vxEPA
United States
Environmental Protection
Agency
Office of Research and
Development
Washington DC 20460
Guide to
Cleaner
Technologies
Alternative
Metal Finishes
EPW625/R-94/007
September 1994
-------
-------
EPA/625/R-94/007
September 1994
GUIDE TO CLEANER TECHNOLOGIES
ALTERNATIVE METAL FINISHES
Office of Research and Development
United States Environmental Protection Agency
Cincinnati, OH 45268
-------
NOTICE
This guide has been subjected to the U.S. Environmental Protection Agency's peer and administrative review and
approved for publication. Approval does itiot signify that the contents necessarily reflect the views and policies
of the U.S. Environmental Protection Agency, nor does mention of trade names or commercial products constitute
endorsement or recommendation for use. This document is intended as advisory guidance only to metal finishers
in developing approaches for pollution prevention. Compliance with environmental and occupational safety and
health laws is the responsibility of each individual business and is not the focus of this document.
Users are encouraged to duplicate portions of this publication as needed to implement a waste minimization plan.
-------
ACKNOWLEDGMENTS
This guide was prepared under the direction and coordination of Douglas Williams of the U.S. Environmental
Protection Agency's (EPA's) Center for Environmental Research Information (CERI) and Paul Randall of the
EPA Risk Reduction Engineering Laboratory (RREL), both located in Cincinnati, Ohio. Eastern Research
Group, Inc. (ERG) of Lexington, Massachusetts, and Battelle of Columbus, Ohio, under contract to CERI,
compiled and prepared the information used in this guide.
The following individuals participated in the development and review of this document. Their assistance is
kindly appreciated.
Frank Altmayer
Scientific Control Laboratories, me.
3158 S.Kolin Avenue
Chicago, IL 60623-4889
JackW. Dini
Lawrence Livermore National Laboratory
University of California
P.O. Box 808 L-332
Livermore, CA 94557
Theresa Marten
Risk Reduction Engineering Laboratory
U. S. Environmental Protection Agency
Cincinnati, OH 45268
William Sontag
National Association of Metal Finishers
1101 Connecticut Avenue NW, Suite 700
Washington, DC 20036
-------
-------
CONTENTS
age
Section One Introduction { 1
Section Two Pollutants of Concern in the Metal Finishing Industry 9
Section Three Available Technologies . i 15
Non-Cyanide Copper Plating i 15
Non-Cyanide Metal Stripping 19
Zinc-Alloy Electroplating i 22
Blackhole Technology : 28
Ion Vapor Deposition of Aluminum (TVD) 34
Physical Vapor Deposition (PVD) : 39
Chromium-Free Surface Treatments for Aluminum and Zinc I :. .42
Metal Spray Coating 44
Section Four Emerging Technologies '. 47
Nickel-Tungsten-Silicon Carbide Plating ].. 47
Nickel-Tungsten-Boron Alloy Plating ; 49
In-Mold Plating ', 51
Section Five Pollution Prevention Strategies I 53
Section Six
Information Sources ; 57
-------
-------
Section One
SECTION ONE
INTRODUCTION
What is a Cleaner
Technology?
Why Finish Metals?
A cleaner technology is a source reduction or recycle method applied to
eliminate or significantly reduce the amount of any hazardous substance,
pollutant, or contaminant released to the environment. The emphasis of
cleaner technologies is on process changes that can prevent pollution.
Pollution prevention occurs through source reduction, i.e., reductions in the
volume of wastes generated, and source control (input material changes,
technology changes, or improved operating practices).
Cleaner technologies include process changes that reduce the toxicity or
environmental impact of wastes or emissions. Processes that reduce waste
toxicity by transferring pollutants from one environmental media to another
(e.g., from wastewater to sludge or from air emissions to scrubber wastes) are
not inherently cleaner and are not considered to be source reduction.
Cleaner technologies also include recycle methods, but recycling should be
considered only after source reduction alternatives have been evaluated and
implemented where technically feasible. Where they are used, recycling
techniques should take occur in an environmentally ^afe manner.
!
Without metal finishing, products made from metals would last only a fraction
of their present life-span. Metal finishing alters the surface of metal products
to enhance properties such as corrosion resistance, wear resistance, electrical
conductivity, electrical resistance, reflectivity, appearance, torque tolerance,
solderability, tarnish resistance, chemical resistance, ability to bond to rubber
(vulcanizing), and a number of other special properties (electropolishing
sterilizes stainless steel, for example). Industries that use metal finishing in
their manufacturing processes include:
*• Automotive
> Telecommunications
»• Heavy Equipment
>• Electronics
»• Hardware
*• Appliances
»• Aerospace
> Jewelry
> Tires
A wide variety of materials, processes, and products are used to clean, etch,
and plate metallic and non-metallic surfaces. Typically, metal parts or
workpieces undergo one or more physical, chemical, and electrochemical
processes. Physical processes include buffing, grinding, polishing, and
blasting. Chemical processes include degreasing, clpaning, pickling, etching,
polishing,'and electroless plating. Electrochemical 'processes include plating,
electropolishing, and anodizing.
Pagel
-------
Section One
Pollution Problem
Regulatory
Environment
All metal finishing processes tend to create pollution problems and to' generate
wastes to varying degrees. Of particular jmportance are those'processes that
use highly toxic or carcinogenic ingredients that are difficult to destroy or
stabilize and dispose of in an environmentally sound manner.- Some of these
processes are: .!v , '•.';>.••• " *
'.-.'•;• - , .- - i" "5-'
> Cadmium plating. •.<>;•-•
';- - - -... •••'••' -4t ,-• •
> Cyanide-based plating, especially zinc, copper, brass, bronze and
silver plating.
•. - * Chromium plating and conversion coatings based on hexavalent
chromium compounds. •
. i ' -- .- • '- ; *
*•• Lead and lead-tin plating.
*• Numerous other processes.
"•> \
This guide presents information on process alternatives that can reduce or
eliminate the generation of some of these wastes and emissions from metal
finishing operations.
The : metal finishing industry is heavily regulated .unders> numerous
environmental statutes, including th&.Clean Water Act (CWA), Resource
Conservation and Recovery Act (RCRA), Clean Air Act Amendments
(CAAA), and additional state and local authorities. Emissions of cadmium,
chromium, and cyanides are targeted for voluntary reduction under the U.S.
EPA's 33/50 program, and emissions reporting for all three is required under
the EPA's Toxic Release Inventory (TRI).- These programs provide additional
incentives to metal finishing facilities to reduce their waste generation and
emissions.
In addition to RCRA requirements for a waste minimization program for all
hazardous wastes, the Pollution Prevention Act of 1990 establishes a hierarchy
that is to be used for addressing pollution problems. The Act emphasizes
prevention of pollution at the source as the preferred alternative, with recycling
and treatment and disposal identified as less desirable options. Many states
have embraced the pollution prevention .approach and now require certain
categories of industrial facilities to'prepare and submit pollution prevention
plans detailing their efforts to reduce waste and prevent pollution.
As further regulations are passed or .existing standards ,are revised the
allowable concentrations of pollutants in emissions from metal finishing
operations may continue to decrease, creating ongoing economic and
compliance concerns for metal finishing industry. '
Page 2
-------
Section One
Follow-Up
Investigation
Procedures
Who Should Use this
Guide?
What's in this Guide?
This guide covers several cleaner alternative metal f inishing systems that are
applicable under different sets of product and operating conditions. If one or
more of these are sufficiently attractive for your operations, the next step
would be to contact vendors or users of the technology to obtain detailed
engineering data that will facilitate an in-depth evaluation of its potential for
your facility. Section Five of this guide provides an extensive list of trade and
technical associations that may be contacted for further information
concerning one or more of these technologies, including vendor
recommendations.
This guide should be valuable to metal finishing firms that apply all types of
metal finishes to both metallic and non-metallic parts and components. Firms
that apply cadmium and chromium finishes, as well as finishers that use
cyanide-based baths or copper/formaldehyde solutions, will find information
on alternative "cleaner" technology systems particularly useful.
The information contained in the guide can enable plant process and system
design engineers to evaluate cleaner technology options for existing plants and
proposed new metal finishing operations.
This guide describes cleaner technologies that can be used to reduce waste and
emissions from metal finishing operations. The objectives of the guide are:
*• To identify potentially viable clean technologies that can reduce waste
and emissions by modifying the metal finishing process.
> To provide resources for obtaining more detailed engineering and
economic information about these technologies.
The following are the main pollution prevention issues discussed in the guide.
In evaluating potential alternative processes and technologies, the reader is
advised to explore these questions as thoroughly as possible:
> What alternate metal finishing processes are available or emerging
that could significantly reduce or eliminate the pollution and/or health
hazards associated with processes currently in use?
»: What advantages would the alternate processes offer over those
currently used? ;
Page 3
-------
Section One
What difficulties would arise and need to be overcome or controlled
if the alternate processes were used, including:
• Would new or different
pollution and health problems
arise as a result of adopting it?
• Would the product quality be
different from present?
• Would the process require
significantly different procedures
for handling rejects?
• Would production personnel
need to develop significantly
different skills?
• Would there be a need for
significant capital investment?
• Would the process require
significantly different process
controls?
• Would the consumer accept the
substitute?
• Would production rates be
affected?
• Would production costs be
increased?
Organization of this
Guide
This guide has been designed to provide sufficient information to users to help
in selecting one or more candidate cleaner technologies for further analysis and
in-plant testing. The guide does not recommend any single technology over
any other, since site-specific and application-specific factors often can affect
the relative attractiveness of alternatives. ;
The gui.de presents concise summaries of applications, and operating
information that can be used to support preliminary selection of clean
technologies for testing in specific production settings. It is hoped that
sufficient detail is provided to allow identification of possible technologies for
immediate consideration in programs to eliminate or reduce waste production
ortoxicilty.
This guide is organized into five sections. Section One is an introduction to
metal finishing and pollution prevention issues for the metal finishing industry.
It identifies the principal metal finishing processes th^t give rise to
environmental concerns. Section Two describes the environmental issues in
further detail and serves as background to the discussions of cleaner
technology alternatives addressed in Sections Three and Four. Section Three
provides in-depth profiles of alternative cleaner technologies that partially or
completely alleviate one or more of the environmental concerns discussed in
Section Two. The technologies addressed in Section Three are considered to
be "available", i.e., well-established and in use in a variety of metal finishing
settings. Technologies discussed in Section Four, on the other hand, are more
"emerging" in nature. They include techniques that, while not yet widespread
Page 4
-------
Section One
in use, are receiving increased attention for their pollution prevention potential.
Section Five is a strategy section that provides an overview of the role of
individual cleaner technologies in addressing specific environmental concerns
of metal finishing facilities.
In reviewing the available and emerging technologies the reader should be
aware that the need to reduce wastes and emissions has led to a considerable
research effort into the development of cleaner teclinologies for metal
finishing. Process alternatives developed from this research are in a constant
state of refinement and evaluation. New developments in this area can be
monitored in leading industry publications such as Metal Finishing, Products
Finishing, and Plating and Surface Finishing. The trade associations listed
in Section Six of this document are also an important source of additional
information.
Keyword List
The table on the next page presents keywords that enable the reader to scan the
list of technologies and identify those that are generally available and those
that are less widely used. Some but not all of the emerging technologies may
still be in development or pilot stages.
The distinction between "available" and "emerging" technologies made in this
guide is based upon the relative state of development of each group of
technologies. It is not intended to reflect judgement:? concerning the ultimate
potential for any one technology over any other. \
PageS
-------
Section One
Table 1. Keyword list - cleaner technologies for metal finishing.
General
Keywords
Available
Technologies
Technologies Under
Development
Cleaner technology
Pollution prevention
Source reduction
Source control
Recycling
Non-cyanide copper plating
Non-cyanide metal stripping
Non-cyanide zinc plating
Zinc/zinc-alloy plating
Blackhole Technology
Ion vapor deposition (IVD)
Physical vapor deposition (PVD)
Chromium-free substitutes for selected
immersion processes
Metal spray coating
Trivalent chromium plating
for decorative applications
Nickel-tungsten-silicon
carbide substitute for
chromium
Nickel-tungsten-boron
substitute for chromium
In-mold plating
Summary of Benefits
The cleaner technologies described in this guide are categorized as either
"available" or "emerging", depending on their level of development and extent
of adoption of each technology within the industry. Available technologies
include more commercially available processes that have been adopted by
numerous metal finishers and are perhaps being used for more than one
application. Emerging technologies are typically in a less developed state and
may be currently in the advanced pilot plant stages.
Table 2 summarizes the pollution prevention, operational? and economic
benefits of these metal finishing process alternatives. The reader may wish, to
scan this summary table to identify the cleaner technology options that best fit
the operations and needs of his or her company. Detailed discussions of the
benefits and operational aspects for each cleaner technology are provided in
Sections Three and Four.
Page 6
-------
Section One
c3
i
c
•a
i
•a
o
1
I
I
a
c
|
en
^
3
j.1
•| o 1
ill'
w
J5*« S1
E> Q H
M
£ i
SH
H"O w'S.
•8 .s
•S te eo
a ,a
M
Polluti
Prevent
W o
.2
Page 7
-------
-------
Section Two
SECTION TWO
POLLUTANTS OF CONCERN IN
THE METAL FINISHING INDUSTRY
Introduction
Hazardous Materials
and Processes
This section describes the major pollutants of concern in the metal finishing
industry and the unit processes and operations that give rise to wastes and
pollutants addressed by this cleaner technology guide.
The metals finishing industry is concerned with pollution and wastes
generated by all processes but especially those generated by the use of four
specific materials in finishing processes: (1) the use of cadmium as a plating
material, (2) the use of chromium as a plating material, (3) the use of
cyanide-based electroplating solutions, and (4) the use of
copper/formaldehyde-based electroless copper solutions. This section
discusses the use, benefits, and hazards of each of 'these materials hi further
detail. The information presented provides background to the detailed
profiles on individual pollution prevention technologies that are presented
in Sections Three and Four. Most of these technologies address concerns
related to cadmium and chromium plating and the use of
copper/formaldehyde and cyanide-based plating solutions.
Cadmium
Cadmium is a common plating material that has properties superior to other
metal coatings in some applications. Besides its excellent corrosion
resistance, cadmium is valued for its natural lubricity. It is commonly used
for plating fasteners to ensure that the fasteners pass torque-tolerance tests.
These tests simulate the action of a power wrench tightening a nut on a bolt.
The nut should tighten quickly under properly applied torque and hold
securely thereafter. Cadmium is a soft metal with natural lubricity; these
properties give cadmium good torque tolerance and bendability. Cadmium
also exhibits good corrosion resistance, and meets the salt-spray test
requirements of the automotive industry. It is a readily solderable metal and
is toxic to fungus and mold growth. In the past;, numerous military
specifications have specified the use of cadmium,
The major cadmium complex used in electroplating baths is cadmium
cyanide, or Cd(CN)f. Other plating electrolytes include cadmium sulfate,
sulfamate, chloride, fluoroborate, and pyrophosphate. Cadmium fluobOrates
are used with fluoroboric acid for electrodeposition of cadmium on high-
strength steels. Cadmium oxide is dissolved in excess sodium cyanide to
form the cadmium complex used in the bath most commonly used to plate
cadmium.
Page 9
-------
Section Two
Cyanide solutions
Sodium and potassium cyanide are used in electroplating bath formulations
for the deposition of copper, zinc, cadmium, silver, gold, and alloys such as
brass, bronze, and alballoy (copper-tin-zinc). Electroplating baths may also
utilize cyanide compounds of the metal being plated, such as copper
cyanide, potassium gold cyanide, or silver cyanide. As the plating solution
is consumed, complex cyanides are formed from the reaction 'between metals
dissolved at the anode from dropped parts and the sodium or potassium
cyanide-(called "free" cyanide). In a well-designed wastewater treatment
system, most cyanides can be destroyed (oxidized) to concentrations that
comply with the CWA. Some of the complexed cyanides formed during
plating, however, are resistant to conventional oxidation methods and
become part of the solid waste stream (EPA Hazardous Waste Number F-
006) generated by the system. Cyanides used in stripping solutions,
especially those for stripping nickel, are similarly resistant to oxidation and
typically must be disposed of in bulk at a high cost
Copper/formaldehyde solutions
Electroless copper deposits are frequently used to apply a conductive base
to non-conductive substrates such as plastics. A thin copper deposit
provides abase for an additional decorative or functional coating of copper,
nickel, etc. One important application is in the coating of printed circuit
boards. :
Formaldehyde, a suspected carcinogen and water pollutant, is used as the
reducing agent in electroless copper baths. Caustic mists resulting from
hydrogen evolution and air sparging in the baths present an additional
hazard.
Chromium
Chromium plating falls into two basic categories depending on the service
feature desired. When the goal is mainly a pleasing appearance and
maintenance of appearance over time, the plating is considered "decorative".
Decorative chromium plating is almost always applied over a bright nickel
plated deposit, which in turn can be easily deposited on steel, aluminum,
plastic, copper alloys, and zinc die castings. When chromium is applied for
almost any other purpose, or when appearance is an incidental or lesser
important feature, the deposit is commonly referred to as "hard chromium
plating," or more appropriately, "functional chromium plating." Functional
chromium plating is normally not applied over bright nickel plating,
although In some cases, nickel or other deposits are applied first to enhance
corrosion resistance.
Page 10
-------
Section Two
Functional chromium plating tends to be relatively thick, ranging from 0.1
mils to more than 10 mils. Common applications of functional chromium
include hydraulic cylinders and rods, crankshafts, printing plates/rolls,
pistons for internal combustion engines, molds for plastic and fiberglass part
manufacture, and cutting tools. Functional chromium is commonly
specified for rebuilding worn parts such as rolls, molding dies, cylinder
liners, and crankshafts.
Decorative chromium plating is most often less than 0.05 mils in thickness,
and typically ranges from 0.005 mils to 0.01 mils;. Decorative chromium
plating can be found on numerous consumer items, including appliances,
jewelry, plastic knobs, hardware, hand tools, and automotive trim.
Hexavalent chromium—Traditionally, chromium deposits are produced
from an electrolyte containing hexavalent chromium ions. These deposits
have a pleasing bluish-white appearance. Chemical compounds containing
hexavalent chromium are used in several metal finishing operations,
including plating, conversion coating, sealing of anodic coating, and
enhanced adhesion of paint films on phosphated steel. Chromium plate is
applied to a variety of substrates for abrasion resistance (hardness) and its
resistance to household chemicals, as well as its ability to "hold" lubricants
such as oils on the surface and the pleasing appearance (when plated over
a bright nickel).
The main ingredient in all hexavalent chromium plating solutions is
chromium trioxide (Cr03), a compound that contains approximately 25
percent hexavalent chromium. Other ingredients, typically present only at
very low concentrations, are considered to be either catalysts or impurities.
Hexavalent chromium has been linked to cancer in humans following
prolonged inhalation, and is toxic to aquatic life at relatively low
concentrations. Hexavalent chromium in rinsewater can be treated to very
low concentrations using reducing agents such as bisulfites and sulfur
dioxide.
Plating solutions based on hexavalent chromium are very low in current
efficiency. As a result, much of the current (as much as 90 percent) goes
towards decomposing water into oxygen and hydrogen gas. As the
hydrogen and oxygen break the surface of the bath, they carry with them the
bath constituents, including chromic acid, as a fine mist spray. The mist is
exhausted through a ventilation system on the plating tank and captured hi
either a scrubber or mesh pad system. Hexavalent chromium emissions
from decorative and functional chromium plating operations soon will be
regulated under provisions of the Clean Air Act. These emissions are
presently regulated on the local level throughout the U.S.
Page 11
-------
Section Two
Hexavalent chromium plating solutions typically use lead anodes which
decompose over time, forming lead chromates that must;be treated and
disposed of as hazardous wastes. These solutions also are frequently treated
with barium compounds to control the sulfate concentration, which creates
a barium sulfate that is typically soaked with chromium plating solution, and
which must be disposed of as a hazardous waste. !
Fugitive air emissions, water emissions from poorly treated rinsewater, and
solid waste generated from hexavalent chromium plating processes can have
a detrimental impact on the environment. This impact can be eliminated or
reduced if a cleaner technology is used.
It is particularly difficult to substitute alternate materials for chromium
because of chromium's hardness, bright appearance, resistance to commonly
encountered corrosive environments, ease of application, and low cost.
Hexavalent chromium chemicals, such as chromic acid, are frequently used
in metal plating applications to provide chromium coatings exhibiting
hardness and aesthetic appeal. Chromium plating is used to provide a
working surface for a part. It is also the standard method for improving
hardness and smoothness for a wide variety of substrates, as well as the
resistance to wear, abrasion, galling, or high temperatures. Typical
applications are cylinder liners and pistons for internal, combustion engines,
and cylinders and rams for hydraulic pistons (Guffie, 1986). Chromium
plating will continue to be needed for specific applications, but alternatives
are available for many traditional uses. Because of environmental concerns,
design engineers will be required to explore alternative technologies and be
more selective in specifying chromium plating in the future.
Trivalenit chromium—Decorative chromium plating is produced using
aqueous solutions that contain either hexavalent or trivalent chromium
compounds. The trivalent chromium process has been available for 20 years
and is considered less toxic and more environmentally friendly because of
the lower toxicity of trivalent chromium and the lower content of chromium
in the plating solution. Over the last few years, several competitive plating
processes based on trivalent chromium have been developed. Some of these
processes yield a deposit that more closely resembles the plating produced
by a hexavalent solution, albeit at a slightly higher cost and requiring more
careful control of plating conditions. Functional chromium plating
presently is available commercially only from the hexavalent formulation,
although recent efforts to optimize trivalent chromium formulations and
bath operation for hard plating show promise (Kudryavtsev and
Schachameyer, 1994).
Waste Generation and
Waste Handling
Page 12
The major pollutants of concern in the metal finishing industry are spent
solutions containing heavy metals and other toxic and noxibus chemicals.
Metal finishing operations typically treat these solutions in wastewater
-------
Section Two
pretreatment systems designed to meet CWA requirements. These systems
in turn generate solid and liquid wastes that are regulated under the
provisions of RCRA. The air emissions from many metal finishing
processes must be controlled using scrubbing equipment. These can
generate further wastes that must also be treated, disposed, or recycled.
Some of the processing solutions used in metal finishing have a finite life,
especially conversion coating solutions, acid dips, cleaners and electroless
plating baths. These processes yield additional concentrated wastes that
must be treated and disposed of.
Physical processes such as abrasive blasting, grinding, buffing, and
polishing do not contribute as much to hazardous waste generation as
chemical and electrochemical processes. The chemical and electrochemical
processes are typically performed in chemical baths that are followed by
rinsing operations. The most common hazardous WEiste sources are rinse
water effluent and spent process baths.
It is important to recognize that wastes are created as a result of the
production activities of the metal finishing facility, not the operation of
wastewater pretreatment and air scrubbing systems. If the finishing
processes were inherently "cleaner," significant progress could be made
toward reducing environmental impacts.
Page 13
-------
-------
Section Three
SECTION THREE
AVAILABLE TECHNOLOGIES
Introduction
This chapter describes cleaner technologies commercially available for the
metal finishing industry that can reduce the finisher's reliance on one or
more materials of environmental concern (e.g., cadmium, chromium,
cyanide, copper/formaldehyde).
NON-CYANIDE COPPER PLATING
Pollution Prevention
Benefits
How Does it Work?
Why Choose this
Technology?
Alkaline non-cyanide copper plating solutions eliminate cyanide from rinse
water and sludges generated during waste treatment of the rinsewater. Non-
cyanide baths contain one-half to one-quarter as much copper as full
strength cyanide processes, resulting in lower sludge volume generation
rates. The sludges from waste treatment of cyanide bearing rinsewater (EPA
Hazardous Waste Number F-006) can be particularly difficult to dispose of
because of residual cyanide content, which is regulated by RCRA to a
maximum of 590 mg/kg of total cyanide and 30 mg/kg of cyanide amenable
to chlorination. By eliminating cyanide from the rinsewater, compliance
with cyanide regulations in wastewater discharges is ensured (in the absence
of other cyanide bearing processes). Rinsewater from alkaline non-cyanide
copper plating only requires pH adjustment to precipitate copper as the
hydroxide. This eliminates the need for a two-stage chlorination system
from the waste treatment system and avoids the. use of chemicals such as
chlorine and sodium hypochlorite. :
Non-cyanide copper plating is an electrolytic process similar to its
cyanide-based counterpart. Operating conditions and procedures are similar,
and existing equipment usually will suffice when converting from a
cyanide-based process to a non-cyanide process. Alkaline non-cyanide
processes operate in a pH range of 8.8 to 9.8 compared to a pH of 13 to 14
for the cyanide processes. At least one proprietary process requires the
addition of a purification/oxidation cell to the plating tank.
Applications
Non-cyanide copper plating baths are commercially available for coating
steel, brass, lead-tin alloy, zinc die cast metal, and zincated aluminum; The
process can be used for rack or barrel plating. Other applications include
fasteners, marine hardware, plumbing hardware, textile machinery,
automotive and aerospace parts, masking applications, electro-magnetic
interference (EMI) shielding, and heat treatment stop-off. Non-cyanide
copper plating can be applied as a strike (thin deposit), or as a heavy plate.
Page 15
-------
Section Three
Operating Features
Non-cyanide copper plating has the following characteristics:
•• Bath temperatures typically are elevated (110°F to 140°F).
The pH is in the range of 8.8 to 9.8. Throwing power is as
good as that of cyanide-based processes.
»• Deposits have a matte appearance with a dense,
fine-grained amorphous microstructure. Semi-bright to
bright appearances can be obtained with the use of
additives,.
'• Copper ions are present in the Cu-H- state as compared to
Cu+ for cyanide-based baths, providing a faster plating
speed at the same current density.
»• Changing over to a non-cyanide process requires a lined
tank and a purification compartment outside of the plating
tank (for at least one commercial process). Good filtration
and carbon treatment are also mandatory.
Assuming 100 percent cathode efficiency, a non-cyanide bath requires twice
as much current to plate a given weight of copper as a cyanide copper bath.
The non-cyanide process, however, can operate at higher current densities,
yielding plating speeds that are equivalent to or faster (in barrel plating) than
the cyanide process.
Required Skill Level
Non-cyanide copper plating requires more frequent bath analysis and
adjustment than does cyanide-based plating. Cyanide-based copper plating
baths are relatively forgiving to bath composition. Operating personnel
should be capable of operating the non-cyanide process as easily as the
cyanide-based process. ;
Cost :
Operating costs for the bath itself are substantially higher for the
non-cyanide process than the cyanide process. Because replacing the
cyanide-based bath with a non-cyanide bath eliminates the need for
treatment of cyanide-containing solutions, however, the cost differential
between the two processes is greatly reduced. Unless a facility faces
substantial compliance costs for cyanide emissions, the higher operating
costs of the non-cyanide process may not justify conversion on a cost
comparison basis alone.
Page 16
-------
Section Three
Reported Applications
The use of non-cyanide copper plating baths is not widespread in industry.
One industry consultant reports that the number of companies running non-
cyanide plating trials is small but growing (Altmayer, 1994). Of the
companies that have tried the process several have switched back due to the
higher costs of the non-cyanide alternative.
One application for non-cyanide plating that could be attractive from a cost
perspective alone is selective carburizing. This process is used widely in the
heavy equipment industry for hardening portions: of coated parts such as
gear teeth. Gears must be hard at the edges b\it not throughout, since
hardness throughout could cause the part to become brittle. To achieve this
selective hardening, a copper mask is applied to that portion of the part
which is not targeted for hardening, and the part is then treated with carbon
monoxide and other gases. In addition to eliminating the use of cyanide,
non-cyanide copper baths can improve production efficiency of this masking
process and produce a more dense carbon deposit,
Availability
Non-cyanide processes are commercially available from several sources.
These sources typically advertise in the following trade journals:
Metal Finishing
Plating and Surface Finishing
Products Finishing
Industrial Finishing
Operational and
Product Benefits
Non-cyanide copper plating has the following benefits:
»• Greatly reduces safety risks to workers.
*• Greatly reduces the costs and complexity of treating spent
plating solutions.
*• Drag-out to an acidic bath poses no risk of HCN evolution.
*• Plating solution does not have to be treated for carbonates.
Replacement of cyanide-based plating baths greatly reduces safety risks to
workers. Cyanide is extremely toxic and electropllaters are most at risk for
exposure to hydrogen cyanide (HCN) through ingestion and inhalation. Skin
contact with dissolved cyanide salts is somewhat less dangerous but will
cause skin irritation and rashes. The most likely scenario for exposure to
lethal doses of HCN is an accident involving the addition of an acid to a
cyanide-containing electroplating bath or the mixing of cyanide wastes with
acid-containing waste streams.
Page 17
-------
Section Three
Hazards and
Limitations
Summary of
Unknowns/State of
Development
REFERENCES
Cyanide-based baths remove impurities so that coatings are not
compromised. Non-cyanide baths are less tolerant of poor surface cleaning,
so thorough cleaning and activation of the surface to be coated is critical.
With one exception, alkaline non-cyanide processes are unable to deposit
adherent copper on zinc die castings and zincated aluminum parts. The
exception is a supplier that claims to be able to plate such parts using a
proprietary process. Several facilities are currently testing this process on
a pilot scale (Altmayer, 1994). Two facilities using the process reported mat
the application costs approximately two to three times as.much as other
processes, even when waste treatment and disposal costs are included. One
of the facilities discontinued use of the process, while the other facility
believed that the added safety and compliance insurance was worth the cost
and has continued with the process.
Non-cyanide copper plating baths typically are developed by, manufacturers
of bath solutions. Chemical compositions and their formulae are proprietary
information and are outside the public domain. As a result, very little has
been published on development activities. According to one manufacturer,
product improvement will continue for some time, although no major
developments are expected.
Altmayer, F. 1994. Personal communication between Frank Altmayer,
Scientific Laboratories, Inc. and Jeff Cantin, Eastern Research Group, Inc.
April, 1994.
Altmayer, F. 1993. Comparing substitutes for Cr and Cu, to prevent
pollution, Plating and Surface Finishing. February, pp. 40-43.
Barnes, C. 1981. Non-cyanide copper plating solution based on a cuprous
salt Annual Technical Conference - Institute of Metal Finishing. Harrogate,
England (May 5-9). London: Institute of Metal Finishing.
Humphreys, P.O. 1989. New line plates non-cyanide cadmium. Products
Finishing. May. pp. 80-90.
Janikowski, S.K. et al. 1989. Noncyanide stripper placement program. Air
Force Engineering & Services Center. ESL-TR-89-07. May.
Kline, G.A. 1990. Cyanide-free copper plating process. U.S. Patent
4,933,051. June 12,1990.
Kline, G.A. and J.M. Szotek. 1990. Alkaline non-cyanide copper plating.
Asia Pacific Interftnish '90: Growth Opportunities in the 1990s. Singapore
(November 19-22). Victoria, Australia: Australasian Institute of Metal
Finishing.
Page 18
-------
Section Three
Krishnan, R.M. 1990. A noncyanide copper plating electrolyte for direct
plating on mild steel. Bulletin of Electrochemistry. 6(11). November, pp.
870-872. '' ! '
NON-CYANIDE METAL STRIPPING
Pollution Prevention
Benefits
How Does it Work?
Why Choose this
Technology?
The use of cyanide-based metal strippers results in the generation of
cyanide-contaminated solutions. These solutions require special treatment
and disposal procedures. The use of a non-cyanide: stripper eliminates cya-
nide from the spent stripper solution. In general, these non-cyanide strippers
are less toxic than their cyanide-based counterparts and more susceptible to
biological and chemical degradation, resulting in simpler and less expensive
treatment and disposal of spent solutions.
In addition, the use of a non-cyanide stripper can simplify the removal of
metals from spent solutions. These metals are difficult to remove from
cyanide-based solutions because they form a strong complex with the
cyanide ligand.
Metal strippers are used to remove metallic coatings previously deposited
on parts. Metal stripping is a common practice that, might be required when
defective coatings have been applied, or when reconditioning of parts and
reapplication of worn coatings is required. Another common use of metal
strippers is rack plating where it is employed to remove coatings that build
up on part holders. Cyanide-based stripping solutions act by assisting in the
oxidation of the coating metal. The oxidized metal complexes with the
cyanide ligand and is subsequently solubilized.
Because non-cyanide stripping solutions are typically proprietary
formulations, the detailed chemistry of coating removal is not known for
most solutions. Stripping solutions are available for a wide variety of
coating metal/base metal combinations. Some of the stripping processes are
electrolytic; others are not. Processing temperatures, bath life, ease of
disposal, and other operating characteristics vary widely.
Applications
Metal strippers can be purchased for a wide variety of coating and substrate
metals. The U.S. Air Force has performed testing on a number of
non-cyanide strippers, particularly nickel and silver non-cyanide strippers.
Several of these strippers have been adopted at Kelly Air Force Base.
Applications are not limited to aerospace, however, and industries such as
railroads (locomotive crankshafts), automotive pacts, and silverware all use
stripping agents prior to refinishing. In addition, sitripping is a normal step
Page 19
-------
Section Three
iaany production line using rack plating, as racking equipment will become
encrusted with plate material and must be removed on a regular basis.
Operating Features
The wide variety of non-cyanide strippers makes it difficult to generalize
about operating parameters. Some strippers are designed to operate at
ambient bath temperatures, Whereas others are recommended for
temperatures as high as 180°F. Stripping processes range! from acidic to
basic. In general, the same equipment used for cyanide-based stripping can
be used for non-cyanide stripping. With acidic solutions, however, tank
• liners might be needed to prevent corrosion.
Required Skill Level J
Personnel trained in the use of cyanide-based strippers should also be able
to use non-cyanide strippers. For example,, the U.S. Air Force reported that
higher skill levels were not required for the non-cyanide metal strippers
implemented at Kelly Air Force Base.
Cost
i
Non-cyanide strippers will have some impact on costsr
*•• Waste treatment costs will be reduced when switching to
non-cyanide strippers. If cyanide-based solutions are not
used elsewhere in the facility, the cyanide treatment system
can be eliminated.
> A large capital outlay is not required when switching to a
non-cyanide stripper because the equipment requirements
are generally the same.
>• The costs; of the makeup solutions will increase slightly.
Reported Applications
Non-cyanide strippers have been available for many years. Major
drawbacks of this new technology include lack of speed, etching of some
substrates, and the need for electric current. As the disposal costs of
cyanide-based strippers continue to escalate, however, many companies
have switched to non-cyanide stripping methods. Production cycles have
been adjusted to account for the slower stripping speed.
Page 20
-------
Section Three
Availability
i -
A partial list of companies that supply non-cyanide strippers is found below.
This list does not constitute a recommendation.
Circuit Chemistry Corp.
Electrochemical, Inc.
Frederick Gumm Chemical
Company
Kiesow International
MacDermid Inc.
Metalline Chemical Corp.
Metalx Inc.;
OMI International
Patclin Chemical Company
Witco Corporation
Operational and
Product Benefits
Cyanide based strippers typically contain chelating agents and strong metal-
cyanide complexes that make waste treatment of spent strippers and
rinsewater extremely difficult. The use of non-cyanide based strippers
improves waste treatment, making it easier and mipre efficient.
At least one proprietary non-cyanide stripping process can crystallize
stripped nickel coatings. Crystallization extends the life of the stripping
solution indefinitely and creates a product that is readily recycled by
commercial firms. ,
Non-cyanide metal strippers have the following benefits:
> Significant potential for reducing waste treatment costs.
*• Often easier to recover metals from spent solutions.
>• Bath life is longer because higher metal concentrations can
be tolerated.
One of the main incentives for eliminating the use of cyanide-based
stripping processes is to reduce health hazards to personnel. Although
cyanide in solution is itself very toxic, one of the main dangers for
electroplaters.is the accidental addition of acid into the cyanide bath,
resulting in the formation of hydrogen cyanide gas, HCN. Dermal contact
with dissolved cyanide salts is less dangerous than inhaling HCN or
ingesting cyanide, but it nonetheless will still cause skin irritation and
rashes.
Page 21
-------
Section Three
Hazards and
Limitations
Facilities that consider switching to non-cyanide strippers must consider the
health and safety aspects of the substitute, such as higher operating
temperatures, corrosivity, and so on.
Non-cyanide metal strippers have some disadvantages: ;
*• For some strippers, the recommended process temperatures
are high enough to cause safety problems. Operating at
lower temperatures can slow down the stripping reaction
and result in a loss of effectiveness.
» Stripping rates for certain coatings might be lower than for
cyanide-based counterparts.
» Some strippers can produce undesirable effects on substrate
metals, even if the stripper has been recommended by the
manufacturer for the application in question.
Summary of
Unknowns/State of
Development
REFERENCES
The removal of nickel coatings is a major use for non-cyanide strippers.
Advances in non-cyanide alternatives for nickel have been spawned by the
difficulty of treating nickel-cyanide waste streams. Opportunities for further
improvement still remain, however, as non-cyanide ;processes are
significantly slower than cyanide processes (8 hours versus 1 hour). Future
development will focus on speeding up the process and adjusting the
product to handle different metal coatings (e.g., silver) and substrates.
Janikowski, S.K., et al. 1989. Noncyanide Stripper Placement Program. Air
Force Engineering & Services Center. ESL-TR-89-07. May.
ZINC-ALLOY ELECTROPLATING
Pollution Prevention
Benefits
How Does it Work?
Alloys of zinc can be used to replace cadmium coatings in a variety of
applications. Cadmium is a heavy metal that is toxic to humans. In addition,
electroplated cadmium coating processes normally are performed hi plating
solutions containing cyanide. Cyanide is highly toxic to humans and animal
life. The use of both cadmium and cyanide can be, eliminated by
substituting an acid or non-cyanide alkaline zinc-alloy coating process for
a cyanide-based cadmium electroplating process. :
Both zinc and zinc-alloy electroplating processes are very common and have
a long history in the electroplating industry. Recently, however, these
processes have been considered as possible replacements for cadmium
coatings (Zaki, 1993). Viable replacements for cadmium should provide
Page 22
-------
Section Three
equivalent properties, such as corrosion protection and lubricity, at an
affordable cost. The ideal cadmium coating' replacement is also a
non-cyanide-based process, because this also eliminate cyanide waste and
associated treatment costs.
Among the zinc and .zinc-alloy processes evaluated as cadmium
replacements, the most promising are the following:
>• Zinc-nickel
»• Zinc-cobalt
i
Zinc alone can provide corrosion protection equivalent to cadmium at
plating thicknesses above 1 mil. For thinner deposits, however, cadmium
will outperform zinc. Additionally, zinc coatings? cannot match the other
properties for which cadmium is valued, e.g., lubricity. For this reason, zinc
is not considered to have wide potential for replacing cadmium (Brooman,
1993). Similarly, alloys such as zinc-iron may not qualify because they
cannot match cadmium's appearance attributes. Tin-zinc is a potential
substitute for cadmium (Blunden and Killmeyer, 1993) but will probably
remain prohibitively expensive for most applications.
Table 3 compares relevant properties for several zinc alloys. The
identification of zinc-nickel and zinc-cobalt as the alloys with the greatest
potential for as a cadmium substitute is based on their properties and on the
range of applications for which these alloys have already seen commercial
use (see below).
Why Choose this
Technology?
Reported Applications
The ability of any alternative coating to replace cadmium depends on the
properties required by the application in question. Some zinc alloys have
as good and in some cases better resistance to corrosion, as measured in salt
spray tests. Few match cadmium for natural lubricity in applications such
as fasteners, however. In addition, where cadmium is selected for its low
coefficient of friction or for its low electrical contact resistance, none of the
candidates mentioned above may be suitable. Table 3 indicates that
applications requiring heat treatment would eliminate zinc-cobalt alloys as
a substitute. !
Operating Features
Some of the operating features of the zinc-nickel and zinc-cobalt alloys are
listed in Table 4. Both zinc-nickel and zinc-cobalt cant be plated from acid
or alkaline baths. i
Page 23
-------
Section Three
TableS. Comparison of zinc alloy processes.
Deposit properties
Appearance
Solderability
Abrasion resistance
Whisker
Ductility
Corrosion resistance
To white rust
To red rust
To white rust
To red rust
To white rust
To red rust
Bath characteristics
Throwing power
Plating speed
Covering power
Bath control
Analysis &
measurement
X-ray fluorescence
Coulometric
X-ray fluorescence
Wet analysis
Anodes
Alkaline
Zinc
Good
Fair
Fair
Fair
Fair
Fair
Fair
Poor
Poor
Fair
Fair
Good
Fair
Fair
Good
Good
Good
Good
Good
Separate
Alkaline
Zinc-
Nickel
Good
Fair
Good
Good
Fair
Excellent
Excellent
Good
Good
Good
Good
Excellent
Poor
Fair
Fair
Good
Good
Good
Good
Zinc
Bath Type
Neutral Alkaline
Tin-Zinc Zinc-Iron
:
Fair Good
Excellent Fair
.Poor Fair
Fair- Fair
Good
Excellent Fair
As plated
Fair Excellent
Excellent Good
Heat treated
Poor Poor
Fair Poor
After bending
Fair Fair
Excellent Fair
Poor Good ;
Good Fair
Excellent Fair
Fair Fair
Thickness
Good Good
Good Good
Alloy ratio
Good Poor
Good Fair
Alloy Zinc
Acid Zinc-
Cobalt
Excellent
Fair
Fair
Fair
Fair
Fair
Good
Poor
Poor
Fair
Fair
Poor
Good
Fair
Fair
Good
Good
Fair
Fair
Zinc
Source: Budman and Sizelove (1993).
Page 24
-------
SectionThree
Required Skill Level
Switching to a zinc or zinc-nickel coating process does not require any
increase in operator skill level. These are conventional electroplating
processes that require little or no retraining. Increased attention to bath
monitoring and adjustment might be necessary because these processes are
more sensitive to bath contaminants and variations in bath parameters than
cyanide-based baths.
Table 4. Bath parameters for zinc-nickel and zinc-cobalt plating.
Properties
Bath contents
pH
Temp'C
Cathode CD
A/dm2
Anode CD
A/dm2
Anodes
Acid
Zinc-
Nickel
(rack
plating)
Zinc
chloride,
nickel
chloride,
potassium
chloride
5.0-6.0
24-30
. 0.1-4.0
n/a
Zinc and
nickel
separately
Acid
Zinc-
Nickel
(barrel
plating)
Zinc
chloride,
nickel
chloride
5.0-6.0
35-40
0.5-3.0
n/a
Zinc and
nickel
separately
Plating bath
Alkaline
Zinc-
Nickel
Zinc metal,
nickel
metal.
sodium
hydroxide
n/a
23-26
2-10
5-7
Pure zinc
AcidZinc-
: Cobalt
, Zinc metal,
potassium
chloride,
ammonium
chloride,
cobalt (as
metal),
boric acid
5.0-6.0
21-38
0.1-5.0
n/a
Pure zinc
Alkaline
Zinc-Cobalt
Zinc,
caustic
soda, cobalt
metal
n/a
21-32
2.0-4.0
n/a
Steel
Source: Budroan and Sizelove (1993). '
Acid zinc-nickel delivers a higher nickel content than the alkaline bath (10
percent to 14 percent versus 6 percent to 9 percenit). Corrosion protection
increases with nickel content up to about 15 percent, thus favoring the acid
bath. Acid solutions, however, tend to produce deposits with poorer
thickness distribution and greater alloy variation! between high and low
current density areas. Alkaline baths produce a deposit featuring columnar
Page 25
-------
Section Three
structures (which tend not to favor applications that require bendability), as
opposed to the laminar structure deposited by the acid system. Alkaline
baths are simpler to operate and are similar to conventional noncyanide zinc
processes (Budman and Sizelove, 1993).
Zinc-cobalt deposits contain approximately 1 percent cobalt with the
remainder made up of zinc. The acid bath has a high cathode efficiency and
high plating speed, with reduced hydrogen embrittlement compared to
alkaline systems. Thickness distribution of the acid bath varies substantially
with the current density. ,
Cost
Existing electroplating equipment can be used for any of these alternative
processes. Therefore, a large capital expenditures would not be required to
switch to an alternative process. Conversion to an acid bath, however, does
require existing tanks to be relined. With older equipment, new tanks might
possibly have to be installed to provide the necessary corrosion resistance.
The costs associated with cyanide waste treatment can be eliminated for any
process line in which a cyanide-based cadmium process is replaced.
Reported Applications
Acid baths have been used for some time in zinc and zinc alloy plating. The
desire to eliminate cyanide from the plating process has resulted in the
development of non-cyanide alkaline baths and chloride-based baths for zinc
coatings. The use of zinc-nickel alloys has gained ground because of their
potential to replace cadmium, particularly in Japan and other countries
where the use of cadmium coatings has been curtailed or prohibited for
several years. Zinc-nickel alloys have been introduced in Japan and
Germany in the automotive industry for fuel lines and rails, fasteners, air
conditioning components, cooling system pumps, coils and couplings
(Budman and Sizelove, 1993). Improved warranty provisions from vehicle
manufacturers such as Honda, Toyota and Mazda further boosted
applications for zinc alloys. Chrysler followed with new specifications for
zinc-nickel and zinc-cobalt in 1989, and Ford developed specs for alkaline
zinc-nickel to replace cadmium in 1990 (Zaki, 1993). Additional
applications include electrical power transmitting equipment, lock
components, and the maritime, marine, and aerospace industries. Zinc-
nickel coatings have also reportedly been substituted for cadmium on
fasteners for electrical transmission structures and on television coaxial
cable connecters (Brooman, 1993). :
Availability
Zinc alloy plating systems are commercially available from numerous
manufacturers. Suppliers can be identified through articles or
Page 26
-------
Section Three
Operational and
Product Benefits
advertisements appearing in trade journals such as Metal Finishing, Plating
and Surface Finishing, and Products Finishing.
Replacing cyanide-based cadmium coating with one of the processes
described eliminates workplace exposure to both cadmium and cyanide, and
reduces environmental releases of both these chemicals.
Additional operational benefits may result depending on the properties of
the alloy relative to the cadmium deposit being replaced:
>• Corrosion resistance for zinc is as good as cadmium for
many applications.
>• Zinc-nickel alloys have better wear resistance than
cadmium.
>• Zinc-cobalt deposits show good resistance to atmospheres
containing SO2.
As discussed, the desired properties for the application must be matched to
the properties of the alloy.
Hazards and
Limitations
Summary of
Unknowns/State of
Development
Zinc and zinc-nickel alloy electroplating processes have the following
disadvantages:
»• Electrical contact resistance is higher for zinc than for
cadmium.
>• Zinc and zinc-nickel alloy coatings do not have the
lubricity of cadmium coatings.
*• Acid zinc coatings have comparatively poorer throwing
power than cadmium, and deposits: are not fully bright.
•> In general, plating with non cyanide-based plating
processes requires that parts be cleaner than for cyanide
based processes.
The processes outlined above are well-developed and are available from
numerous vendors. These alternatives, however, have only recently been
considered as replacements for cadmium coatings. Industry recognizes that
the move away from cadmium plating is well underway and zinc alloys are
expected to play an important role as substitute (Zafci, 1993). Nonetheless,
more work needs to be done to compare these iilternative coatings to
cadmium for specific applications.
Page 27
-------
Section Three
REFERENCES
Blunden, SJ. and AJ. Killmeyer. 1993. Tin-zinc alloy plating: a non-
cyanide alkaline deposition process. 1993 SUR/FIN. pp. 1077-1081.
Brooman, E. 1993. Alternatives to cadmium coatings for
electrical/electronic applications. Plating and Surface Finishing. February.
pp. 29-35
Budman, E. and R. Sizelove. 1993. Zinc alloy plating. 1993 Products
Finishing Directory, pp. 290-294.
Courier, E. 1990. Zinc-nickel alloy electroplating of components: corrosion
resistance is selling point for autos. American Metal Market. May 17. p. 17.
DM, J.W. 1977. Electrodeposition of zinc-nickel alloy coatings. Workshop
on Alternatives for Cadmium Electroplating in Metal Finishing.
Gaithersburg, MD (October 4). Washington: U.S. Dept. of Energy. 38 pp.
Hsu, G.F. 1984. Zinc-nickel alloy plating: an alternative to cadmium.
Plating and Surface Finishing. April, pp. 52-55.
Sharpies, T.E. 1988. Zinc/zinc alloy plating. Products Finishing. April, pp.
50-56.
Sizelove, R.R. 1991. Developments in alkaline zinc-nickel alloy plating.
Plating and Surface Finishing. March, pp. 26-30.
Wilcox,, G.D. and D.R. Gabe. 1993. Electrodeposited zinc alloy coatings.
Corrosion Science. 35(5-8). p. 1251-8.
Zaki, N, 1993. Zinc alloy plating. 7995 Products Finishing Directory, pp.
199-205
BLACKHOLE TECHNOLOGY
Pollution Prevention
Benefits
The BlaDkhole Technology Process is an alternative to the electroless copper
method used in printed wire board manufacturing. The following qualities
make it environmentally attractive:
Fewer process steps
Reduced health and safety concerns
Reduced waste treatment requirements
Less water required
Reduced air pollution
Page 28
-------
Section Three
The chemistry in the Blackhole process avoids the use of metals (copper,
palladium, tin) and formaldehyde used in electroliess copper processes. The
smaller number of process steps reduces the use; of rinse water, decreasing
waste treatment requirements.
How Does it Work?
Why Choose this
Technology?
The Blackhole Technology Process uses an aqueous carbon black dispersion
(suspension) at room temperature for preparing through-holes in printed
wire boards (PWBs) for subsequent copper electroplating. The carbon film
that is obtained provides the conductivity needed for electroplating copper
in the through-holes. The process steps are described in the following
paragraphs and compared with the process steps used for the electroless
copper method,
Applications
The Blackhole Technology Process eliminate!? the need for electroless
copper metalization of through-holes prior to electrolytic plating in the PWB
industry. Formaldehyde, a suspected carcinogen and water pollutant, is an
ingredient of the electroless copper plating process, The Blackhole process
eliminates this waste stream and avoids costs and environmental/health risks
associated with disposal or treatment of spent electroless copper plating
solutions,
Operating Features
PWBs must be pretteated for desmear/etchback in both the Blackhole
Technology and electroless copper processes. Permanganate is the preferred
desmear process for Blackhole Technology because of its wide operating
conditions and the resulting hole-wall topography.
Process Comparison
PWB manufacturers typically use the electroless copper process to plate
through-holes. The electroless copper process consists of the following
operational steps:
Page 29
-------
Section Three
1. Acid cleaner
2. Rinse
3. Micro etch (sodium persulfate
solution)
4. Rinse
5. Activator pre-dip
6. Catalyst
7. Rinse
8. Rinse
9. Accelerator
10. Rinse
11. Electroless copper bath
12. Rinse
13. Sulfuric acid (10 percent) dip
14. Rinse
15. Anti-tarnish dip
16. Rinse
17. Deionized water rinse
18. Forced air dry
These steps are performed in order on a process line that uses an automated
hoist to move racks of parts from tank to tank. All of the rinses are single
use and generate large quantities of wastewater that contains copper. The
rinses following the electroless copper, bath (from Step 11 on) contain
complexed copper, which is hard to treat using typical wastewater treatment
technology, such as metal hydroxide precipitation.
The Blackhole Technology process replaces the electroless copper process
for through-hole plating with a carbon black dispersion in water. The
Blackhole Technology process consists of the following process steps:
1. Blackhole alkaline cleaner
2. Rinse
3. Blackhole alkaline conditioner
4. Rinse
5. Blackhole bath
6. Dry
7. Micro-etch
8. Rinse
9. Anti-tarnish dip
10. Rinse
11. Dry
Steps 1 through 6 are performed, then repeated. Steps 7 through 11
complete the process. All process steps are performed automatically on
either a horizontal conveyor system or using existing hoists and bath
systems (see Figure 1).
Page 30
-------
Section Three
Figure 1
Blackhole Technology Plating Line
-_ _- t -_—_—_- ^—„
Blackhole mx Blackhole D^er
Qeaner
Bath#l
Conditioner 115 C
Wns* Blackhole HeateA D|yer
Bath #2
Blackhole Blackhote
Afflcrodean Antt-Tamish
Hollmuller Combisf em CS-65
Source: MacDermid Inc.
Page 31
-------
Section Three
The Blackhole Technology Process first uses a slightly alkaline cleaning
solution containing a weak complexing agent. The solution is operated at
135°F (57"C) to remove drilling debris from the hole-wall, to clean the
copper surfaces, and to prepare the hole-wall surface for the subsequent
conditioning step.
A second alkaline solution containing a weak complexing agent serves as
the conditioner. This solution is applied at room temperature. The condi-
tioner neutralizes the negative charge on the dielectric surfaces, which helps
to increase the absorption of the carbon in the next step.
The Blackhole Technology step uses a slightly alkaline, aqueous carbon
black-based suspension operating at room temperature. The viscosity of the
solution is very close to water. The carbon particles have a diameter of 150
to 250 nanometers (1500 Angstroms to 2500 Angstroms).
Conventional plating tanks and horizontal conveyorized systems can be
used for the Blackhole Technology Process.
Material and Energy Requirements.
Compared to electroless copper, the Blackhole Technology Process uses
fewer individual process steps. Some process steps are repeated, which
reduces the floor space needed for the process baths. The number of
chemicals used also is reduced. The energy requirements should be about
the same, because both processes use a drier and several heated solutions.
Required Skill Level ',
The skill level required of system operators running the Blackhole process
is the same as or less than that for electroless copper processing.
Cost
If existing process equipment is used, the only installation cost is the
disposal of the electroless copper solutions, cleaning of the tanks, and
replacement with the Blackhole Technology process solutions.
Reported Applications
The Blackhole Technology process has been available commercially since
1989. The technology is currently used by PWB manufacturers but is
gaining acceptance. Military Standard MIL-P-55110D now permits
through-hole plating technologies other than electroless copper.
Page 32
-------
Section Three
Availability
The Blackhole Technology process is sold by Mac Dermid (formerly Olin
Hunt).
Operational and
Product Benefits
Hazards and
Limitations
State of Development
REFERENCES
Process Simplification—The Blackhole technology requires fewer process
steps as well as associated chemicals and rinses, greatly reducing waste
streams from PWB plating.
Contamination Reduction—Unlike the electroless copper process, the
Blackhole Technology Process does not use formaldehyde.
Ease of Implementation—Because the Blackhole process uses existing
equipment in an electroless copper process line,, it should be very easy to
implement.
Acceptable Product Quality—Product quality should not be affected. The
Blackhole Technology process is accepted under MIL-P-5511OD.
Lower Operating Costs—The Blackhole process results in reduced costs for
chemicals, water, and wastewater treatment.
By using a carbon black suspension, the Blackhole process avoids the use
of metals (copper, palladium, and tin) and formaldehyde. The process
solutions used in the Blackhole process are mildly alkaline and pose a small
skin/eye irritation hazard. Overall health risks would be significantly
reduced if the electroless copper process was replaced by the Blackhole
Technology Process.
The Blackhole Technology is commercially available.
Battisti, AJ. 1986. Blackhole: beyond electroless copper. In Proceedings,
National Electronic Packaging and Production Conference. Anaheim, CA:
February 25-27. Vol. 2. pp. 271-37.
Olin Hunt Undated. Blackhole Technology. Olm Hunt, 5 Garret Mountain
Plaza, West Paterson, NJ 07424. Product literature.
Plakovic, F. 1988. Blackhole - a description and evaluation. Presented at
IPC Fall Meeting. Anaheim, CA: October 24-28,, IPC-TP-754.
Printed Circuit Fabrication. 1990. Blackhole upidate. 13(5). May. pp. 36-
42. i
Page 33
-------
Section Three
ION VAPOR DEPOSITION OF ALUMINUM (I VD)
Pollution Prevention
Benefits
How Does it Work?
Electroplated cadmium coating processes normally use plating solutions that
contain cyanide. Cadmium is a heavy metal mat is toxic to humans. In
addition, cyanide is highly toxic to humans and animal life. Aluminum
coatings deposited through ion vapor deposition (TVD) can replace cadmium
coatings in some applications, eliminating the use of both cadmium and
cyanide. Aluminum is considered nontoxic, and IVD does not employ or
create any hazardous materials.
In IVD, the coating metal is evaporated and partially ionized before being
deposited on the substrate. A typical IVD system consists of a steel vacuum
chamber (measuring 6 feet in diameter by 12 feet in length), a pumping
system, a parts holder, an evaporation source, and a high-voltage power
supply.
Parts to be coated must be clean to ensure good adhesion of the coating. To
minimize surface contamination, parts are treated frequently with a dry
blasting process using pure aluminum oxide mesh (150-220 mesh). Parts
then are loaded into the chamber on racks, or suspended on hooks from the
ceiling. Hie chamber may hold as few as 2 large parts to as many as 1,000
small parts.
Once loaded, a vacuum is drawn on the chamber to remove trace gases and
vapors fro>m the parts, racks, and chamber shields. The chamber is then
backfilled with argon to 10 microns, and a large negative potential is applied
between the evaporation source and the parts to be coated. The argon ions
created by the potential difference bombard the part surfaces, dislodging
substrate atoms and removing surface contamination (sputtering). As this
occurs, the parts typically emit a glow of light. This gas cleaning cycle lasts
approximately 10 to 20 minutes.
The evaporation apparatus consists of a series of concave ceramic "boats"
through which a thin strand of aluminum wire is continuously fed. These
boats can move back and forth between the parts to ensure even coverage.
A high current supplied to the boat melts and vaporizes the aluminum. Once
evaporated, the aluminum atoms collide with high-energy electrons in the
chamber and become ionized. The positively aluminum charged ions
accelerate toward the negatively charged substrate, condensing to form a
protective metal coating. ;
The coating process itself can take between 1 hour and 2.5 hours, depending
on the configuration of the parts and the desired coating thickness.
Page 34
-------
Section Three
Why Choose this
Technology?
Applications
IVD aluminum coatings can be applied to a wide variety of metallic
substrates, including aluminum alloys, and most recently, to
plastic/composite substrates. To date, IVD has been mainly used on high-
strength steels in the aerospace industry and for some marine applications.
According to Nevill (1993), IVD and paint currently are specified as the
prime coatings on three leading Department of Defense missile contracts
(Patriot, Amraam, and Lantirn). IVD has replaced anodize on fatigue-
critical structures such as wing sections and bulkheads on both military and
commercial aircrafts. Lansky (1993) reports that approximately 80 percent
of aircraft parts currently coated with cadmium cam be coated with IVD
aluminum with no change in corrosion control or performance.
IVD aluminum coatings tend to be porous when applied. Burnishing with
glass media often is used to reduce porosity and improve the durability of
the finish. Thin coatings of IVD aluminum (0.001 inches) may exhibit low
corrosion resistance. Such parts are often chromated after the coating is
applied to improve corrosion resistance.
IVD coatings tend to be brittle on fatigue-prone substrates and are applied
most often to parts that are not subject to fatigue in service. A common
application is steel fasteners on aluminum parts/which must be coated to
avoid galvanic corrosion in service. IVD aluminum is ideal since identical
metal provides for zero galvanic corrosion potential, and the steel core
provides much higher strength than solid aluminum fasteners.
Advantages of IVD aluminum coatings are the uniformity of thickness and
the excellent "throwing power" that results from the scattering of metal ions.
Deposition is not limited strictly to "line of sight" aj(plications, and parts
with complex shapes, such as fasteners, can be coated successfully. The
process is limited, however, in its ability to deposit coating into deep holes
and recesses. In configurations where hole depth exceeds the diameter, for
example, thickness distribution can drop off substantially. The reduced
thickness in these areas may not be significant since the relevant military
specification (MEL-C-83488C) requires coating of recessed areas without
specifying the required thickness of the deposit.
i
Operating Features
IVD has the following operating features:
* Large and/or complex parts can be plated.
* Somewhat limited to "line of sight" applications.
*• There is no buildup of the coating on sharp edges, such as
can occur in electroplating.
Page 35
-------
Section Three
Required Skill Level
Although equipment for IVD is entirely different that used in electroplating,
operators who have performed cadmium electroplating have sufficient skills
and education to be retrained to perform IVD. Maintenance of the
equipment would require significant retraining. Although the equipment
requires less routine maintenance overall, proper maintenance of vacuum
pumps, in particular, is critical to the operation.
Cost
Capital costs and operating costs for aluminum IVD equipment are
significantly higher than electroplating, but are partially offset by reduced
waste treatment and disposal costs. IVD does not generate hazardous waste,
and it requires less maintenance than tank electroplating. IVD also does not
require handling of hazardous chemicals, ventilation systems, plating
solutions, and rinse tanks.
A typical JVD system can cost in excess of $500,000 with another $500,000
for installation. Electroplating equipment and wastewater treatment for
producing the same amount of plated work would be approximately 1/4 to
1/6 that amount (Altmayer, 1994). The costs of the aluminum IVD process
are higher than those for cadmium physical vapor deposition (PVD), but
lower than those for either the low-embrittlement or diffused
nickel-cadmium processes. Costs for cadmium electroplating are likely to
keep rising because of ever-increasing hazardous waste disposal costs. In
contrast, more widespread use of IVD aluminum will probably lead to cost
reductions.
Reported Applications
The aluminum IVD process is used by a large number of U.S. Department
of Defense contractors, and is incorporated into several military and
industrial specifications as an option for cadmium plating. Applications
include pneumatic line fittings, steel fasteners and rivets, electrical bonding,
EMI and RFI shielding, and coatings for plastic/composite materials (Nevill,
1993). Non-military applications include the coating of steel houses for
trolling motors used on fishing vessels and for exhaust manifold headers on
high-performance speed boats.
Availability
The aluminum IVD process was developed in large part by the McDonnell
Aircraft Company (a subsidiary of McDonnell-Douglas) of St. Louis,
Missouri. The trade name of the process equipment developed by
McDonnell is the Ivadizer. In 1987, McDonnell sold the rights to the
process to the Abar-lpsen Co. of Bensalem, Pennsylvania. Abar-lpsen
Page 36
-------
Section Three
currently manufactures the equipment Other companies have licenses to use
the technology..
Operational and
Product Benefits
Health and safety risks can be greatly reduced when IVD is used in place of
cadmium electroplating. Cadmium is a significant health hazard, as is the
cyanide bath often used in cadmium electroplating.
For many applications, a chromate conversion coating is used on top of both
cadmium and aluminum IVD coatings to improve corrosion resistance and
adherence of subsequent organic coatings. The use of chromate conversion
coatings generates some hazardous waste. Switching to an aluminum IVD
process, however, should not increase the use of these coatings.
The greatest advantage of aluminum IVD is thai: the process significantly
reduces the generation of hazardous wastes, and potentially eliminates the
' need for special pollution control systems. Some waste is generated in
alkaline cleaning and stripping although these wastes can be neutralized and
disposed of as special (i.e., non-hazardous) wastes. Odier potential
advantages of aluminum IVD coatings are listed below (Nevill, 1993):
*- Outperforms cadmium coatings in preventing corrosion in
acidic environments.
1 *- Can be used at temperatures up to 925 °F, as compared to
450°F for cadmium coatings. \
*•- Can be used to coat high-strengtli steels without danger of
hydrogen embrittlement. Unlike cadmium electroplating,
the aluminum IVD process does not expose the substrate to
hydrogen gas. ;
*• Can be used in contact with titanium without causing solid
metal conversion problems.
>" Can be used in contact with fuels.
*• Superior to the vacuum-applied cadmium process hi
resisting particle impact (e.g., can withstand burnishing
pressures up to 90 psi as compared to 40 psi for
vacuum-applied cadmium coatings),,
»• Permits coatings of several mils compared to about 1 mil
for electroplated and vacuum-applied cadmium coatings,
increasing corrosion resistance.
Page 37
-------
Section Three
Provides better uniformity of coatings on the edges of parts
than does electroplating.
Hazards and
Limitations
State of Development
Some of the disadvantages of IVD coatings are:
»• It is difficult to coat the interiors of blind holes or cavities
that have a depth greater than their diameter.
»• Compared to cadmium, aluminum IVD coatings have a
higher electrodeposit coefficient of friction as well as
inadequate lubricity. Application of a lubricant is
sometimes required for proper torque-tension of fasteners.
When lubricants cannot be used, inadequate lubrication
might be a significant limitation.
»• Unlike cadmium, aluminum IVD cannot be combined with
nickel to provide an erosion-resistant surface.
*• Unlike electroplating, there is no simple way to repair
damaged aluminum IVD coatings.
>• Aluminum IVD is slower than cadmium electroplating
(above a certain level of plating throughput) due to
capacity limits of the IVD system. For high-strength parts,
however, reduced speed is not an issue because these parts
would have to undergo hydrogen embrittlement relief after
cadmium electroplating.
»• Parts coated by aluminum IVD do not require
time-consuming heat treatment for hydrogen embrittlement
(hydrogen stress cracking) relief, thus compensating for the
slower application speed.
•• Because IVD aluminum coatings have a columnar structure
and tend to be porous, parts might need to be peened with
glass beads to improve fatigue and corrosion resistance.
Peening can add to production costs and slow productivity.
Cadmium electroplating has neither of these disadvantages.
The IVD aluminum coating process is a mature technology that has been
commercially available for a decade and is suitable for specialized
applications.
Page 38
-------
Section Three
REFERENCES
Hinton, B.R.W. and WJ. Pollock., 1991. Ion vapouir deposited aluminum
coatings for the corrosion protection of high strength steel. Aeronautical
Research Laboratories (Australia). Government Research Announcements
and Index. April. 52 pp.
Hinton, B.R.W. et al. 1987. Ion vapor deposited aluminum coatings for
corrosion protection of steel. Corrosion Australasia. June. pp. 15-20.
Holmes, VJL, DJE. Muehlberger, and J.J. Reilly. 1989. Hie substitution of
IVD aluminum for cadmium. Final report. EG&G Idaho. Report No. AD-
A215 633/9/XAB. 201 pp.
Lansky, D. 1993, IVD: eliminating tank electroplating solutions for
cadmium. Plating and.Surface Finishing. Janusiry 1993. pp. 20-21.
Legge, G. 1992. High volume automotive-type aluminum coatings by ion
vapor deposition. SUR/FIN'92. Vol 1. Atlanta, GA (June 22-25). Orlando,
FL: American Electroplaters and Surface Finishers Society, Inc.
Nevill, B.T. 1993a. An alternative to cadmiumi: ion vapor deposition of
aluminum. Plating and Surface Finishing. January 1993. pp. 14-19.
Nevill, B.T. 1993b. Diverse applications of IVD aluminum. Proceedings
of the 36th Annual Technical Conference, Dallas!, TX. Albuquerque, MM:
Society of Vacuum Coaters. pp. 379-384.
Nevill, B.T. 1992. Ion vapor deposition of aluminum. Atlanta, GA (June
22-25). Orlando, FL: American Electroplaters and Surface Finishers
Society, Inc.
Ressl, R. and J. Spessard. Evaluation of ion vapor deposition as a
replacement for cadmium electroplating at Anniston Army Depot. Final
Report. FT Environmental Programs. Government Research Announcements
and Index. May. 128. pp. , i
PHYSICAL VAPOR DEPOSITION (PVD)
Pollution Prevention
Benefits
Hexavalent chromium is extremely toxic and is a knovm carcinogen. Health
and safety considerations as well as rising disposal costs have prompted the
plating industry to consider alternatives for coating processes that involve
hexavalent chromium. Physical vapor deposition (PVD) of alternative
materials is one candidate for replacing chromium electroplating.
Page 39
-------
Section Three
How Does it Work?
Operating Features
PVD encompasses several deposition processes in which atoms are removed
by physical means from a source and deposited on a substrate. Thermal
energy and ion bombardment are the methods used to convert the source
material into a vapor.
The thoroughly cleaned workpiece is placed in a vacuum chamber, and a
very high vacuum is drawn. The chamber is heated to between 400 and
900°F, depending on the specific process. A plasma is created from an inert
gas such as argon. The workpiece is first plasma-etched to further clean the
surface. The coating metal is then forced into the gas phase by one of the
three methods described below:
*• Evaporation
*• Sputtering
> Ion plating
Evaporation
High-current electron beams or resistive heaters are used to evaporate
material from a crucible. The evaporated material forms a cloud which fills
the deposition chamber and then condenses onto the substrate to produce the
desired film. Atoms take on a relatively low energy state (0.2 to 0.6 eV) and
the deposited films, as a result, are not excessively adherent or dense.
Deposition of a uniform coating may require complex rotation of the
substrate since the vapor flux is localized and directional. Despite this,
evaporation is probably the most widely used PVD process.;
Sputtering
The surface of the source material is bombarded with energetic ions, usually
an ionized inert gas environment such as argon. The physical erosion of
atoms from the coating material that results from this bombardment is
known as sputtering. The substrate is placed to intercept the flux of
displaced or sputtered atoms from the target Sputtering deposits atoms with
energies in the range of 4.0 to 10.0 eV onto the substrate. Although
sputtering is more controllable than evaporation it is an inefficient way to
produce vapor. Energy costs are typically 3 to 10 times that of evaporation.
Ion plating
Ion plating produces superior coatings adhesion by bombarding the
substrate with energy before and during deposition. Particles accelerate
towards the substrate and arrive with energy levels up to the hundreds of eV
range. These atoms sputter off some of the substrate material resulting in a
cleaner, more adherent deposit. This cleaning continues as the substrate is
coated. The film grows as over time because the sputtering or cleaning rate
Page 40
-------
Section Three
is slower than the deposition rate. High gas pressure results in greater
scattering of the vapor and a more uniform deposit on the substrate.
i
An important variation on these process involve the introduction of a gas
such as oxygen or nitrogen into the chamber to form oxide or nitride
deposits, respectively. These reactive deposition processes are used to
deposit films of material such as titanium nitride, silicon dioxide, and
aluminum oxide.
PVD coatings are typically thin coatings between 2 sind 5 microns.
Titanium nitride is a prime candidate for replacing chromium coatings using
PVD. Titanium nitride is much harder than cliromium but can be cost
effectively applied in much thinner coatings. Because of the thin, hard
nature of the coating, titanium nitride is inferior to chromium as a coating
in highpoint or line-load applications. Titanium nitride coatings also do not
provide as much corrosion protection as do thicker, crack-free chromium
coatings.
Substrates coated with titanium nitride and other PVD coatings are not
subject to hydrogen embrittlement. PVD results in a thin, uniform coating
that is much less likely to require machining after application. However,
PVD is a line-of-sight coating process, and parts with complex shapes are
difficult to coat.
Reported Applications
REFERENCES
Titanium nitride coatings have already gained wide acceptance in the cutting
tool industry. They are now being examined by a variety of industries,
including the aerospace industry.
Comello, Vic. 1992. Tough Coatings Are a Cinch with New PVD Method.
R&D Magazine, January pp.59-60. I
Dini, J.W. 1993b. Ion plating can improve coating adhesion. Metal
Finishing. September 1993. pp. 15-20. j
Dini, J.W. 1993a. An electroplater's view of PVD processing. Plating and
Surface Finishing. January, 1993. pp. 26-29.
Johnson, P. 1989. Physical vapor deposition of thin films. Plating and
Surface Finishing. 76(6)30-33. June 1989.
Konig, W. and D. Kammermeier. 1992. New ways toward better
exploitation of physical vapour deposition coatings. 19th International
Conference on Metallurgical Coatings and Thin Films, II. San Diego, CA
(April 6-10). pp. 470-475. ;
Page 41
-------
I
Section Three
Podob, M. and J.H. Richter. 1992. CVD and PVD hardcoatings for*
extending the life of tools used in the stamping industry. Proceedings:
Manufacturing Solutions, v. 2. Nashville, IN (Feb. 23-26). Richmond Hts,
OH: Precision Metalforming Association.
Russell, T.W.F., B.N. Baron, S.C. Jackson, and R.E. Rocheleau. 1989.
Physical vapor deposition reactors. Advances in Chemistry Series.
Washington, DC: ACS, Books and Journals Division, pp. 171-198.
Vagle, M.C. and A.S. Gates. 1990. PVD coatings on carbide cutting tools.
High Speed Machining: Solutions for Productivity. San Diego, CA (Nov.
13-15). Materials Park, OH: ASM International.
Zega, B. 1989. Hard decorative coatings by reactive physical vapor
deposition - 12 years of .development. 16th International Conference on
Metallurgical Coatings (ICMC), Part 2, San Diego, CA (April 17-21). In:
Surface and Coatings Technol. 39(40):507-520.
CHROMIUM-FREE SURFACE TREATMENTS FOR ALUMINUM AND ZINC
Description
One of the many uses of chromium in the metal finishing industry is for
conversion coatings, which are used to treat nonferrous metal surfaces
(mainly magnesium, aluminum, zinc, and cadmium) for corrosion
protection or to improve adhesion of subsequent organic coatings.
Unfortunately, chromates, the form of chromium used for treatment, are
carcinogenic and highly toxic. Small amounts of chromic acid or potassium
dichromate will cause kidney failure, liver damage, blood disorders and
eventually death. Prolonged skin exposure can cause rashes, blisters, and
other dermatological problems. Chromate mists entering the lungs may
eventually cause lung cancer.
These health and safety considerations and the increasing cost of disposal
of chromium-containing finishing wastes have prompted users to look at
alternatives to treatment of aluminum, zinc, and other substrates with
chromates. Although a number of alternative treatments have been
examined, very few provide even close to the corrosion protection afforded
by chromate conversion coatings. Even fewer have been developed to the
point where their commercial viability can be assessed.
Sulfuric acid anodizing can substitute for some chromium conversion
coatings, although the coatings are more brittle and significantly thicker
than chromare films. '
One of the few commercially proven, non-chromate surface treatments for
aluminum is an inorganic conversion coating based on zirconium oxide.
Page 42
-------
Section Three
This treatment usually involves immersion of the substrate in an aqueous
solution containing a polymeric material and a zirconium salt. The
zirconium deposits on the surface in the form.of a zirconium oxide. These
coatings have been used on aluminum cans for some time, but they have not
been tested in the kind of environments in "which chromate conversion
coatings are typically used. Wider application of this coating must await
this type of testing.
Another process 'showing promise is the SANCHEM-CC chromium-free
aluminum pretreatment system developed by Dr. John Bibber of Sanchem,
Inc. This process can be summarized as follows:
Stage One—Use of boiling deionized water or steam to form a
hydrated aluminum oxide film. • .
Stage Two—Treat in proprietary aluminum salt solution for at least
1 minute at 205 °F or higher.
Stage Three—Treat in a proprietary permanganate solution at 135
to 145 °F for at least one minute.
A fourth stage of the process exists for cases where maximum corrosion
resistance is required for certain aluminum alloys, he developers claim that
the film produced by this process closely matches the performance of a
chromate conversion process.
A recent chrome-free post-rinse process has been developed for use on
phosphated steel, zinc, and aluminum surfaces prior to painting. The new
rinse, known as Gardolene VP 4683, contains neither hexavalent or trivalent
chrome. It contains only inorganic metallic compounds as the active
ingredient. The rinse is applied at temperatures ranging to 100 °F and at a
slightly acidic pH. The manufacturer describes tests showing corrosion
protection and paint adhesion equal to that of hexavalent chrome (Finishers'
Management, 1990).
. - ' i
Some of the other possible alternatives to chromate conversion coatings that
have been examined are molybdate conversion coatings, rare earth metal
salts, silanes, titanates, thioglycollates, and alkoxides. These alternatives are
discussed in detail in Hinton (1991).
REFERENCES
Finishers' Management, 1990. Chrome free piassivating post-rinse for
phosphate coatings reduces toxicity. May, 1990. pp. 51-52.
Hinton, 1991. Corrosion prevention and chromates: the end of an era?
Metal Finishing. Part I, September, pp. 55-61. Part II, October, pp. 15-20.
Page 43
-------
Section Three
METAL SPRAY COATING
Description
Metal spray coating refers to a group of related techniques in which molten
metal is atomized and directed toward a substrate with sufficient velocity to
form a dense and adherent coating. Metal spray coating has been used in a
wide variety of applications, as shown in Table 5. The technique avoids use
of plating solutions and associated rinses, thereby reducing wastes.
However, the parts to be sprayed still need to be cleaned prior to spraying.
The individual techniques vary mainly in how the coating is melted and in
the form of the coating prior to melting. The three basic means for melting
the metal are as follows:
Molten Metal—The metal is heated by some suitable means (either
resistance heating or a burner) and then supplied to the atomizing
source in molten form.
Fuel/Oxldant—Oxygen/acetylene flames are typically used. The
metal melts as it is continuously fed to the flame in die form of a
wire or powder. The flame itself is not the atomizing source.
Instead, the flame is surrounded by a jet of compressed air or inert
gas that is used to propel the molten metal toward the substrate.
Electric arc—In this method an electric arc is maintained between
two wires that are continuously fed as they melt at the arc.
Compressed air atomizes the molten metal at the arc and propels it
toward the substrate. DC plasma arc spraying and vacuum plasma
spraying are variations of this technique in which an inert gas
(usually argon) is used to create a plasma between the electrodes.
The technologies for thermal spraying of metals are well developed, but they
tend to have their own market niche and are not typically thought of as a
replacement for electroplating. As the costs of hazardous waste treatment
and disposal rises, however, this family of techniques may become
cost-effective replacements for coating applications currently performed by
electroplating. The coatings can be applied to a wide range of substrates,
including paper, plastic, glass, metals, and ceramics with choice of suitable
materials and control of the coating parameter.
Page 44
-------
Section Three
Table5. Applications of thermal spray.
Wear resistance
Dimensional
Restoration
Corrosion
Resistance
Thermal Barriers
Abrasion
Dielectrics
Conduction
RFI/EMI
Shielding
Metals, carbides, ceramics, and plastics are used to
resist abrasion, erosion, cavitation, friction, and
fretting. Coating hardness range from < 20 to > 70 Re
are attainable on practically any substrate.
Coatings can be applied up to 0.100 inch thick to
restore worn dimensions and mismachined surfaces.
Ceramics, metals, and plastics resist acids and
atmospheric corrosion either by the inert nature of
the coating or by galvanic protection. Nonporous
coatings must be applied.
Zirconia (ZrO2) coatings are applied to insulate base
metals from the high-temperature oxidation, thermal
transients, and adhesion by molten metals.
Softer coatings such as aluminum, polyester, graphite,
or combinations are used for clearance control,
allowing rotating parts to "machine in" their own
tolerance during operation.
Alumina (A1203) is generally usisd to resist electrical
conductivity. These coatings have a dielectric strength
of 250 V/mil of coating thickness.
Materials are selected for their intrinsic thermal or
electrical conductivity. Copper, aluminum, and silver
are frequently used for this application.
These conductive coatings are designed to shield
electronic components against radio frequency or
electromagnetic interference. Aluminum and zinc are
often selected.
Medical Implants Relatively new porous coatings of cobalt-base,
titanium-base, or ceramic materials sire applied to
dental or orthopedic devices to provide excellent
adhesive bases or surfaces for bone ingrowth.
Source: Kutner (1988).
Page 45
-------
Section Three
REFERENCES
Kutner, Gerald. 1988. Thermal spray by design. Advanced Materials &
Processes. October, pp. 63-68.
Thorpe, Merle L. 1988. Thermal spray applications grow. Advanced
Materials & Processes. October, pp. 69-70.
Herman, Herbert. 1990. Advances in thermal spray technology. Advanced
Materials & Processes. April, pp. 41-45.
Page 46
-------
Section Four
SECTION FOUR
EMERGING TECHNOLOGIES
Introduction
Three emerging clean process changes for metal finishing are presented in
this section:
»• Nickel-tungsten-silicon carbide plating to replace
chromium coatings
*• Nickel-tungsten-boron plating to replace chromium
coatings
> In-mold plating to replace electroless plating followed by
electrolytic plating.
NICKEL-TUNGSTEN-SILICON CARBIDE PLATING
Description
The nickel-tungsten-silicon carbide (Ni-W-SiC) composite electroplating
process is a patented process (Takada, 1990) that can be used to replace
functional (hard) chromium coatings in some applications. Nickel and
tungsten ions become absorbed on the suspended silicon carbide particles
in the plating solution. The attached ions are then [adsorbed on the cathode
surface and discharged. The silicon carbide partide becomes entrapped in
the growing metallic matrix.
The composition and operating conditions for the Ni-W-SiC plating bath are
given in Table 6.
Chromium electroplating processes generate toxic mists and wastewater
containing hexavalent chromium. Hexavalent chromium has a number of
toxic effects including lung cancer and irritation of the upper respiratory
tract, skin irritation and ulcers. These toxic emissions are coming under
increasingly stringent regulations and are difficult to treat and dispose of. In
addition to hazardous waste reduction, the Ni-W-SiC process has the
following benefits:
Higher Plating Rates—The Ni-W-SiC process wdiibits much higher
plating rates than for chromium. Plating rates ranged from 1.7 to 3.3
mils/hr at 300 ASF, compared to the typical hard chromium plating
rate of less than 1 mil/hr.
Higher Cathode Current Efficiencies—Current efficiencies are
approximately double those for chromium plating. Current effi-
Page 47
-------
Section Four
ciencies range from 24 percent to 35 percent, whereas typical
chromium plating current efficiencies range from 12 percent to 15
percent.
Table 6, Composition and operating conditions for Ni-W-SiC
composite plating
Composition
Operating conditions
Nickel sulfate NiSO4 6H2O
Sodium tungstate Na2WO4
Ammonium citrate NH4HC6H5O7
Silicon carbide (0.8 -1.5 urn particles)
pH (adjust with ammonium hydroxide
or citric acid)
Bath temperature
Cathode current density
30 - 40 gA
55-75g/l
70-110g/l
10 - 50 g/1
6.0 - 8.0
150-175°F
100 - 300 ASF
Better Throwing Power—Cathode current efficiencies for the Ni-
W-SiC process decrease with increasing current density. This
results in much better throwing power than for chromium plating.
In chromium plating baths, current efficiency increases with current
density, which results in poor throwing power.
Better Wear Resistance—Precipitation-hardened and relief-baked
Ni-W-SiC composite coatings all showed better wear resistance
than a chromium coating in tests using a Taber Abraser.
The main disadvantage of Ni-W-SiC process uncovered so far is that the
plating bath is more susceptible to metallic and biological contamination.
As a result, many questions remain to be answered before widespread use
will occur. Some of the unknowns include:
Susceptibility of coated parts to hydrogen embrittlement
Fatigue life of coated parts
Corrosion resistance of coated parts
Maximum thickness of coating before cracking or flaking
occurs
Effect of coating parameters on internal stresses in deposit
Page 48
-------
Section Four
Lubricity of coated parts
Maximum service temperature for coating
Stripping techniques for coated parts
Processing techniques for promoting adhesion to various
surfaces
Grinding characteristics
Ability to plate complex shapes
Repair of damaged coatings
Facility requirements.
REFERENCES
Takada, 1990. Method of nickel-tungsten-silcon carbide composite plating.
U.S. Patent 4,892,627. January.
Takada, K. 1991. Alternative to hard chrome plating. SAE (Soc.
Automotive Engineers). 100:24-27.
NICKEL-TUNGSTEN-BORON ALLOY PLATING
Description
Properties
Following several years of development, a new chromium alternative based
on an alloy of nickel, tungsten, and boron has bsen recently introduced
(Scruggs et al., 1993). A family of these alloys is patented under the trade
name AMPLATE. Properties for one specific alloy, known as AMPLATE
"U" have been reported by the developers in the literature. This alloy
consists of approximately 59.5 percent nickel, 39.5 percent tungsten, and 1
percent boron.
Unlike most metals which exhibit a crystalline structure at ambient
temperatures, the AMPLATE alloys are structureless. Metals of this type are
often described as "amorphous" and have "glasslike" properties that render
substrate surfaces smooth and free of the defects that are exhibited by
lattice-structured metals. Because of the smoothness and hardness of their
surfaces, amorphous metals have excellent corrosion and abrasion resistance
properties.
The properties of this alloy and its advantages as a coating are summarized
as follows (Scruggs et al., 1993):
Appearance—The alloy is reflective and has an appearance of
bright metal similar to chromium, bright silver, or bright nickel.
Being amorphous, it adopts the surface characteristics of the
substrate being coated (e.g., etching, patterning, or irregularities on
the substrate surface will show through the coating).
Page 49
-------
action Four
Hardness—When deposited, the Ni-W-B alloy has a hardness of
about 600 Vickers. Heat treatment for 4 hours at 60°F will raise the
hardness to about HV1000. Other properties are unaffected.
Abrasion/Wear Resistance—-The alloy compares comparably to
chromium and electroless nickel. In one test, rollers were plated
with chromium and the AMPLATE U alloy and rotated at 600 and
700 RPM with a load of 102 Newtons. The chromium coating
failed within 60 to 100 minutes while at the end of 1300 minutes
the alloy showed little oxidative wear.
Corrosion—The alloy exhibits corrosion resistance properties far
superior to .those of chromium. In testing, pieces coated with
chromium were immersed in a 5 percent NaCI brine acidified with
acetic acid to pH 2 and saturated with hydrogen sulfide. Following
iseven days of immersion, the chromium was completely stripped
and the substrate had been heavily attacked. A similar coating of
the U alloy showed no signs of corrosion.
Ductility—^The coating exhibits surprising ductility. In one test, a
foil of the coating was obtained by dissolving the substrate. The
foil could be tied in a loose knot and ben 18 degrees on itself.
Plated items were successfully bent 9 degrees over a quarter-inch
mandrel with no separation of the plating material.
Heat Resistance—The structure of the amorphous coating is
unaffected by heat to at least 1200°F. The finish remains bright
upon short exposure to temperatures of 400°F. Treatment in air can
lead to yellowing due to oxidation of the tungsten. This coloration
can be removed by polishing or avoided by heat treating in an inert
gas environment.
The plating system is operated at temperature range of 115°F to 125°F and
a pH of 8.2 to 8.6. Optimum concentrations of Ni, W, and B are maintained
by adding liquid concentrates containing dissolved salts of the three metals.
Deposition Characteristics
Two versions of the alloy solution are available (UA and UA-B), the
difference in the "B" formulation being the addition of abrightener and a
lower metal concentration. This results in a deposition rate approximately
half that of UA. The UA solution is recommended for heavier applications
where the surface will be subsequently dimensioned by grinding and
polishiag. The UA-B solution will produce a fully bright coating often
mils thick or more and can be used for both decorative and engineering
purposes. Thinner deposits of 1-2 mils over bright nickel have the
appearance of chromium but with superior corrosion resistance.
Operating Conditions
Page 50
-------
Section Four
Cost and Efficiency
Environmental
REFERENCES
Equipment Requirements
Standard plating equipment is suitable for plating with the Ni-W-B alloy.
Automated chemical feed equipment is recommended for optimizing
concentrations of ammonia and the metals.
Surface Preparation
Extra attention is needed to ensure that parts to be plated are absolutely clear
of contaminants. When plating with amorphous coatings, even minute
defects can become stress inducing points or pore generating sites.
Coating efficiency is around 38 percent or three times that of chromium.
This reduces energy and plating costs. Savings iire also generated due to
reduced need to "grind back" chromium to obtain suitable surfaces and sizes.
The plating solution is only slightly alkaline and is operated at relatively
low temperature. There are virtually no hazardous or carcinogenic
emissions associated with the process. Mild ammonia odors can be
controlled through proper ventilation.
Because the UA-B deposit remains bright and smooth at thicknesses up to
ten mils or more, the need for grinding and polishing is greatly reduced. In
addition to reducing costs, this also minimizes atmospheric contamination.
Scruggs, D., J. Croopnick, and J. Donaldson. 1993. An electroplated
nickel/tungsten/boron alloy replacement for cliromium. 1993 AESF
Symposium on the Search for Environmentally Safer Deposition Processes
for Electronics.
IN-MOLD PLATING
Description
In-mold plating is the name given to a process developed and patented by
Battelle, Columbus, Ohio. This process combines high-speed plating and
injection molding to apply metal coatings to plastics in the following
manner. First, the mold is cleaned and prepared, then a plating fixture is
placed on top and a metal, such as copper or zinc, is applied by a high-speed
plating technique. When the required thickness has: been reached, the mold
cavity is emptied, the deposit is rinsed and dried in situ, and the coated mold
is transferred to the injection molding machine. A plastic is then injected,
the mold cooled and a metal-coated plastic part ejected. The plastic typically
is a thermosetting resin, but it may be filled with particles or fibers to
improve, stability or toughness. Similarly, a foamed plastic can be used
Page 51
-------
Section Four
because the coated mold surface defines the surface of the finished part, not
the plastic material. Besides injection molding, the process can be adapted
for compression molding. The process has several advantages:
•> It has fewer process steps than conventional techniques for
plating plastics.
> It does not generate any waste etching or sensitizing
solutions that contain organics, heavy metals, or precious
metals.
>• It avoids the use of electroless copper to initially metalize
the surface. .
»• It deposits only the amounts of metal required and only in
the areas that require coating; thus it conserves materials
and energy.
» It provides a very broad range of metal coating and plastic
combinations that can be processed.
While potentially reducing and minimizing some waste streams, the process
itself only replaces the need for etching and sanitizing the plastic part prior
to plating. It still utilizes a plating process to plate the mold (and therefore
will generate wastewater and wastes to dispose of). Skillful fixturing is
required to deposit an adequate plate or sequence of plates into the mold.
Improper cleaning and preparation can cause the metal to stay on the mold,
requiring chemical stripping (generates waste) and possibly a need for
polishing.
The appearance of the final product is directly related to the surface
condition of the mold itself, since the plating replicates the surface. The
appearance therefore will not match the luster of bright nickel plated plastic
parts thai: are processed conventionally. Also, the process is labor intensive
and very difficult and expensive to automate. It has only specialized
applications.
Although in-mold plating is not available commercially, several companies
are exploring its use in such applications as decorative finishes, plumbing
and architectural hardware, and EMI/RFI protection for electronic
components.
REFERENCES
PF. 1983. New way to plate on plastics. Products Finishing. March, pp.
75-76.
AMM. 1986. Battelle adopts technology for in-mold plating. American
Metal Market. December!, p. 8.
Page 52
-------
Section Five
SECTION FIVE
POLLUTION PREVENTION STRATEGIES
Introduction
Cadmium plating
Cyanide-based plating
solutions
Alternate technologies are presently available, arid others are under
development, for the reduction or elimination of use of cadmium, cyanide,
chromium, and copper/formaldehyde in specific metal finishing
applications. These alternate technologies tend to fall into two main
categories:
t
Alternate finishes—(e.g., aluminum, zinc or zinc alloys, and nickel-
tungsten-silicon carbide) replace traditional cadmium and
chromium finishes.
Process substitutions—{e.g., Blackhole Technology, ion vapor
deposition, physical vapor deposition, in-mo Id plating, and metal
spray) use different technologies for metal finishes.
Both types of changes have the potential to reduce costs (through reduction
in waste volumes or toxicity and associated savings in disposal costs) and
improve environmental health and safety. Barriers to acceptance of these
alternate processes often include high capital cost, higher maintenance costs,
high levels of required skill, difficulty in automation or bulk processing of
large volumes of parts, and inferior properties of the alternate process
coating.
The vast majority of cadmium plating is performed using cyanide-based
chemistry for a number of reasons, including:
» Ability to cover complex shapes somewhat uniformly (high
throwing power).
+ High tolerance to impurities.
*• High tolerance to improperly cleaned surfaces.
* Ability to obtain a porous deposit that allows for hydrogen
embrittlement relief.
»• Ability to obtain a ductile deposit at high thicknesses.
>• High adhesion to substrates.
A growing number of platers have successfully (substituted non-cyanide
cadmium plating solutions based on proprietary chemistries substituting
sulfate and/or chloride salts and organic, additives for the cyanide.
Alternates to cyanide processes for other plating solutions are also available
and in the developmental stage. For example, significant progress has been
made in developing mildly alkaline, non-cyanide copper plating processes
for application in both, rack and barrel plating on ferrous parts, on zinc die
castings, and on zincated aluminum die castings. These proprietary
Page 53
-------
Section Five
processes are available from at least four commercial suppliers (Lea-Renal,
Harshaw-Atotech, Enthone-OMI, and Electrochemical Products). In addition
to the cyanide free alkaline copper and the acid cadmium processes, non
cyanide formulations for plating gold and silver have been available for
many years. Additional progress in process control and lowering of
operating costs is required to allow these substitutes to. more readily
compete with the cyanide based formulations.
Chromium plating
Nickel-Tungsten-
Silicon Carbide and
Nickel-Tungsten-
Boron Alloy Plating
To find a suitable substitute for chromium, an alternate coating must be
found that offers the combination of benefits provided: wear, corrosion
protection, ability to hold oil/lubricants in microcracks, high temperature
wear resistance, low coefficient of friction, ability to produce very thick
deposits (10 mils and more), ease of solution maintenance, ease of
embrittlement relief (due to micro-cracked structure), ease of stripping
rejects, and high tolerance of impurities.
There is no single other metallic coating that offers the above combination
of beneficial properties and processing advantages. However, alternative
coatings presently in the research and pilot plant stage, show promise hi
providing some of the noted properties, and can be used as substitutes in
selected applications. For example, advanced ceramic and composite
materials have been tested as replacements for chromium plated parts hi
internal combustion engines. Hard coatings such as titanium nitride have
been applied using sophisticated (expensive) equipment that produces the
coating by condensing vaporized metals inside a vacuum chamber.
The deposits obtained from these alternatives are normally very thin and can
exceed chromium in hardness, but do not match up to chromium electroplate
hi economy, ability to produce thick coatings, corrosion resistance, ease of
stripping reject parts, or ability to deposit into deep recesses.
A significant effort is being made in the aerospace industry to evaluate
chromium substitutes produced from alternate aqueous electroplating
processes. The main focus of these efforts is the application of an alloy of
nickel and tungsten containing finely dispersed particles of silicon carbide,
molybdenum plating, and an alloy of nickel-tungsten-boron. The nickel
tungsten alloy electrodeposits offer better wear resistance and coefficient of
friction than chromium plate. The plating solution is approximately 50
percent to 100 percent faster in plating speed than typical functional
chromium plating solutions (although one supplier of proprietary chromium
plating chemicals has developed a process that would be 20 percent faster
that the nickel tungsten alloy solution).
A primary concern of the nickel-tungsten substitutes is that they contain
ingredients that have similar health/environmental concerns as hexavalent
chromium. Additionally, these substitutes utilize a plating solution that
produces a wastewater that requires treatment, the solutions themselves are
Page 54
-------
Section Five
Hexavalent chromium
Other solutions
subject to biological decomposition and offer cuiTent efficiencies that are
only marginally - more efficient .that functional chromium plating
formulations. The tungsten .compound used in the process (sodium
tungstate) is very expensive and not readily available. Parts that have been
- plated with nickel-tungsten alloys are typically very difficult to strip, if a
: defective deposit is placed, and the plating solution is more sensitive to
impurities. At least one of these processes (Ni-W-B) uses platinized titanium
anodes encased in a membrane cell. This is expensive and the membrane is
subject to fouling, and expensive to replace. Considerable process control
problems can be encountered when attempting to deposit an alloy, especially
one with three alloying elements (Ni-W-B).
Trivalent chromium solutions require much greeiter care in operation to
minimize contamination by metallic impurities than hexavalent solutions.
These metallic impurities can affect the color of the deposit, and if not
controlled to a steady state, the deposit will vary In color (darkness) from
week to week. When carefully controlled, these solutions are capable of
producing thin chromium deposits for decorative parts that are equivalent
in color, corrosion resistance, and abrasion resistance to thin deposits from
hexavalent chromium plating solutions.
Since decorative applications of chromium may be optional for some parts,
those parts can also be engineered/designed to be functional in the absence
of the chromium deposit If the parts are molded from plastic, or formed/cast
from stainless steel, they may not need plating a.t all! to function and be
"decorative". The surface of the molded plastic part would be much softer
than a chromium plated part. The stainless steel part would also be softer
and would be far more expensive to produce than a part made from zinc and
nickel-chromium plated.
Most other metals commonly used for consumer items (zinc, aluminum,
carbon steel) require some form of protective coating, since those metals
corrode to an unpleasant and possibly un-functional condition upon
exposure to humidity, salt, water, and household chemical products.
Alternative finishes need to provide a pleasing appearance along with high
corrosion resistance and (sometimes) high abrasion resistance in order to
adequately replace a nickel-chromium electroplate!
Hexavalent chromium compounds are also utilized in conversion coatings
produced on aluminum, zinc, cadmium, magnesium, copper, copper alloy,
silver, and tin surfaces. There are a number of other metal finishing
operations that utilize solutions containing hexavalent chromium
compounds, including phosphating and passivation of certain stainless steel
alloys.
The surface of aluminum parts can be converted to an oxide coating in a
number of solutions, by making the part anodic (positively charged, direct
Page 55
-------
Section Five
current). When fatigue failure and corrosion by trapped anodizing solution
in crevices and faying surfaces is of concern, the anodizing solution is
formulated from chromic acid, a hexavalent chromium compound.
Some anodic coatings are further processed through a sealing operation
consisting of an aqueous solution of sodium dichromate, The sealing
operation further enhances fatigue resistance and "seals" the pores in the
coating to enhance the corrosion resistance.
Page 56
-------
Section Six
SECTION SIX
INFORMATION SOURCES
Trade Associations
The following is a list of trade, professional, and standard-setting organizations that provide technical and other
types of support to various segments of the metals finishing industry. Readers are invited to contact these trade
associations and request their assistance in identifying one or more companies that could provide the desired
technological capabilities.
Abrasive Engineering Society
108 Elliot Dr.
Butler, PA 16001
412/282-6210
American Chemical Society
(ACS)
11-55 16th St., N.W
Washington, DC 20036
202/872-4600
202/872-6067 FAX
American Institute of Chemical
Engineers (AIChE)
345 E. 47th St.
New York, NY 10017
212/705-7338
212/752-3297 FAX
American Society for Quality
Control (ASQC)
310 W. Wisconsin Ave.
Milwaukee, Wl 53203
414/272-8575
414/272-1734 FAX
American Zinc Association
1112-16th St., N.W, Ste. 240
Washington, DC 20036
202/835-0164
202/835-0155 FAX
Aluminum Anodizers Council
1000 N. Rand Rd, Ste. 214
Wauconda, IL 60084
708/526-2010
708/526-3993 FAX
American Electroplaters' and
Surface Finishers' Society
(AESF)
12644 Research Pkwy.
Orlando, FL 32826
407/281-6441
407/281-6446 FAX
American National Standards
Institute (ANSI)
11 West 42nd St., 13th Floor
New York, NY 10036
212/642-4900
212/398-0023 FAX
American Society for Testing
Materials (ASTM)
1916 Race St.
Philadelphia, PA 19103-1187
215/299-5400
215/977-9679 FAX
ASM International
Materials Park, OH 44073
216/338-5151
216/338-4634 FAX
Aluminum .Association
900 19th St., N.W,
Washington, DC 20005
202/862-5100
202 862-5164 FAX
American Galvanizers
Association
12200 E. Iliff Ave., Ste. 204
Aurora, CO 80014-1252
303/750-2900
303/750-2909 FAX
American Society for
Nondestructive Testing (ASNT)
1711 Arlington Lane
P.O. Box 28518
Columbus, OH 43228-0518
614/274-6003
800/222-2768
614/27^-6899 FAX
American Society of
Electroplated Plastics (ASEP)
1101 14th St., N.W, Ste. 1100
Washington, DC 20005
202/371-1323
202/371-1090 FAX
Associacio Brasileira De
Tratmetitos De Superficie
(ABTS)
Av. Paulista, 1313,9° Andar
Conj. 913 Cep 01311
Sao Paulo, SP Brazil
55112897501
55 11 251 25 88 FAX
Page 57
-------
Section Six
Association Francaise Des
Ingenieurs Et Technicians De
UElectrolyseEtDes
Traitements De Surface
SrueLeBua
Paris 75020 France
14 030 06 80
Cadmium Council Inc.
12110 Sunset Hills Rd, Ste. 110
Reston,VA 22090
703^709-1400
703/709-1402 FAX
Coated Abrasives
Manufacturers' Institute
1300SumnerAve.
Cleveland, OH 44115-2851
216/241-7333
216/241-0105 FAX
Electrochemical Society (ECS)
10 S. Main St.
Pennington,NJ 08534
609/737-1902
609/737-2743 FAX
Halogenated Solvents Industry
Alliance
2001LSt.,N.W.,Ste. 506
Washington, DC 20036
202/775-2790
202/223-7225 FAX
International Copper
Association Ltd.
260 Madison Ave.
New York, NY 10016
212/251-7240
212/251-7245 FAX
Australasian Institute of Metal
Finishing
Clunies Ross House
191 Royal Parade
Parkville, Victoria 3052 ,
Australia
613 347 2299
613 347 9162 FAX
Canadian Association of Metal
Finishers
14 Vintage Ln.
Thomhill, Ontario
L3T 1X6 Canada
416/731-4458
416/731-5884 FAX
Copper Development
Association Inc.
260 Madison Ave., 16th Fl.
New York, NY 10016
212/251-7200
212/251-7234 FAX
Gas Research Institute
8600 W. Bryn Mawr Ave.
Chicago, IL 60631
313/399-8100
312/399-8170 FAX
Institute for Interconnecting &
Packaging Electronic Circuits
(H'C)
7380 N. Lincoln Ave.,
• Lincolnwood, IL 60646
708/677-2850
708/677-9570 FAX
International Hard Anodizing
Association
14300 Meyers Rd.
Detroit, Ml 48227
313/834-5000
313/834-5422 FAX
Bumper Recycling Association
of North America (BRANA)
1730 N.Lynn St., Ste. 502
Arlington, VA 22209
703/525-1191
703/276-8196 FAX
Chemical Coaters Association
International (CCAI)
P.O. Box 54316
Cincinnati, OH 45254
513/624-6767
513/624-0601 FAX
Deutsche Gesellschaft fur
Galvano und Oberflach-
entechnike.V. (DGO)
Horionplalz 6, D-4000
Dusseldorf, Germany
211132381
Gold Institute
111216thSt.,N.W,Ste.240
Washington, DC 20036
202/835-0185
202/835-0155 FAX
Institute of Metal Finishing
(IMF)
Exeter House
48 Holloway Head, Birmingham
Bl INQ England
44 21622 73 87
44 21666 63 FAX
International Lead Zinc
Research (ILZR)
2525 Meridian Parkway
Research Triangle Park, NC
27709
919/361-4647
919/361-1957 FAX
Page 58
-------
Section Six
International Magnesium
Association
1303 Vincent PL, Ste. 1
McLean, VA 22101
703/442-8888
703/821-1824 FAX
International Thermal Spray
Association
12 Thompson Rd.
East Windsor, CT 06088
203/623-9901
203/623-4657 FAX
Mass Finishing Job Shops
Association
1859 Onion CneekRd.
Colville,WA 99114-9623
509/732-6191
509/732-6191 FAX
National Association of
Architectural Metal Manu-
facturers (NAAMM)
600 5. Federal St., Ste. 400
Chicago, IL 60605
312/922-6222
312/922-2734 FAX
Nickel Development Institute
214 King StW, Ste. 510
Toronto, Ontario
M5H 356 Canada
416/591-7999
416/591-7987 FAX
Society of Automotive
Engineers (SAE)
400 Commonweallh Dr.
Warrendale, PA 15096
412/772-7129
412/776-2103 FAX
International Precious Metals
Institute (IPMT)
4905 Tilghman St.
Allentown, PA 18104
215/395-9700
215/395-5855 FAX
Lead Industries Association Inc.
295 Madison Ave.
New York, NY 10017
212/578-4750
212/684-7714 FAX
Metal Finishing Association
Federation House
10 Vyse St.
Birmingham B18 6LT England
44 21 236 26 57
44 21236 39 21 FAX
National Association of
Corrosion Engineers (NACE)
1440 S. Creek Dr.
Houston, TX 77084-4906
713/492-0535
713/492-8254 FAX
Porcelain Enamel Institute
1101 Connecticut Ave. N.W.,
Ste. 700
Washington, DC 20036
202/857-1134
202/223-4579 FAX
Society of Manufacturing
Engineers (SME)
One SME Dr., P.O. Box 930
Dearborn, MI 48121
313/271-1500
313/271-2861 FAX
International Society for Hybrid
Microelectronics (ISHM)
P.O. Box 2698
Reston, VA 22090-2698
703/471-0066
800/232-4746
703/471-1937 FAX
Manufacturers Jewelers &
Silversmiths of America
100 India Street
Providence, Rl 02903
401/2743840
401/274-0265 FAX
Metal Finishing Suppliers'
Association (MFSA)
80 IN. CassAve.
Westmont, IL 60559
708/887-0797
708/887-0799 FAX
National Association of Metal
Finishers (NAMF)
401 N. ]Vfichigan Ave.
Chicago, IL 606114267
312/644-6610
312/321-6869 FAX
Society for the Advancement of
Material and. Process
Engineering (SAMPE)
1611 Parkins Dr.
Covina, CA 91724
818/331-0616
818/332-8929 FAX
•i
Society of Plastics Engineers
(SPE)
14FairfieldDr.
Brookfield, CT 06804-0403
203/775-0471
203/775-8490 FAX
Page 59
-------
Section Six
Society of Vacuum Coaters
(SVC)
440 Live Oak Loop
Albuquerque, NM 87122
505/298-7624
505/298-7942 FAX
Tin Information Center
1353 Perry St.
Columbus, OH 43201
614/424/6200
614/424-6924 FAX
Titanium Development
Association
4141 Arapahoe Ave., Ste. 100
Boulder, CO 80303
303/443-7515
303/443-4406 FAX
Page 60
•&U.S. GOVERNMENT PRINTING OFFICE: 1994 - 550-001/00200
-------
-------
-------
-------
o o m c:
5-033
S. i> £ !?
3000.
Ifflg
-— -« CD g>
§
.
=> CD
0> O
II
33 >
CD (Q
O) CD
CD 3
SJ J
o ^
I
0>
-o
-o 8
s S»
5-fiF
ID
>
O
cb
en
------- |