
VANE #34-7
(TOP- AS POLISHED AFTER H.T.)
425X
~
VANE#34-2
(TOP- ETCHED
425X
BEFORE
H. T.)
,I
, ",
I
. ., '. , ,
t. " " "." '''&-, ..:\ l' ~, \~ ~-'." -; :!J'[l :.f!Z~~\f
, . ; r.:: .,:-:: i1r,t: ;~:~ ~, ':. "; V,, .r' ,= ~ . I' ,"( ~ !J','.}I
'" -\ !.' -. I ' :--: I : ,,'\ i -:,"".,;
" I' " I: " . -: 'j ','
, , .\ \' ,I '-,-.
'.,:.,.-,1~.~:.~,~:';i,:_,1j.,~~.:' ft_i:~.: ;,' .,;;f.;~.:-~- .~:~.-,: :.:;::':,.: ~ :)T,-:,;,:.),;~C~'.'~,~.{j,';:~..~~.\~~~f~
f1':~.;-;"* '-t'.".;"""t.-':~"-;"\';"'J~'iN~ "'.;"'~\'\..~~' i'.,J.4t~~
~-~!~~"F';~'~':':;'" ;-1i;-:;-:::~:~~\\! ,~;\" fl.. '%;""~'-~;'-";:-:~- if'~~
"..~~, :t;,y;i~:;:j!k"it;}i:;.,>;~.~:ft.~~"I~.wFI"" ''';. ," ;m.~~"'~
.t;~~~~~ ~Ł~~~').\*~" ,~:!\!'?.>-)~~J' . .~,.~c:;.;~,
VANE #34-7
(TOP- ETCHED AFTER
425X
H . T.)
Effect of Post-Deposition Heat Treatmen~ on, a Sputtered Plati~um Over-
layer on Vapor Deposited CoCrA1Y, Coatlng lS on an FT-4 Turblne Vane.
Note the diffusion of the platinum into the CoCrA1Y after 4 hours at
1 080oC.
FIGURE 25.
455
-------
---
. i ,'.
"
~\ ....
.. .
\
. \
J .
.j:-.
1I1
'"
\
'" ;a.-",
FIGURE 26.
--
---
/
""'~'J.'\ .;. ~".. ''--:( ..
.' : :' ',' ....
. .'
,
I .
,:., '~\.' \', -, .-.:. .
.-
.... :,.", .
,.. .:... '" ~ ." '"..
''If: . ' "
\
. '.
)
.. .' -
. J,
"
,.
~.
. . '."
" "", ..
I
l
)
/
...
~
"\
\.
~
~
-----
LM2500 Blade with Sputtered CoCrA1Y Coatings over a Production PVD
CoCrA1Y Coating. Sputtered coatings from two experiments are visible.
The first (bottom arrow) has a high aluminum content than the second
(top arrow). Two interruptions occurred early during the first ex-
periment (bottom arrow) and these produced the two visible interfaces
in this coating.
"
." ,
'oJ' ,
. .,#
-------
150
14
.......
(/)
~
~
+.>
g' 130
OJ
~
+.>
(/)
OJ
r-
If)
c
~ 120
OJ
+.>
OJ
E
+.>
r-
~
110
100
Figure 27.
COPPER PLUS
. 0.25% S.C.
. O. 50% S. c.
A O. 15% Zr
. 0.15% Zr
0.05% Mg
0.40% Cr
J
lJO
260
3Jo
Substrate Temperature ( C)
Tensile Strength vs. Substrate Deposition Temperature for Several
Copper Alloys. The decrease in tensile strength with increasing
substrate temperature is the result of two factors -- an increase
in grain size and a coarser distribution of the second phase. Both
factors depend upon the amount of diffusion occurring on the surface
of the growing deposit before the structure is "frozen in."
457
-------
- Ie?
E
u
.
c:
~ 104
>
l-
V')
V')
~ let
HI
10
108
107
106
1
T
T/~
fJ.
.l
~
In (-8mm2)
CdS-
In ORAl
40
280
80
120 160 200
SUBSTRATE TEMPERATURE (oC)
240
FIGURE 28. Influence of Substrate Temperature on the Electrical Resistivity of
Sputtered CdS.
458
-------
Appendix
SPUTTERING RELATED PUBLICATIONS AND REPORTS
TO SPONSORS ON WORK PERFORMED BY BATTELLE-NORTHWEST
Sponsor:
US Atomic Energy Commission
ED McClanahan, RW Moss and R Busch. Application of Sputtering to the Fabrication
of Neutron Detector Anodes, BNWL-553, November 1967.
SD Dahlgren. Replica Electron Micrographs of a Sputtered Delta-Stablized
Pu Alloy, J.Nucl. Mater., 333, 1968.
SD Dahlgren and ED McClanahan. High-Rate Sputtering of Stainless Steel,
Proceedings of Third Symposium on the Deposition of Thin Films by Sputtering,
Rochester, NY, Sept. 9-10, 1969.
SD Dahlgren, ED McClanahan, JW Johnston, and AG Graybeal. Microstructure of
Sputter-Deposited 304L Stainless Steel, J.Vac Sci and Tech., vol. 7, No.3,
pp. 398-402, May/June 1970.
SD Dahlgren and AG Graybeal. Reduced Nickel Concentration in a
Stainless-Steel Deposit from Bias Sputtering, J.Applied Physics, 41, No.7, 3181,
June 1970.
SD Dahlgren. Equilibrium Phases in 304L Stainless Steel Obtained by Sputter-
Deposition, Metallurgical Transactions, vol. 1, pp. 3095-3099, Nov. 1970.
SD Dahlgren. Production of Smooth Deposit Thickness Profiles and Homogeneous
Alloys from Parallel Strip Sources, J.Applied Physics, 41, No. 12, pp. 5004-5008,
November 1970.
GL Guthrie, B Mastel, HE Kissinger and ER Bradley. Absence of Voids in Neutron
Irradiated Sputtered Nickel, J.Nuc. Matls, 37, pp. 343-344, 1970.
MD Merz and SD Dahlgren. Tempering Behavior of Iron-Carbon Sputter Deposits with
o to 5 wt% C, Met. Trans. 2, p. 3123, 1971.
N. Laegreid and SD Dahlgren. Wall Sputtering and Wall Life Criteria, Summary
of Meeting, Fusion Reactor First Wall Materials, USAEC Report WASH-1206,
Germantown, MD, p. 69, Jan. 1972.
N. Laegreid and SD Dahlgren. Controlled Thermonuclear Reactor First Wall
Sputtering and Wall Life Estimates, J.Appl. Phys., 44, 2093, 1973.
SD Dahlgren and DM Kroeger. High Critical Current Densities Found
for Thick Nb12A11Ge Superconducting Deposits Made by High-Rate Sputtering,
J.Appl. Phys.,-V01. 44, No. 12, pp. 5595-5598, December 1973.
SD Dahlgren. High-Rate Sputtering of Nb-Al-Ge and Nb-Al Superconductors,
September 30, 1974.
Sponsor:
US Energy Research and Development Administration
SD Dahlgren, M. Suenaga, and TS Luhman. High Field Critical C~rrent Densities
for a Thick Nb Al Ge Superconductor Made by High-Rate Sputterlng, J.Appl. Phys.,
45, 5462, 1974~2--3
459
-------
Sponsor:
US Energy Research and Development Administration -- continued
R. Wang and RP Allen. Structure Transformation in Sputter-Deposited Sm2Co17'
Proceedings of 20th Annual Conference on Magnetism and Magnetic MateriaTs, pp. 683,
1974.
SD Dahlgren. High-Rate Sputtering of Nb-A1-Ge and Nb-A1 Superconductors, Pro-
ceedings of the 1974 Applied Superconductivity Conference, Sept. 30 - Oct. 1-2, 1974,
Chicago, Illinois, IEEE Trans on Magnetics, Vol. Mag 11, p. 217. 1975.
RP Allen, SD Dahlgren, and MD Merz. Preparation and Characterization of Thick
Metastable S utter De osits, Proceedings of the 2nd International Conference on
Rapidly Quenched Metals Section I): MIT, Cambridge, Massachusetts, 1975.
R. Wang and MD Merz.
Nature, March 1976.
R Wang and MA Bayne. Sputter-Deposited Electrical Insulators for CTR Applications,
Proceedings of the 2nd Topical Meeting on the Technology of Controlled Nuclear Fusion,
September 21-23, 1976, Richland, Washington, vol. II, p. 477.
Noncrystallinity and Polymorphism in Elemental Solids,
RP Allen, SD Dahlgren, and R. Wang. Sputter-Deposition of Metastable Ta-Pu,
Ag-Pu, and Co-Pu Alloys, Plutonium 1975 and Other Actinides, Ed. H. Blank
and R. Lindner, (North-Holland Pub. Co. Amsterdam, Oxford, American Elsevier
Publishing Co., Inc., New York), p. 61,1976.
SD Dahlgren. High-Rate Sputter Deposition and Heat Treatment of Nb-Al-Ge
and Nb-Al Superconductors, Met. Trans. A, 7A, 1375, 1976.
WT Pawlewicz and N Laegreid. Sputter-Deposited Materials for Photovoltaic Devices,
in Proceedings of the ERDA Photovoltaic Advanced Materials R&D Program Review Meeting,
Washington, DC, March 1977.
R Wang and MD Merz. Polymorphic Bonding and Thermal Stability of Elemental
Noncrystalline Solids, Physica Status Solidi, 39, p 697, 1977.
Sponsor:
Advanced Research Projects Agency
SD Dahlgren and MD Merz. Solid Solutions in Sputter-Deposits of Iron with 0 to
5 wt% C, Metallurgical Trans., vol. 2, pp. 1753-1760, July 1971.
JW Patten, ED McClanahan, and JW Johnston. Room-Temperature Recrystallization
in Thick Bias-Sbuttered Copper Deposits, J.Appl. Phys., vol. 42, No. 11, pp.
4371-4377, Octo er 1971.
SD Dahlgren and ED McClanahan. Reduced Sputtering Yields for Two-Phase Ag-Ni
and Ag-Co Targets, J.Appl. Phys., vol. 43, No.4, April 1972.
JW Patten and ED McClanahan. Effect of Substrate Bias and Deposition Temperature
on the Properties of Thick Sputtered Chromium Deposit J.Appl. Phys., vol. 43,
No. 11, November 1972.
JW Patten and ED McClanahan. Effects of Deposition Temperature and Substrate
Bias on Orientation and Hardness of Thick Sputter Deposited Beryllium Foils
J. of the Less-Common Metals, 30, pp. 351-359, 1973.
460
-------
Sponsor:
Advanced Research Projects Agency -- (continued)
RW Stewart. Materials Synthesis by Sputter Deposition --
December 1, 1970 to June 1, 1971
RW Stewart. Materials Synthesis by Sputter Deposition --
June 1, 1971 to June 1, 1972
RW Stewart. Materials Synthesis by Sputter Deposition --
June 1, 1972 to June 1, 1973
RW Stewart. Investigate Material Systems for Mirrors Used in High Power CO
and C02 Lasers, Semiannual Technical Report December 1972.
RW Stewart. Investi ate Material S stems for Mirrors Used in Hi h Power CO
and C02 Lasers, Semlannual Technlca Report - August 1973.
RW Stewart. Investigate Material Systems for Mirrors Used in High Power CO
and C02 Lasers, Final Technical Report - November 1974.
R. Busch and JW Patten. Lamellar Composites Formed by Sputter Deposition, Annual
Technical Report June 1974.
R. Busch and JW Patten. Lamellar Composites Formed by Sputter Deposition;
Properties and Potential Application to Turbine Blades. Annual Technical Report
July 1975.
R. Busch and JW. Patten. Application of Sputter-Deposited Lamellar Composite
Technology to the Development of High Temperature Turbine Blade Materials
and Airfoil Fabrication, Annual Technical Report - October 1976.
Sponsor:
Battelle Memorial Institute
R. Wang and SD Dahlgren. Observation of Twin Faults in Sputter-Deposited
High-Purity Nickel, J.of Mat. Sci., 10, 1456, 1975.
MD Merz and SD Dahlgren. Tensile Strength and Work Hardening of Ultrafine Grain
Copper. J.Appl. Phys., 46, p. 3235, 1975.
MD Merz, SO Dahlgren, R. Busch and R. Wang. Mechanical Properties of Ultrafine-
Grained Copper and Copper-Zirconium Sputter Deposits, Proc. 2nd intern. Conf.
on Mechanical Behavior of Materials, Fed. of Mat'ls. Soc., p. 58, 1976.
SO Dahlgren, WL Nicholson, MD Merz, W. Bollmann, JF Devlin and R. Wang. Micro-
structural Analysis and Tensile Properties of Thick Copper and Nickel Spu~Deposits,
Thin Films, 40, p. 345, 1977.
N Laegreid, R Wang and WT Pawlewicz. Fabrication of Low Cost Thin-Film Solar
Cells, in Proceedings of DARPA Materials Research Council Summer Meeting, LaJolla, CA.
1974.
JW Patten. Implications of Metal Foam Experiments for Fluid Flow Effects on
Materials System Processed in Zero Gravity, invited paper presented at the
conference "Applications of Space Flight in Materials Science and Technology,"
NASA and NBS, National Bureau of Standards, Gaithersburg, MD, April 1977. extended
abstract published in Proceedings.
JW Patten. Materials Processing in Space, invited paper presented at the "Symposium
on Use of Space Shuttle for Science and Engineering," NASA and AVS, Ames Research
Center, Mountain View, CA, May 1977, extended abstract published in Proceedings.
461
-------
Sponsor:
Naval Ship Engineering Center (Naval Sea Systems Command)
EO McClanahan, RW Moss, R Busch, JW Patten, JW Johnston, IB Mann and HR Gardner.
Investigate Feasibility of Using Sputter Deposition to Produce an Adhere~t Sulfidation
Resistant Coating of CoCrA1Y on Superalloy Turbine Components to be SerVlce Tested
by NAVSEC. Two-Qtr Report - February 2, 1973 to August 6, 1973.
JW Patten, EO McClanahan, RW Moss, 00 Hays, JW Johnston, lK Fetrow, and HR Gardner.
Investigate Feasibility of Using Sputter Deposition to Produce an Adhere~t Sulfidation
Resistant Coating of CoCrA1Y on Superalloy Turbine Components to be SerVlce Tested
by NAVSEC. Report Period - August 7. 1973 to March 28, 1974.
EO McClanahan, R. Busch, JW Patten (BNW), and J Fairbanks (NAVSEC). Initial Work
on the Application of Protective Coatings to Marine Gas Turbine Components by High-
Rate Sputtering, ASME publication #74-GT-100. Presented at the Gas Turbine Conference
and Products Show, Zurich, Switzerland, March 30 - April 4, 1974.
JW Patten, EO McClanahan, RW Moss, JW Johnston, and RA Lundgren. Preliminary Report
on the Sputter Deposition of Platinum Coatings on Superalloy Pins. Report Period -
July 1, 1973 to September 15, 1973.
DO Hays and JW Patten. Burner Rig Testing of Sputter-Deposited and Physical Vapor
Deposited CoCrA1Y Coatings. Report Period - February 27. 1975 to January 15, 1976.
JW Patten, RW Moss, DO Hays, ED McClanahan, RA Lundgren and HR Gardner.
Extend CoCrA1Y and Pt Sputter-Deposition Technology to Provide Coatings on FT4 Turbine
Vanes for At-Sea Evaluation. Report Period - February 27, 1975 to January 15, 1976.
JW Patten, RW Moss, DO Hays, ED McClanahan and RA Lundgren. Extend CoCrA1Y and
Pt Sputter-Deposition Technology to Provide Coatings on FT4 Turbine Vanes for
At-Sea Evaluation. Report Period January 16, 1976 to December 31, 1976.
JW Patten, DO Hays, RW Moss (Battelle-Northwest), JW Fairbanks (NAVSEC).
Recent Development in the Application of High-Rate Sputtering Technology to the
Formation of Hot Corrosion-Resistant Metallic Coatings on Marine Gas Turbine
First-Stage Vanes and Blades, contributed by the American Society of Mechanical
Engineers for presentation at 1977 Tokyo Joint Gas Turbine Congress held in
Tokyo, on May 22 to 27, 1977 under the co-sponsorship of Gas Turbine Society of
Japan, the Japan Society of Mechanical Engineers and the American Society of
Mechanical Engineers.
R Busch, RW Moss, and HG Barrus. Investi ate Feasibilit of Usin S utter De osition
to Produce an Adherent Zirconia (ZrO? Coating on Superalloy Test Pins for Evaluation
by NAVSEC in a Burner Rig. Report Period - November 5, 1973 to March 28, 1974.
R Busch. Develop Sputter Deposited, Graded Metal-ZrO Coating Technology for
Application to Turbine Hot Section Components. Reporf Period - February 27, 1975
to November 20, 1975.
R Busch. Develop Sputter Deposited, Graded Metal-ZrQ Coating Technology for
Application to Turbine Hot Section Components. Reporf Period - November 21, 1975
to September 30, 1976.
Sponsor:
Northwest Mutual Life Insurance Company/Battelle Memorial Institute
WT Pawlewicz, RP Allen, HG Barrus and N Laegried. Structure and Properties of Sputter-
Deposited CdTe, Proceedings 2nd International Conference Cadmium Telluride, Strasbourg,
France, in Revue de Physique Appliquee, vol. 12, No.2, 417-422, February 1977.
462
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Sponsor: Air Force Materials Laboratory (AFML) - Wright Patteron Air Force Base
MD Merz, RP Allen and SD Dahlgren. Elastic Constant Increases Upon Crystallization
of a Sputter Deposited Amorphous Alloy, J. Applied Physics, Sept. 1974.
RD Nelson. Research in the Production of Rare-Earth-Coba1t Permanent Magnet
Material by Sputter Deposition, May 1974.
Sponsor:
Rock Island Arsenal
RH Jone~, RW Moss, ED McClanahan and HL Butts. The Sputter Deposition and
Evaluatlon of Tungsten and Chromium Coatings for Use in Small Arms Components,
December 18, 1974.
RH Jones. An Evaluation of Chromium Deposited by High-Rate Sputtering, Metal-
lurgical Transactions, vol. 7A, pp. 1333-1339, September 1976.
Sponsor:
NASA-Lewis Research Center
ED McClanahan, R. Busch and RW Moss. Property Investigation and Sputter Deposition
of Dispersion-Hardened Copper for Fatigue Specimen Fabrication, November 12, 1973.
R. Busch and MA Bayne. Development of Sputtered High Temperature Coatings
for Thrust Chambers, August 9, 1976.
Sponsor:
NASA-Space Processing Program
JW Patten and EN Greenwe'l. Closed-Cell Foams Produced from Sputter-
De~osited Aluminum, Proceedings AIAA 15th Aerospace Sciences Meeting, Los Angeles,
Ca ifornia, January 24-26, 1977.
Sponsors: Advanced Research Projects Agency, US Atomic Energy Commission
(Div. of Physical Research), and Battelle Memorial Institute
R. Busch and ED McClanahan. Copper-Base Materials Formed by High-Rate Sputtering,
Technical Report - March 1977.
463
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464
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Evaluation of Alternatives
Session V
Thursday Morning 9:30
CADMIUM AS A COMMODITY
John M. Lucas
John M. Hague
U. S. Bureau of Mines
Washington, D.C. 20241
Cadmium is associated geochemica1ly with zinc ores and is separated by
necessity as a byproduct of zinc mining and processing. Until 1975 when Japan
became the world's major producer of cadmium, the United States w~s the largest
producer. The United States continues to consume more than any other nation,
about 30 percent of world supply. In the United States six companies are
primary producers of cadmium metal, and two of these also produce cadmium oxide
and other compounds. Other nations with TI~jor cadmium metal production are the
U.S.S.R., Canada, Federal Republic of Germany, and Belgium. Ore reserves
available to domestic producers are a function of zinc ore reserves, and future
resources will probably continue to be closely related to zinc development
projects. Cadmium-zinc resources exist on all continents. Countries with
major resources are the United States, Canada, Australia, and the U.S.S.R.
Cadmium is used for plating or coating small steel parts to impart
corrosion resistance. It is a component of nickel-cadmium and silver-cadmium
batteries. Cadmium compounds form yellow and red pigments and serve as heat
stabilizers in plastics. Cadmium is used in fluorescent phosphors, low-melting
alloys, as a hardener for copper wire, and in nuclear reactor control rods. In
some electroplating applications, zinc can be substituted for cadmium, and in
some pigments iron or zinc compounds can be used for red or yellow, but they
are not as brilliant nor as stable as cadmium compounds.
Much of the research on cadmium has dealt with its toxic effects on
human health and the environment. Cadmium has been identified by the Environ-
mental Protection Agency (EPA) as a dangerous toxic pollutant.
Looking forward
production, may
about 3 percent
to 2000, U.S. cadmium production, which is related to zinc
reach 5,000 tons per year. Demand is expected to grow at
per year and remain at least twice the domestic production.
465
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CADMIUM AS A COMMODITY
By John M. Lucas and
John M. Hague
D.S. Bureau of Mines
2401 ESt., NW.
Washington, D.C. 20241
Cadmium, like many widely used and accepted metals, is used in a multitude
of necessary though obscure applications.
Daily, we unconsciously rely
upon cadmium and its numerous compounds to protect our metal goods from
damaging corrosion, to power our portable radios and calculators, and to
protect our living, working, and storage spaces from the ravages of fire.
Historical Review
This useful metal was discovered in 1817 by F. Strohmeyer, a professor
of metallurgy at Germany's Goettingen University.
During a routine
examination the professor noticed an unusual slightly yellow coloration
in a sample of calamine or zinc carbonate, obtained for testing from the
zinc works at Sa1zgitter, Germany.
After thoroughly testing the sample
for the presence of iron or other known elements which may also produce
a yellow stain the professor rightly concluded that the negative results
of his tests indicated the presence of a new element.
Further testing
confirmed his suspicion and cadmium was thus added to the rapidly expanding
list of newly discovered elements.
Strohmeyer's serendipitous discovery
only slightly preceeded the nearly simultaneous detection of cadmium by
other independent analysts.
Therefore, the name "cadmium" proposed by
the professor fortunately took precedence over other names such as jumonium,
me1inum, or k1aprothium suggested by the other, later discoverers.
466
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Few practical applications were immediately found for the new metal and
for a period of over 60 years following its discovery Germany was the
only country producing significant quantities of cadmium on a commercial
basis.
Commercial production of the metal commenced in the United States
in 1907 and by the beginning of the First World War a number of domestic
smelters were recovering cadmium as a byproduct of their zinc smelting
operations.
Following the wartime termination of trade with Germany,
production of cadmium in the United States expanded rapidly and by 1917
this country was the world's leading producer of the refined metal, a
position that was retained until 1975.
During the First World War cadmium was employed as a substitute for scarce
tin in the production of solders and other alloys.
This usage, together
with the development of a practical commercial cadmium electroplating
process by the Udylite Company in 1919, greatly stimulated the uses of
cadmium throughout the industrialized world.
Today, due to the importance
of minimizing corrosion, cadmium electroplating plays an important role in
both the developed and developing nations of the world.
Physical Properties and Occurrence
Cadmium is a soft, malleable metal slightly heavier than iron.
A freshly
cut surface exhibits a silvery-white color tinged with blue.
This bright
surface when exposed to a humid or corrosive atmosphere will quickly
develop a thin dull protective coating of cadmium oxide.
the vapor or compound form, is toxic and must be handled with care to
The metal, in
avoid acute exposure and accidental release to the environment.
467
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When compared with many of the metals commonly used in modern industry
cadmium is a relatively rare element.
Of the nearly 100 naturally occurring
elements, cadmium ranks 66th in order of abundance and on the average the
earth's crust contains less than two parts of cadmium in 10 million.
For
the most part, cadmium occurs combined with various types of zinc ores.
The most common cadmium mineral, greenockite, a cadmium sulfide, occurs
as a yellow coating or stain on the principal zinc mineral
sphalerite,
or zinc sulfide.
Greenockite may have been the yellow mineral which
earlier had captured the attention of Professor Strohmeyer.
Cadmium
minerals may occur to a lesser extent with lead and copper ores containing
zinc, however, most of the metal recovered today for commercial usage
comes from smelters which deal principally with zinc sulfide ores.
At
these zinc smelters cadmium is usually recovered as the major byproduct
metal.
The minerals of cadmium occur in nature in such small quantities that
they are neither sufficiently abundant nor in quantities great enough
to constitute a minable ore body.
As a byproduct of
zinc,
cadmium production worldwide is directly dependent
upon the production and smelting of zinc ores.
Canada, as the world's
leading miner of zinc, also leads the world in mine production of cadmium.
Hence, over 70 percent of the world's mine production of cadmium comes
from Europe and North America, primarily Canada.
While most of the
cadmium-bearing zinc ore mined in the United States is smelted west of
the Mississippi River, refined cadmium metal and its compounds, from
both domestic and imported sources, is generally consumed east of the
Mississippi.
468
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Geology and Exploration
Zinc deposits containing cadmium occur within a variety of geological
environments though in general the more economically important types of
deposits fall within four broad categories.
The most important type of
deposits are those known as stratabound or Mississippi Valley type
deposits.
These deposits which may be found in districts covering
hundreds of square miles are generally massive, flat lying, irregularly
shaped bodies of zinc and cadmium sulfides which are scattered along
favorable zones within certain carbonate rocks.
The zinc deposits of
the old Tri-State District of Missouri-Oklahoma-Kansas and those of central
and eastern Tennessee are prime examples of stratabound deposits.
Other types of zinc-cadmium deposits of importance, though somewhat lesser
commercial significance than the stratabound deposits, are the replacement
deposits such as those mined at Bingham and Park City. Utah, the vein
type deposits like those of the Coeur d'Alene District of Idaho and the
lens-shaped stratiform deposits in metamorphic rocks such as those found
in the Broken Hill and Mount Isa Districts of Australia.
Exploration
aimed at finding these various types of zinc deposits can be both
expensive and time consuming and even under the best of conditions the
rate of success is extremely low and becoming lower every year.
In order to illustrate the magnitude and complexity of some of the
problems which must be faced during exploration, the following rather
simplistic model is presented.
For example, the shape, form, and relative
4~
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position of stratabound ore bodies is difficult to describe without
going beyond the scope of this paper.
Imagine if you will, a multilayered
chocolate chip cake in which only some of the layers contain chocolate
chips and only some of the chips are real chocolate.
The real chocolate
chips in this case represent ore bodies and the nonchocolate chips represent
subeconomic bodies of cadmium-zinc sulfides or other minerals.
Further
imagine being given the task of locating the chips present in each layer
with the rules of the game being that the only tool you would be allowed
to use would be a small thin-walled glass tube which you could insert into
the cake but only through the top layer.
Each time you probed or returned
a core sample of the cake it could cost you $10,000 or $20,000 or more
and if you were fortunate enough to spear through a chip, it mayor may
not prove to be the real chocolate which you were seeking.
To make this
illustration or model more realistic, the cake should be allowed to slide
off the table and impact on the floor and thus reproduce the fractured and
folded rock layers encountered in nature, then it should be covered with
a thick green icing to represent soil and vegetation.
Location and
extraction of a real chip could ultimately return about 5 percent profit
over and above the risk and expense of finding and recovering it.
Production and Consumption
The United States annually consumes about 12 million pounds or nearly
33 percent of the world's annual production of cadmium.
Of this total,
about one third is imported either in the form of refined metal or as
a component of zinc concentrates or in flue dusts originating from
About 75 percent of the concentrates which this country
has received in recent years were imported from Canada and Mexico.
470
zinc processing.
-------
Cadmium, regardless of its market demand must be recovered at an early
stage during the zinc smelting process.
Early recovery is necessary
both to avoid later interference by cadmium with the smelting or refining
process and to prevent or reduce dispersal of cadmium via the zinc end.
product, which for many applications must be as pure as possible.
The separation of cadmium from zinc at the smelter begins when concentrated
ores from the mill are roasted to convert the zinc sulfide to oxide.
The
volatilized cadmium is collected as fumes or flue dust in baghouse
collectors.
The fume or flue dust may be further processed directly to
produce cadmium metal.
In electrolytic zinc plants the dust may be
recombined with the roasted or sintered feed material, which is then
taken into solution with sulfuric acid.
A zinc-cadmium sludge is
precipitated by adding zinc dust to the solution.
The sludge is then
processed to recover metallic cadmium by either the electrolytic or
distillation methods of separation.
The metallic cadmium is melted and
cast into various commercial shapes such as balls, sticks or slabs.
The smelter recovery of cadmium from zinc ores on a worldwide basis
average about 5 pounds of cadmium metal per 1000 pounds of recovered
metallic zinc.
As a result of this fairly constant relationship
between zinc and cadmium any sustained reduction in the production of
primary zinc due to smelter closures or lower capacity utilization for
example, is ultimately reflected in the availability and price of
cadmium supplies.
471
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There are presently in the United States, six companies operating seven
plants producing cadmium from domestic and imported ores.
The value of
this production in 1976 was over $17 million.
The current producer price
of cadmium is $3 per pound.
However, over the past 20 years the price
has fluctuated widely in the marketplace in response to supply and demand,
technological changes, and general world economics.
As a result of numerous domestic smelter closures since 1969 for economic,
technologic, or environmental reasons our reliance upon imported cadmium
metal has climbed from below 10 percent to more than 60 percent of America's
annual consumption.
New zinc mines and additional zinc smelter capacity
slated to come on stream in the near future should contribute to a
moderate reduction in the volume of imported cadmium required to meet
our industrial needs.
Reserves
Throughout the world the reserves of cadmium contained in known or
currently recoverable zinc deposits amount to about 830,000 short tons
of metal, 305,000 tons of which are contained in North American deposits.
The total identified world resources of cadmium are estimated at over
20 million short tons; however, because of the low-grade of this material
only a small percentage of this volume could be recovered using current
technology.
Uses of Cadmium
In 1976 over 45 percent of the cadmium consumed in the United States
was used in corrosion-resistant applications; 20 percent was used to
produce various pigments; and the remaining 35 percent was consumed in
alloys, plastic stabilizers, batteries, and other uses.
472
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Conservation of natural resources such as petroleum and metals is one of
the goals of the present administration.
The National Commission on Materials
Policy recently estimated that losses attributed to rusting and corrosion
cost the nation roughly $15 billion, every year.
No doubt this figure would
be much higher if the use of corrosion-resistant coatings such as paint,
resins, zinc, and cadmium, were restricted or severely limited.
For certain
corrosion-resistant applications cadmium plating is far superior to that
afforded by zinc.
Galvanized or zinc plated hardware when used in highly
alkaline, marine and/or tropical environments quickly develops a weak,
crumbly, surface coating composed of various zinc compounds.
The bulky
coating in turn tends to interfere with the movement and operation of intricate
mechanisms.
Cadmium, on the other hand, when exposed to similar environments
develops a firm, thin, weathered surface free of undesirable deposits which
provides protection equal to a coating of zinc 4 or 5 times as thick as the
cadmium coating.
An illustration of the consideration that must be given to the use of substi-
tutes is the use of cadmium plating on the clips which hold machine gun
cartridges together as a belt.
If these clips are painted or plated with zinc,
for instance, 50 calibre machine guns used at sea, unless constantly
maintained, would quickly jam as the products of oxidation interfered with
the feeding and firing mechanisms.
Since cadmium is both highly conductive and easily soldered using noncorrosive
fluxes cadmium plated components such as contacts and solid circuits are often
employed in electrical and electronic devices, especially those which are to
be exposed to marine or other severe environments.
473
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The high ductility or stretchability of cadmium makes it extremely attractive
for use in conjunction with metals which are to be formed by bending or die
stamping.
When cadmium plated sheet metal or flat stock is stamped or formed
the thin ductile plating stretches and shrinks in concert with its base metal
host without cracking around curves or otherwise separating from its substrate.
One advantage to plating prior to forming is that it eliminates problems
associated with cleaning and draining electrolyte from intricate or closed
forms.
Another is that plating coverage of uniform thickness can be maintained
and assured throughout the end product.
In aircraft usage cadmium plating of steel fittings which will be in contact
with aluminum is effective in overcoming a galvanic difference between the
steel and aluminum.
Eliminating the galvanic difference prevents corrosive
failure of the metals at the point of contact.
Cadmium compounds are widely employed in the manufacture of pigments used in
such products as paint, plastics, inks, and rubber.
Colors such as yellow,
orange, red, and maroon are prepared from cadmium compounds.
Cadmium pigments
extended by the addition of barium sulfate are known as lithopones and are widely
used in the pigment industry.
They are popular because of their excellent
lightfastness or ability to withstand fading, darkening, dulling, or loss of
hiding power after long exposure to light.
Because of the toxicity of cadmium,
cadmium-based pigments are not used in materials destined for use in food
storage or handling, children's products, or products which come into direct
contact with water supplies.
474
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During the manufacture of plastics which are formed at high temperatures,
cadmium compounds are added as stabilizers to minimize undesirable properties
which would otherwise develop during the molding process.
Toxicity of the end
product is again a factor which is avoided where necessary by the use of more
expensive and sometimes less effective cadmium-free stabilizers.
When combined in varying proportions with other metals cadmium forms a number
of alloys ranging from tarnish resistant silver to metal which melts in
boiling water.
The latter, known as fusible alloy, is often used to pot or
encapsulate oddly-shaped or delicate objects during the manufacturing process.
For example, the flat end of aircraft turbine blades are mounted in a block of
fusible alloy which can then be clamped to the machine which cuts and finishes
the dovetailed end by which the blade is attached to the turbine rotor.
When
machining is complete the blade and alloy are placed in boiling water where
the alloy melts away from the finished blade.
The fusible alloy is entirely
reclaimed and used again for later potting operations.
The addition of up to I percent cadmium to copper increased the tensile
strength of copper wire and enhances its resistance to wear caused by sparking
and abrasion which may occur in overhead wires such as those used by
trolleybuses and electric railways.
Other cadmium alloys are employed in nuclear reactor control rods, bearings,
and special purpose solders.
Cadmium was at one time combined with mercury.
another toxic substance, for use as a dental amalgam which, fortunately for
the dentist and patient alike, is no longer in use.
475
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The rapidly expanding use of cadmium in nickel-cadmium batteries and cadmium
sulfide solar cells may offset the decline in consumption of cadmium for
dissipative uses, resulting from the change to alternative materials.
In
addition to the use of cadmium in the small, increasingly popular rechargeable
ni-cad batteries which are available for flashlights, pocket calculators,
and other consumer electronic goods.
A positive aspect of these new
applications is that recycling of discarded products can be encouraged and
implemented through a system of returnable deposits and/or obsolescence
promoted via improved technology.
The average growth rate for cadmium consumption between now and the end of
the century is estimated to be on the order of about 2.7 percent per year for
the United States and 3 percent per year for the rest of the world.
In the
United States storage batteries, plastics, and synthetics are forecast to be
the major areas of cadmium consumption.
The total annual world consumption
in the year 2000 is expected to amount to about 41,000 short tons compared
with nearly 19,000 short tons in 1976.
Assuming that the supply/demand trends
established for both cadmium and zinc over the past 20 years remain valid,
then the supply of cadmium available for industrial usage worldwide should be
mOre than adequate to meet all requirements.
Environm~~tqt and Strategic Considerations
Cadmium is distributed throughout our environment as a result of the breakdown
and exposure by weathering of cadmium-bearing rocks and minerals.
Consequently,
the soils of some areas may contain naturally high (eg. 0.01 percent cadmium,
East Tennessee) concentrations of cadmium while the soils of other areas may not.
476
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Natural contaminants of one sort or another abound in nature and like the
uncontrollable ecological disasters frequently caused by forest fires, floods,
and volcanic eruptions there is little that can be done to avoid some
contamination.
The industrial dispersal of cadmium into the environment has
for some time been recognized as a cause for concern by both government and
by the industries involved in its production and usage.
This concern has been
translated into a notable reduction of cadmium emissions to the environment
from a multitude of controllable sources.
The recent interest in the use of substitutes for cadmium is being intensified
not only from the standpoint of attempting to reduce further those emissions
of cadmium which are due to its dissipative uses, but also to assure that in
the event of a national emergency, which might curtail imports of metals of
all sorts, that adequate substitute materials will be available and ready
to meet certain strategic applications without long delays due to testing and
evaluation.
In the interest of brevity only the most salient technical features related
to cadmium have been presented here today.
One of the many activities of
the U.S. Bureau of Mines is to assemble and disseminate economic, and technical
data on the supply/demand relationships of about 100 commodities, including
cadmium.
The Bureau regularly publishes numerous comprehensive technical
reports designed to help both government and industry to keep abreast of the
ever-changing status of national and international mineral resources.
Its
publications include the Minerals Yearbook, Mineral Facts and Problems, the
Mineral Industry Surveys series and many specialized reports dealing with
current events of mineral commodities.
477
For those of you who may be interested
-------
in two of our recent publications dealing with cadmium I have a limited
number available here for distribution.
I have here also a number of
forms which may be used to order various Bureau of Mines commodity reports,
including those pertaining to cadmium.
Selected Bureau of Mines Publications
Mineral Industry Surveys, "Cadmium"
Published quarterly and annually.
Bureau of Mines Minerals Yearbook,
"Cadmium," 1975 preprint.
Mineral Facts and Problems,
"Cadmium," 1975 preprint.
Commodity Data Summaries 1977
Mineral Trade Notes
Mineral Trends and Forecasts, 1976
Status of the Mineral Industries, 1977
Minerals & Materials/A Monthly Survey
Minerals in the u.S. Economy, 1977
These and other publications are available from:
Division of Technical Reports
Office of Mineral Information
Bureau of Mines
u.S. Department of the Interior
2401 E Street, NW.
Washington, D.C. 20241
or
The Branch of Publication Distribution
U.S. Bureau of Mines
4800 Forbes Avenue
Pittsburgh, Pa. 15213
478
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Evaluation of Alternatives
Session V
Thursday Morning 10:05
REPLACEMENT OF CADMIUM ELECTROPLATING
ON IBM HARDWARE
Allen W. Grobin, Jr.
IBM Corporation
Pouch Keepsie, New York 12602
The paper briefly describes IBM's efforts, initiated in 1973, to
identify and replace cadmium electroplated hardware parts.
Types of electroplating are identified on part drawings by code
numbers. Through the use of a corporate central file records system,
approximately 2 million part drawings were search by computer. The searci1
identified approximately 2500 parts that were electroplated with cadmium.
These parts were further sorted by application or function as well as
engineering group of control.
Of these 2500 parts,
the metallurgical properties
rosion protection.
only 60 were electroplated with cadmium for
of cadmium. The rest merely required cor-
Parts requiring corrosion protection were changed to zinc elec-
troplating. Parts requiring lubricity for sliding action were evaluated
using zinc elect~op1ating and a water-emulsion wax post treatment and
electroless nickel. Parts requiring solderability were evaluated with
tin and tin-lead alloys. The description of the code number represent-
ing cadmium electroplating was changed to zinc and only those parts re-
quiring tin or e1ectro1ess nickel electroplating required an engineer-
ing change.
479
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REPLACEHEr~T OF CAmnUri I:Lr::CTROPLA'I'EJG ON 1m-I HARD\vARE
A. W. Grobin, Jr.
International Business Machines
Poughkeepsie, 2Jew York
corporation
12602
This paper describes the sequence of events, the.
mechanisms, and procedures that were used by IBM ~n
the orderly replacement of cadmium electroplated
parts. It also draws parallels for the h~ndling of
similar concerns such as energy conservat~on and
material shortages.
The IBM Poughkeepsie facility had technical respon-
sibility for electrodeposited coating and related
finishes for the corporation. In February 1973, the
Materials Laboratory at Poughkeepsie was notified by
the IBM manufacturing facility in Fujisawa, Japan
that the Japanese government was about to place
severe restrictions on the production and use of
cadmium electroplate. Consequently, the identifica-
tion of cadmium coated parts became necessary.
Telephone communication with Japan made us fully
aware of the environmental problem in and around
Toyama Prefecture and of the so-called Itai-itai
disease and brought to focus the potential magnitude
of the problem on a world-wide basis. This problem
had apparently been brought about by increased
production and by faulty treatment of waste water
from the Hamioka cadmium mine during World War II.
Polluted water from the Jintsu River was used to
irrigate the rice fields. Shellfish at the mouth of
the river were also contaminated. Thus cadmium
entered the food chain and the drinking water. It
appeared that governmental authorities, in an effort
to remedy the situation, were going to set standards
for cadmium in effluent that went beyond the capa-
bility of the small job shop electroplater. Cadmium
electroplating would have to be carried out in
completely new facilities designed to meet these pro-
posed standards. This would, of course, make the
electroplating of cadmium impractical, if not impos-
sible, in the local job shops where the bulk of metal
finishing work is done.
With the growing world-wide awareness of the need for
pollution control, it was reasonable to expect a
number of other countries to follow the lead set by
the government of Japan. We therefore included in
our planning for the solution of the immediate problem
the premise that cadmium electroplating would become
unavailable except under priority conditions.
At the time, IBM had about two and one-half million
active part numbers being used in the product line
and being ma~ufac~ured in fifty U.S. and foreign
plants. Eng~neer~ng control was the responsibility
of a dozen development laboratories. Keeping track
of these parts and their use is the function of the
corporate central file. This is a unique computer-
ized file that records and updates all the vital
information fo: each part, including laboratory of
~ontrcl and us~ng manufacturing sites. Also included
~s the raw material~ fin~sh, and a description of the
part. based o~ key d~mens~onal or functional parameters.
The J.i1.format~on about each part is in the form of code
Tlumbe:s. Thes~ ~ode numbers are used to callout
mate~~al.and f~~~sh on each part drawing. Suppliers
are.turn~shed w~th a regularly updated booklet which
d8f~nes these code numbers.
480
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The latest edition of the IBM supplier guide, "IBM
Materials, Finishes and Processes," was published in
January 1977. The booklet is issued under the IBM
standardization program as C-P 0-0205-001 and is sent
to all of our suppliers, fabricators, and subcontrac-
tors. The latest specification covering the material
or finish is identified.
A detailed description of the central file can be
found in Fred Groppuso, "How IBM Computerized Its
Control System for More than Two Million Machine
Parts," Computers and Automation, September 1973,
and reprinted in Standards Engineering, February 1974.
To investigate the use of cadmium, a routine inquiry
was made to the central file requesting a listing of
all part numbers using any of several cadmium
finishing codes. Here is a page from a recent central
file report. The report form is flexible and can be
tailored to the user's needs. In addition to storing
information on materials and finishes, the file con-
tains physical dimensions, laboratory of engineering
control, manufacturing sites using the part, and
sources, to name a few records.
The part number is shown in column one. Included
elsewhere in the printout are codes that indicate
whether the number is for a detail part or assembly
and whether it has an active, obsolete, or field
replacement status.
The second column is a one-word part name.
461
-------
------~---
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U"*T ...1 "/11/77 ,.. ALLU A08nl
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----------------------------------------~---------
- --------------------------------------~-----------------
This is the code for the laboratory of engineering
control. The controlling group is responsible for
all changes to the part. All IBM parts are available
for multiple use. A new user of a part establishes
usage through the records system and is thereafter
consulted by the laboratory of engineering control
prior to any change.
The data classification number appears next. This
code identifies groups of similar parts. This number
has a variety of uses such as searching existing
parts for application in a new design or determining
the part function without seeing the actual drawing.
This is a page from the "IBM Data Classification
Manual," highlighting the description of code
14-621.
Indicated here on the central file report is the
current engineering change level number and its data.
482
-------
._------------------------------------~------------
---------------------niW"-Oi'flJtI,M,1.-liIf"-6ili.Y-------------
ttPOlT ...1 '''''177 ,.~ AlLl!!II 5ItOe11ll
"ACt: 1l1li7
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!CADI- II' IMI[Id-. 0Mi- - -- - - - --------- - ---- --- ------ ------- ----- --- -- --- - - --- - - - - - - ----
:::::::::::::::::::--~::J_'-'J_L:~--~J-:::~-:::::::::e:;:::
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. n--n--_--_u_----f...r-r~r-Lf'"t"-6Mi..y-__n_-n_. -
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:::::::::::::::::::~:~::=::-~I____'_'-C---:-:::=~~:-
- ''''I 2250 250 9116 I 10{ 01-"0 57
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ADQm,,,,gJ6 _~.:>_E__n____O}_O_---__-'___I_1)_O-'_-_~__H!_l__-!_C-----------~~_!!_OJ~---
AOOOQ5J!1 J7 TIUIr------lI'T'Ir--T-----J1i'5TO"-~~---l:"----------TJlI~T-"UTDT5""---
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---------------------------------------------------------------------
n - - -- ------------ - ---- - - - - - --- - - - - ~---- -- --- -- --- - - --- ----- -- - - - --- - - --
The code number used on the drawing to represent the
base material is next. In this case, the code 06-060
represents AISI 1010 steel in tempers 1 through 5.
The last
finish.
chromium
column shows the code
Finish code number 45
electroplating.
used to define the
represents hard
The IBM supplier guide will direct the supplier
to IBM specification C-H 6-4104-500 for the require-
ments of the finish. The use of code numbers
instead of actual materials and finishes allows for
economical changes to drawings as well as providing
a rapid assessment of usage and application.
The complete printout was received by mail in three
days. Optionally, it could have been transmitted
via telephone line and terminal printer. An analysis
of the printout showed that 35 manufacturing sites
used cadmium electroplating for machine parts either
in house or at a job shop. The total number of parts
involved was about 2500. An examination of the data
classification code number very rapidly showed that
most of the parts were electroplated for corrosion
protection, but only about 60 parts required detailed
examination to determine why cadmium was specified.
Only six sites were involved with engineering control
of the sixty parts.
483
-------
50 Discontinued. Use Zinc 90
51 Discontinued. Use Zinc 90
52 Discontinued. Use Z1nc 92
53 Discontinued - Use Zinc 90
55 Cadll1uII 2.5.8 ~. C-H
(.0001-.0003 In) 6-4105-500
Char (hro.lte convers1on
(See restriction pari. 5.2.2)
56 Cld81u8 2.5-8 ~. C-H
(.0001-.0003 tn) 6-4105-500
Iridescent chra.IU cony-ers1on
(See restriction P.r. 5.2.2)
The controlling engineering groups were notified
that these parts should be changed from cadmium to
some other finish. The materials laboratory at every
site was notified that no new parts could be released
with a cadmium finish unless there was no alternative.
The bulk of the parts plated with cadmium were simply
and automatically changed to the corresponding zinc
electroplating by changing the description of the
code number from cadmium to zinc. This technique of
changing the description of the code number used to
describe a material or finish on a part drawing pro-
vides an inexpensive means of making extensive
changes. This wholesale change was not without its
problems; the few problem parts became evident very
rapidly.
For example, some cast iron and nitrided parts
not be adequately covered in the standard zinc
bath. However, adequate coverage was obtained
of noncyanide zinc plating baths.
Replacement electroplatings were found and tested for
the 60 parts that had required the functional proper-
ties of cadmium. For sliding wear, the substitute
was autocatalytic nickel, hard chromium, or a dry-
film lubricant such as electrodeposited molybdenum
disulfide. In one case the base material was changed
from steel to aluminum and the surface anodized with
a codeposit of TFE. Where solderability was a
factor, tin electroplating was substituted.
could
cyanide
by use
Previous corrosion studies showed that zinc was equal
to, or better than, cadmium for our applications.
Therefore, the wholesale switch from cadmium to zinc
for the bulk of the parts where corrosion protection
was the objective could be made.
In September 1973, after all testing of replacement
finishes for cadmium was completed, a revised speci-
fication for the three cadmium electroplating code
numbers used on drawings was issued. This document
had the two following special clauses: "RESTRICTION.
Cadmium plating shall only be used where its specific
required metallurgical properties differ from zinc.
For corrosion protection use zinc plating Codes 90,
92, or 93. Consult your local Materials Laboratory,
Technical Services Group or Metallurgical Function."
and "EXISTING DRAWINGS. After 1 January 1974, IBM
part drawings calling out cadmium plating will be
plated in zinc according to the schedule below unless
a note on the drawing states a metallurgical need for
cadmium.
Cadmium 55 - use Zinc 90
Cadmium 56 - use Zinc 93
Cadmium 57 - use Zinc 92"
The materials and finishes guide for suppliers
carries the restriction and existing drawing notice
in each edition.
Today, of the approximately 100,000 parts that are
subject to a metal finishing operation, no more than
a dozen parts require cadmium finish. Other finishes
with the functional properties of cadmium are in use.
We have learned to design without a dependence on
cadmium.
484
-------
This,does not mean that our parts are totally free of
cadm~um. In some instances, commercial items and
assemblies are available only with cadmium electro-
plating. Where possible, we have had the finish of
these items changed. However, the bulk of these
items are finished to a federal or military specifi-
cation and our small volume cannot justify a
second finishing operation by the manufacturer.
Our studies have shown that zinc more than adequately
protects our parts from corrosion and, in fact, with
the advent of the cyanide-free zinc baths the protec-
tion exceeds that of cadmium with an added overall
cost reduction.
The cadmium situation is not unique. Materials gener-
ally are coming under greater scrutiny, not only from
the standpoint of toxicity and flammability, but also
from the concern of availability. Added to these con-
cerns are energy conservation, productivity, and
cost reduction. More and more we are going to need
to identify what we are using, where we are using it,
and how much we are using.
I have attempted to show that what might have been a
very difficult, time consuming and expensive task was
accomplished easily and quickly and, in fact, produced
a net cost savings through the use of automated
computer control of part drawings.
Our use of codes on drawings to represent materials
and finishes combined with our method of codifying
part drawings allows our record system to compile a
where-used trace for materials and finishes. In
addition, the automated record system allows for
multiple use of parts and single sourcing for
multiple plant usage, thereby providing economic
advantage in fabrication, finishing, waste treatment,
and energy consumption.
485
-------
Replacement of Cadmium Electroplating on IBM Hardware
Discussion Period
MR. HRATKO:
Bill Hratko, Sundstrand. When you
substituted zinc for cadmium, did you find that the corrosion
resistant properties were equivalent, or did you have to
compensate by plating more zinc versus cad?
MR. GROBIN:
We didn't have to compensate.
You have
to look at the application of the part.
It has been brought
out that zinc protects better than cadmium in industrial
environments which have a higher sulfide contaminant level.
We found that direct substitution actually improved the
resistance.
I noted in personally examining a number of parts
at test sites that the corrosion on cadmium was far greater
than the corrosion on zinc for equal thicknesses and equal
conversion coating.
MR. JORCZYK:
Ed Jorczyk, 3M Company.
Do you
specify the type of bath the zinc shall be plated in?
MR. GROBIN:
No, we do not.
We feel that it is
much better to specify the end requirement and allow the
finisher to use whatever innovative techniques are
available to him to provide us the best quality at the
most economical price.
We review his process before we
accept it, but we allow the supplier to use all the metal
486
-------
techniques and knowledge at his command.
We feel that the
metal finisher is a highly skilled, very technically
oriented person who is quite capable of managing the
finishing operation.
We come to an agreement with him
on the finishing operation, but we allow him as much
latitude as possible.
MR. COOK:
Albert Cook, ILZRO.
Could you go
into more detail about the dozen parts which are still
being cadmium plated?
MR. GROBIN:
I only talk about a few of them and
they primarily had problems with adhesive bonds.
As pointed
out in one of the previous papers, it is very difficult to
get good adhesive bonding to zinc electroplating while
cadmium electroplating gives very good adhesive bonding.
We are still looking at the problem, looking at new
adhesives.
We are looking at some of the individual
zinc
electroplating and zinc coatings.
We want to include
mechanical coating.
We do use them; we have specifications
to cover them.
There appear to be some differences in properties
in the various zincs.
In ASTM Committee B-8, we are going
to be testing the differences in types of zincs to see if
that situation is real or not.
MR. CLANTON:
Jim Clanton, RCA, Camden, New Jersey.
Mr. Grobin, Did you state that you realized the importance
of this problem in 1973?
487
-------
MR. GROBIN:
Yes.
MR. CLANTON:
You made a major turn around in four
years and it is amazing how you replaced cadmium in a lot
of applications.
Without some major history of tests, were
you faced with any major problems?
MR. GROBIN:
Sure.
We did it in approximately
five months.
We issued the specifications in September of
1973, and they went into force January 1, 1974.
We have
been regularly in production since that time.
Each laboratory
got that specification as it was published.
They immediately
became aware of the parts that they had under their control.
They had equal access to the file.
They went to the file
and asked for all the part numbers that were plated in
cadmium.
They looked at them to see what their logistics
problems were going to be and immediately started locating
zinc electroplaters to handle the switch over, and notifying
the cadmium electroplaters that they were going to stop plating
in cadmium.
They looked for parts which might present a
difficulty.
I mentioned a few, such as the cast iron parts
and the carbonitrided parts.
My office was asked what to do on those parts
which couldn't be plated in zinc.
We located a company
that had developed a new noncyanide zinc bath, and
we bought a quantity for evaluation.
They also informed us
that other people were using the bath and had been satisfied
with it.
Our test results showed that the bath lived up to
488
-------
everything that they stated.
Indeed, it plated on cast iron
parts, and it actually did a better job than cadmium.
One benefit was a lower rejection rate of parts.
We found that more attention had to be paid to the cleaning
of the part.
You know, cadmium is very easy to electroplate.
I would swear you could plate cadmium on paper if you tried
That is the one thing that got cadmium really going.
Unfortunately, cadmium will plate over poorly prepared
it.
surfaces and they will creep through into the product.
But on the zinc plated parts, this is not 80.
Your bad
parts come out, and your plater has to be more careful in
his preparation cycle.
MR. CLANTON:
Were military contracts treated
in a similar manner?
MR. GROBIN:
No.
Military contracts are executed
to everyone on the same basis.
IBM has no different treat-
mente
When the government issues us a contract, we plate it
according to the government's specifications.
If they want
cadmium on it, we put cadmium on it.
MR. HOVEY:
Ralph Hovey.
At Amphenol we have not
been as fortunate as you.
We have tried zinc on some
products, and, from our lab testing, there was a beautiful
change, but our customers, being electronics people,
invariably run their systems through freon.
tolerate freon, and freon does not tolerate
zinc just doesn't
zinc.
The two
are incompatible.
One of the big notes on all freon equipment
instructions is that under no circumstances zinc should enter
489
-------
into these solution.
You can imagine what happens to elec-
tronic equipment when zinc is put on it.
With out our
knowledge, our customers used freon in their cleaning sys-
terns prior to soldering and other processes.
This meant that where we had used zinc, we had to
very carefully evaluate everything, assuming that the cus-
tomer was going to use a freon degreasing.
There are a lot
of little things that are not immediately obvious to people.
You have to find out what your customer is going to do with
the plated product before you can get home clean and free.
MR. GROBIN:
That is right.
We had a similar
problem, and primarily used tin electroplating.
We used tin
in a number of ways:
We used tin plating by itself, tin
over nickel plating, a tinzinc plating, and tinlead.
MR. GORDON:
Phil Gordon, CulterHammer.
The
impression you have left is that in this changeover the bulk
of the replacement of cadmium with zinc was based on consi-
dered engineering judgment.
I think the question was
directed at how much evaluation and testing after the fact,
or perhaps you had it as a history before the fact, was
involved in this particular aspect?
To what extent was your
judgment right, and where did you have to pull in your horns
and turn around?
MR. GROBIN:
There was a very intensive effort
between February and September in evaluating the parts.
As
you can imagine, there are many people who, when they hear
490
-------
a change, will scream loud and long.
We put this out as being
a directive and remaining in cadmium had to be justified,
meaning that the person who really had a problem had to prove
it.
It is not hard to prove that you have a problem.
If you have a part that will not work because of being
changed to a zinc electroplating, you can demonstrate that.
But if you are talking about a bracket fastener that is
going to be used to hold a switch onto the frame of a computer,
it is going to be very difficult to justify staying in cadmium
for corrosion protection.
Primarily, our parts are coated for
corrosion protection.
As I indicated here, 2500 parts in cadmium and only
60 of them were using functional properties, or appeared to
be using functional properties, of cadmium.
So primarily, our
parts are plated for corrosion protection.
MR. ZEHNDER:
Joe Zehnder, Enthone, New Haven,
Connecticut.
I can appreciate IBM's concern with pollution
of the environment due to cadmium electroplate, but has any
attempt been made to reduce this pollution by reduction of
cadmium pigments or nickel cadmium batteries?
MR. GROBIN:
I really can't answer that because
I don't know what pigments are used in our paints.
a requirement that our paints be non-toxic so I doubt that
We have
cadmium pigments are used in them, but I can't state that
definitely.
As far as nickel cadmium batteries are concerned,
491
-------
that area is handled by someone else who has a responsi-
bility similar to mine and I don't know what he has done.
MR. ZEHNDER:
It seems as though the electroplater
is bearing the brunt of cadmium pollution.
According to the
data we were given the other day, 54 percent of the cadmium
consumed is used in electroplating.
I just wonder if anyone
has any data showing what percentage of the pollution is due
to uses of cadmium other than electroplating.
MR. GROBIN:
I think you have a very good point.
It would probably be better brought up at the Panel discus-
sion this afternoon.
MR. PON:
Hy name is Kee Pone
I'm with the Naval
Ship Engineering Center.
Earlier you mentioned that when
you supply hardware to the military, you follow military
specifications.
Bear in mind, many of the specifications
are old and the specifications are normally prepared to suit
what is available.
In the case where you have already
trimlined to use something else, I think it is an easy test
just to inform your procurement agency that new substitutes
are available and that it would be to the government's
benefit to use the new ones.
Normally such requests are
granted where justified.
MR. GROBIN:
We are aware of that.
Sometimes that
works and sometimes it doesn't.
It is a problem of the
government having policies and individuals to carry out
these policies.
Some people are more reasonable than others.
492
-------
Marty White, Cadmium Association.
You say this replacement from cadmium to zinc was started
MR. WHITE:
by reports that the Japanese government was going to introduce
very stringent control measures.
Out of the 2500 parts that
were
cadmium plated, how many were plated in Japan?
MR. GROBIN:
The actual number that were plated in
Japan was several hundred.
I don't recall the exact number.
Primarily, they were fasteners and brackets.
They were used
in large quantities so while the number was perhaps 200,
the volume would be rather high.
MR. WHITE:
But you didn't contemplate just changing
those particular ones to zinc?
I am thinking of the cost.
You
seem to react very quickly to something that was happening several
thousand miles away.
Some of your U.K. factories were very upset
about your change from zinc to cadmium because of pressures
that were not affecting them in the slightest.
MR. GROBIN:
Yes.
They always seem to be upset
with everything I do.
I spend more time going to the U.K.
than to any other country because of that.
MR. COOK:
Albert Cook of ILZRO.
It seems to me
that IBM is fortunate in this respect.
On the one hand
your corrosive environment is not as severe as some, and
on the other hand, your choice of alternatives of zinc
plating has been extremely well documented.
You have plenty
of data available on zinc plating.
Could you comment a little
more on the sort of corrosive environment that you normally
493
-------
meet and how you feel about going to other than zinc plating
for use in a marine environment?
MR. GROBIN:
We actually go into marine environ-
ments.
We go into every type of environment in this world.
Our product is sold allover the world.
We find that the
greatest usage is obviously in the industrialized nations.
Various reports will show that the industrialized nations
are the greatest consumers of energy, and among the by-
products of consuming energy are sulfur dioxide and hydrogen
sulfide. 50 these atmospheres are prevalent.
I think it was pointed out yesterday that opera-
tional aircraft on aircraft carriers are having problems
from the sulfur dioxide coming from the stacks of the oil
being burned to run the ship.
The sulfur dioxide problem is
worldwide, while salt corrosion is not.
These problems have
to be taken care of.
I think some of the new alloys that we are seeing
probably will end up being the answer.
But that is only a
guess on my part.
I don't think that we will ever get rid
of cadmium for electroplating completely.
I think it
serves
some very vital functions.
I believe it is overused.
I
don't see any new thinking or very much new thinking in the
area.
Designers seem to use what they used last year.
I
think we have to get back to the designers and tell them
that it is their mission to start looking at new materials.
It is up to them to start the initiation of using these
things and having them tested and evaluated.
4~
-------
Evaluation of Alternatives
Session V
Thursday Morning 10:40
EVALUATION OF COATED FASTENERS:
ALTERNATIVES TO CADMIUM PLATING
Howard J. Dolejs and Raymond E. Geisert
Gould Inc. Ocean Systems Division
Cleveland, Ohio 44117
A variety of coatings for steel fasteners are being evaluated as altern-
atfves for cadmium plating for improved corrosion resistance. The requirements
for the coatings are that they withstand a variety of corrosive environments
and be compatible with the aluminum alloys. Also, the application process
should not affect the base metal properties of the fastener. Other fastener
coatings such as black oxide and mechanically applied cadmium offer les~ cor-
rosion resistance than electroplated cadmium. The six types of vendor applied
coatings evaluated consisted of electroplated aluminum, IVD aluminum, thermal
decomposition aluminum, chrome-zinc plating, diffused nickel cadmium, and
baked polymer over cadmium plating. The coated fasteners were tested per MIL
Standard 1312 for hardness and stress durability and were exposed to a 5% salt
spray to failure or 45 days, whichever came first. Potential Qeasurements of
the various coatings were made and compared to 7039 aluminum alloy which is
used for the torpedo shells. Environmental tests in the engine exhaust and in
Otto Fuel/sea water vapors are in progress. The galvanic current generated by
each type of fastener coating when connected to 7039 aluminum alloy is being
measured. Results to date show that only the polymer coated cadmium plating
meets the requirements. Other tests are in progress.
495
-------
EVALUATION OF COATED FASTENERS
ALTERNATIVES TO CADMIUM PLATING
by
H. J. Dolejs and R. E. Geisert
Gould Inc. Ocean Systems Div.
18901 Euclid Ave.
Cleveland, OH. 44117
INTRODUCTION
A variety of threaded fasteners are used in the underwater
systems designed and manufactured by Gould Inc. These
underwater systems are of modular construction and are
typically made up of several separate alurainum alloy sec-
tions. The sections house the electronics, and propulsion
sub-systems and are also used for fuel tanks. The mo~ular
construction allows for ease of assembly and disassembly,
testing, maintenance and change in configuration fron. prac-
tice to warshot conuition.
The majority of the fasteners are cadmium plated with a
chromdte conversion coating. Other fasteners have a black
oxide coating. All are either MS or NAS aircraft quality
type socket head CEp screws or custom machined to Gould
design. The sizes range from 4-40 to 9/16-18. During SCd
trials and in storage the fasteners are exposed to a varie~y
of corrosive environments including:
a.
b.
c.
d.
seC:iv2 ter
fuel and seawater, both liquid and vapor
high temperatures
combustion products - cyanides, acids, and
reducing gases
The cadmium plated fasteners are exposed to all these environ-
ments and black oxide coated fasteners to only the latter two.
Cadmium plated fasteners are also used on electronic comDonents
within protected environments. . ~
A company funded research program was initi21ted to find c02.tinus
with better corrosion resistance than the ones presently used.~
Black oxide coatings corrode rapidly. Cadmium plating lasts
longer, but may corrode after two or three sea runs in the
practice units. Acceptable parameters for a new coating(s)
were:
a.
Better corrosion resistance than electro-
plated cadmium.
496
-------
c.
Application of coating must not affect the
base metal properties of the fasteners no
hydrogen embrittlement and no loss of ~ech-
anical strength.
Co~patibility from a dissimilar metal stand
point with the aluminum alloys in the system.
NOTE: One alloy used is 7039, an aluminum-
magnesium-zinc alloy that is one of the more
a~odic aluminum alloys. Its corrosion potcn-
tlal approaches that of zinc.
b.
A review of reports on fastener coatings and trade liter~t~re
was made to select promising coatings. One report surveyed
various coatings for the harsh environment of aircraft carrier
catapults [ref (1)]. The Air Force and NAVAIR were also inter-
ested in aluminum coatinrJs for high performance aircraft [ref (2)].
A fastener manufacturer related that a diffused nickel cadmium
coating was being used by some aircraft manufacturers. Other
coatings mentioned in trade literature, were proprietary volymer
coating and a chromium zinc flake coating that is used in the
automotive industry. The program WaS established to evalu2te
these types of coatings.
Cadmium coatings other than electroplated had been examined
briefly, but were not included in the program. It was fOGnd
that mechanically applied cadmium did not afford the desired
corrosion protection, nor could it be sucessfully applied to
the fine threads of the smaller fasteners. Vacuum cadmium,
did withstand the salt spray corrosion test, but did not offer
significant improvement over electroplated cadmium. Emphasis
was placed on coatings that would offer clear advantages over
electroplated cadffiium.
TEST PROCEDURE
Procurement of Fasteners
To facilitate the use of the test fasteners in future sea runs,
a standard fastener size MS 16998-29 (10-32 x 3/4" socket head
cap screws), except without plating, was.selecte~. However,
it was discovered that plain, uncoated hlgh tenslle strength
fasteners were difficult to obtain. Eventually one t~ousand
unplated fasteners were purchased; unfortunate~y they we~e all
coated with a black scale produced by a quenchlng operatlon.
To remove this scale prior to coating, and without int~oducing
hydrogen embrittlement, the screws were cleaned mechanlcally
by fine abrasive blasting.
497
-------
Application for Protective Coatings
After cleaning, lots of 50 fasteners were sent to selected
vendors for coating with their specialty coatings. The
types of vendor-applied coatings evaluated consisted of
electroplated aluminum (0.3 mil), IVD aluminum (0.3 - 0.5 mils),
thermal decomposition aluminum, chromium-zinc flake coating,
diffused nickel cadmium (AMS 2416), and baked polymer over
cadmium and over chromate coated IVD aluminum. Additional
protective coatings such as chemical conversion (chromate)
coatings per MIL-C-5541 and/or a proprietary silicone polymer
coating were applied to aluminum coated fasteners by Gould.
Testing of Coated Fasteners
The coated fasteners were tested per MIL-STD-1312 [ref (3))
for Hardness (test no. 6), Stress Durability (test no. 5),
and Corrosion Resistance (test no. 1). The corrosion resis-
tance test which consisted of exposure to a 5% salt spray,
was continued until the test samples either failed or until
an arbitrary 45 day test limit had been reached. All incoming
lots of production fasteners are routinely subjected to these
tests, except that the salt spray requirement is 96 hours.
Since standard fasteners that are used in marine vehicles
are often exposed to fuels, seawater and their vapors, as
well as to combustion product environments, ~he experimental
test fasteners were also exposed to these atrnosph2res under
controlled laboratory conditions and in a propu~sion test
stand run.
Accelerated corrosion can occur when dissimilar metals are
electrically coupled and exposed to a corrosive environment.
In galvanic corrosion, the active (anodic) member will corrode
in preference to the noble (cathodic) member. The galvanic
series which is based on difference of corrosion potential,
indicates if galvanic corrosion could occur. The current
generated by a dissimilar metal couple is a measure of the
rate of corrosion. To determine compatability, corrosion
potential measurements were made on each of the coated fast-
eners and 7.039 aluminum in synthetic seawa ter (l~.STr-1 1142).
The galvanic current generated by the fastener coatings and
7039 aluminum was also measured.
498
-------
Environmental Tests
The coated fasteners were subjected to the total environments
they would encounter in actual use. Six fasteners with the
various coatings were installed in 6061-T6 aluminum blocks
and,torqued ~o 50 inch pounds, the normal installation torque.
A l~ght coatlng of petrolatum was used as a lubricant on the
aluminum coated fasteners, because there was slight tendency
to gall with the aluminum block. The test was run in duplicate.
The two blocks were mounted in a static test fixture and sub-
jected to a total of 54 minutes of propulsion operation. In
this test, the environment consisted of high temperature, and
propulsion exhaust products. After the runs, one of the blocks
was then subjected to a 24 hour salt spray exposure to determine
the amount of corrosion protection remaining.
In another test, the coated fasteners were exposed to fuel and
seawater. Since the fuel is more dense than water and insoluble,
there was a layer of seawater on top of the fuel. The fasteners
were suspended in both liquid layers and exposed for one week
at 140°F.
This was followed by exposure to the vapors above the liquids
for one week at 140°F. It had been found that the fuel/seawater
vapors were particularly corrosive. In addition to the other
fasteners, this test included IVD coated fasteners with a chromate
conversion coating, and the baked polymer coating previously
mentioned. Of the IVD coatings only the 0.5 mil coating was
exposed in this test.
Electrochemical Tests
Potential measurements were made on the coated fasteners and
compared to 7039 aluminum alloy. wire leads were soldered
to the threaded end of the fastener and then a plastic tube
was pushed over the wire and the fastener to isolate the
solder connection from the synthetic seawater electrolyte.
1hesix fasteners with the various coatings and a 7039 aluminum
alloy specimen were installed in the top of a versatile pol- ,
arization cell using teflon adaptors. [ref (4)]. The top has nlne
threaded holes so that each specimen would be isolated yet exposed
to the same electrolyte. Potential measurements were made using a
Keithly model 616 Digital Electrometer with a Saturated Calomel
Electrode (SCE) as the reference electrode. These measurements
were made daily over a period of four weeks.
Galvanic current generated by the more promisi~g coatings and
7039 aluminum were measured using the zero reslst~nce ammeter
(ZRA) technique [ref (5)J. In this test the speclmens were
connected to a potentiostat set at zero,volts: The ~orrosion
current was measured over a 24 hour perlod uSlng a hlghly
accurate current meter. 499
-------
Standard Tests
The following tests were performed on all coated fasteners in
this program.
Hardness Test (MIL-STD-1312, test no. 6)
Five screws selected at random from each coated fastener lot
(type) were subjected to a hardness test conducted in accor-
dance with MIL-STD-1312, test no. 6. Prior to testing, the
sample screws ,vcre cDbcdded in epoxy resin in a metallurgical
mount, sectioned, and polished to provide a stable flat sur-
face for the test. The hardness measuremcr.ts were made on a
Rock\vel1 Hardness Tester.
Stress Durability (MIL-STD-l312, test no. 5)
Four scre\vs selected at random fre,m each coated fa s t.ener lot
(type) were suhjected to a stress durability test conducted
in accordance with MIL-STD-1312, test no. 5. The samplc
screws were first coated with a grap~ite filled lubricant
conforming to MIL-T-5544, and then threaded into a tempered,
test block and torqued to a predetermined valrie Wllich would
produce a tensile stress on each screw equal to 75% of the
minimum ultimate t.ensile strength of the fasteners. Since
all of the fasteners were of the same size, per MS 16998-29,
the torque value was 50 inch-pounds which produced a tensile
load of 2380 pounds, as determined on a Skidmore Wilhelm
Torque/Tension Tester. This represents 75% of 160,000 psi
min. tensile strength.
After mounting, the screws were allowed to rcmain undisturbed
at room temperature for 200 hours and then were removed from
the test block, cleaned with solvent, and inspected for cracks
and other anomalies.
Corrosion Resistance
(MIL-STD-1312, test no. 1)
Five screws selected at random from each coated fastener
lot (type) were subjected to a corrosion resistance test
conducted in accordance with MIL-S7D-1312, test no. 1.
This test consisted of suspending the fasteners in a
standard rubber lined salt spray chamber (as described in
ASTM-B-117-61) and exposing them to a continuous salt spray
(5%) until failure occurred or until an arbitrary 45 day
test period had expired, whichever came first. After
termination of the test, the fasteners were rinsed with
water, blotted dry with a paper towel and inspected at
low magnification (lOX) for corrosion products.
500
-------
RESULTS AND DISCUSSION
Hardness Test (MIL-STD-1312, Test No.6)
Of the six types of experimentally coated fasteners tested
only on~ failed the ROC~W?11C38-45 hardness requirement of'
the baslc fastener.speclflcation MS 16998. The diffused Ni-Cd,
electroplated alumlnum, IVD aluminum, chromium-zinc-flake
coating, and the baked pOlymer-over-cadmium-plate coated
fasteners all passed. All five of these fastener types had
hardness values between Rc 42.1 and 42.8. The decomposition
aluminum plated fastener type that failed, tested at an
average of R~ 26.5. This reduction in hardness is probably
due to the hlgh temperature of the process. The two production
lots of standard cadmium plated, chromated fasteners both
passed with a Rockwell C hardness of 39.7 and 39.8.
Stress Durability (MIL-STD-13l2, Test No.5)
After exposing four fasteners from each lot and ty~e to 2CO hrs.
of stress at 75% of their minimum ultimate tensile strength,
they were removed and inspected from cracks. ~ll of the fust-
eners passed the test. This indicated that the individual coating
processes had not damaged or ernbrittled the fasteners.
Corrosion Resistance (MIL-STD-1312, Test No.1)
After the coated fasteners had been exposed to the 5~ sslt spray
test until failure had occurred or until the 45 cay test period
had elapsed, they were carefully examined. Test results are
recorded graphically in Figure 1. Standard cadmium plated
fasteners PiN MS16998-62 (O.2 mil & chromate coating) from
stock were used as controls and failed after 15 days exposure
(Figure 2).
IVD coated fasteners per MIL-C-83488 Class 3 (0.3 mil nominal)
Type I (Not chroma ted) [ref (6)] failed after 4 days exposure
(Figure 3). However, it should be noted that the IVD coating
actually measured 0.2 mil [ref (7)]. The addition of a chromate
coating deferred failure to 7 days; addition of a proprietary
silicone coating delayed failure to 8 days; both the chro~ate
plus the silicone coatings over the IVD coat postponed fallure
to 10 days.
IVD coated fasteners conforming to MIL-C-83488 Class 2, Type I
(0.5 mil nominal) were removed from test after 18 days of exposure,
because of the heavy aluminum corros~on prod~cts. However, base
metal corrosion products were not eVldent (Flgure 4). ,It should
be noted that the coating thickness was actually 0.4 mll. \'lh(;n
these fasteners were chromate coated (Class 2, Type II), they.
withstood 45 days of testing. Only one spot of base metal corrOSlon
(red spot) products was evident (Figure 5).
501
-------
Fasteners coated with 0.2 to .3 mils of electroplated aluminum
failed after three day exposure (Figure 6). The addition of a
chromate coating postponed failure to five days. The addition
of a proprietary silicone coating over the chromated fasteners
postponed failure to 10 days. Attempts to obtain t~icker coat~
ings were not sucessful. The vendor was no longer 1n the alum1num
plating business.
Diffused nickel-cadmium plated fasteners failed after 15 days
exposure with red corrosion products evident on most of the
fasteners tested (Figure 7).
A proprietary baked polymer coating over electroplated cadmium
did not fail after 45 days of exposure. The same coating over
IVD aluminum coated fasteners conforming to MIL-C-83488 Class 3,
Type II (chromated) also did not fail after 45 days exposure
(Figure 8).
Chromium-zinc-flake coated fasteners resisted corrosion
twenty days before base metal corrosion products became
The acdition of a proprietary silicone coating deferred
to tw~nty seven days (Figure 9).
for
visible.
failure
The decomposition plated aluminum coated fasteners failed after
four days of test.
Environmental Tests
In the propulsion test stand exposure, the diffused nickel
cadmium and the aluminum plated fasteners appeared to have coatings
remaining on the exposed heads. The diffused nickel cadmium had
changed in appearance from the dark brownish or bluish tint, to a
silvery color, probably due to removal of the chromate treatment
or dye. A spot test to determine if cadmium was still present was
positive. The other coatings had disappeared leaving the bare
fastener. After 24 hours in salt spray, the diffused nickel cad-
mium and the IVD aluminum were intact. The other fasteners rusted.
Figure 10 shows the test block before exposure. Figure 11 shows
the test block after exposure and salt spray. The breakaway torque
after test was equal to or greater than the installation torque,
indicating no damage to the fasteners.
All coatings withstood the one week immersion in fuel and seawater
except the electroplated aluminum, which rusted in three days in the
seawater layer. In the vapor test, the diffused nickel cadmium,
the chromated and polymer coated IVD did not corrode. The standard
cadmium plate discolored as did the polymer coated cadmium plate.
The fasteners with the chromium zinc flake coating and the bare IVD
had red rust showing.
502
-------
Based on,these tests, the diffused nickel cadmium and chromated
IVD alumlnum appear tO,withstand all of the environments of
the underwater propulsl0n system. The 0.5 mil thickness of the
IVD affords more protect~on than does the 0.3 mil coating. It
was reporte~ th~t the,thlnner coating was difficult to control,
and would glve lnconslstent results. Also the chromate conversion
coating affords additonal protection to th~ IVD aluminum.
Electrochemical Tests
Initia~ly, the corrosion potentials of the various coatings were
ca~hodlc to ?039, excep~ for the chromium zinc flake coating
WhlCh was Sllghtly anodlc. (Table II). The potential difference
w~s ~ighest with the diffused nickel-cadmium, approximately 400
mllllvolts, as compared to (1200 millivolt difference with the
other coatings. The chrom~,;' zinc flake coating was 80 millivolts
more negative, however, after four weeks, the potential of the
coating had become more positive by 360 millivolts which made it
cathodic to the 7039 aluminum.
The potential of the 7039 had shifted by 100 millivolts more
positive during the test and the potential of the IVD shifted
70 millivolts more negative. Based on the potential difference
of the diffused nickel cadmium and the chromium zinc flake
coating, which were more cathodic than 7039, it was felt that
they would not be compatible.
The galvanic current measurements show that the diffused nickel
cadmium would not be compatible with 7039 aluminum. The current
measured 150 pa/cm2 for diffused nickel cadmium as compared to
5 pa/cm2 for bare IVD and 0.25 pa/cm2 for chromated IVD. This
compares to 7.0 pa/cm2 for the standard cadmium plating. While
the weight loss was not determined, these measurements indicate
that the corrosion rate of aluminum with diffused nickel cadmium
would be considerably higher than with cadmium or aluminum coatings.
With the chromated IVD the corrosion rate would be almost nil.
From these data, aluminum coatings appear to offer the desired
corrosion protection for fasteners, if they are at least 0.4 mil
thick. Initially 0.3 mil aluminum coatings, both IVD and electro-
plated were reauested since this is the present thickness of
cadmiu~ plating~on fasteners and it was found that this thickness
was not adequate. Gould's tests showed tha~ 0.3 IVD aluminum,
coating on fasteners failed after 96 hours ln salt spray- ThlS
compared to 768 hours reported for coated steel p~nels [ref (8) ] .
vfuen questioned about this discrepancy the vendor had found that
the process was difficult to control in th~ lower thickness range.
Scanning Electron Micrographs (SEMS) of thlS grou~ of fas~eners
showed the thickness was actually less than 0.2 mll. SEMu of
fasteners with 0.5 mil coatings (nominal), showed the thickness
503
-------
to be approximately 0.4 mil. Specification MIL-C-83488 allows a
tolerance of + 0.1 mil on the 0.5 and 0.3 mil coatings. There-
fore, the first group of coated fasteners did not meet the re-
quirements of the specification while the second group did.
The second group of fasteners with the 0.5 mil coating showed
much better corrosion resistance in salt spray and the environ-
mental test, particularly with the vendor applied chromate
conversion coating. However, this thickness could present
problems in a class three fastener fit, which is a close toler-
ance fit.
The baked polymer coating also shows promise when applied over
both cadmium and aluminum. This coating withstood the salt
spray test with no failures and appears to be satisfactory
in the fuel-salt water test. However, it will not withstand the
engine exhaust environment. Also the additional thickness could
present a problem on fit.
This program had only been concerned with finding coatings that
would be a satisfactory replacement for cadmium fro~ a corrosion
standpoint.
A follow-on program will consider the following:
1. Installation torque values
2. The need for a thread lubricant and if so, which one.
3. Reusability, since the fasteners in the underwater system
are resued many times.
4. Cost and availability
5. Performance in actual field use.
Conclusion
1.
2 .
Ion vapor deposited aluminum per MIL-C-83488 Class 2
Type II appears to be a satisfactory replacement for
cadmium plating.
Questions of fit, galling, and reusability would have
to be studied before the coating could be rccoIT~ended.
Acknowledgment
This work has been sponsored by Gould Inc. I~ & D program
under the sponsorship of the Ocean Systems Division.
504
-------
References
1.
E. Taylor, R. Burkhart, G. Gehring, "Corrosion Control
of Fastening Systems for the Harsh Environments of Air-
craft Carrier Steam Ca tapul ts" Paper No. 178 Corrosion/76.
2.
F. Meyer, Jr., E. Jankowski, "Corrosion Performance of
Ne\" Fastener Coatings on Operational Military Aircraft"
Paper No. 115 Corrosion/73.
3.
Military Standard 1312
Test Hethods."
"Fasteners,
4 .
R. Geisert, N. Greene, V. P-_garwala "A versatile Pol~lrization
Cell System" Corrosion, Vol. 32 No. 10 pp 407-410 (1976)
5.
J. Von Fraunhofer, P - Staheli "'I'he rneasuremen t of Cal vanic
Corrosion Currents in Dental Amalgams" Corrosion Science
Vol. 12, p 767 (1972)
6.
Specification MIL-C-83488 "coating, Aluminum, Ion Vapor
Deposited"
7.
Private communication, McDonnell Aircraft.
8.
Report IVD-080-07 "Ivadize - aluminum Plating by Ion Vapor
Deposition" McDonnell Aircraft Co., Jan 14, 1977.
505
-------
TABLE I
Coated Fastener Evaluation
Physical Test Results
HARDNESS TEST (Rc 38-45)(1) STRESS DURABILITY (200 Hrs)
SAMPLE Per MIL-STD-13l2, Test No. 6 Per MIL-STD-13l2, Test No.
Diffused Nickel-cadmium Rc 42.2 Pass
(MIS 24l6E, electroplated)
Electroplated Aluminum Rc 42.1 Pass
Chromium-Zinc Flake Rc 42.2 Pass
(aqueous Dispersion, Bake)
Cadmium Plated Rc 42.8 Pass
+ Baked Polymer
IVD Aluminum Rc 42.3 Pass
Decomp. Plated Aluminum Rc 26.5 (FAIL) Pass
Control HS 16998-62 Rc 39.8 Pass
NOTES:
1)
2)
Requirement from the basic fastener specification HS 16998
Requirement from QQ-P-416, Cadmium Plating Specification
506
-------
TABLE II
Coated Fasteners - Electrochemical Measurements
Corrosion Potential
Volts vs Sat. Calomel Electrode
Initial 4 weeks
Galvanic Current 2
Coating vs 7039 Aluminum (uai~m )
Initial 2~ hours
Coating
Chromium-Zinc-Flake
(-) 0.567 (-) 0.540
(-) 0.835 (-) 0.796
(-) 1.047 (-) 0.6871
(-) 0.765 (-) O. 788
100
150
Diffused Nickel Cadmium
Electroplated aluminum
Not tested
Ln
~ Cadmium Plate plus
Baked Polymer Coating
Not tested
Cadmium Plate
Chromate Coating
(-) 0.795 (-) 0.864 Not tested
1.3 5.0
(-) 1. 20 (-) 0.93(1) 3.8 0.25
(-) 0.784 (-) 0.792 60.0 7.0
IVD Aluminum 0.3 mil
0.5 mil (bare)
0.5 mil (chromated)
7039 Aluminum Alloy
(-) 0.970
(-) 0.870
Notes: 1) after 24 hours
-------
Diffused Nickel-Cadmium
AHS 2416
Electroplated
Aluminum
Chromium - Zinc
Flake
Electropated Cadmium
+ Baked Polymer
I:.n
o
00 IVD 0.3mil aluminuml
IVD 0.5mil aluminum2
Decomposition plated
aluminum
Control, MS16998-62
as received
+ chromate (Cr)
+ silicone coating
+ Cr + silicone
as received
+ silicone coating
as received
as received
+ chromate (Cr)
+ silicone coating
+ Cr + silicone
as received
+ Cr
+ Cr + baked polymer
1
NOTES:
(1) Actual thickness less than 0.2 mil
(2) Actual thickness 0.4 mil
4
5
6
-l~
Removed at 18 days
10
DAYS TO FAILuRE
Did not fail to 45 day~
Did not fail to 45 days
Did not fail to 45 days
15
20
25
Sa I t Spray Test (5~~)
Figure I.
-------
1
BEFORE
AFTER
CADMIUM PLATING WITH CHROMATE COATING
..
Figure 2
5,1\" ~p"ay C!v ,~o...~. - '''-D~".,
fI,:' :~
I-
~
ft",-"",-,...
" . I.
, . '~ .
.: -, :
BEFORE 1
AFTER
ION VAPOR DEPOSITED ALUMINUM
Figure 3
$ a'" S,-"II Y ~'Y"oS!J'.'" - <Ą./,ys
509
-------
....:~ ,.~-
~., . ~ ~~'i ii-1"':.~. ".\ ,
." , 1. ':to .. ~
.,
.'j ;..
..
r "'-
t........-....-_,.~.,fio,j .
ION VAPOR DEPOSITED ALUMINUM
----1
\
f
0.5"\'4\Ł.. ,
~ ~ .
Figure 4
$al/ Sp1l8'1 Evpos"~e . If ~~y~
ION VAPOR DEPOSITED ALUMINUM
WITH CHROMATE
O.5"Nu..
Figure 5
5./+ :S'If.fEYj#OSf#"~. "'~Da"'J
510
-------
BEFORE
AFTER
ELECTROPLATED ALUMINUM
Figure 6 S;/~ ~plfa'l t;)tp.S"II-t - 'I
-------
f:-- - .-. -,.- .
.~
!, AFTER
BEFORE f
~
/..:N
-------
~
'~#!' t'~f!~T~:;f~~.r:'~~:~i7;':::Y"'~'~f~. ",-' ~,. :..~ /;' .
;.' , ,,:Iii, !"";,, ',',
~ Ą'.-' "
'.(:co. -~.
t 4- ;.o,..w ~~ "~'~1':_',;':: -.
BEFORE
FASTENER TEST SPECIMEN
FASTENER ~EST SPECIMEN
AFTER
--- -
Figure 11
Fasteners ExpoSE:d to Combustion Frcc1~cts
513
-------
Evaluation of Coated Fasteners:
Alternatives to Cadmium Plating
Discussion Period
~1R. TAYLOR:
Ed Taylor, Standard Pressed Steel
Company.
I noticed in your stress test, which is Test
Number five of Mil Standard 1312, you torque to 50 inch
pounds.
MR. GEISERT:
Yes.
MR. TAYLOR:
That is for every coating?
MR. GEISERT:
Right.
HR. TAYLOR:
Are you aware that each coating and
each different surface has a different torque tension
behavior?
When you torque the 50inch panels, you may not
get the same load or the same tension in each case.
MR. GEISERT:
Yes, we are aware of that and felt
that using the graphite grease would equalize this. We
recognized that there could be some difference, but at that
time we didn't want to go into the torque tension relation-
ship for each coating.
MR. TAYLOR:
I have done a significant amount of
work in this field.
In the last two years, we have been
looking for a more sensitive hydrogen embrittlement test and
have found that Test Number Five of Mil Standard 1312 just
does not satisfy our requirements.
~'le are currently employing a hydro torque , which
you are talking about, and we do not use the MilT5544, the
graphite.
We also have discovered that an angle block
514
-------
under the head seems to accelerate failure if hydrogen is
present.
We have also used another technique which automatically
loads the screw to a predetermined load rather than depending on
torque, and we find that this also works.
You may want to be
aware of these things for future testing.
The actual load that you imparted on the screws could
have been less than 75 percent of the minimum alternate tensile
strength because of the fact that the surface conditions are
somewhat different.
We have done the same thing and found
that there is a lot of scatter.
Hydrogen will be a lot easier
to detect under higher loads.
You also mentioned that cadmium vaporizes at 450.
Actually it melts at 612.
The industry does not use it above
450 because of the threat of stress alloy cracking.
What I think is very important, and I will address
this this afternoon, is the subject of post-plate embrittlement.
This is embrittlement that occurs because of the anodic action
of coatings or of structure with steel.
In a marine environment,
when you are coating or when your structure corrodes, you can
develop hydrogen.
This can diffuse into the steel, and you can
get embrittlement.
It doesn't matter what the coating is.
I
would suggest for further evaluation that you use a dead weight
load test in a wet environment with your coatings.
Surround
them with a salt solution, hang them up with 75 percent of the
minimum load on, minimum tensile strength, and see what happens.
I think you will be amazed.
515
-------
MR. MAYER:
Jim Mayer, 3M Company.
We have a little
concern over the conclusions regarding your mechanical plating
sample, and I guess we would like to express our willingness
to make sure that in any confirmation studies which you do,
you have coatings which are representative of what we feel
we would like to be supplying.
MR. GEISERT:
We went to local vendors who were using
the 3M process.
We did have good success with fasteners with
larger thread diameter, larger threads, and we were told by them
that because of the configuration of the threads, that the glass
beads just could not get down into the roots.
Maybe you have improvements over that.
This was a
couple of years ago.
MR. MAYER:
I would like Eddie Davis to answer that
question.
MR. DAVIS:
I think the proof is ~n the samples that
everybody saw yesterday.
MR. GEISERT:
I didn't see any 1032 screws there.
MR. DAVIS:
We can certainly plate into small
thread loops.
MR. GEISERT:
I didn't see the size screws that we
used.
MR. DAVIS:
Whatever the size might be, we will
plate into it.
If you want to do any reevaluation as
opposed to going to a vendor, submit the samples to us.
We will be glad to plate them for you prior to your
evaluation.
516
-------
MR. GEISERT:
Thank you.
MR. MAYER:
I would like to add one other helpful
remark to the previous questioner.
There is a new hydrogen
embrittlement study that is under ARP; I believe that is
aircraft research procedure.
It is a 200-hour pre-load
test.
That mayor may not be helpful to you.
517
-------
Evaluation of Alternatives
Session V
Thursday Morning 11:35
EVALUATION OF PROTECTIVE COATINGS FOR
ARMY ORDNANCE ITEMS
Adolphe Edwards and William E. Isler
Harry Diamond Laboratories
Department of the Army
Adelphi, Maryland 20783
Corrosion protection alternatives to electro-deposited cadmium plating
were evaluated by testing a number of defferent coatings on a currently
produced artillery fuze sleeve. The presently used cadmium plating is
covered by MIL-STD-17l, Class 2, No. 1.1.2.2. with an exception that the
inner surface coating may be 0.15 mils minimum. The dimensional tolerances
of the sleeve allow a minimum clearance of 0.3 mils and the coatings evaluated
conformed to these tolerances so that any acceptable alternative coating
could be substituted without major design changes. The coatings tested in-
clude electroplated aluminum, electroplated zinc, electro less plated nickel,
ion vapor deposited aluminum and an immersion coated zinc flake-chromium
mixture. The coatings were tested for adhesion, porosity, salt spray cor-
rosion resistance, thickness and thickness uniformity. Recommendations were
made regarding the feasibility of using these alternative coatings based upon
the test results.
519
-------
EVALUATION OF PROTECTIVE COATINGS FOR ARMY ORDNANCE ITEMS
Adolphe J. Edwards and William E. Isler
Harry Diamond Laboratories, Adelphi, Maryland 20783
ABSTRACT
Corrosion protection alternatives to electrodeposited cadmium plating
were evaluated by testing a number of different coatings on a currently
produced sle~ve for an Army artillery proximity fuze.
The presently used
cadmium plating is covered by MIL-STD-171, Finish
No. 1.1.2.2, Class 2,
with an exception that the inner surface coating may be 0.15 mil thick
(minimum).
All of the coatings evaluated in this study were judged in
accordance with MIL-STD-171.
The coatings tested were of electroplated
zinc, electroless plated nickel, ion vapor deposited (IVD) aluminum, and an
immersion coated zinc flake/chromate mixture.
The coatings were tested for
thickness, thickness variation, adhesion, porosity, and salt spray corrosion
resistance.
The cadmium and aluminum coatings met all of the necessary
standards.
The zinc flake/chromate mixture met many of the requirements and
warrants further study along with the IVD aluminum as alternatives to cadmium
for corrosion protection on fuze sleeves.
520
-------
EVALUATION OF PROTECTIVE COATINGS FOR ARMY ORDNANCE ITEMS
INTRODUCTION
The possibility of restrictions [lJ on the electroplating of cadmium
and perhaps, as suggested in some countries, restrictions on the use of
cadmium itself is of great concern to the U.S. Army.
Many Army ordnance
items utilize electroplated cadmium for corrosion protection.
The imple-
mentation of the aforementioned restrictions could cause major supply and
logistics problems to the Army and indeed to the entire Department of
Defense.
The Harry Diamond Laboratories (HDL) initiated a study to evaluate
some alternative coatings to determine possible substitutes for electro-
plated cadmium in case restrictions are imposed.
A currently produced
artillery fuze sleeve was selected as the test item for this study.
The
presently used cadmium plating is covered by MIL-STD-171, Finish No. 1.1.2.2,
Class 2, with an exception that the internal surface coating may be 0.15 mil
thick (minimum).
Class 2 designates 0.3 mil thickness with a supplementary
chromate treatment.
The coatings tested in this study were electroplated
zinc (Iridite* supplementary chromate treatment), electroless plated nickel,
ion vapor deposited (IVD) aluminum (chromated), and an immersion coated zinc
t
flake/chromate mixture known as Dacromet 320.
Initially, electroplated
aluminum was to be included in the evaluation, but the specimens could not be
prepared in time for this initial phase of the program.
Electroplated cadmium
specimens, with supplementary chromate treatment, Here included in the tests
as standards for comparison.
The dimensional tolerances of the sleeve are such
*Trademark of Allied Research Products, Inc.
tR .
eglstered trademark of Diamond Shamrock Corporation.
521
-------
that the maximum plating thickness allowable is approximately 0.6 mil.
The
coatings included in this study were intended to conform to this tolerance so
that direct substitutions could be made without dimensional or design changes.
TESTING
The coatings were tested for thickness, thickness variation, adhesion,
porosity, and salt-spray corrosion resistance.
Thickness measurement methods
included magne-gage [2J, electron backscatter [3J, and optical microscopy [4J.
Initially, magne-gage and electron backscatter readings were made on all of
the sleeves.
Subsequent optical measurements were used to obtain calibration
curves from which these readings could be converted to thickness values.
The
calibration curves provide nondestructive thickness test methods for future
specimens.
The optical thickness measurements were made on the smooth exterior
and interior surfaces and on the crowns and roots of the interior threads so
that thickness variations could be determined.
The plating adhesion was tested according to Military Specification QQ-P-416C,
Section 4.5.2.
This Specification allows the alternatives of scraping or
shearing through the plating or repeated bending of plated sections until
rupture occurs.
The second alternative was chosen.
Vertical sections cut from the sleeves were bent back and forth until
rupture occurred.
The edges of the rupture surfaces were then examined at
4X magnification for signs of separation between the plating and the base
metal.
522
-------
The ferroxyl test [5J for porosity was performed on the inner and outer
surfaces of sleeves with each type of coating.
The procedure was as follows:
1.
Coat one side of rag bond paper with 5% NaCl-5% clear gelatin
solution, and then dry the paper.
2.
Wet the test paper with 5% NaCl solution and hold the paper firmly
against a plated surface for 10 mln.
3.
Develop the test paper in 5% potassium ferricyanide solution.
The NaCl solution passes through discontinuities such as pores and
reacts with the base metal to form ferrous chloride.
The ferrous chloride
reacts with the potassium ferricyanide to give a blue precipitate, which
marks the locations of the discontinuities.
No porosity test is specified
for these sleeves, but this information should be indicative of the mechanical
protection offered by the coatings.
This factor is of extreme importance
for nonsacrificial coatings.
Salt spray corrosion resistance was tested on 12 sleeves with each type
of plating.
All sleeves were tested simultaneously under the conditions specified
by ASTM Bl17 for 96 hr.
These conditions are listed in Table I.
The sleeves
were then rinsed with running water (Fig. 1) and blown dry.
The results of
all of the testing were evaluated and compared with those for electroplated
cadmium to determine possible substitutes for this application.
RESULTS
The thickness data for all sleeves are shown in Table II.
For the electro-
plated cadmium, the external surface thickness ranged from 0.3 to 0.4 mil (Fig. 2).
Comparing the averages for t he internal (Fig. 3) and external surface, the
variation is about 0.1 mil.
The coating thickness on the roots and crowns of
the inside threads were above the 0.15 mil specified minimum.
523
The thickness
-------
of the electroplated zinc coatings varied from 0.3 to 0.7 mil.
The thickness
variation between external and internal surfaces was 0.4 mil.
The plating
thickness on the external surface exceeded the 0.6 mil maximum in some
instances.
The coating thickness on the internal threads approached the lower
specified limit.
The electroless plated nickel coatings varied in thickness
from 0.3 to 0.4 mil.
The thickness variation between external and internal
surfaces was actually less than 0.1 mil, which is the least variation of any
of the coatings.
The plating thickness pretty much conformed to specifications
on all surfaces.
The external surface thickness of the IVD aluminum ranged
from 0.5 to 0.8 mil (Fig. 4).
Comparing average external and internal surface
(Fig. 5) thickness values gives a thickness variation of 0.4 mil.
The coating
thickness on the roots of the inside threads is near the lower limit of the
specifications.
The external surface thickness fails to meet the 0.6 mil spe-
cified maximum in some instances.
The zinc flake/chromate mixture coating on
the external surface varied from 0.4 to 0.7 mil (Fig. 6).
Comparing the
averages for the smooth areas of the external and internal surfaces (Fig. 7)
indicates a thickness variation of 0.1 mil.
There were, however, buildups at
the roots of the internal threads (Fig. 8) that far exceed the allowable
maximum of 0.6 mil.
The results of the adhesion tests are shown in Figures 9 and 10.
The
zinc flake/chromate mixture coating should have been tested by the alternative
shearing method Slnce it is applied by immersion.
Under the bending test, this
coating flaked off completely due to the severe bending angles applied (Fig. 9).
None of the other coatings showed evidence of flaking or peeling adjacent to
the rupture surfaces.
An example of an adhesion test specimen which did not
flake or peel is shown in Figure 10.
524
-------
The results of the porosity tests probably really indicate "effective"
porosity since sacrificial coatings would tend to deter any attack on the base
metal.
Indications of porosity or other discontinuities are manifest as dark
(blue) spots on the test papers.
The results are pretty much comparable for
electroplated cadmium (Fig. 11) and electroplated zinc (Fig. 12).
The
electroless plated nickel coatings apparently contain a gross degree of porosity.
particularly on the internal surfaces (Fig. 13).
The results for IVD aluminum
(Fig. 14) indicate a bit more porosity than for the first two coatings particu-
larly on the internal surfaces.
The zinc flake/chromate mixture coating results
(Fig. 15) were essentially comparable to those for electroplated cadmium and
zinc.
For the salt spray test, the specification control drawing [6J for this
sleeve states that "Passing the test will require that no samples show SlgnS
of corrosion on the outside surface of the base of the sleeve from the bottom
of the sleeve up to the first external thread."
The electroplated cadmium
specimens clearly passed this test in that they were completely unmarked
(Fig. 16) after the 96 hr salt spray exposure.
The electroplated zinc (Fig. 17)
and the electroless plated nickel (Fig. 18) just as clearly failed the test as
evidenced by the buildup of corrosion products in the specified area.
The
IVD aluminum coatings met the salt spray requirements spelled out in the
Specification Control Drawing (Fig. 19).
There were, hOT,/ever, areas on the
internal surface where corrosion had proceeded even to the extent of penetrating
the coating.
The performance of the zinc flake/chromate mixture coating VIas
marginal in that superficial markings were evident in the critical area (Fig. 20)
There was, however, no evidence of penetration of the coating on either the
external or the internal surface.
525
-------
CONCLUSIONS
Although the scope of this intial phase of the study was insufficient
to qualify any of the alternative coatings, some definite conclusions were
drawn.
1.
The thickness of the electroless plated nickel met the specifications.
Although this study failed to establish the fact, it is anticipated that zinc
can be electrodeposited to the required thickness specifications.
2.
Adhesion appears to be no real problem for any of the coatings,
although the zinc flake/chromate mixture probably should be tested differently.
3.
?Jros::.ty is noproblem with any except the electroless nickel coating,
for which the problem may be insurmountable.
4.
None of the coatings was as resistant to salt spray corrOSlon as
electroplated cadmium with supplementary chromate treatment (Fig. 21).
The
performances of the electroplated zinc and electroless nickel were clearly
unacceptable.
The performance of the IVD aluminum was acceptable, and that
of the zinc flake/chromate mixture was sufficiently close to the MIL-STD to
warrant further consideration.
PLANS
-
The search for suitable alternatives to electroplated cadmium for corro-
sion protection of Army ordnance items include the fallowing:
1.
Further testing of IVD aluminum and zinc flake/chromate mixture
specimens that are prepared to strict thickness and thickness variation
standards.
2.
Testing of electroplated zinc coatings that have a more substantial
,
supplementary chromate treatment.
526
-------
3.
Testing of electroplated aluminum coatings with supplementary
chromate treatment.
4.
Testing of other organic, inorganic, and plastic coatings.
ACKNOWLEDGEMENTS
We appreciate the encouragement and support of H. Suminski of HDL.
We
also thank J. A. de Riddler and J. R. Kovelan of Diamond Shamrock Corporation
and E. R. Fannin and J. J. Reilly of McDonnell Aircraft Co. for supplying some
of the coated specimens.
527
-------
TABLE I
ASTM Bl17
P,~RAMETER
SUSPENSION
SALT SOLUT I O~~
pH RANGE (ATOMJZED AT 30oC)
CO~PRESSED AIR SUPPLY
TE~p. OF EXPOSURE ZONE OF
CHMlBER
DATA
15 TO 30 DEG FROM VERTICAL
5 ~ 1:95 NACL:H20
6,5 TO 7,2
10 TO 25 PSI
35 + 1.1 - 1. 70C
528
-------
TABLE II
COATING THICKNESS (~IL)
I
INTERNAL INT~R~~L
EXTERNAL I ~nERNAL THRE.l\D THRE~D
~~ATER I AL SURF,l\CE SURFACE VA ~ I l\ T I O~1 RrJOT CPOHN
ELECTRO-
PLATED
CADM I U~ 0.4 0,) 0,1 0.2+ 0,3
ELECTRO-
PLATED ZINC f),7 0,3 O,l.1
ELECTRO LESS
~rATED 0.) 0,2 0,1 0,2+ 0 ,I-~
; CKEL
ION VAPOR
DEPOS I TED 0,) 0,4 f),2- I),)
~LUMINUM 0,7
ZINC FLl\KE/
CHRO~ATE MIXTURE 0.4 0,5 0,1 5,0 f) ?
I 1/-
529
-------
REFERENCES CITED
1.
Code of Federal Regulations:
Part 413.
Title 40 - Pro~ection of Environment,
2.
Brenner, A. J., Res. Nat'l Bur. Stds., 18, 565 (1937).
3.
Clarke, E., et. al., Elec. Eng., ~, 35 (1951).
4.
Burns, R. M., and Bradley, W. W., Protective Coatings for Metals,
Reinhold, (1967). p. 330.
5.
Burns, R. M., and Bradley, W. W., ibid., p. 336.
6.
HDL Specification Control Drawing #19202.
530
-------
\;,-,,"":- ';~'"';c.; 't
u-,
w
-
l
t- ;.
Fig. 1
Salt spray chamber with test specimens in place
J
-------
Fig. 2
Section showing Cd plating thickness
on external surface 250X
Fig. 4
Section showing IVD Al coating thickness
on eXternal surface 250X
Fig. 3
Section showing Cd plating thickness
on internal surface 250X'
Fig. 5
Section showing !VD Al coating thickness
CD internal surface 250X
532
-------
coating
- ~- -
II, ,
""'... .,..."
i'~'
.18
...:'4f
. ;"~
:.. '-
Fig. 8 . "," .~
roots of ~ulldup of zin
lnternal threa~ flake/chromate
s 25QX coating in
533
.
,.
Fig.;~ Zinr -
te-t - fld~D/-.
:0 specir-:-ler.jC" - '_.,rCTTictte :r:;'Jo.-,
..c> ~,. '. 'jr.::-
flar-e/chromatp
250% - ~0dting
-------
Fig. 10
IVD aluminum coated adhesion test specimens.
Fig. 12 Results of porosity test on electroplated zinc
coa~i~ External surfaces at top--interna1 surfaces
at bot"Com
53+
~'
...- ,~
"
Fig. 11 R:sults of porosity tes~ on electroplated
cadmium External surfaces at top--internal surfaces
at bottom
Fi~13Resuits of porosity test on electroless plated
nickel coating External surfaces at top--internal
surfaces at bottom.
-------
...~ 't': " :
,(,~. '%.'LA'~
";'/:"""),'i:;'-.'..'~.'.
~.- 0'" ',:.- ~ ~ ~,
. ..... : - "t.
:.. O{; I
rig, 14 R 1
esu ts of posos~ test on IVD aluminum
coating External surfaces at top--internal surfaces
at bottom
,--.J
Fig, 16 Electroplated c:a<1llilllll salt spray test specimens
'."
.
4'
.' "~I
,.
~) -< ~
Results of porosity test on zinc
flake/chromate coatin~s External surfaces at
top--internal surfaces at bottom
Fig. 17
Electroplated zinc salt spray test specimens
535
-------
~~~~
8. _:
~..,
Fig. 18
E1ectro1ess plated nickel salt spray test
Fig. 19 IVD aluminum coated $alt spray test spec~ens
Fig. 20
Zinc flake/chromate coated salt spray test specimens
536
-------
tTt
W
"'L
Salt spray test specimens of (from left to right) electroplated
zinc, IVD aluminum, electroplated cadmium, zinc flake/chromate
mixture, and electroless plated nickel coatings
-------
Evaluation of Protective Coatings for Army Ordinance Items
Discussion Period
MR. KOVELAN:
John Kovelan, Diamond Shamrock.
Thank you very much for your study-
One of the things I
mentioned during my talk was that there are a lot of people
that don't accept the salt spray box as a test.
There are
diversities in them.
We found in most cases we exceeded the
standards, and I think we met your requirements.
They may
have been marginal in a few places, but our field tests at
Curry Beach, and those performed by Dualvast Corporation
over a twoyear period were excellent.
The only way we can
look at these tests objectively is to use them in an opera-
tional, functional way.
HR. EDWARDS:
Well, I agree that high performance
in the field is a lot more important than high performance
in the salt spray chamber.
I feel that probably your pro-
cess parameters were such that they could pass the salt
spray test, were they adjusted.
HR. HAYER:
Jim Mayer, 3M Company.
What consider-
ation did you give to mechanically applied cadmium or zinc
coatings for your testings?
MR. EDWARDS:
When this study was initiated, we
made contact with as many vendors as we could to supply us
with coatings, but there were only a limited number that we
contacted due to the limited amount of time.
Certainly
future Dlans would include such coatings.
538
-------
We would like to have you look at
both of those, and perhaps consider the use of our sulfate
MR. MAYER:
cadmium plating bath as a comparison to the cyanide with which
you are working.
MR. EDWARDS:
We would be happy to do so.
Joe Zehnder, Enthone Incorporated.
I was very surprised to see the results you found with
MR. ZEHNDER:
electroplated zinc because people are plating zinc and are
getting 96 hour salt spray resistance every day.
I would like
to comment on the unrealiability of the salt spray tests.
Committee B-8 of ASTM is actively investigating
the variations that are observed from cabinet to cabinet.
If there is anybody here that would like to get involved
in this evaluation, they should contact Mr. Cobb at ASTM.
I am sure that he could make arrangements for them to participate
in this.
There has been some data received from Australia
recently where they had five test boxes that they ran these
same specimens through and they got five different answers.
MR. EDWARDS:
That is entirely possible.
That was
the reason for our including the cadmium standards in the same
chamber at the same time.
All the specimens
were
in the
chamber at the same time and were exposed to the same conditions,
and I think it is meaningful that cadmium did not have a mark
on it and some of the other coatings were pretty well deteriorated.
MR. ZEHNDER:
I agree with you, but there are different
chromate coatings for zinc than there are for cadmium.
539
-------
MR. EDWARDS:
We do plan to look at zinc with a more
substantial chromate coating.
540
-------
Evaluation of Alternatives
Session V
ThursdayMorning 12:10
CORROSION PERFORMANCE OF NEW FASTENER
COATINGS ON OPERATIONAL MILITARY AIRCRAFT
Edward Jankowsky
Fred H. Meyer, Jr.
Air Force Materials Laboratory
Department of the Air Force
Wright-Patterson Air Force Base, Ohio 45433
. Cadmium plating as currently used for the sacrifical corrosion pro-
tect~on of steel fasteners used in aircraft has a relatively short service
life on operational equipment. Many potential replacement coatings with
greater durability have been proposed throughout industry but very little
actual service experience has been available to properly evaluate the
coatings.
The commonly accepted practice of applying 0.2 mil of ~admium plate per
QQ-P-4l6, Type II, Class 3, as fastener protection has been totally inade-
quate for aeronautical use and a concerted effort by the Aerospace Industries
Association and others concerned has effected a change to 0.3 mil of cadmium
(QQ-P-4l6, Type II Class 2). This thickness still is not totally satisfactory.
The Air Force Materials Laboratory initiated a program in 1964 to evalu-
ate high purity aluminum coatings on standard aircraft fasteners utilizing an
HC-130H Aircraft.
This pioneering study showed that aluminum coatings performed as well as
a cathodic protection coating for steel fasteners with the added advantage of
compatibility with the primary aluminum airframe materials. It was shown
that the aluminum coatings should be a least .0005 inch thick for extended
service life, however. This places an additional burden in determining the
feasibility of replacing cadmium coatings with aluminum coatings. Since the
period of this earlier study a number of more economical aluminum coating
processes have been developed.
The program which is the subject of this paper was initiated in 1969 as
an expansion of the earlier program. Many candidate coatings were offered by
a wide cross section of the aerospace industry for screening in this program.
This program is but a first step in the final selection of new fastener coat-
ings for general usage since side effects such as torque-tension relation-
ship must be evaluated along with joint fatigue strengths.
541
-------
CORROSION PERFORMANCE OF NEW FASTENER
COATINGS ON OPERATIONAL MILITARY AIRCRAFT
Fred H. Meyer, Jr.
Air Force Materials Laboratory, Wright-Patterson AFB, Ohio
Edward J. Jankowsky
Naval Air Development Center, Warminster, Pennsylvania
INTRODUCTION:
Cadmium plating as currently used for the sacrificial corrosion pro-
tection of steel fasteners used in aircraft has a relatively short service
life on operational equipment. Many potential replacement coatings with
greater durability have been proposed throughout industry but very little
actual service experience has been available to properly evaluate the
coatings.
The commonly accepted practice of applying 0.2 mil of cadmium plate
per QQ-P-4l6, Type II, Class 3, as fastener protection has been totally
inadequate for aeronautical use and a concerted effort by AlA and others
concerned have effected a change to 0.3 mil of cadmium (QQ-P-4l6, Type II,
Class 2). This thickness still is not totally satisfactory.
The Air Force Materials Laboratory initiated a program in 1964 to
evaluate high purity aluminum coatings on standard aircraft fasteners util-
izing an HC-130H Aircraft. Results of this study are available in Refer-
ence 1 and 2.
This pioneering study showed that aluminum coatings performed well as a
cathodic protection coating for steel fasteners with the added advantage of
compatibility with the primary aluminum airframe materials. It was shown
that the aluminum coatings should be at least .0005 inch thick for extended
service life, however. This places an additional burden in determining the
feasibility of replacing cadmium coatings with aluminum coatings. Since
the period of this earlier study a number of economical aluminum coating
processes have been developed.
The program which is the subject of this paper was initiated in 1969 as
an expansion of the earlier program. Many candidate coatings were offered
by a wide cross section of the aerospace industry for screening in this pro-
gram. This program is but a first step in the final selection of new fasten-
er coatings for general usage since side effects such as torque-tension re-
lationship must be evaluated along with joint fatigue strengths.
Four operational C-l4l Aircraft were utilized as flying laboratories
by the Air Force for the exposure candidate materials supplied by a wide
cross section of industrial corporations. A-7 and RA-5 Aircraft were util-
ized by the Navy. The use of aircraft was deemed necessary since accelerated
~2
-------
screening tests have been proven to be unreliable as a basis for the pre-
diction of performance of coatings in service. Since the operational en-
vironment profiles of Naval and Air Force aircraft are somewhat different,
a number of the same coatings were also tested on A-7 and~-5 Aircraft
under the direction of the Naval Air Development Center.
TESTING PROCEDURES
To reduce the variability of basis metal quality all
Air Force program were supplied in the uncoated condition
pants by one supplier. The Navy chose to strip fasteners
tory for replating by the participants.
fasteners in the
to all partici-
from field inven-
Three specific panel locations were chosen on each Air Force test air-
craft type to allow a spectrum of environmental exposure to affect the
fasteners, i.e. one panel was chosen on top of the aircraft, one on the side
and one on the bottom. The standard fasteners were removed on the panels
chosen for test and replaced with triplicate specimens of each type of fas-
tener candidate. NAS 1203 standard fasteners were used for the C-141 program.
All participants were asked to supply their fasteners with a nominal .3 - .4
mil coating. Some of the candidate materials were supplied in greater thick-
nesses. However, these were tested as received. The suitability of the
coating will be based on the supplied thickness. This will impose an ad-
ditional economic competitive burden on those suppliers who for one reason
or another were unable to meet the 0.3 - 0.4 mil criteria. Costing thick-
nesses of supplied fasteners were checked using microscopic sectioning per
ASTM B 487-72.
Arrangements were made with Military Airlift Command personnel at McGuire
AFB to inspect the C-141 aircraft fasteners at six month intervals or less,
for corrosion. Assistance was also provided by the Naval Air Development
Center and by the SPS Company in evaluating fastener corrosion. Final test-
ing and removal was planned for a two years total exposure. A complete
itinerary of each C-141 by theater of operation was maintained by the MAC
office for use in determining the environmental profile of each of the test
installation.
Navy fasteners were also inspected at six month intervals. Navy tests
were for a total exposure time of one year-six months on a carrier and six
months of land based operations with short trips to a carrier and back.
The holes were examined for any observable corrosion at the time of the
fastener removals. Identical fasteners of most of the candidate materials
were also exposed on ground environmental test racks at.McGuire.AFB, ~e~
Jersey and McChord AFB, Washington. Coatings were consldered dlsquallfled
for further testing when all the coating had been expended on the head of
the fastener and were then removed from the aircraft or rack.
543
-------
RESULTS
An analysis of the test results obtained showed a marked greater level
of corrosion severity on nearly all coatings on the top of the aircraft
where the fast~ner heads were directly exposed to weather conditions. On
the side and bottom of the aircraft many coatings survived which failed on
the top of the aircraft. Very little evidence of damage was observed on the
airframe countersink areas around the fasteners. For purposes of choice for
further testing the survivability of the coating on the top of the aircraft
for the two year test period has been chosen as the acceptability criteria.
Results of test by the Air Force and the Navy are in good agreement in
spite of differences in environmental conditions. Slight differences that
exist may be accounted for by the shorter Navy exposre time.
CONCLUSIONS
Those candidates based on aluminum coatings deposited by either an
electro-deposition from an ether based process or ion vapor deposition show
a marked superiority over "standard" cadmium plate in survivability. Also
one type of a proprietary metallic ceramic also survived. Minimum coating
thicknesses of 0.4 mils appear to be desirable for consistent performance.
From the production process standpoint the ion vapor deposition process is
currently the most practical technique. Reference to the presentation by
McDonnell Douglas on Tuesday is advised. A MIL-SPEC-MIL-C-83488(USAF)
covers this process.
REFERENCES
1. W. C. Herron, Service Evaluation of Aircraft Experimental Fasteners, AFML
TR-67-360, November 1967.
2. W. A. Boggs, W. C. Herron, Evaluation of Fasteners and Corrosion Prevention
Techniques on HC l30H SIN 64-14861, Lockheed Georgia Co. ER 9587-5, 31 December
1969.
3. E. J. Jankowsky, Fastener Coating Service Evaluation Progress Report, Naval
Air Development Center NADC-MA-7l5l, 11 February 1972.
544
-------
PERFORMANCE OF COATINGS ON
C-141 AIRCRAFT
2 YEAR EXPOSURE
MONTHS
mE ~ E
CADM I UM PLATE 0.3 10
CADMIUM PLATE + 1.0 15
INHIBITIVE SEALANT
ALUM I NUM PLATE 0.4 10
(FUSED SALT)
ALUMINUM PLATE 0.7 24 +
(ETHER BATH)
ALUMINU~1 PLATE 0.6 24 +
DUAL EPOXY 0.8 21
IVD ALUMINUM 0,5 24 +
TI-CD + CONV COATING 0.4 10
ALUMINUM PLATE 0.3 24 +
(FUSED SALT)
ALUMINUM PLATE 0,5 21
IMMERSION 545
-------
PERFORMANCE OF COATINGS ON
C-141 AIRCRAFT
2 YEAR EXPOSURE
TYPE
SERMETEL 556
MONTHS
THICKNESS/MILS AVERAGE TO FAILURE
0.3
12
SERMETEL W
0.8 21
0.7 14
0.7 14
0.4 11
SERMETEL 554
SERMETEL 555
ALUMINUM PLATE
(ETHER BATH)
SWAGED ALUMINUM WASHER
10
0.4 10
0.4 10
13
CAD-TIN-MECH PLATE
CAD-MECH PLATE
ARMCO PROPR INORGANIC
COAT INGS (I-V)
546
-------
PERFORMANCE OF COATING ON A-7 AND RA-5 AIRCRAFT
1 YEAR EXPOSURE - CARRIER SERVICE
lYEE
CADr1IUM PLATE
ALUMINUM PLATE
ETHER BATH
DUAL EPOXY
TI-CD + CONV COAT
ALUMINUr~ PLATE
FUSED SALT
ALUMINUM PLATE
IMMERSION
SERMET AL W
ALUMI NU~1 PLATE
ETHER BATH
PACK CEMENTATION
(SI MG-AL)
TIN OVER CD
OBSERVATIONS AT END
- O~
~ RA-5 (TOP)
llilCKNESSLI1il
0.3
GOOD (-)
GOOD
0.7
0.4
0.3
GOOD (-)
POOR (+)
GOOD
0.5
GOOD
0.7
0.4
POOR (+)
GOOD
POOR
FAIR
547
POOR
POOR
POOR (+)
FAIR (-)
FAIR (-)
POOR (+)
GOOD
POOR
FAIR
-------
, 'f:
~.:"
'~~ .-~';;f
."'"
"'~
~.
~- ..
..
f ~ .
')
~
Oil ,\1 Plat.:>
~." ettiA n;J.
~. ..1 ~"'IIff,:1..
fl"t~.' 7'0 .t:f:.
~. v.
""j:,;
',~ ~'~:7' ',».'" .
~-> '. ;,.~
? ~ ~."!....
~'"
,~; ;:p."4
~
of.
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S e 1: e me tel 5 5 6
.,;
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~.
...............- - -- - . ---
*,-,-
.
.
.8
;. J ~
~
,
. ."
,>,~ {;;,~i;Łt:~,","",,",,, ," .
C-14L Aircraft 6~-622
fastener installation
"
Lac IWtlcd l,<}.
."t
.
7%
CAD PLat.:
"
-.
Panel f90 on test
date 28 Dee 1970.
Seri.es 3
.
~)
....
00
""
U"\
(~
.".
..
-------
fI
Ir
U'
AIR FORCE
.~-
C7\
-
-------
Corrosion PerforDance of New Fastener Coatings
on Operational Military Aircraft
Discussion Period
MR. SIMMONS:
Gene Simmons, Sermetel Incorporated.
There seems to be a misunderstanding about the possibly
proprietary nature of Sermetel coatings.
The particular
coatings you listed are not proprietary.
Within our range
of coatings, there is only one process which is proprietary,
and that is our 5375 process.
There are a number of classes of Sermetel coatings
which conform to the MILC8l75l spec.
Some of those classes
are sacrificial and some are not.
I believe there is a good
possibility that some of the classes tested were not of the
sacrificial variety-
You may wish to take a look at some of
those in your follow-on testing.
As you pointed out, our coating is designed for
high temperature testing and high temperature use, rather
than strictly corrosion resistance.
But under certain
conditions, we have developed a series of chromate conver-
sion type topcoats which helps to seal porocity and extend
the life of those coatings.
We would hope that these would
be included in your follow-on testing.
MR. MEYER:
I would like to point out that I never
discussed the cost of the system or the coating composition
with the vendors.
I had only a vague knowledge of how it
was put on.
I wasn't concerned with that.
I was concerned
with a product and its performance.
550
-------
In other words, if the 554 Sermetel were commercially
available, it would probably be as useful as the IVD.
The
only reason we discount the others is that the Sermetel requires
a bake which may create problems, and the ether bath has some
processing problems.
I rank them in order from the standpoint
of general, workable processes.
I didn't mean to imply that
your processes and products were proprietary.
MR. SIMMONS:
I just wanted to make sure it is
understood that those are on the market in every case.
MR. MEYER:
If you have any of these candidates,
we would like to get them into the program.
We are using
the same fastener on the C-l4Is.
We are using a different
type of fastener, naturally, on the ground equipment.
I have
the data and the instructions for those interested in getting
test materials on the aircraft or ground equipment.
We have
places to put them.
MR. GROBIN:
Allen Grobin, IBM Corporation.
The
tin over cadmium coating which AFML pioneered in the early
fifties is a very interesting coating system, but it is
very tricky to apply.
The success of that coating really
depends upon the degree of diffusion at the interface of the
two metals.
A coating can appear very poor in performance
if it isn't properly handled. In evaluating that type of
coating, you should get involved with the plater and make
551
-------
certain that he bakes the coating sufficiently after plating to
get a diffusion zone.
MR. MEYER:
We used the mechanically plated tin-cad.
The Navy used some tin over cad which was apparently electroplate.
MR. GROBIN:
That is what I am talking about.
MR. MEYER:
We tested the Ti-Cad, which is
a delta process.
It was a process developed mainly for
landing gears.
We didn't actually test tin-cad in our
program.
MR. GROBIN:
It might be worthwhile to pay attention
to the diffusion zone.
MR. COOK:
Bert Cook, International Lead/Zinc
Research.
You mentioned that you were obliged to limit the
thickness of the cadmium coating so that you are in the
position of comparing 0.3 mils of cadmium against thicker
coatings of other materials.
Comparison of equal thicknesses
is one way of doing it.
How about equal cost comparisons?
Could you comment on coatings of equal cost?
MR. MEYER:
The latest cost estimate comparing cad and
the IVD coating was made by McDonnell Douglas about two years
ago.
They compared the costs per 25,000 fasteners for a particu-
lar hypothetical aircraft.
They figured a cost of about
$5800 dollars for 25,000 fasteners plated with cadmium with
the present system.
They figured about $8,000 dollars with
IVD aluminum, and about $18,000 only if the fasteners were
of the 13-5, 13-4 MO stainless steel.
If we consider that
552
-------
data to be valid, particularly in the situation where we have
many cadmium plating facilities against a rather small base
for IVD aluminum, and if they can produce IVD aluminum at
that cost with the corrosion performance we have shown, it
seems to me we have a very cost effective product.
We frequently come to the point where we can't
afford a product.
When you have a base price of three dollars
a pound for cadmium and thirty or forty cents a pound for
aluminum, the base materials costs are going to be less if
you can get the process costs down.
MR. JANKOWSKY:
Edward Jankowsky, Naval Air Development
Center.
I just wanted to answer Mr. Grobin's question about
Cad-Tin.
The coating that we tried was not the conventional
Cad-Tin coating.
It was a double layer coating with tin
on top instead of the normal Cad-Tin which has the tin on
the bottom, the cad on top, and then the diffusion.
I don't
know why it was submitted.
Some manufacturer thought it
would work.
MR. GROBIN:
A number of manufacturers use that
coating based on Benny Cohen's work in 1956.
you need diffusion of the tin into cadmium.
For good coating,
That means that
as soon as you finish the coating with the tin on top of the
d ' l't l'nto an oven and give it a baking
ca mlum, you must get
process, or you can get a separation zone.
What you want
is a three layer system.
cadmium alloy layer, and a tin layer.
You want a caQmium layer, a tin-
Then you have a good
system.
The baking step does that.
553
-------
MR. MEYER:
how it was produced.
In both cases we didn't really pry into
We were simply testing candidates.
554
-------
Evaluation of Alternatives
Session V
Thursday Afternoon 1:45
THE IDEAL AEROSPACE FASTENER COATING
Edward Taylor and John Laurilliard
Standard Pressed Steel Co.
Jenkintown, Pennsylvania, 19046
This paper presents a compilation of fastener
and research performed at the Standard Pressed Steel
past several years.
coating evaluations
Company during the
Evaluations and comparisons of many types of coatings were made not
only on the effects of the coating on the mechanical and chemical functionality
of the fastener and fastener joint, but also on the effects and capabilities of
the coating process on the fastener.
Some specific factors considered in evaluating a fastener coating include:
corrosion resistance; temperature limitations; hydrogen embrittlement, effects
on fatigue life, torque vs. induced load, and stress corrosion cracking re-
sistance; dimensional change; adhesion; thickness and distribution; galvanic
compatibility of coating with adjacent joint material; and the limitation of the
coating process due to fastener material, size and shape.
The ultimate question of economics is also considered as related to the
coating process and the market place.
The determining factors for selecting a coating to replace cadmium as a
fastener coating should be related to the intended use of the fastener.
555
-------
The Ideal Aerospace Fastener Coating
by
Edward Taylor and John Laurilliard
Standard Pressed Steel Company
Jenkintown, Pa. 19046
to be presented at
Government - Industry Workshop
on Alternatives for Cadmium Electroplating
in Metal Finishing
October 4-6, 1977
National Bureau of Standards
Garthersburg, Maryland
556
-------
INTRODUCTION
Aerospace fasteners are precision manufactured from alloys ranging from
the exotic to the common. They differ from the commercial fastener
grades with respect to quality. Coatings are sometimes employed with
corrosion resistant alloys. usually to satisfy lubrication or galvanic
compatibility requirements. However, coatings are almost always used
with alloys which corrode in natural or hostile environments, not only
to protect the fastener, but the surrounding structure as well sometimes.
This thin coating, measured in ten thousandths of an inch, is depended
upon to provide corrosion free protection to a mechanical joint for many
thousands of hours.
A threaded fastener appears to be a simple mechanical device. Usually
taken for granted, its protective coating is selected to resist a corrosive
environment. This simplistic conception does not consider the many critical
physical, mechanical, and chemical properties aerospace fasteners are
required to have.
Ideally, a coating for an aerospace fastener should provide useful
functional properties which cannot be achieved by the bare alloy and will
not cause significant degradation of substrate or adjacent structure. The
coating process should lend itself to the end product, as veIl. Let's take
a closer look at some properties and process considerations.
557
-------
Physical Properties
1.
Adhesion is necessary to provide reliable protection after mechanical
installation. The threads and drive are often scraped, torn, cut
or gouged as a result of metal to metal contact. Figure 1 shows the
results of good and bad adhesion.
A1860R
A1286R
F12ure 1.
After scraping the threads with a sharp knife, the coating
on the left has been cut away. S~ilar action on the right
resulted in peeling of the coating, . condition indicating
poor adhesion.
558
-------
2.
Distribution of a fastener coati
tolerance control for optimu n~ i. determined in order to maintain
Figure 2, the thickness dist~i~~ianical and chemical performance. In
for an aerospace fastener. on of an aluminum coating is shown
.4
.5
.5 Top of Head
.6 Head a.D.
Underhead
Upper
Shank
.4 Fillet
.5 Mid Shank
Lower
Shank .6
Thread. 6 .5 Root
Runout .3 Flank
.7 Crest
.3 Fl ank
Fi2ure 2.
Distribution of an aluminum coating on a titanium aerospace
fastener. Thickness in mils, (1 mil equals .001 inches).
3.
Cosmetic appearance is an important attribute for aerospace fasteners
since it is associated with quality and integrity. Unpainted fasteners
must withstand weathering, maintenance formulations and domestic spillage.
Fasteners destined to be painted should have a conversion coating which
will promote adhesion without affecting mechanical performance.
559
-------
Mechanical Properties
Torque-Tension is one of the most important fastener properties
because it describes the quantity of tightening which can be
achieved with the joint components and a given amount of wrenching
effortt )Figure 3 shows how several coatings compared in a previous
study. 1
1.
2000
(J)
"'CI
r:::
:s
o
(l,
1500
~
r:::
o
-..4
(J)
r:::
(II
H
1000
500
250
Electroplated
Cadmium
Fused
Salt
Deposition
o
50
100 150
Torque, inch-pounds
200
Fi2ure 3.
Torque-tension relationship for cadmium and aluminum coated
AISI 8740 alloy steel bolts. (No lubrication)
560
-------
2.
Fatigue is a very important aerospace fastener parameter because of
the cyclic loading of joints. It doesn't matter whether fatigue
degradation is a result of the coating process or the presence of
the coating in service.
S-N curves. as in Figure 4 below, show the negative effect of the
coating on the fastener at various stress levels. The lack of 2
million cycle runouts for coated bolts at specification load is
cause for Some concern.
.,, '.L
, , ..J.j,'
1/1
~
c::
::!
o
Q.
IT'--II"!- ~ iT! -.- .-- - -- r~'-;-~-r;, [[-f-[!I"
, : I : I', I I I
I I; I l:! I I . I I' .
, ; 0 ':; !q' I: ,I, I I: I
: i : I i Ii: i \ I; :
!_, ; '! ~ L, + ~'.: J i, . t ,;.,~JrL1-JI.-I-'h;1 . ~, ;1' ~, 1--'
! ! I I' !:' I I I: I, I I 1 I
, i' i: i : ' ~ A;~ t:' I , : i
+:+1 :+~,!i H . ~ : r'm,-Illi : \ i .
. i . -+1-.' ~. 1 -1- 1 I" I . I , I ,I '
i : !'~ i, I: il I ' ! \ rl: 1:- \,:". tl 'i'
: 1 ! :.~: i-I: 01; t-"~-' '; 'I .,
l'i'I",mi!'1 !,' "j I, :
i : i 'I: i!: ! 'I 1 ' I 'i I : "
If.OO~~t;NU~, I~: : ii :'i +It''J-- -~ I 1'1' -i, iT
GO~S;~:'; I~!i, : I, \llli' ,~-' I::
'I . j ! ' ! I I I ~'.. I
' : . i : I ; : iii' + .... 'it, I ; ! i' t-- i ,: i,
11/00 'I' ,1111 . '",,:., ,II . I II
~'Yg'-~~~~Jl H- :..~*n~ !':r LLl-~.l, 'I' \-- "'\-r'
1200 ,.; i' :. , . I ': ' 'I i,! !i I : :
t "),! ; j ! I I; 'I I j I, :
'~, : : ' I!! ,t ~Hi"'r 1 :,y-'~ '~t~:. --;
1 Q.. , . . ; : i . I l i I' , i :. I .
: . :,;-1 'i~ -:::r~lltHt,-! I
\ ' , ' J 1 ""
, ~,
Cycles to Failure
'1
l~O~
2.,/00 ':
i
21°Oi
I
2600 i
I
1800'
~
cu
.3
~
Qj
'"
.-4
Q.
Q.
<
1000'
,
800:
I."
~\;
ii,
Fi2ure 4.
(1/4-28. flush head) exhibit
aluminum coating process on
Titanium Hi Lok fasteners
the negative effect of 8n
fatigue life. 561
-------
3.
Installation Force is required for skin fasteners which have a
diameter larger than the structural hole. Lubricant. aid the
bucking or pounding of these shear fasteners which help structural
fatigue life by providing beneficial compressive stresses around
the hole. Lower installation forces are normally l~SS costly. Table
I shows the results obtained in a previous study.(l
TABLE I.
Force Required for Installation of Coated Titanium Skin
Fasteners with 0.004 to 0.006 inch Interference Fit in
7075-T65l Aluminum Alloy.
Coating
Bare
. ". 11111
II
Cadmium + Dichromate
........ 11# ..11111 III t II It It---1t
---i
Ether Bath Al
+ Alodine 12005
~.J- ..... I
-4-u - t -.-41
Fused Salt Al
+ Modine l200S
I I
I I I III .
II
SerrneTe1 W
--++~~
SerrneTe1 W + A10dine 1200S
"..1111 I
SerrneTe1 W + Alodine 407-47
~t- u_~
800 1200 1600 2000 2400 2800 3200
INSTALLATION FORCE. lbs.
Note: Cetyl alcohol lubric ant employed over all 8urface
cond it ions.
562
-------
4.
Reusability
Maintenance often dictates the disassembly and reassembly of specific
joints. Some joints employ locknuts to prevent loosening caused by
vibration. The reusability of these fastening components ia normally
assumed unless they are mechanically damaged or severely corroded.
Aerospace fastener specifications often require fifteen reuses within
a stated torque range. The ability of a locknut to meet this requirement
depends largely upon the lubricity of the coating system.
Figure 5 show. the apparent differences in performance by three different
coating systema on bolts and locknuts. The absolute value of torque has
no real significance since it can be adjusted by the degree of deformation
on the locknut. Cadmium provides a consistent installation prevailing
torque level while the other coatings exhibit a continuing but comparable
percentage decrease. Repeated uaage of these fsstening systems results
in eventual loss of the locking feature and a free spinning nut.
50:
...
4
z,
We
30 ...
(I) 0
"0
~
::I C.A t) M I V M
0 +, 0
Po
I 0 . o-~ O-()-o-,
.J:: U 0 0 0
u
~ 20 0 +, +
H
."
0 '.
10 l)AC ~O~E., !
oa- D-p-Q..Dp-p-JL~
~ P"
0, 3 5 7 9 11 13 1,
1 Cyc le
Figure 5.
Reusability of
Fasteners used
waxed. Average
three coatings shows different behavior.
were 1/4-20x2 SHCS, 20FA-420 Flexloc Nut,
of 5 pieces.
563
-------
Chemical Properties
1.
Salt Spray Resistance is an industry wide requirement maintained
primarily for quality control purposes rather than to simulate the
anticipated service environment. Some c04t~ngs are extremely
protective in their intended application,(2) but '{~ rapidly consumed
in a 5% salt spray cabinet as shown in Figure 6. ( Until specifications
and test methods are modified, freedom from rust in a salt spray
cabinet will continue to be a primary requirement for coated fasteners.
Test Discontinued
'0 --
800
VI
VI
~ 800
~
~
J
r 400
VI
>-
~
f'OO ~
o
I- 30
~
i=
zo
PVD
CVO
'VO
IELO
PCB
VAC
CAD
Fis1;ure 6.
5% Salt Spray Resistance of Aluminum Coatings
PVD (Physical Vapor Deposition)
CVD (Chemical Vapor Deposition)
IVD (Ion Vapor Deposition)
ELD (Electro Deposition)
PCB (Phosphate Chromate Bonded)
VAC CAD (Vacuum Deposited Cadmium)
564
on Alloy Steel Bolts.
-------
2.
Stress Corrosion Cracking resistance is an important parameter for bolts
with strength levels higher than 175,000 pounds per square inch. The
protective quality of variov~)coatings on 260,000 psi strength level
bolts is shown in Figure 7. Noble coatings, such as nickel, have
proven to be unpredictable. While sacrificial coatings provide more
reliable protection. the best performance is achieved by a combination
of noble and sacrificial coatings.
-=m:=J
o Bare
Ntdu:1
Dodecyl Akohol
~ AlumInum
?hos phate &. Oil
PVC
Nickel Cadmium - Diffu8ed .. UndlHu8ed
Nickel" Delta c;...dmium 8
Nickel" SermeTel W
sooo
100
Fi2ure 7.
on stre88 corrosion cracking re8i8tance
Effect of coating
of H-ll bolca.
565
-------
3.
HydrORen Embrittlement
Delayed brittle failure of high strength fasteners is usually caused
by hydrogen, introduced either from metal finishing or environmental
corrosion. The former is well known as hydrogen embrittlement but
the latter condition, post plating embrittlement, has recently
received increasing attention.
All aqueous electroplating processes introduce hydrogen into the
plated object, normally resulting in embrittlement. Relief is
accomplished by baking for 3 to 23 hours depending upon the tensile
strength, coating type and thickness.
Recent studies have shown bright cyanide cadmium provides superior
resistance to post plating ef~rittlement even though it is one of the
most embrittling processes.( Conversely, vaccum cadmium causes no
process embrittlement, but allows in-service corrosion to produce post
plating hydrogen embrittlement.
Although many alternate coatings have been reported to be free from
process embrittlement, the ability of environmental corrosion to
cause post plating embrittlement has not yet been determined. New
candidate coatings, which are very sacrificial, should be thoroughly
evaluated in this respect.
ProcessinR for Best CoatinRs
1.
Surface Preparation
Good adhesion is a prime requisite for fUnctional coatings. Fastener
coatings must be capable of withstanding some mechanical abuse without
flaking, chipping or peeling. Satisfactory adhesion is dependent on
proper surface preparation llDmediately prior to the costing process.
This includes oxide and scale removed in addition to the normal oil,
dirt and soil removal.
The methods used to prepare the surface for coating should have a
minimal effect on dimensions and the mechanical properties of the
bolt. For example, acid pickling to remove heat treat scale from a
high strength precision bolt is unsatisfactory. It causes hydrogen
embrittlement, reduced fatigue life, and a loss of critical dimensions.
Any method of surface preparation that removes more than 0.0001" of
basis metal should be avoided, unless it is consistent and reproducible.
Adequate removal of soil can be accomplished by alkaline cleaning,
but grit blasting is best to remove rust and scale. Corrosion resistant
alloys may require activation (chemical or electrochemical) prior to
coating to get satisfactory adhesion.
566
-------
2.
Size Limitation
The coating process .hould have a capability of handling both large and
small fastener8 with respect to uniformity, quality and adhesion without
physically damaging or abusing them. Some procesaes work very well for
large or small fasteners. but not both.
3.
Coatina Distribution
The ideal finishing process should have the capability of providing a
uniformly distributed coating. This coating should be uniform from
area to area, piece to piece, and batch to batch. On an individual
baai., a mtn~ thickness must be present in recessed areas without
exceeding a max~ thickness on functionally prominent areas, such as
the starting thread. If the first few threads of a bolt are over size
dtmen.ionally due to excessive coating buildup, the bolt will jam during
installation even though the remainder of the threads and the rest of
the bolt are dimen8ionally correct.
4.
Tolerance
Aerospace fa8tener shanks and threads are especially manufactured to
very close dimensional tolerances and undersized to allow for coating
buildup. A tolerance is required for the variation in thickness from
area to area, piece to piece and batch to batch.
Finished fa8teners are manufactured to the same close dimensional limits
whether coated or bare. If coated, less dimensional variation is permitted
prior to coating because some of the total variation allowed on the finished
faatener i. consumed by the variation in costing thickness.
Coating tolerances are normally 0.0002". This tolerance becomes more
difficult to maintain as the nominal coating thickness increases,
because of the irregular behavior of electroplating on different
surfaces. Whereas the maximum thickness i8 100% greater than the
minimum for 0.0002" to 0.0004" coatings, this latitude reduces to
66% and 40% for 0.0003" to 0.0005" and 0.0005" to 0.0007" respectively,
necessitating close process control.
5.
Economics
Initially most alternate coatings will be applied in job shops until
sufficien~ volume is reached, at which time it may be opportune to
install an in-house facility. If a high volume cadmium plating
facility were the only coating system in a manufacturing plant, its
abandonment would require installation of multiple alternative coating
processes or force the use of outside coating vendors at increased
processing costs.
1 ff rd one or two alternate coating
Assuming a manufacturer can on Y a 0
facilities he may have to utilize the resources of several coating
vendors. This in turn causes quality problems which increase proportionately
d d their Physical distance. The costs incurred are
with the number of ven orB an
significantly higher than for in-house quality control.
567
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5.
ECQn081c8
(Cont . )
Some alternate coating processes are so different from plating, their
use requires capital expenditures and increased operating costs. This
is because they are sophisticated and require multi-skilled operators
and expensive maintenance.
Even though the relative costs for cadmium and alternate coatings are
not far apart, the real fastener expense lie8 in the life installed cost.
This takes into account the effect of higher torque and subsequent early
damage to head drives and threads; greater number of fasteners due to
decreased clamping capability; and corrosion induced damage in marine
environments where cadmium is best.
DISCUSSION
We have seen that coatings should provide several of the more critical
technical properties described in this paper while being economically compatible
with the aerospace fastener. Common coatings comprise about 5% or less of
the total fa8tener cost whereas many alternatives are generally much higher.
Even though better, but more expensive, coatings will eventually reduce
maintenance expenditures. observation has indicated a continued shortage of
purchasing dollars for engineering and maintenance requirements. hence the
ever constant disparity between satisfactory and super performance.
Superior coatings will always be in demand for those applications where nothing
else will suffice. The less demanding applications present the most perplexing
problems because the difference in cost between the common marginal performance
coatings and the opt~ solution for the job often seems unreasonable. It
is only when the costs for maintenance are figured. that the true value of the
coating can be assessed.
Although corrosion resistant alloys are now noticeable as aerospace fasteners.
the lions' share still goes to plated or coated steel. For these applications,
the ideal coating system requires functionality a8 well as an attractive
c08metic appearance.
A wide spectrum of requirement8 must be satisfied by the alternative coatings
for cadmium. a8 heavily stressed in this paper. The primary advantage of using
one wide spectrum coating for most applications instead of several more specific
use coatings is to simplify purchasing requirements and reduce process costs.
This concept has universal appeal and will ultimately influence the selection
of candidate alternative coatings for cadmium.
The ideal aerospace fastener coating has not yet appeared in the marketplace,
but cadmium is still much closer to being ideal than any other commercially
available coating system.
If a combination could be made of the lubricity and salt spray resistance of
cadmium. the high temperature capability and low toxicity of aluminum. the
economy and sacrificiality of zinc, as well as the barrier protection of
nickel and chromium, a super coating would result. Perhaps it would be the
ideal coating for aerospace fasteners.
568
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REFERENCES:
1.
E. Taylor, "SermeTel W Aluminum Coating for Aerospace Fasteners",
SPS Report No. 5392, March 24, 1972.
2.
F. H. Meyer, Jr. and E. J. Jankowsky, "Corrosion Performance of New
Fastener Coatings on Operational Military Aircraft", Paper 115 at
1973 NACE Symposium.
3.
E. Taylor, "Stress Corrosion Crack Protection from Coatings on High
Strength H-ll Steel Aerospace Bolts", ASTM STP 518, 1972, pp. 131-138.
4.
D. Altura, "Postplating Embrittlement", Metal Finishing, September
1974, pp. 45-50.
569
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APPENDIX I
Panel Discussion
"Are Specifications and Standards Barriers to Change?"
571
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APPENDIX I
Panel Discussion #1 - '~re Specifications and Standards Barriers
to Change?"
Questions
1.
Are specifications and standards barriers to change?
2.
What role will specifications and standards play in the adoption
of materials and processes that are identified as viable alternatives
to cadmium electroplating in metal finishing?
3.
What means should be adopted
and coatings for exploration
e1ectrodeposited cadmium?
for the selection of materials, methods,
as candidates for use in lieu of
4.
Many Government and technical society specifications and standards
call for the use of electrodeposited cadmium as a corrosion pro-
tective coating for hardware.
What would be the time, cost, and procedures involved in adopting
alternative materials, methods, and coatings to replace electrode-
posited cadmium in these and related documents?
5.
Does the use of materials vis-a-vis performance specifications
influence the time and cost involved in changing over from
e1ectrodeposited cadmium to potential alternative materials, methods,
or coatings?
Panel Members
Mattie F. McFaddenf Raytheon Co./Aerospace Industries Association
Nathan E. Promisel, Society for Automotive Engineers
Walter Conrardy, Air Force Materials Laboratory
John Sarvis, Defense Materiel Specifications and Standards Office
William Quittman, Defense Industrial Supply Center
H. M. Cobb, American Society for Testing and Materials
.,~ Chairperson
572
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PANEL DISCUSSION:
Are Specifications and Standards Barriers to Change?
At this time. I would like to introduce Mattie McFadden from
Raytheon Corporation. She is also with the Aerospace I d t
A .. d h', n us r y
ssoc~at~on an s e w~ll be cha~ring this afternoon' I d' ,
" S 'f' . s pane ~scuss~on.
Are pec~ ~cat~ons and Standards Barriers to Change?"
MS: MCFADDEN: I am Mattie McFadden.
Company in the Missile Systems Division.
I work for the Raytheon
For all too long, I have been in the materials and process business
and for the past 20 years in the management of the Materials and Process
Department. Three years ago I joined the staff of the manager of
Product Assurance in our Division.
By education, I am a metallurgical engineer. By experience, 1
specialize in all kinds of materials, finishes and processes.
I am a generalist. I am currently the Chairman of AlA's Materials
and Structures Committee. For many past years 1 was active and a
Committee Chairman in SAE's Aerospace and Materials Division. 1 had
the pleasure last year of working on a National Academy NMAB study on
specifications and standards.
First, I would like to introduce Mr. Nathan Promise I.
you tell us a little bit about yourself?
Nate. would
MR. PROMISEL: I started my professional life as an electro-chemist,
and went into industrial research, in the field of electroplating. Then.
as in the case of the Chairperson. I wound up doing all kinds of things
on all kinds of materials and all kinds of processes.
This period was followed by some years in the Navy Department in
research and development, production control and product control,
specializing in the subject area of specifications and standards.
Then followed a period at the National Academy of Sciences where
I covered all kinds of subjects. including standards and specifications.
I am presently a consultant to industry. universities. research labs.
Congress, other parts of the government. and a few foreign countries.
MS. MCFADDEN:
Thank you, Nate.
Next is Mr. Walter Conrardy.
MR. CONRARDY: I have been with the Air Force Materials Laboratory
all of my professional career, which goes back,some 25 years. ,1
functioned as a project engineer in both organ~c and metallurg~cal. . .
materials. My present activity of interest is the role that the D~v~s~on
I head plays in the acquisition of new weapon systems.
573
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We have a key role in approving those materials that will be
used in new systems, so alternatives to cadmium are a very vital
issue to us. We are in the specification business. We write them.
We approve those that other organizations write for use in Air Force
systems. We look for alternatives, not only to pollution problems
but to the strategic materials question. We are constantly alert to
this kind of activity to be sure that the Department of the Air Force
is not caught short in a materials crunch by some arbitrary edict
that would discontinue the availability of any material.
MS. MCFADDEN:
Thank you, Walt.
Next is Mr. John Sarvis.
MR. SARVIS: Before my three years with the professional staff
of the Defense Materiel Specification and Standards Office, I spent
14 years as an Army Project Engineer in the utilization of materials
on small arms and aircraft weapon ordinance.
At the present time, I am with the
for the Defense Materiel Specifications
office is the day to day manager of the
which is the result of Public Law 1028,
tion Act.
DMSSO, which is the Secretariat
and Standards Board. Our
Defense Standardization Program,
the Cataloging and Standardiza-
MS. MCFADDEN: Thank you, John.
the Defense Industrial Supply Center.
Mr. William Quittman is with
MR. QUITTMAN: More specifically, I am with the Engineering and
Standardization Directorate at DISC. DISC is a Defense Department
assignee activity on standards and specifications. We review these
documents as they are written by the preparing activities such as AFML.
My responsibilities lie in the Federal Stock Class 95, which
embraces raw materials. I am not directly involved with plating.
MS. MCFADDEN:
Thank you.
Mr. Cobb of the American Society for Testing and Materials (ASTM)
is the final panel member.
MR. COBB: Prior to joining ASTM about 12 years ago, I was in
industry in a metallurgical capacity, associated mainly with the
companies involved with the manufacture of jet engines and nuclear
fue 1.
In ASTM, we have 128 main technical committees, of which several
are involved with electrodeposition and the testing of coatings. The
major one is Committee B-8 on E1ectrodeposited Coatings and Related
Finishes. This committee was established in 1945 and now has 150
members, some of whom are in the audience.
The committee has developed about 60 standards, including some
15 or 20 specifications, and some 40 or 45 test methods for determining
coating characteristics and recommended practices for preparation of
substrates.
574
-------
This committee, as well as Committee r-l C .
d. 6 J on orrOS10n of Metals
an Comm1ttee F-I on Fasteners which has b. '
d ' a new su -comm1ttee on
coate fasteners, are the areas of activ1"t " ASTM h.
h I Y 1n w 1ch are of
concern to tee ectrodeposition and coatings industry.
MS. MCFADDEN: Thank you. On one hand we re . d I
.. , ce1ve severa
quest10ns concern1ng specifications and standards' I 0 h
, 1n genera. n t e
~ther'k~e ve.h~ar~l~he concern and even frustration that people feel
1n ~or 1ng W1t m1 1tary and federal specifications, and technical
~oc1ety docu~ents. In this aspect, Walt Conrardy and I will engage
1n a short d1alogue to get this discussion oriented. I have several
questions to address to specific members of the panel. As we go
along, I am sure many of you will elect to ask questions that have
come to you as you hear the dialogue.
Walt, you and I have both discussed many times the difference
between the two words, "Specifications and Standards'.'
How do they work? What are they? Who issues them? What is the
platform for the words, "Specifications and Standards" as you know
them?
MR. CONRARDY: A specification is a device that, within the
Department of Defense, is used to describe a material or product
in terms of composition or dimensions of geometry. It defines quality
standards and levels that are the minimum that the DoD will accept
when we procure something. It includes test methods. It describes
ways of determining that quality, and it provides some packaging and
transportation instructions or intended use information at the end.
Specifications usually identify deliverable end items, whether
they be materials or ''widgets.'' Standards, on the other hand, are
more philosophical documents describing acceptable and unacceptable
practices for, specific manufacturing, chemical, or metallurgical
processes, such as electroplating or heat treating or shot peening.
Specifications create a great deal of frustration for people,
since it is difficult to elicit the complete agreement of everybody
on any given spec. Everybody has his own point of view and axe to
grind, but specs represent compromises between the vendor and the
user that reflect at least the minimum needs of both, and that one
agrees to provide when the other one so orders.
They are slow in evolving, and they are slow in ge~ting chan~ed
unless some crisis situation precipitates some fast act10n. We w111
probably get into some of that procedure if we go on with ~his discussion
in terms of whether the specifications are or are not barr1ers to
introducing alternatives to cadmium.
MS. MCFADDEN: Depending on the origin of the docum~nt, some
organizat" or agencies elect to call all the1r documents
10ns, groups, d . ASTM A .
standards. It is a group that defines a standar ; as 1n , mer1can
575
-------
Society for Testing and Materials; as in SAE, Society for Automotive
Engineers; AMS or Aerospace Materials Specification.
This morning in one of the papers there was a slide that listed
some specific ASTM and AMS numbers relating to cadmium. They didn't
list QQ-P-41~ which is the Federal cadmium plating standard.
I would
will be done
on fasteners
like to address one of the questions that came up, '~at
about MS specifications," it says, "requiring cadmium
for military, particularly Naval applications?"
MR. CONRARDY: When a new process is introduced which has
been sufficiently characterized with a data base adequate for writing
a definitive spec, the obvious way to get that new product into use is
to describe it in a specification. The mere issuance of a materials
spec or a process spec does not get this new process in use immediately
or over a substantial period of time. A process that is applied to
some end item is described in its own specifications or drawings.
The MS sheet that Mattie referred to is a single page. There are
literally hundreds of these in the military system specifically
describing fasteners. All kinds of fasteners with a variety of thread
sizes and shank diameters and head recesses and thread pitch, and numbers
per inch are described.
Each one of them describes the material composition that applies
to that fastener, and includes a description of the kind and amount of
protective coating that will be put on that fastener, so it is easy for
the materials community to issue a new spec. The Air Force did that about
a year ago on IVD aluminum. But you can't go out in the marketplace,
except perhaps in St. Louis near McDonnell, and buy any IVD aluminum
on aerospace parts. The industry is not geared up to provide it, and
it will be sometime before this is available.
In addition, the individual MS sheets which procurement people cite
when they want to buy something have to be changed. If we elect to use
some alternative to cadmium, that has to be so noted on that drawing
and the drawing reissued. Then, when procurement people reference it,
they can require some coating other than electroplated cadmium.
Hardware items are not controlled by the materials people, nor by
corrosion engineers. That expertise resides in the Air Force Materials
Lab. The people who buy and manage the hardware are elsewhere. There
is a tremendous logistics problem of identifying all of the other documents
that call for a specific process, for example, electroplated cadmium, and
getting each one of those changed.
We can't do it by edict. You have to go to the individual who is
responsible for that particular end item, determine why he needs a
particular coating; and then select the best alternative for his item
and have that document changed.
576
-------
There is a very
job to get them all
barrier. Given the
barrier.
large number
changed. In
resources to
of MS sheets and it will be a substantial
that sense, specifications could be a
do all of this, they need not be a
MS. MCFADDEN: That brings up an interesting question that I would
like to ask of John Sarvis and of Nate Promise I.
John, is there an inter-agency time-table that has been established
to eliminate cadmium specs by way of substitution of alternate? Is an
edict from high above required to make government and industry move?"
MR. SARVIS: On the first question about an inter-agency timetable
for eliminating Cd specs by substitution of alternative means I am not
aware of any inter-agency date for such elimination. From wh~t I have
heard here over the past two days, it may not be advisable to come out
with a date for automatic elimination of all cadmium in the specifica-
tions for all items. There may be a case-by-case basis where we might
want to avoid such things.
Is an edict required to make the Government and industry move on
this? No. Our office, the Defense Materiel Specs and Standards
Office, communicated with Deputy Assistant Secretary Marienthal's
office some months ago on the problem of fluorocarbons. Our office is
in the process of inquiring about the use of fluorocarbons in items
used by the Department of Defense on which it has specs.
So an edict isn't required. We are already doing this in the case
of fluorocarbons in DoD. I am sure we will be doing it in the case of
cadmium, not necessarily to eliminate everything that contains cadmium,
but to make an investigation of what is entailed in its use.
Perhaps I should refer the industry portion of the question to
Mr. Promise 1.
I don't
one emerged
a mandatory
know of any timetable, and
except perhaps in the form
affair at this stage.
I would really be surprised if
of a target or a goal, but not
In terms of edicts this is not in line with Government operation
and Government activities. Such a situation could occur in the industry.
however, through stricter controls being mandated.which would. then,
persuade industry to voluntarily change its pract~ces. In th~s context
I think an edict from EPA or some other source may indeed accelerate some
action in both industry and government.
I think the spec writing societies such as ASTM and SAE are well
aware of the risks of cadmium pollution. Even two or three years ago,
h " . D" sion of SAE began to take a
t e Aerospace Materiel Spec~f~cat~on ~v~
hard look at specifications to see what they could introduce a~ ~ha~ h
time, anticipating problems not only with respect to.safe~y an ea t ,
which is the main consideration with respect to cadm~um hr~ght n?w,.but
'I SAE and the ot er soc~et~es
also with respect to critical mater~a s.
577
-------
would be very cooperative and very anxious to help do this on a
progressional, rational, realistic, economic and safe procedure.
think we can expect full cooperation from outfits such as SAE.
I
MS. MCFADDEN:
ASTM might take?
Mr. Cobb, would you like to comment on the position
MR. COBB: I think it is important to keep in mind that when we
refer to ASTM or SAE we really mean the people from industry,
Government, and universities who are members of these committees.
What needs to happen will happen. If a group of people need a new
document or a revised document, they come together at the meetings
and they produce it.
MS. MCFADDEN: There was another question related to this. It
says, "Does the DoD specify cadmium plating for all hardware exposed
to the environment; that is, marine environment, upper atmosphere
and so forth?"
MR. CONRARDY: I think we could flatly say gŁ,
everything to be coated with cadmium or this would
world. A battleship going sailing down Chesapeake
big gleaming coat of cadmium plating -- obviously,
we do not require
be a cadmium
Bay with one great
this isn't true.
Any weapon system is an assembly of its individual parts and
components. When each one is designed, a drawing is issued that gives
its geometry and its tolerances, and includes the materials with
which it is constructed. A finishing system is specified to provide
any particular functional purpose that may be required, whether it is
chrome plating for hardness on bearing surfaces or cadmium plate for
environmental resistance. These things are usually reviewed by
materials engineers or corrosion engineers, as appropriate, to judge
whether the right material and process were selected to ensure that
it will survive for the timeframe that the Department intends to use
it.
Through experience, we have learned that if an aircraft is designed
for 15 years, we look for processes that will keep it flying for 30
because that is the way we utilize our equipment.
There is no arbitrary overall policy that says, "Everything in a
marine environment will be Cd-plated or any other kind of process."
It is looked at on a piece by piece basis. Undoubtedly a philosophy
that says, "Very serious consideration will be given to corrosion
resistance," and it will not be an after the fact banda;tl type opera-
tion to try to make it work after you slip it off the drydock.
The Navy is very corrosion conscious, and they select basic materials
and finishes with a very aggressive environment in mind, but this can
take the form of many different materials and processes.
578
-------
MR. PROMISEL: Just to underline the neg t' h
' a ~ve answer to t at
ques~~~n, there ar~ in fact places where cadmium is forbidden and
proh~b~ted from be~ng used, depending Upon the te h' I'd'
c n~ca cons~ erat~ons
such as temperature restraints and cadmium contact 'th t't' d
' . , w~ ~ an~um un er
certa~n cond~t~ons. Not only is it not mandatory universally, there
are cases where the use of cadmium is not permitted.
, MS. ~CFADDEN: Thank you. Following up a bit on your comment, Walt,
~f anyth~ng was done to reduce the usage of cadmium, would it be
retroactive on existing drawings, or would it affect only new designs?
MR. CONRARDY: I would envision an action requiring all new
systems not to use cadmium. Then might come new specs and new standards
for new finishes. In an evolutionary sense, this could take place over
a number of years, and all of the hardware that is now in the field and
has parts with cadmium finishes would remain that way.
MS. MCFADDEN: So nobody is going to ring the chimes at midnight
and eliminate cadmium?
MR. CONRARDY:
I can't imagine that happening.
MR. QUITTMAN: There are 18 Federal Stock Classes that weare
responsible for at DISC, including a variety of items: nuts, bolts,
screws, washers, and bearings. Many of the specifications that cover
these items have an alternate protective coating or an alternate
material.
In the smaller hardware items, you have these options. Alternatives
could be specified in a contract or a purchase description or something
like that, and you could eliminate or reduce the usage of cadmium.
You wouldn't have to start fresh and write a new specification.
MS. MCFADDEN: In other words,
these finishes, and then there are
been documented.
there are documents for some of
some finishes that haven't yet
MR. PROMISEL: Walt, what would be the possibility of the Air Force,
the Navy, or the Army issuing a document, making,it pe~iss~ble to modify
contracts under certain conditions and for certa~n appl~cat~ons to
specify the use of alternatives to cadmium where appropriate, necessary,
convenient, and practical on old systems?
MR. CONRARDY: I think that would be a very constructive way to
encourage the change on a broader basis.
As I indicated earlier our aircraft have a very long life. That
means they get overhauled ~ny times during their lifetime. S~e of
th h 1 t 1 deta~led ~n their disassembly, r~ght down
ose over au s are ex reme y L L
to removing individual fasteners to treat corrosion.
579
-------
We are doing a complete tear-down, for example, on C-131 wings
right now that goes all the way to the removal of the last fastener.
There is an opportunity to reassemble the wing with whatever new and
approved schemes are practical, cost-effective, and help alleviate
any environmental problems.
MR. PROMISEL: Mattie, there are two numbers which might be
impressive. One is that there were about 4,000 specifications on
materials and processes listed in the DoD Index of Specifications
and Standards. There are just about that many non-Government
standards. Therefore, we are talking about maybe 8,000 pieces of
paper not counting the drawings that Walter mentioned originally.
Not all of these are related to cadmium certainly, just a small
percentage. However, you can begin to see what a tremendous area
we are dealing with when we are talking just about materials and
processes.
We all know that in mass production pulling something out of the
line and putting something else in is costly. From my company's
point of view, we would feel very strongly about that, especially
if we had to absorb the costs. We would be very much against it.
On new design coming up or physically reworking an
can hold in my hands, yes, I can see it on that basis,
automatic production run, I find that very difficult.
item that I
but on an
MR. CONRARDY: As Nate indicated, it would be done on a voluntary
basis, and I suspect that a lot of end users might want to do it, even
in ongoing production. At least some would use it to develop their
own experience with this new alternate and develop vendors and
suppliers so that when the switchover comes, they will have these
people all lined up.
MS. MCFADDEN: Yes, I can see that point.
there that has a question, yes?
There is a gentleman
MR. BOOKER: I am John Booker. Since you are talking about changing
over standards, is there a systems approach that can be used in changing
coatings, or is every individual item considered? For example, an
aluminum screw on a stainless steel panel on an airplane resulted in
the airplane being overhauled after two years rather than after five
years as scheduled. They repaired it with a different part, but every
new plane produced still had the aluminum bolt on the stainless steel
panel. Is there a way of changing such components or coatings during
production runs? From what you said, that would be almost an impossible
task.
MS. MCFADDEN: There are changes every day in production lines.
think we know this. In my case, I was referring to a plating system
that would be replaced by something else that probably would require
a totally new finishing system.
I
580
-------
It can be done, but it would
a fastener which is an item that
You generally purchase it rather
the fas tener.
be much more costly than
doesn't involve a lot of
than buy the machines to
to replace
equipment.
make the
It is much simpler to switch a fastener than it is to
plating process on the shop floor, but both can be done.
on how much money you want to invest in doing it.
switch a
It depends
MR. CONRARDY: There are a few examples of what you mentioned.
When we buy a new weapons system, the drawings are prepared by the
contractor who builds it. In the case of the F-15, for example,
McDonnell designed it and they prepared drawings of each piece of
the aircraft, and they specified the finish that is on each piece.
This was done by the original design engineers. Two years later,
after the aircraft is out of production, it becomes a chronic
maintenance problem for the Air Force because the proper engineering
expertise is no longer available to id entify any prob lems in des ign
and recommend a substitute material. The point is, you never get back
to the engineer who specified the coating in the first place.
MR. WILSON: Verner Wilson, 3M Company. Recently, a certain
Northeastern city stated that no more Cd could be plated in their
particular city. I don't know if it was just a ban on Cd plating,
or if Cd effluents were limited. However, it was clear that there
would have to be zero discharge of cadmium to the municipal waste
treatment system.
Are you familiar with this?
MR. LAURILLIARD: Due to their license for
Atlantic off of Maryland, Philadelphia has had
content of their sludge, particularly cadmium.
dumping sludge in the
to reduce heavy metal
The Water Commissioner concluded that the cadmium in the sludge
came from electroplating shops.
In Philadelphia, there is not much waste tre~tment or ~rea~ment of
the rinse water other than maybe some type of aCid neutralizatL~n.step
Whatever heavy metals are in the rinse water go down to the municipal
waste treatment plant.
Plating shops that can keep the Cd metal below about
b . they
part per million are allowed to continue, ut Since
waste treatment it would be difficult to reach that low
,
one tenth of a
don't have any
limit.
MR. WILSON: What do our standards and spec people do if Philadelphia
bans the plating of a certain metal?
. b. gat least it is fortunate that
MR CONRARDY' For the time ein, ,
.. h ld You can run over to
Philadelphia doesn't constitute t e wor. kl New York I am
W'l . a run up to Broo yn, .
1 mington, Delaware, or you c n k of it but that is
h h. b h s that could ta e care ,
Sure t ere are ot er JO s op '11 see this more and more
only a symptom of the problem. Perhaps we WL
581
-------
as time goes on and as people become aware of the pollution problem
that is occurring.
I am sure it is an inconvenience for people in the Philadelphia
area who have been depending on those job shops, but those kinds of
edicts are unpredictable. The only thing I would predict is that they
may occur more frequently. Philadelphia wouldn't have acted if
somebody hadn't threatened them with a pile of solid waste that they
had no place to put.
MS. MCFADDEN: Before I take any more questions, there are two
written questions that were turned in. I would like to address them.
One question addressed to me says, "Does your company or the
Association you represent foresee any critical usages of cadmium in
the aerospace industry, particularly for electrical or electronic
purposes or functions?"
In answer to this question, the Materials and Structures Committee
of AIA distributed the questions that were prepared for the panel to
our members, one person from each of the major aerospace companies, to
express their opinions, and we collated that. The National Aerospace
Standards Committee of AIA also polled its members and some fastener
vendors. You may obtain copies of these reports from Jack Reese or
myself. (AIA REPORT IS AN APPENDIX IN THESE PROCEEDINGS)
Someone remembers World War II stockpiles, as I do, and many of us
here do. Will the Government maintain a strategic stockpile of cadmium
for defense purposes?
MR. QUITTMAN: This is a possibility, because these materials might
have a specific use, and therefore, they would be stockpiled
MR. CONRARDY: Yesterday somebody showed a pie chart that described
the principal uses of cadmium. This included nickel Cd batteries,
pigments, and stabilizers as the major uses, in addition to electroplating.
Certainly, for nickel cadmium batteries alone I believe the Government
would in fact continue to stockpile cadmium. We use a great deal of
nickel cadmium batteries in aircraft systems. Of course the bulk form
largely does not represent as serious a pollution problem. It is in the
use of cadmium as a protective coating where most of our problems are
introduced.
MS. MCFADDEN: Mr. Cobb, would you like to give any last minute
comments on our topic?
MR. COBB: I don't look on standards and specifications as barriers
to change. Standards are agreed upon ways of doing something, buying a
product or performing some task. Standards and specifications are
necessary in buying a new product or modifying an old one. It seems to
me that the standards-writing community must keep abreast of the new
needs of the industrial community and prepare those documents that are
needed.
582
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MS. MCFADDEN:
Thank you.
Walt, do you have any summary comments?
MR. CONRARDY: AFML has been looking for alternatives to cadmium
because fasteners in aircraft structures are the Sl'n 1 b' t
. g e 19ges source
of corrOS1on problems. We have had this problem for many years with
cadmium. In his paper tomorrow Fred Meyer will describe the field
experience we have obtained.
As these things evolve, we write and issue specifications. IVD
aluminum may be used as an example to facilitate the procurement and
general introduction of new processes.
Specs, then, are not a barrier, but they facilitate the entry of a
new material or process. I think we will see an increasing use of
alternatives as time goes on. We will gradually decrease the amount
of electroplated Cd used for both performance reasons and pollution
reasons.
MS. MCFADDEN:
Thank you.
John, do you have any further comments?
MR. SARVIS: I wonder if this question should actually read, "Are
specifications and standards vehicles to change?" In truth, a specifica-
tion is an authorized description of something that works. This means
that a certain amount of testing has to be done to make sure that it
works under those conditions in which it must operate.
The standards of course are agreed-upon engineering limitations.
I would say that a specification tends to be at the end and is perhaps
the goal of development in that we need to express its culmination on
a piece of paper in order for the procuring contracting officer to buy
it.
We could say that specs are vehicles for change, operable only when
the development people have done their homework well.
MS. MCFADDEN:
Thank you.
Nate, do you have further comments?
MR. PROMISEL: I certainly do not feel that specifications and
standards are barriers to change. I think intrinsically they are not.
Here and there you may stumble over a transie~t obstacle, but ~asically
they are not barriers, and the obstacles in time, of course, will be
removed.
One of the bigger problems, perhaps, is the t~ming aspect of it. ?
Can specs, standards, and directives, be changed in a very short or~er,
S t' h' f the obstacles we encounter. It takes a little
orne 1mes, t at 1S one 0 ,
1 h f Id l;ke to see but again it is only a tranSient
anger t an some 0 us wou ~ ,
situation, by no means a barrier in any true sense.
, oSl'tive aspects of specifications. They
I th1nk there are some very p ",
, b' t' S that are desired in introducing changes.
can contr1bute to the 0 Jec lve h't f 11
They can contribute to health and safety, aspects t at weren u y
dd h lth safety and pollution were not matters
a ressed years ago when ea ,
of concern in specifications.
533
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They can contribute
and interchangeability.
protection.
to conservation through introducing substitutes
They certainly can contribute to environmental
They can serve as documents to identify new techniques which are
advantageous in terms of all the things I have mentioned and even
economics. There could 'well be economic incentives. Sometimes you
want to change when you recognize what the new techniques can offer.
Of cours~, they serve as a mechanism for certifying -- I am not
sure that is the correct word -- new processes and new materials which
can be used and sometimes perhaps must be used.
Then there is a section in specs on notes. One can put a lot of
very good and useful information under notes which serve as a guide.
They are not mandatory requirements, but they are very helpful and can
serve as a guide.
There are a number of very positive things about specs.
just a question about the quote, "barriers."
It isn't
MS. MCFADDEN;
Thank you gentlemen.
The panel is adjourned.
534
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APPENDIX II
Panel Discussion
"How Essential is Electrodeposited Cadmium?"
585
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APPENDIX I I
Panel Discussion 112 - "How Essential Is Electrodeposited Cadmium?"
Questions
1.
Are most alternatives to electroplated cadmium available today?
2.
What is the economic significance of electroplated cadmium?
3.
What would be the economic effect of removing electroplated cadmium
from the market?
4.
What is the environmental/health significance of electroplated
cadmium?
5.
What would be the effect on the "quality of life" in the U.S.
resulting from no longer having electroplated cadmium available
or using an alternative product?
6.
For what applications of electroplated cadmium are there no
alternatives?
7.
What alternatives to electroplated cadmium were not covered in
the Workshop?
Members
Martin White, Cadmium Association
Gerald Kraft, Kraft Chemical Company
W. E. Snyder,* Metal Finishers Association of Southern California
Albert R. Cook, International Lead Zinc Research Institute
Allen W. Grobin, Jr., IBM Corporation
J. Laurilliard, Standard Pressed Steel Company
"k Chairperson
586
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Panel Discussion:
How Essential Is Electrodeposited Cadmium?
This afternoon's panel will address
the questions that EPA may ask in the future concerning the
HR. DYCKMAN:
essentiality of cadmium.
A letter from the National Association of Metal
Finishers, has been distributed to you at the \vorkshop.
It
makes the statement,
"We, the National Association of Metal
Finishers, believe cadmium is essential."
However, it is
not enough to believe in essentiality, you have to prove it.
This panel will go one small step in that direction.
I would like to introduce our panel chairman, Bill
Snyder.
MR. SNYDER:
Let's introduce the rest of the panel
members:
Martin White from the Cadmium Association, Allen
Grobin from IBM, Bert Cook from the International Lead Zinc
Research Organization, and John Laurilliard from SPS.
Bill Snyder from the Metal Finishers Association of Southern
I am
California.
I am an electroplater.
I would like to address the question,
alternatives to electroplated cadmium available today?"
"Are most
From the standpoint of the airplane plater, until any
proposed alternative is qualified by a prime contractor ~
define prime contractors as Boeing, Douglas, et al.), it
isn't available to use on their hardware.
587
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Qualification historically has been both expensive
and time consuming.
The prime contractor has to involve his
process, his engineering, his design engineering, his quality
engineering, and his procurement people in attempting to qualify
a given process.
He may then elect not to permit its use
until each individual supplier has been qualified.
We do some fairly large fasteners, and I've heard
a lot about small chamber barrel type coatings at this
workshop.
I pose for your consideration the following.
My shop may receive three to four pieces at a time of a
main landing gear drag brake.
This part is approximately
four and a half feet long, eight and a half inches wide at
an eye-beam section.
It has a bearing bore and a neck down
face on each end.
In the web section there are a lot of deep
pockets.
A typical plating requirement would be two to three
tenths in the bearing bore, three to five tenths on the bore
face, seven tenths minimum allover.
I am not sure that I
have heard an alternative material and process at this workshop
that will handle that.
We have talked a lot about increased thicknesses, and
I haven't heard much discussion of weight.
I will guarantee
you that in the airplane business and more particularly in the
aerospace end of things, weight is a rather vital consideration.
I think right now I would like to ask Al Grobin
if he has any comments on that.
588
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On a number of specialty items, the
alternative to cadmium plating would have to be very carefully
MR. GROBIN:
studied.
Keep in mind that some three hundred or four hundred
lives will depend upon the ability of that substitute to do
what cadmium does today.
On the other hand, we have a lot of
other hardware which can be readily substituted.
So we
have two ways to go.
I think it is up to those of us who
do not have hardware that has a life dependency to start the
ball rolling and gather the experiences necessary to qualify
these alternatives before the airplane people.
The advent of a problem has just corne about.
It
is going to take a long time to qualify alternative materials.
MR. SNYDER:
The question was asked, "What would
be the economic effect of removing electroplated cadmium
from the marke t" ?
I would like to change that to, "What
would be the economic effect of going to the alternatives"?
I believe it is the consensus, from what I have
heard in the last few days, that no single proposed
alternative will replace cadmium totally.
Thus, we have
a situation where platers may be required to install two
or more processes to replace one.
That is going to be
difficult, if not impossible, due to a few operating
restrictions that we platers are laboring under.
Most of us by now have sewage discharge permits
of one form or another.
I can't speak for the rest of the
589
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country, but in Southern California the permits make it
clear that you don't put any more tanks in.
You can take
one out and put another one in, but you don't add any process.
We have air pollution control permits.
At the
moment, we can still add to those.
There is considerable
expense involved, but as far as the air people are concerned
we can still expand our facilities.
Many of us have energy problems.
Our local power
suppliers don't want us to add another substation.
Many of
us have fuel quotas.
Many of us, and particularly in Southern
California, have water use restrictions.
Thus, the installation
of alternate processes may not be possible.
If it is possible,
it will always be expensive} and I would mention to those of
you from the governmental airplane users
to think one thing.
As an electroplater, I may be about the sixth man down the tier
in the production of a part.
If I must add fifty cents a part
to cover my increased operating costs, by the time you get to
see it,
it is going to look more like $3.75.
Everybody in each
tier up is going to take my fifty cents and put his percentage
on it.
You are going to have some expensive aircraft.
MR. WHITE:
I wonder if I may comment on where we
should look for economic benefits or economic losses.
First of all, it is often forgotten that cadmium is
produced by zinc producers.
Cadmium brings in profits.
The
zinc price is very depressed at the present moment and not
being able to sell their cadmium may be the straw that breaks
590
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the camel's back.
The zinc producer has to be able to sell
his cadmium.
You also have to look at the man-hours spent in
devising and testing new specifications.
We have all heard
that salt spray is not the answer.
You have to do in-service
evaluation~and that takes time and man hours.
I think there
is almost a need for a specification on how to compare coating
techniques, because everyone is busy comparing them using
different criteria.
Of course, you have a loss of materials due to
corrosion, if you are going to put up with a material that
doesn't give you the same service life.
You have increased
imports of costly materials.
You heard this morning how much
cadmium is imported into this country.
I think this is true
of a lot of other materials.
You have to be very careful
not to run up a very large import bill by making the country
very dependent on another country for the supply.
You have
investments in new plants.
Some of these alternative
techniques are just great, but can the small plater afford
them?
If he can't, what is going to happen to his employment
situation?
Finally, you must consider energy.
I know that the
U.S. government is very well aware of the energy problem.
I think that several of the processes we have discussed require
considerable energy input in terms of heat or electrical
power.
I think all of these things have to be considered and
591
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not just the question of how much does this particular
component plated with cadmium cost, compared with Sermetel.
MR. LAURILLIARD:
I get the feeling from talking to
a few of you that you are really not well aware of the
significance of high strength fasteners.
Fasteners are
normally the last thing to be considered when you are making
an assembly.
At the last moment, a rush order is put in, or
somebody runs down to the hardware store to get whatever they
can to hold the assembly together.
I guess it is because fasteners, nuts, and bolts
are so relatively simple.
Can you imagine anything simpler
than a bolt?
Except maybe a safety pin or a straight pin.
When you get to the field of high strength fasteners, the
uses are normally in critical applications.
These are applica-
tions where life is at stake.
If you could just imagine for a
minute that all the fasteners in the world disappeared, you
could imagine cars blowing apart, bridges blowing down, and
airplanes falling out of the sky.
You can see that fasteners
do have some very critical applications.
What we are selling or buying in high strength
fasteners is clamping force or clamping ability-
The clamping
force, the tighter that we can clamp a fastener or clamp a
joint together, the better that joint is going to be in
resisting failure due to fatigue or looseness.
When you
are at 30,000 feet in an airplane, and you look out the
window to see the wing flapping up and down, what kind of
592
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fasteners do you want holding that wing on?
When you are
landing, what kind of fasteners do you want holding that
landing gear on?
In those critical applications, I don't
think we should substitute a coating that will not give us
what cadmium will give.
MR. SNYDER:
I want to digress just a moment to
what I picture as the original reason that this conference
took place.
I don't think we are here to explore technology
for technology sake.
If you will recall the letters announcing
the conference, the topic dealt with the toxicity of cadmium.
We have heard about its impingement upon the food chain.
Recently the State Department of Health in California
put forth a proposed limit of 25 parts per million of cadmium
in the sewage sludge if that sludge was to be used as a soil
amendment agent for agriculture.
Now this limit was put forth
on an informal basis.
In response,
the Metal Finishers
Association was fortunate enough to avail themselves of the
services of a data link base at USC.
Through that data link we got into the data bases of NASA
and the Department of Agriculture, Department of Health, and
four other data bases.
We extracted a list of well over 400
documents that have been written in America, Japan, Germany,
and the U.K..
We then obtained a consultant to evaluate these
documents.
We presented a summary report of the State of California
and they withdrew their proposed guidelines.
593
They are seeking
-------
now to go another route.
I would like to quote briefly from
the report that we presented to the State of California.
I
want you to remember that there was no original analytical
work done here.
This is a paperwork report.
We took the
available literature, we read it, we evaluated it, we set down
what we thought we saw in it.
The comments are as follows:
"Cadmium uptake by
plants is much more complex and the extensive literature
accumulated appears to be very confusing and contradictory
indicating insufficient knowledge.
Cadmium uptake by plants
appears to be related to pH of the soil; soil texture;
microbial action in the soil; concentration of other
heavy metals; available phosphorous and/or nitrogen; method,
frequency, and loading of sludge.
"Again, the problem regarding cadmium is very
complex with contradictions appearing in the literature.
These are due in part to insufficient knowledge or
control of experimental parameters, and even the methods
used to analyze cad contents of such low concentrations
can be doubtful and suspect, as indicated by the WHOFAO
report. "
I believe we heard mention of that report and its
comments on analytical capabilities by a gentleman from FDA.
I would like to quote from "U.S. EPA Guidelines on
Sludge Utilization and Disposal.
A Review of Its Impact on
Municipal Waste Water Treatment Agencies," Report Number
5-94
-------
75-20, Municipal Sanitation District of Greater Chicago.
The report was published in October 1975.
"The actual conclusions presented are:
(1) u.S.
EPA proposals were not supported by current and available
relevant research and full scale data.
(2) Proposals have
seemingly ignored data generated by their own organization
and by other organizations.
(3) Proposals are based on the
assumption that metals will accumulate to harmful levels in
the edible parts of plants.
This assumption is not supported
by available data."
Copies of the report that I mentioned can be obtained
from the California office of the Metal Finishers Association.
A bibliography is included in each report.
MR. COOK:
I would like to look at the more general
picture here.
I would like to congratulate Ed Dyckman and
the Steering Committee on bringing together this type of
conference.
It has been very enjoyable and very instructive
to all of us.
I would, however, suggest some improvements.
One improvement would have been to hold this conference
considerably earlier in the decision making stage of the
proceeding.
Another improvement would have been representation
on the Steering Committee by industry and by overseas delegates,
perhaps NATO, to bring in a world picture.
important points for any other materials that may be dealt with
I think these are
in this manner in the future.
We are all equally concerned with the environment.
We all want to see safe operations.
595
It is up to the United
-------
States government to issue regulations to insure safe operation.
These regulations will have an economic impact on cadmium plating.
If that economic impact is such that other alternatives
come to the fore, then the cadmium plating industry would defer
to that situation.
However, it seems to me that because of the
feeling that cadmium is toxic under the circumstances of use,
then decisions may have been made to eliminate cadmium
electroplating.
I would like to suggest that cadmium electroplating can
be made safe at some cost.
If the cost is too high, we will
accept the consequences.
To eliminate cadmium plating by an
apparent "gentleman's agreement" is unfair to an industry.
"Are most alternatives to electroplated cadmium
available today?"
Mr. Laurilliard has demonstrated that
there is no universal substitute for cadmium plating, and
that there is no one coating which will do the job.
Mr. Grobin has demonstrated that if you are
interested in a specific characteristic, such as corrosion
resistance, then zinc electroplating can do the job.
Each
individual application must be looked at on its merits, and
looked at with a full awareness of all the different
characteristics demanded by that particular application.
The effect on the quality of life could be serious
if somebody were to use a poor protective coating for the
landing gear of a jet plane, or for automotive applications.
We must make these changes responsibly.
596
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I do not think alternatives are available until we
have (a) done correct testing, including seller's testing, and
(b) until we have specifications which cover the situation
adequately.
MR. ISLER:
Bill Isler, Harry Diamond Laboratories.
I would like to say that the quality of life should be discussed
in all aspects.
I think the people who got the disease which
is called "Itai-Itai", are also concerned about the quality of
life.
MR. GROBIN:
I think it is most important to look
at the reference that has been written about that, which is called
"Cadmium in the Environment" put out by the Chemical Rubber
Company.
It clearly points out that there were other factors
here.
These people had a severe Vitamin D deficiency which had
an impact on the uptake of the cadmium.
The cadmium may not
have been the culprit.
There is no conclusive evidence that
cadmium is the culprit.
It was the first item to be pointed
out.
Again, the cadmium in their food chain came about by
abuse and by careless operations, which is generally not the
case here in the united States.
MR. SNYDER:
And the water pollution came about from
a mining operation rather than an electroplater.
There is,
of course, considerable difference.
MR. ISLER:
The studies that Mr. Snyder mentioned
were not universally accepted.
It is like any other thing,
be it smoking or whatever. I think people who are concerned
about health are going to choose one side or the other.
597
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If we cut down on cadmium, it is going to hurt the
standard of living of people who work in that industry.
The
picture painted by this panel is that airplanes are going to fall
from the skies without cadmium.
This mayor may not be true.
Most people think that if you really need cadmium for an
application, then use it.
This was the result of the IBM study.
They kept cadmium where they really needed it.
But to argue that
the whole industry has to be saved in the face of the potential
health hazards is not acceptable.
MR. SNYDER:
My point was that the literature produced
by very reputable organizations is, in fact, quite contradictory.
What I am calling for is a further study, a study which hopefully
will ease out the contradictions.
We platers work here, but
we live here too.
In fact, most of us live near our shops, and
we get the impact from pollution right away close to home.
What we are asking for is to remove the contradictions
in the study and define the real problem, not to wipe out a
segment of an industry if we don't have to.
If we do have to,
fine,
let's do it.
But let's make sure that its necessary first.
Let's bear in mind that we platers are also under rather rigid
restraints with respect to water pollution.
It may get
more rigid over night.
I refer to HR 3199.
We may wind up
going to such exotic pollution control systems that we are
going to be at zero discharge anyway.
So before we
completely remove cadmium from the list of things to be used,
let's consider all of this in the same mode and mood that we
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did here over the last few days.
I am tremendously pleased to
have been here.
I am just really pleased that such a session
was held.
I will wave the flag.
I think it is a fine example
of how democracy is supposed to work.
MR. ISLER:
The only point I wanted to make was that
in setting up the workshop we tried to include view points on
all aspects of the problem.
This afternoon, for the last few
minutes,
it has been very one-sided.
MR. COOK:
May I say that the gentleman seems to
place himself on one side of the fence, and the panel on the
other.
That should not be.
I don't see it that way.
I see
us on the same side of the fence.
The heavy metals industry is
saying it can operate safely.
The regulatory agencies have a
responsibility, and the law will be obeyed.
Given that, you have
safe operations for cadmium plating.
We are not, therefore,
talking about anything other than the economics of the situation.
Of course, the environmental restrictions will affect the
economics,
and that is acceptable.
MR. MEYER:
Fred Meyer, Air Force Materials Lab.
I think you have led to some misrepresentations of the use
of electroplated cadmium on landing gears.
We prohibit the
use of electroplated cadmium on most of the landing gears
with 180,000 psi or greater strength steels.
We have used
vacuum deposited cadmium for the Air Force military and
very probably the commercial airlines.
The high strength
steels are very susceptible to hydrogen embrittlement.
599
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The major landing gear manufacturers have been using vacuum
deposited cadmium for a number of years.
MR. SNYDER:
The Douglas DClO has many major compo-
nents of its landing gear made from 300-M steel.
The stress
level is 275,000 to 305,000 psi.
These parts are plated with
low hydrogen embrittlement cadmium.
The space shuttle utilized
the same stress level, and the same material.
The parts were
plated with titanium cadmium.
The same is true of the L-lOll.
The same is true with variations in material and stress levels
of the 747 and 727.
I know this since I plate these parts.
MS. ZILEK:
I am Ms. Zilek from the Ford Motor Com-
pany. According to Mr. Menzie of the Fish and Wildlife Service,
the zinc levels that were deleterious to the health of fish
were far more harmful than cadmium was to fish.
Is this
another inconsistency, or is it true?
If it is true, then why
aren't we addressing zinc alternatives?
If it isn't, then the
environmental evidence is very weak and needs a lot more
investigation before alternatives should be addressed.
MR. COOK:
I think I would agree with you.
We need a
good deal more medical evidence.
Zinc has a relatively high
toxicity to marine life.
However, most of us in this audience
are probably zinc deficient and would probably benefit by
taking zinc supplements.
The point I am making is that there
is a tendency to generalize from effects on fish to effects on
humans.
We must be absolutely sure of our facts first.
600
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It really doesn't make any difference
whether we are talking about electroplated cadmium or vacuum
MR. GROBIN:
deposited cadmium.
Either one of those articles is going to
add cadmium back into the environment.
80 I think we have a
larger question.
Is it the electroplating or metal finishing
industry that is adding this cadmium to the environment and
creating the "so-called cadmium hazard"?
Is it the naturally
occurring cadmium bearing ores that are putting the cadmium
into the environment?
Is it the use of cadmium pigment?
Is it the use of cadmium catalysts?
We really don't know which of these items is the
culprit, if there is one.
The burning of coal is another
one.
There are many, many sources which release heavy
metals into the environment.
I think people have jumped to
the conclusion that the electroplating industry is the culprit.
I don't think the electroplating industry alone is guilty.
MR. WHITE:
Actually, an EPA report does suggest
that the manufacturer of nickel-cadmium batteries pollutes
the environment in making the sintered plates.
I haven't
seen a workshop on alternatives to nickel-cadmium batteries
being arranged.
MR. COOK:
The International Lead Zinc Research
Organization is charged with research in these areas, finding
new applications of metals, lead, zinc, and cadmium.
very substantial part of our budget is related to hygiene
A
601
-------
aspects of cadmium.
The industry is doing its part in
this direction.
We are looking for research areas on nickel-
cadmium batteries which can be helpful in reducing
environmental losses.
One way would be to assure the
efficient recycling of the cadmium from the nickel-
cadmium batteries.
We at ILZRO are looking into this
very seriously.
Perhaps the most beneficial applications
for cadmium will turn out to be those where very close
control on the recycling can be achieved.
MR. DAGE:
I am Elbert Dage from the Office of
Toxic Substances, Environmental Protection Agency and one
of the co-sponsors for this workshop.
We seem to be
drifting away from the topic question.
I personally agree
with many of the statements made here concerning the
controversy over toxicity and environmental effects, and
many of the other comments that were made about having
industry involved earlier in this kind of discussion.
In my opinion, it is very early in the game even at
this point to be holding such a workshop.
However,
it was
felt by the various agencies involved that we wanted to
begin this kind of discussion, to learn more about the
usage, to learn whether it is possible to clean up the
electroplating industry with respect to cadmium, and to
learn whether it is possible to find alternatives which
might be less toxic or safer for the environment.
This
is the purpose of the workshop.
602
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I think the question we are working on now is
"How essential is the electrodeposited cadmium?"
I am
not so sure that a lengthy discussion of the debatable
aspects of the health effects is appropriate here except
to say that cadmium is not the only toxic metal that is
used in metal finishing.
MR. SNYDER:
I think we were addressing the
economic effect of removing electroplated cadmium as it
pertained to each of us.
MR. BOOKER:
Jonathan Booker of Brush Wellman.
We are talking about cadmium now as a toxic material.
In substituting for cadmium, one of the considerations
is that cadmium is a heavy metal.
The substitutes
that I have heard suggested most often are also heavy
metals and also have evidence of toxicity associated with
them.
My overall question is whether or not this is just
a beginning, or whether we should consider all of these
things in the proper context as to what we need to do in
order to relieve the input of toxic materials to the
environment.
Will we next be discussing zinc, tin, or
lead in this manner?
Is this just the beginning?
Was
this Workshop on cadmium meant to save the cadmium
industry, or to take the larger issue of heavy metal
pollution into consideration?
MR. GORDON:
Phil Gordon, Cutler-Hammer.
I think there is a language difficulty in the subject for
603
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the panel, and I would like to respond to Mr. Dage's
comment.
The title is, "How essential" et cetera.
You
don't put those two words together.
It is like saying
something is "very unique".
It is either essential or
it is not essential.
More appropriately we are looking
at what are the essential uses of cadmium.
The unessential
uses are defined by those applications for which acceptable
alternates can be found, if there is motivation to change.
That way, the environmentalists, the people who support
life, can make their case by saying that there are social,
political, and economic benefits to limiting the use of
cadmium in a specific application at the cost of this
observable adequate substitute.
In applications where we have no substitute,
that is a victory for the other side.
Ultimately, that
is what we have to find out.
MR. SNYDER:
There are about four of us here
who have talked about being on sides.
I really hope that
we are not.
I hope that this is a cooperative effort,
one that we are trying to put together to everybody's
advantage; the environment, the industry.
I, for one,
will quickly say that I forego any thought of being
on one team or the other.
I really hope we can put
this thing together and make it work.
The hope that
I am trying hardest to establish dovetails with
604
-------
Bert Cook's.
It is my personal belief that we can, if
given the opportunity, establish controls so that cadmium
electroplating can continue to exist.
MR. BAYNE:
Mike Bayne, Battelle-Northwest.
Obviously from my talk, you knew that I was very unfamiliar
with what cadmium plating was until I came here this week.
I have really had an education.
One thing has crossed my
mind.
No matter what we do, the earth is always going
to have "X" amount of cadmium.
We are not going to destroy
it, we are not going to make any more.
When man starts
using the natural resources, he is redistributing material.
That is all he is doing, just redistributing material.
If it becomes concentrated in an area and it is a bad
material, it can affect the other things around it.
We can go ahead and use it, realizing that it
may have some bad effects with a high concentration in a
populated area.
It may mean that some process has to be
moved to a more isolated area.
That is another alternative
that has not really been discussed.
Cadmium effects are
worse when you bring the large volume processing into an
area where you have a large population concentration.
If
you could move large volume processing to low population
density areas, I think it would considerably alleviate
the prob lem.'
MR. SNYDER:
Thank you.
Hearing nothing more
from the floor, I would like to take this opportunity to
605
-------
extend my personal thanks to all of you for your courtesy.
MR. DYCKMAN:
In closing, I think something
important has happened during the last three days.
I
think we have had a dialogue that could possibly determine
the fate of a material.
The purpose of sessions such as
this is to bring out such issues and increase our mutual
state of knowledge.
This Workshop is now adjourned.
606
-------
APPENDIX III
Attendance List
607
-------
APPENDIX III
GOVERNMENT-INDUSTRY WORKSHOP ON ALTERNATIVES
FOR CADMIUM ELECTROPLATING IN METAL FINISHING
National Bureau of Standards
Gaithersburg, Maryland
October 4-6, 1977
Registration List
Devereaux Barnes
EPA
401 M Street
Washington, DC
20460
David G Blundell
Naval Undorwater Systems Center
Bldg. 990 Third Floor Code 36122
Newport, RI 02840
Charles S. Bartek
RCA Corporation
Corporate Standards
Building 204-1
Camden, NJ 08027
Engineering
Jonathan Booker
Brush Wellman
17876 St. Clair Avenue
Cleveland, OR 44110
1. Bartkey
Institute for Materials Research
National Bureau of Standards
Washington, DC 20234
John E. Breen
Ray Cheom. Company
Sudbury, MA 01776
Don W. Baudrand
Allied- Kelite Division
Richardson Company
29lll Milford Road
New Hudson, MI 48165
Bob Brookshire
B rooktronics Engr.
405 Main Street
Laurel, MD 20810
Corp.
M. A. Bayne
Battelle- Northwest
231-Z Building
200-W Area
Richland, WA 99352
Norm Camire
G & H Technology. Inc.
1649 - 17th Street
Santa Monica, CA 90404
C. R. Campbell
Monsanto Chemical Intermediates Co.
P. O. Box 12830
Pensacola, FL 32575
John Bihl
Tin Research Institute
483 West Sixth Avenue
Columbus, OR 43201
Douglas A. Cardwell
Goodyear Aerospace Corporation
1210 Massillon Road
Akron, OR 44315
John F. Binnie, Jr.
Hughes Aircraft Co.
P. O. Box 11337
Tucson, AZ 85734
J ames A. Clan ton
RCA Corporation
Building 17A3-1
Camden, NJ 08102
Michael L. Bless
Naval Air Engineering
Code 9151 Bldg. 562
Lakehurst, NJ 08733
608
Lester Coch
Waldes Kohinoor, Inc.
47-16 Austel Place
Long Island City, NY 1ll0l
Center
-------
Frank J. Cole
Republic Steel
2906 Liggett
Parma, OH 44134
Richard J. Comp
Burndy Corporation
Richards Avenue
Norwalk, CT 06856
Walter P. Conrardy
U . S. Air Force Materials Lab.
AFML/MX
Wright Patterson AFB, OH 45433
Albert R. Cook
International Lead Zinc
Organization Inc.
292 Madison Avenue
New York, NY 10017
Research
Anthony Corvelli
Naval Underwater Systems Center
Newport, RI 02840
Henry Crein
Engineering Directorate
Rock Island Arsenal
313 E. Central Pk. ,
Davenport, IA 52803
Elbert L. Dage
Environmental Protection Agency
Office of Toxic Substances
401 IIM'! Street, S. W., WH-557
Washington, DC 20460
E. A. Davis
3M Company
23923 Research Drive
Farmington, MI 48024
Wentzle R. Deboskey
IBM E81/BlOl
P.O. Box 12195
Research Triangle Park,
NC 27709
P. Debruyn
National Bureau of Standards
Washington, DC 20234
609
Jon A. deRidder
Diamond Shamrock Corp.
P.O. Box 127
Chardon, OH 44024
William E. Desjardins
Reilly Plating Company
17725 Dora Avenue
Melvin dale , MI 48122
J. W. Dini
Sandia Laboratories
Division 8312
P. O. Box 969
Livermore, CA 94550
A. P. Divecha
Naval Surface Weapons Ctr.
White Oak Lab
Silver Spring, MD 20910
(WR-32)
Howard J. Dolejs
Gould Inc.
18901 Euclid Avenue
Cleveland, OH 44117
John G. Donaldson
ITT Cannon
666 East Dyer Road
Santa Ana, CA 92702
Fred W. Drosten
U. S. Army Aviation Research
and Development Command (AVRADCOM)
DRSAV-EQA
P - O. Box 209
St. Louis, MO 63166
Edward J. Dyckman
DOD-Defense Industrial Resources
Support Office
Cameron Station
Alexandria, V A 22314
Adolphe J. Edwards
Harry Diamond Laboratories
2800 Powder Mill Road
Adelphi, MD 20783
-------
John Edwards
Bunner Hill Co.
P.O. Box 29
Kellogg, ID 83837
Edwin Eiswerth
Copper Range Company
Hussey Metals
310 Washington, ST.
Leetsdale, P A 15056
Anthony O. Facciolo
Alexandria Metal Finishers, Inc.
100-106 S. Early Street
Alexandria, VA 22304
E. R. Fannin
McDonnell Douglas
Box 516
St. Louis, MO 63166
James P- Flashery
Lockheed Missiles & Space Co.
121 Smith Creek Drive
Los Gatos, CA 95030
Diana B. Friedman
U . S. Dept. of Commerce-
BDC-Materials Division
Washington, DC 20230
John Fogarty
Bendix Corporation
E.C.D.
Sidney, NY 13838
Richard Funke
Allen-Bradley Company
1201 South Second Street
Milwaukee, WI 53204
R. E. Geisert
Gould Incorporated
18901 Euclid Avenue
Cleveland, OH 44117
Rein H. Gercke
Mail Stop 1/467
Aeronutroruc Division
Ford Aerospace & Comm. Corp.
Ford Road
Newport Be3.ch, CA 92663
Ralph W. Gertz
Westinghouse Plant Apparatus
Division
P. O. Box 1047
Pitts burgh, P A 15230
E. Gileadi
Institute of Chemistry
Tel Aviv University
Ramat Aviv
ISRAEL
Thomas L. Gleason. III
U.S. EPA ORD/OAWU RD682
401 M Street SW
Washington, DC 20046
Philip M. Gordon
Cutler-Hammer, Inc.
4201 N. 27th Street
Milwaukee, WI 53216
Allen W. Grobin, Jr.
IBM Corporation
P. O. Box 390
Poughkeepsie, NY 12602
Earl Groshart
The Boenig Company
20304 N. Tapps Hwy
Sumner, W A 98390
Gail M. Grove
Dow Corning Corporation
Business Research Dept.
3295 E. Wackerly Road
Midland, MI 48640
Rafael Guio
Amphenol Connector Operations
2801 South 25th
Broadview, IL 60153
William K. Halnan
Airco Temescal
2850 Seventh Street
Berkeley, CA 94710
610
Edward R. Hanna
Red River Army Depot
Production Engineering Division
Building 315/3
Texarkana, TX 75501
-------
Lawrence D. Haworth
Raytheon Company
141 Spring Street
Lexington, MA 02173
Bob Heidersbach
Ocean Technology, Inc.
Box 450
Middletown, RI 02840
F. T. Henry
Lockheed-Georgia Company
Department 71-11, Zone 54
86 South Cobb Drive
Marietta, GA 30063
John Herron
Switchcraft, Inc.
5555 N. Elston Avenue
Chicago, IL 60630
Harry Hicks
Boeing Commercial Airplane Co.
Org. B-3020, MIS 64-05
P. O. Box 3707
Seattle, W A 98124
John D. Hoffman
Institute for Materials Research
National Bureau of Standards
Washington, DC 20234
Philip Horelick
Allied Metal Finishing Corporation
4000-4008 E. Monument Street
Baltimore, MD 21205
E. Horowitz
Institute for Materials Research
National Bureau of Standards
Washington, DC 20234
Ralph J. Hovey
Amphenol
2801 S. 25th A venue
Broadview, IL 60153
William Hratko
Sundstrand Aviation
4747 Harrison Avenue
Rockford, lL 61101
611
William E. Isler
Harry Diamond Laboratories
2800 Powder Mill Road
Adelphi, MD 20783
Edward Jankowsky
Naval Air Development Center
Code 30221
Warminster, PA 18974
Martin A . Jaros
Rockford Products Corporation
707 Harrison Avenue
Rockford, IL 61101
James V. Jeffreys
Defense Construction Supply
3990 E. Broad Street
Columbus, OR 43215
CentedSE
Ronald B. Johnson
Institute for Materials Research
National Bureau of Standards
Washington, DC 20234
Jack L. Johnston
Naval Mine Engineering Facility
(NA VMINENGRF AC)
Test Engineering Department
Yorktown , VA 23691
Edward Jorczyk
3M Company
Plating Systems Department
Building 53-1
367 Grove Street
St. Paul, MN 55101
Sam Kann
TRW/Cinch
1500 Morse Avenue
Elk Grove, IL 60007
William B. Kerfoot
Environmental Devices
Tower Building
Marion, MA 02738
Ed Killian
Wa1des Kohinoor, Ine.
47-16 Austel Place
Long Island City, NY 11101
Corporation
-------
John R. KoveJan
Diamond Shamrock
Metal Coatings Division
P.O. Box 127
Chardon, OH 44132
Theodore J. Kozan
Boeing Wichita Company
Material and Processes Engineer
3801 South Oliver
Wichita, KA 67210
Gerald G. Kraft
Kraft Chemical Company
917 West 18th Street
Chicago, IL 60608
Paul A. Krasley
Bureau of Engraving and Printing
14th and C Streets, SW
Washington, DC 20228
David R. Kverek
Martin-Marietta Aerospace
MP 194
P. O. Box 5837
Orlando, FL 32805
W. W. Ladyman
Vought Corporation
P - O. Box 5907
Dallas, TX 75222
Robert W. Lancaster
Bradford National Corporation
2 Research Place
Rockville, Nil) 20850
Paul Lancer
Consumer Product Safety
5401 Westbard Avenue
Room 732
Bethesda, Nil) 20207
Commission
John Lavrilliard
Standard Pressed Steel Company
Highland Avenue & Mt. Carmel Ave.
Jenkintown, PA 19046
F. W. Lawrence
Empigard Corp.
2820 E. 90th Street
Cleveland, OH 44104
Mark Lazarz
Cutler-Hammer Inc.
4201 N. 27th Street
Milwaukee, WI 53216
G. M. Legard
Bunker Hill Co.
P. O. Box 29
Kellogg, ID 83837
Patrick Leonard
Army Materials & Mechanical
Research Center
Watertown, MA 02172
C. Levy
U.S. AMMRC
Arsenal Street, Bldg. 312
Watertown, MA 02172
Donald V. Levy
Lockheed Research 5235/204
3251 Hanover
Palo Alto, CA 94304
Jack B. Levy
General Electric Company
120 Erie Blvd.
Schenectady, NY 12305
Elmer A. Lord
Harshaw Chemical Company
1945 East 97th Street
Cleveland, OH 44106
John M. Lucas
U.S. Bureau of Mines
2401 E. Street NW
Washington, DC 20241
Donald Lyman
International Lead Zine
Research Organization
292 Madison A venue
New.York, NY 10017
612
-------
. Albert Lyon
Fag Bearing Corporation
42 Bennett Street
Stamford, CT 06907
Joseph W. Macedo
Martin Marietta Corporation
4613 Longworth Drive
Orlando, FL 32806
Robert F. Martin
Institute for Materials Research
National Bureau of Standards
Washington, DC 20234
James M. Mayer
3M Company
3M Center 223-4NE
St. Paul, MN 55119
L. McClendon
Institute for Materials Research
National Bureau of Standards
Washington, DC 20234
Kenneth E. McCullough
Standard Pressed Steel Co.
Jenkintown, PA 19046
Mattie F. McFadden
Raytheon Company
Hartwell Road
Bedford, MA 01730
Fred R. Meyer, Jr.
Air Force Materials Lab
Wright Patterson AFB, OR 45433
Guy F. Morris
Northkop Corporation
Aircraft Division
3901 West Broadway
Hawthorne, CA 90250
Donald E. Muehlberger
McDonnell Douglas Corporation
P. O. Box 516
St. Louis, MO 63166
613
R. A. Munson
Bureau of Mines
2401 E. Street NW
Washington, DC 20241
E. E. Oberland
Chesapeake Metal Finishing Corporation
4010 North Point Blvd.
Baltimore, MD 21222
F. Ogburn
National Bureau of Standards
Washington, DC 20234
William L. Pagels
Grumman Aerospace Corporation
Bethpage, NY 11714
Marlin D. Peace
Red River Army Depot
Production Engineering Djvision
Building 3]5/3
Texarkana, TX 75501
Edward A. Peak
Fitzgerald Plating Co.
17450 Filer
Detroit, MI 48154
Walter Petro
Ideal Corporation
1000 Pennsylvania A venue
Brooklyn, NY 11207
Theodore M. Pochily
U. S. Department of Army
Watervliet Arsenal
736 Pearse Road
Schenectady, NY 12309
Kee J. Pon
Naval Ship Engineering Center
Code 610lD
Washington, DC 20362
Richard Pope
The Weatherhead Company
300 East 131 Street
Cleveland, OR 44108
-------
Edward H. Poplawski
Sperry Gyro Company
Union Turnpike
Great Neck, NY 11020
William H. Quittman
Defense Industrial Supply
DISC-ECl\!
700 Robbins Avenue
Philadelphia, P A 19111
Center
A. J. Raffalovich
U. S. Army Electronics Command
DRSEL-TL-ME
Fort Monmouth, NJ 07703
C. Reimann
Institute for Materials Research
National Bureau of Standards
Washington, DC 20234
Dell L. Replogle
Reytheon Co.
Electromagnetic Sys. Div.
6380 Hollister Ave.
P. O. Box 1542
Goleta, CA 93017
George A. Risko
Chrysler Corp.
Sterling Defense Division
6000 East 17 Mile Road
Sterline Heights, MI 48078
N arvel L. Rogers
Bell Helicopter Textron
P. O. Box 482
Fort Worth, TX 76101
Donald J. Sargent
ElM Lubricants, Inc.
P. O. Box 2200
W. Lafayette, IN 47906
Bruce D. Sartwell
U. S. Bureau of Mines
College Park Metallurgy Res. Ctr.
College Park, MD 20740
614
J. W. Sarvis
Department of Defense
D.M.S.S.O.
Cameron Station
Alexandria , VA 22314
Robert Scannell
McDonnell Douglas
2600 N. 3rd
St. Charles, MO 63301
S. R. Schachameyer
Cu tler- Hammer, Inc.
4201 N. 27th Street
Milwaukee, WI 53216
James E. Schell
Alumatec Corporation
332 No. "A" Street
Lompoc, CA 93436
A. J. Schwarz
Gould Inc.
Valve & Fittings Division
6300 West Howard Street
Chicago, IL 60648
Daniel Seymour, Jr.
Physical Sciences Laboratory
Sacramento Air Logistics Command
McClellan Air Force Base
Sacramento, CA 95652
Gene Simmons
Sermetel Inc.
155 South Limerick Road
Limerick, P A 19468
James R. Simmons
MS 3516
Martin Marietta Aerospace
P. O. Box 29304
New Orleans, LA 70189
Bonnie Simpers
Grumman Aerospace Corporation
Plant 12, Dept. 447
Bethpage, NY ll714
-------
John H. Sizer, Jr.
Pratt & Whitney Aircraft
Mail Stop MERLJ Bldg.
400 Main Street
East Hartford, CT 06066
Samuel Sizgorich
Defense Industrial Supply Center
(DISC-E)
700 Robbins Avenue
Philadelphia, P A 19111
R. P. Skow
B. F. Goodrich
Engineered Systems
Box 340
Troy, OH 45373
W. E. Snyder
MFASC
236 Pageantry
Placentia, CA
Division
Drive
Jerry Stockdale
Naval Avionics Facility
1510 N. Leland
Indianapolis, IN
Harry Stollberg
Allen-Bradley Company
1201 South Second Street
Milwaukee, WI 53204
Richard Sussman
A VCO, Lycoming Division
550 S. Main Street
Stratford, CT 06497
Edward Taylor
Standard Pressed Steel Company
Highland Avenue
Jenkintown, PA 19046
Don Teter
Techno-Economic Services Co.
8343 Hammerly Blvd.
Houston, TX 77055
615
J. N. Tuttle, Jr.
Rust Proofing & Metal Finishing Corp
55 Commercial Street
Medford, MA 02155
Luther Vaaler
Battelle Columbus Laboratories
505 King Avenue
Columbus, OH 43201
Ed J. Violante
Ford Motor Company
Am Road
Dearborn, MI 48126
James E. Voytko
Western Electric Co. Inc.
2000 NE Expressway
Atlanta, GA 30071
George Waldes
Waldes Kohinoor, Inc.
47-16 Austel Place
Long Island City, NY mOl
Sheldon Wesson
American Metal Market
665 National Press Building
Washington, DC 20045
Leslie Wester ling
B. F. Goodrich Company
Box 340
Troy, OH 45373
Martin S. White
Cadmium Association
34 Berkeley Square
London, UK
Vernon H. Wilson
3M Company
Plating Systems Department
3M Center, Bldg. 223-4M. E .
S1. Paul, MN 55101
Alan Winchell
General Electric Company
Box 5000 MD070
Binghamton, NY 13902
-------
LuVern J. Wooge
Naval Ordnance Station
Indian Head
Indian Head, MD 20640
Jack Yost
Purdue University
West Lafayette, IN 47906
Joseph A. Zehnder
Enthone Inc.
P. o. Box 1900
New Haven, CT 06508
Hank Zielinski
Federal Screw Works
3401 Martin
Detroit, MI 48210
Carolyn Zilek
Ford Motor
Bldg 5 Room 1008
Dan Mich
Dearborn, MI 48121
616
-------
APPENDIX IV
Sponsoring Agencies and Representatives
617
-------
APPENDIX IV
MEMBERS OF THE INTERAGENCY STEERING COMMITTEE RESPONSIBLE
FOR PLANNING THE GOVERNMENT-INDUSTRY WORKSHOP ON
ALTERNATIVES FOR CADMIUM IN METAL FINISHING
Mr. Dev Barnes
Effluent Guidelines Division
Office of Water Planning & Standards
WH-552
Environmental Protection Agency
401 M Street, S.W.
Washington, D.C. 20460
Phone 426-2586
Mr. Ernst Hall
Effluent Guidelines Division
Office of Water Planning & Standards
WH-552
Environmental Protection Agency
401 M Street, S.W.
Washington, D.C. 20460
Phone: 426-2576
Mr. Allen Cywin
Senior Science Advisor
OWHM (WH-556)
Environmental Protection
401 M Street, S.W.
Washington, D.C. 20460
Phone: 755-0330
Agency
Mr. William Isler
Bldg. 204, 4C-104
Harry Diamond Labs
2800 Powder Mill Road
Adelphi, MD 20783
Phone: 394-3190
Mr. Elbert Dage *
Hazard Assessment Group
Office of Toxic Substances
WH-557
Environmental Protection Agency
401 M Street, S.W.
Washington, D.C. 20460
Phone: 755-2110
Mr. Paul Lancer
Bureau of Engineering Sciences
Consumer Product Safety Commission
Room 900
5401 Westbard Avenue
Bethesda, MD 20207
Mr. Edward Dyckman **
Defense Industrial Resources
Support Office
Cameron Station
Alexandria, VA 22314
Phone: 274-7222
Mr. Pope Lawrence
Office of Federal Activities
(1).-104)
Environmental Protection Agency
Washington, D.C. 20460
Phone: 245-3006
Mr. John Flack
Standards & Quality Control
Federal Supply Service
General Services Administration
Washington, D.C. 20406
Phone: 557-8660 or 7537
Dr. Joseph McLaughlin
Bureau of Biomedical Science
Consumer Product Safety Commission
5401 Westbard Avenue
Bethesda, MD 20207
Phone: 492-6480
Mr. John Hague
U.S. Bureau of Mines
2401 E Street, N.W.
Washington, D.C. 20241
Phone: 634-1063
Mr. Calvin Menzie
Division of Habitat
Research
Fish and Wildlife
Department of the
Washington, D.C.
Phone: 343-4670
Preservation
Service
Interior
20240
* CHa-i rman
** Coordinator
618
-------
Mr. Fielding Ogburn
Metallurgy Division
Institute for Materials Research
National Bureau of Standards
Washington, D.C. 20234
Phone: 921-2957
Mr. Wade Talbot
Office of Health & Ecological
Effects/ORD
RD-683
Environmental Protection Agency
401 M Street, S.W.
Washington, D.C. 20460
Phone: 755-9722
Mr. Grover Wrenn, Director
Division of Health Standards
Occupational Safety and Health
Administration
Department of Labor
200 Constitution Avenue
Washington, D.C. 20210
Phone: 523-7177
619
-------
APPENDIX V
Aerospace Industries Association
Surveys on Alternatives to Cadmium Plating
621
-------
AEROSPACE INDUSTRIES ASSOCIATION OF AMERICA. INC.
1725 DE SALES STREET. N W . WASHINGTON. 0 C" 20036 TEL. 347-2315
December 20, 1977
Mr. Edward J. Dyckman
Defense Industrial Resources
Department of Defense
Dwyer Building
Cameron Station
Alexandria, Virginia 22314
Support Office
Reference:
AlA Surveys on Alternatives to Cadmium Plating
Government/Industry Workshop - October 4=6, 1977
Subject:
(B)
Summary and Comments to AlA Survey on Cadmium
Plating Replacement
Summary of Comments to AlA Survey on Role of
Specifications and Standards on Adoption of
Alternatives for Cadmium Electroplating in
Metal Finishing
Enclosure:
(A)
Dear Mr. Dyckman:
The enclosures are two AlA surveys conducted on alternatives for cadmium
electroplating.
The survey of Enclosure (A) was conducted by the National Aerospace
Standards Committee with the objective of determining feasible alternatives
should restrictions be placed on the use of cadmium plating.
Enclosure (B) contains the results of a survey conducted by the Materials
and Structures Committee to provide comments for the workshop panel discussion:
"Are Specifications and Standards Barriers to Change?"
You are free to use this material in your Workshop Proceedings if you
so desire.
Very truly yours,
JPR/s fe
cc: M. McFadden
AEROSPACE TEC~N~CAL COUNCIL
-"" ~ /)'
- "'\j:: ,'" -~..... ._--
~ P. Reese, Executive Secretary
Materials and Structures Committee
622
-------
I\LLJcIIlIlCI1L (A)
Page 1 of 4
SUMMARY AND COMMENTS TO
AEROSPACE INDUSTRIES ASSOCIATION SURVEY QUESTIONNAIRE
ON CADMIUM PLATING REPLACEMENT
Twenty (20) users and seven (7) suppliers responded to
the survey
1.
If E.P.A. requirements eliminate the use of cadmium plating, what
alternate fastener finish would you use of general application when
installed in the following structure.
1.1 Aluminum Sheet
1.1.1
Aluminum, IVD Coating
(7) Users
(2) Suppliers
1.1.2
Aluminum Coating
(7) Users
(1) Supplier
Zinc (Plate or IVD)
1.1.3
(4) Users
1.1.4
Polysulfide Sealant
(1) User
1.1.5
Fused Tin or Solderplate
(1) User
1.1.6
Wet Sealant
(1) User
1.1.7
Primer
(1) User
1.1.8
Nickel or Chrome
(1) User
A286 or Chrome Fastener
1.1.9
(3) Users
(1) Supplier
623
-------
Page 2
1,2 Titanium
1.2.1
1.2.2
1. 2.3
1.2.4
1. 2.5
1. 2.6
1. 2.7
Aluminum IVD Coating
(4) Users
(2) Suppliers
Aluminum Coating
(4) Users
(1) Supplier
Tin
(2) Users
Polysulphide Sealant
(1) User
(1) Supp 1 i er
Nickel or Chrome
(1) User
Dry Fi 1 m Lube
(1) User
A286 or Cres Fasteners
(5) Users
(1) Supplier
1. 3.1
1.3 Low Carbon Steel
Zine
1.3.2
1.3.3
1.3.4
(7) Users
(2) Suppliers
Aluminum IVD
(6) Users
(1) Supplier
Aluminum Coating
(6) Users
(1) Supplier
Nickel or Chrome
(2) Users
624
-------
Page 3
1.3.5
1.3.6
1.3.7
Polysulphide Sealant
(1) User
Fused Tin or Solder
(1) User
A286 or Cre5 Fastener
(2) Users
(1) Supplier
1. 4 Alloy S tee 1
1.4.1
1.4.2
1.4.3
1.4.4
1.4.5
1.4.6
1.4.7
Aluminum IVD
(7) Users
(1) Supplier
Aluminum Coating
(5) Users
(2) Supp 1 i ers
Zinc
(6) Users
(2) Suppliers
PolysulfideSealant
(1) User
Nickel or Chrome
(1) User
Fused Tin or Solderplate
(1) User
A285 or Cres Fasteners
(3) Users
(1) Suppl ier
1.5 Composite Material
1. 5.1
Titanium
(6) Users
625
-------
Page 4
1. 5. 2
Alumi~um IVD
(4) Users
Polysulfide Sealant
1.5.3
(1) User
1.5.4
Fused Tin or Solderplate
(1) User
1.5.5
Aluminum Coating
(1) User
1. 5.6
Nickel or Chrome
(1) User
1. 5.7
Zinc
(1) User
1. 5.8
A286 or Crew Fasteners
(5) Users
(1) Supplier
2.
Do you expect to develop such substitute capability in the future, and
if so, what date?
Yes: (7) Users, (4) Suppliers
Available Now: (3) Users, (1) Supplier
1978: (1) User
1980: (1) User
Unknown: (2) Users, (6) Suppliers
No: (10) Users, (3) Suppliers
3.
Do you expect any significant availability or cost problems to be
associated with these substitute finishes?
No: (4) Users, (1) Supplier
SITght: (6) Users, (1) Supplier
Some possible usage, acceptance or method problems:
(5) Users
626
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Attachment (8)
AEROSPACE INDUSTRIES ASSOCIATION
SUMMARY OF COMMENTS
Survey on Role of Specifications and Standards on Adoption
of Alternatives For Cadmium Electroplating in Metal Finishing
(1)
Are specifications and standards barriers to change?
(A)
Yes they are - especially when working on military contracts. In
order t~ instit~te a change an excessive period of time is required
along wlth conslderable test documentation and even then the outcome
is uncertain.
(B)
Yes. Procedural specifications and standards tend to act as temporary
road blocks which are slow and costly to move.
The widely used specifications require excessive coordination times
and because they are specified for almost every contract, tend to
have the key requirements diluted to the point of ineffectiveness.
(C)
No. Requalification of alternate materials, methods and coatings to
meet specifications will be required. The requirements will be the
same as or very near those for cadmium plating. Rewriting will be
required, but there should be no barrier to change, except for time
and cost.
(D)
No, these are not barriers to change. The greatest barrier is sub-
stantiation of changes by performance testing.
(F)
Yes. Since specifications and standards require investment in Plant
Facilities, the capjtalization or amortization of facilities is a
barrier.
(G)
Yes. Any new thinking is resisted by Government personnel unless long,
costly programs with the accompanying data are available. Even then,
(Government) personnel would rather sit on what they have (provided no
problems exist) than make a change based on costs or ease to the
manufacturer.
(H)
To a degree. Specifications and standards are invoked contractua:ly
and require contractual deviations to use something else, and devla-
tions are usually avoided.
(J)
Yes. Once hundreds of drawings callout a specification, it is costly
to change.
(K)
Yes.
Yes, a careful check will have to be made to determine th~ effect of
the change on the standard or specification and the assoclated con-
tractual obligations involved.
(L)
(M)
Yes, when they specify electroplated Cad as the required finish.
e.g. standard attaching parts.
627
-------
Attachment
SUMMARY OF
Page -2-
(B)
COMMENTS
Question (1) cont'd.
(2)
(N)
No, if we see more performance type specifications and fewer
recipe types.
(0)
Yes, since contractual requirements specifically callout cadmium
plating to a Federal Specification, prime contractors specifications,
and other related specifications such as AMS 2400 or AMS 2401.
(P)
Specifications and standards must be barriers to undesired and/or
uncontrolled changes, otherwise they would not be doing their job.
Sometimes desired changes are delayed more than we would like, but
the delay may be necessary and valuable in uncovering unexpected
complications during the change substantiation effort.
(Q)
Yes, when a process or material reaches the point in development where
it is possible to describe it's requirements in a specification, and
this is done, there is a tendancy to no longer pursue better ways or
materials to do the job, rather, just to use the proved method or
material. With time and experience these proved processes and materials
become entrenched. The only motivation for any further improvements
is usually brought about by a problem.
(R)
Since aerospace procurement is largely controlled by specification and
standards requirements, they will be barriers to change.
What role will specifications and standards play in the adoption of materials
and processes that are identified as viable alternatives to cadmium electro-
plating in metal finishing?
(A)
They will have to be incorporated in MIL and FED standards dealing
with protective coatings - as acceptable alternates.
(B)
When specs and standards identify performance requirements instead of
what has to be used, how thick and how it must be applied, then viable,
cost effective alternates can and will be selected and used by the
aerospace industry.
The priorities and sequence should be: (~) Identification of viable
alternates (this workshop); (b) Thorough performance testing - laboratory
and field; (c) Selected service applications (government approved con-
tractor specifications); and (d) Industry, then government specifications.
(C)
Standards and specifications will be required to use alternatives to
cadmium plating.
(D)
Specifications and standards establish the fundamental basis for
utilization of alternatives.
(F)
Since substitution of mechanical or vapor deposition may not fulfill the
application spectrum of electroplate, additional substitutes (Zinc-rich
coatings, etc) would probably result in a multiplicity of specifications
and standards for alternates.
628
-------
Attachment
SUMMARY OF
Page -3-
(B)
COMMENTS
Question (2) cont'd.
(R)
(G)
A major role. Specifications or standards of
a~l users the necessity of writing individual
w1th th: required back-up data to justify the
protect1ve systems.
materials will relieve
requests for changes,
change, to the new
(H)
If specifications and standards are created, and recognized (in MIL
Bulletin 400, MIL-E-5400, etc). they are more apt to be utilized.
(J)
If customers require the use of new coatings, these new materials
will be adopted.
(K)
Essential.
(L)
A very active role. It is anticipated that there is no one alternative
system which can be invoked to replace our present cadmium plating.
Specifications and standards will be necessary to insure uniform
of approved alternatives to cadmium electroplating and to aid in
use of the alternative coatings.
(M)
quality
proper
(N)
Unless specifications and standards are initiated by some organization,
changes will be long in coming.
(0)
The existing viable alternatives specifications and standards will
control what process or processes will be used as a substitute for
cadmium.
(P)
They will provide a needed common approach,
users, for earlier attainment of uniformity
control and test methodology.
shared by many aerospace
of quality. thickness
(Q)
The existing requirements as described in the existing specifications
and standards would continue to be the governing standard for any
viable alternative to cadmium electroplating. The alternative must be
equal to or better than the existing requirements.
Affected specifications and standards will require "tailoring" to
include and permit use of viable alternatives to cadmium electroplating
as identified following demonstration of feasibility.
(3)
What means should be adopted for the selection of materials, methods, and
coatings for exploration as candidates for use in lieu of electrodeposited
cadmium?
(A)
(1) Costs; (2) Ease of application - (minimize complicated equipment);
. h cadm{um,' (4) Types of surface
(3) Comparative corrosion tests w~t ~
629
-------
Attachment
SUMMARY OF
Page -4-
(B)
COMMENTS
Question (3) cont'd.
(B)
Government sponsored competitive research, incentive type research
allowances in system hardware contracts for technological improve-
ments in environmental protection alternates for electrodeposited
cadmium.
An industry-wide survey could provide data for a
of cadmium electroplating utilization and assist
guidelines for acceptability of alternates.
parametric analysis
in establishment of
Candidate alternative characteristics to be determined include:
(a)
Coating performance: Corrosion resistance, paint adhesion,
wear resistance, and base for solid film lubricants.
(b)
Porosity, galvanic potential and hardness.
Coating properties:
.(c)
Effects of coating: Hydrogen embrittlement, liquid metal embrittle-
ment, stress corrosion and galvanic coupling.
(d)
configuration limits, thickness controls and
Process control:
appearance.
(C)
All applications must be identified and analyzed to determine why
cadmium was chosen for each of the applications. Based on this infor-
mation, alternate materials or simple redesign will eliminate many uses
of cadmium. Intelligent choices of alternates cannot be made until
this survey is completed and analyzed.
(D)
Proposed alternatives must be tested and proven
restriction so that each particular application
requalified.
equivalent without
does not have to be
(F)
Cost, technical and environmental complexities indicate
programs be implemented for industrial applications and
applications.
that separate
for military
(G)
Suggest that a six-month notice be given to coating manufacturers to
provide alternative recommendations with data, to a select committee.
The committee to select materials for evaluation based on the area of
use, i.e., aircraft, ground support, electronics, small or major user
shop. An evaluation program be written and provided to a select group
of users (with Government funds) the responsibility of testing and
providing the data for the select committee to evaluate alternative
materials. The select committee to subsequently write the required
specification (performance) and standards for the alternative materials.
(H)
RFQ's for study contracts should be issued to applicable industry
sources.
630
-------
Attachment
SUMMARY OF
Page -5-
(II)
COMMENTS
Question (3) cont'd.
(J)
Industry groups such as AIAA or SAE should select candidate materials
and gather data on real-time performance. Study should examine problem
at,t~o ievels; routine corrosion protection (non-structural parts) and
fcrltlca corrosion pŁotection (structural parts such as high strength
asteners).
(K)
Environmental exposure
Mechanical properties,
have to be considered.
and corrosion tests are primary factors.
coating cycle time and equipment cost also
(L)
A co~plete,outline of all the available possible changes to coatings/
platlngs wlll have to be set up outlining the differences with a
comparison of properties and costs to present cadmium pla~e. Extensive
testing may be involved to determine the effect of changes.
(1) Compile candidate materials from all available sources; (2)
reduce the list to a limited number of viable candidates by survey,
society correspondence, etc.; (3) survey government contractors for
applications where none oi these candidates will work; (4) analyze
problem areas individually.
(M)
(N)
Action by the EPA in connection with some government subsidies would
force the changes. However, off-the-shelf processes are available
now without additional research.
(0)
Processes that parallel electrodeposited cadmium, i.e., electro-
deposited zinc should be compared against cadmium by salt fog testing,
thickness-for-thickness. These two specifications, QQ-P-416 and
QQ-Z-325, are more closely similar that any other processes available
as substitutes.
(P)
A tentative list should be submitted to AIA/MSC for ballot selection
of the candidates of greatest interest.
(Q)
Means - as money. Research money to replace cadmium electroplating
might be hard to justify in that everything is already geared up to
use it. This is particularly true of in-house funds where the only
justification for change would be of necessity to meet a new require-
ment for pollution control or something of that nature.
Means - as testing procedures. Cadmium electroplating is primarily used
in controlling corrosion. In order to evaluate alternatives, the tests
would be various environmental exposure tests such as salt (fog) spray,
high humidity, and outside exposure conducted us~ng te~t pieces and
actual parts. Cadmium, by nature, offers a coatlng WhlCh has an
established performance to resist fretting, galling and subsequent
.. 1 f d' m should be evaluated for
fatlgue fallure. Any rep acement or ca mlU
I' f' 1. ,[' g' etc OLher applica-
this property, e.g. fasteners, s lp lt uusnn s, .
. ,. . 1 b. , In this case some sort of wear
tlons for cadmlum lS ln u rlcatlon. ,
testing would be required.
631
-------
Attachment
SUMMARY OF
Page -6-
(B)
COMMENTS
Question (3) cont'd.
(4)
(R)
A listing of promising candidate materials, methods and coatings
should be jointly prepared -- designate an organization (company,
lab, etc.) having the necessary capabilities and expertise to con-
duct the required development, evaluations and testing to prove
feasibility of alternatives. The appropriate government agency
should provide financial support and monitor/approve the effort and
results.
Many Government and technical society specifications and standards call for
the use of electrodeposited cadmium as a corrosion protective coating for
hardware. What would be the time, cost and procedures involved in adopting
alternative materials, methods and coatings to replace electrodeposited
cadmium in these and related documents?
(A)
This could be very time consuming.
(B)
Time - 3 to 5 years. Cost - dependent on number of candidates.
Major cost impact which needs to be evaluated separately for each
application:
(a)
Fasteners: Coating thickness, effect on torque values, hydrogen
embrittlement, fatigue, temperature limitations, galvanic and
crevice corrosion and cost.
(b)
Primary Structure: Hydrogen embrittlement, paint adhesion,
corrosion resistance, environmental resistance, galvanic coupling
and raparability.
Procedure: Test, evaluate and compare in programs as recommended in
(2) and (3) above. Viable alternates will probably include zinc, tin,
aluminum, alloy coatings and dry film lubricants with selection de-
pending on substrate and use.
(C)
It will require a long time to change the standards and specifications
because new application criteria must be developed prior to changing
to alternate materials, methods and coatings. It is visualized that
extensive changes will necessitate reissuing new specifications and
standards.
(D)
Specific costs would be dependent upon each application and would vary
also with facilities involved as well as whatever may be determined
as the alternative process.
(F)
We do not have the technological expertise or cost data to formulate a
qualified answer to this question.
(G)
If a concerted effort is
Government, possibly two
632
made, under a schedule mandated and funded by
- three years at a cost of $1,500.000
-------
Attachment
SUMMARY OF
Page -7-
(B)
COMMENTS
Question (4) cont'd.
(H)
The time and cost would be significant'
out industry would also req' h.' Many company standards through-
Ulre c anges. Cancellation of QQ P 416
w~u:d.probably be necessary to assure full compliance. An e~i~t ro-
hlbltlng electrodeposited cadmium might also b p
e necessary.
Time~ cost and procedures. would depend on the alternate protective
coatlng selected and the lntended application. We have already
selected aluminum coatings to replace cadmium If It
f . a ernate materials
are ound, new specifications should be written and imposed on new
programs only.
(J)
(K)
See (3). Minimum lead time of two years after acceptable alternates
have been developed to incorporate I f
in norma manu acturing operations.
(L)
Our estimates are four to five years with overall costs running into
the millions of dollars.
(M)
Time and cost would be large for an immediate change. However,
blanket substitution procedures could save both time and cost.
(N)
Unable to answer.
(0)
The processing equipment might involve the greatest cost and time con-
sideration in replacing cadmium if impact deposition were used. The
least replacement cost in time and procedures would be the use of electro-
deposited zinc. This would merely involve replacing the electrolyte.
(P)
For a completely new coating on critically stressed parts, would
estimate a minimum of three years of laboratory, rig and full-scale
product testing, including adjustments in the initially developed
coating, followed by two to three years of field testing under nonnal
and severe conditions. Thus, well over five year could elapse prior
to production use, following initial development. Cost would depend
on circumstances, but could be several million dollars for some applica-
tions. Most practical solution is to retain the ability to use cad
plate, utilizing whatever means necessary to protect the environment.
Obviously there will be no single alternative which can be applied
across the board. New designs can, and in some instances already do,
utilize suitable replacements selected according to the specific needs,
and there may be little or no cost penalty in so doing.
There is however no way to change all existing service applications
, , .
without the possibility of adversely affecting critical parts pr~pertles
and, perhaps, some other aspect of our environment. The evaluatlon
of substitutes in all such applications would be a technical and
economic nightmare.
633
-------
Attachment
SUMMARY OF
Page -8-
(B)
COMMENTS
Question (4) cont'd.
(5)
(Q)
This would be an involved testing program over a fairly extensive
period of time in order to assure that the replacement was reliable.
As the testing program progressed, other applications or properties
of cadmium that were not outlined at the outset but were of equal
importance, will come to light and need to be evaluated. It is be-
lieved that there is not a universal substitute for cadmium and each
property and application may require a different substitute material.
(R)
A coordinated, controlled evaluation effort as described in #3 above
would prevent duplications in establishing viable alternatives and
would minimize costs involved. Anticipate at least a year will be
required to determine and verify alternatives, and "tailor" related
documents necessary to implement on a production basis.
Does the use
the time and
to potential
of materials vis-a-vis performance specifications influence
cost involved in changing over from electrodeposited cadmium
alternative materials, methods, or coatings?
(A)
Yes.
(B)
The establishment of performance specifications
ments are less costly and permit the use of the
protective coating from the specific conditions
to define the require-
most cost effective
the hardware will see.
(C)
Yes, dependent on the alternative. Particular attention must be given
to compatibility from the corrosion standpoint. We have to guarantee
that the new coating will meet the same requirements as cadmium for the
specific application. This will necessitate a costly requalification
program in many cases.
(D)
Yes, it is highly dependent on what are the alternative materials,
methods or coatings.
(F)
Materials - Process type specifications cannot be reliably qualified
without verification by performance data.
(G)
Yes, the cost of time, labor and materials required to meet qualifi-
cation requirements of performance specifications always is a concern.
(H)
In some cases, additional costs would be
environmental testing of parts to assure
formance with an alternative coating.
necessary for conducting
meeting contractual per-
(J)
No - drawings still have to be changed and new processing equipment
installed. A material specification is preferred because it allows
better control of the product. Performance tests, such as soft-spray
resistance, should be included in the specification.
A performance
that survives
as on a beach
specification that calls for an unidentified coating
a specific time in a specified test atmosphere, such
exposure rack, is uuacceptable.
634
-------
Attachment
SUMMARY OF
Page -9-
(B)
COMMENTS
Question (5) cont'd.
(K)
Yes.
(L)
Yes.
(M)
Yes - performance specs are not suitable for application when it
is necessarY,to know what coating is used. For example, contact
between cadm~um and titanium is prohibited, zinc is prohibited
where good electrical conductiVity is required, etc. Materials
Specification must be available for drawing callout in order to
assure that parts from all suppliers are interchangeable.
(N)
Performance specifications should shorten the transition period
in any change over.
(0)
Yes. The influence of performance specifications will have a direct
effect in change over from electrodeposited cadmium to other potential
alternative materials, methods or coating. Again the alternative
material and method that more closely parallels electrodeposited
cadmium will have the greatest potential for change over.
(P)
Performance specifications may well be the least expensive approach for
eventual requirements and controls, but the potentially high cost and
time for developing, proving and changing over to each new protective
system will be the same either way.
(Q)
Yes, but some performance specification is necessary to be able to
compare the alternative material with the cadmium plate. However, if
the alternative material is one where experience and testing has
shown that it is equivalent, a performance specification may not be
required and therefore would be less expensive with regard to time and
cost.
(R)
Yes - Other factors involved are pollution control/waste disposal
requirements and costs associated with alternatives developed. Are
they more or less stringent or about the same as that required for
the electrodeposited cadmium coating process.
635
-------
APPENDIX VI
Results of Workshop Questionnaires
637
-------
RESULTS OF QUESTIONAIRE
DISTRIBUTED TO PARTICIPANTS AT THE WORKSHOP
ON
ALTERNATIVES FOR CADMIUM ELECTROPLATING IN METAL FINISHING
Thirty-nine out of 160 or 24% of the Workshop attendees responded to a
feedback questionnaire distributed at the Workshop on Alternatives for
Cadmium Electroplating in Metal Finishing. A summary of the response to
the questionnaire follows. Since a number of respondees gave more than one
answer per question, the responses are categorized in percentages.
QUESTION 1 - "Why have you attended thi s Workshop ?"
RESPONSE
% OF RESPONSE
To learn of alternative materials and processes.
To learn of the future of e1ectrodeposited cadmium.
To keep up with the state-of-the-art in metal finishing.
To represent the interest of cadmium platers.
To learn of issues related to the use of specifications and
standards and the adoption of new materials and processes.
To learn of government and industry activities regarding toxic
substances.
47
21
12
10
6
4
100
QUESTION 2 - "Are you satisfied with the Workshop?"
RESPONSE
% OF RESPONSE
Yes
Somewhat
No
87
10
3
100
QUESTION 2 - "Explain Why or Why Not?"
RESPONSE
Positive:
Most were impressed with the organization, punc-
tuality, balance of views, and comprehensiveness
of the conference.
Negative:
Didn't
Didn't
were
care for panel sessions.
care for some industry papers because
self-serving and not technical.
638
they
-------
RESPONSE
Negative:
(Cont.)
Didn't adequa~ely address alternati"es for cadmium
elect~oplat1ng on electrical and electronic hardware.
Would 11ke to see proceedings issued sooner.
RECOMMENDATIONS:
Should have included both industry
the Steering Committee.
Should have been held even earlier
deliberations on cadmium.
Suggest problems of hazards to the
the entire plating industry in
and NATO representatives on
in the process of government
environment be addressed to
the form of a workshop.
QUESTION 4 - "Unanswered Questions".
What alternatives are there for cadmium electroplating on non-
ferrous substrates in electrical applications? (Philip Gordon,
Cutler-Hammer, Inc.).
What would best solve the problem of cadmium pollution - mandatory
controls by government or voluntary industry adoption of alterna-
tives to cadmium electroplating? (William Hratko, Sundstrand
Aviation).
Has a decision been made by government that effluent guideline con-
trols will not be effective for cadmium pollution and, therefore,
some other regulatory actions needs to be promulgated? (Albert Cook,
International Lead Zinc Research Organization, Inc.).
What are some effective methods of attaining zero discharge of cad-
mium in plating shop effluents other than by a closed loop system?
(Seymour Daniel).
When will restrictions in the use of cadmium be issued by EPA?
(Edward Hanna, Red River Army Depot).
Once these restrictions are announced, how much lead time will be
given to convert to alternative coatings? (E. Hanna).
Once these restrictions are announced, what alternative coatings
will DoDadopt? (E. Hanna).
How should cadmium plated articles be disposed of once their useful
life is over? (LuVern Wooge, Naval Ordnance Station).
What are the views of EPA regarding future restrictions to be placed
on the cadmium plating industry? (Edward Taylor, Standard Pressed
Steel Company).
How will evaluation, qualification, and use of alternatives for 2lec-
trodeposited cadmium by DoD contractors be funded? (Mattie McFadden,
Raytheon Company).
Where will facilities for these alternative processes be installed - in
DoD contractor plants or independent job shops? (M. McFadden).
639
-------
QUESTION 4 - "Unanswered Questions". (Cont.)
Is there any attempt being made to standardize military finish
standards (e.g., MIL-STD - 171, 186, 193, 194 and MIL - F -
14072)? (George Risko, Chrysler Corporation).
What are the exact steps one takes to develop new specifications
and standa~ds? What is the source of funding of this work?
This is in reference to the adoption of alternative materials
and processes for e1ectrodeposited cadmium. (Michael Bayne,
Battelle - Northwest).
Will there be any recommendations generated as a result of this
meeting? (Edward Jankowsky, Naval Air Development Center).
640
-------
TECHNICAL F1EPORT DATA
1. REPORT NO. (Please reaJ lnstrucrions on the rerersc belore complenngl
EPA-')f)() /2- 7q. -()() ~ \ 2. 3. RECIPIENT'S ACCESSION NO'
4. TITLE AND SUBTITLE
PRCCEEDINGS OF THE WORKSHOP ON AL'IERNATIVES FOR 5. REPORT DATE
CADMIUM ElECTROPIATING IN METAL FINISHINGS' _~~O>Y''''h 1 070
October 4-6, 1977 ' 6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
8. PERFORMING ORGANIZATION REPORT NO.
Dage, E., Dyckman, E., Isler, W. and Ogburn, F.
( pch tors)
9. PERFORMING ORGANIZATION NAME AND ADDRESS 10. PROGRAM ELEMENT NO.
Office of Toxic Substances (TS-792)
Environrrental Protection Agency 11. CONTRACT/GRANT NO.
Washington, D.C. 20460
12. SPONSORING AGENCY NAME AND ADDRESS 13. TYPE OF REPORT AND PERIOD COVERED
Environrrental Protection Agency; Consumer Product ' p Procepn i nrrc:
Safety Commission; Dept. of Commerce; Dept. of Defense; 14. SPONSORING AGENCY CODE
Dept. of Health, Education and Welfare; Dept. of the
Interior; Dept. of Labor; General Services Administrati pn
15. SUPPLEMENTARY NOTES
16. ABSTRACT
This publication compiles the proceedings of the Workshop on Al temati ves for
Cadmium Electroplating in Metal Finishing held October 4-6, 1977 which was jointly
sponsored by seven Federal agencies. The workshop was prompted by the concerns
of governrrent agencies for the potential environmental damage resulting from
current cadmium eletroplating pratices and the high rate of goverrurent use of
electrodeposited cadmium. The v.orkshop examined techniques and al temati ves to
minimize the environrrental losses of cadmium from electroplating by (a) applying
cadmium by rrechanisrns that reduce the loss of cadmium during plating and
(b) developing suitable and cost-effective alternative materials, methods, and
coatings. The workshop included presentations on the Federal and industrial
concerns for the commercial significance, environmental effects, and health
effects of cadmium. Panel discussions reviEWed the topics "Are specifications
and standards barriers to change" and "HON essential is electrodeposited
cadmium?".
These proceedings were compiled from statements submitted by the participants for
publication and from edited transcripts of discussion periods.
17. KEY WORDS AND DOCUMENT ANAL YSIS
a. DESCRIPTORS lb. IDENTIFIERS/OPEN ENDED TERMS C. COSA TI held/Group
n-etal finishing water pollution
electroplating waste treatment
cadmium corrosion
zinc manganese
tin phosphate
aluminum fasteners
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