&EPA
United States
Environmental Protection
Agency
Capsule Report
Nickel Plating:
Industry Practices
Control Technology and
Environmental Management
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EPA/625/R-03/005
April 2003
Capsule Report
Nickel Plating: Industry Practices
Control Technologies and
Environmental Management
National Risk Management Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
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Notice
This document has been reviewed in accordance with the U.S. Environmental Protection Agency's peer
and administrative review policies and approved for publication. Mention of trade names or commercial
products does not constitute endorsement or recommendation for use.
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Foreword
The U.S. Environmental Protection Agency (EPA) is charged by Congress with protecting the Nation's land, air, and water
resources. Under a mandate of national environmental laws, the Agency strives to formulate and implement actions
leading to a compatible balance between human activities and the ability of natural systems to support and nurture life. To
meet this mandate, EPA's research program is providing data and technical support for solving environmental problems
today and building a science knowledge base necessary to manage our ecological resources wisely, understand how
pollutants affect our health, and prevent or reduce environmental risks in the future.
The National Risk Management Research Laboratory (NRMRL) is the Agency's center for investigation of technological
and management approaches for preventing and reducing risks from pollution that threaten human health and the
environment. The focus of the Laboratory's research program is on methods and their cost-effectiveness for prevention
and control of pollution to air, land, water, and subsurface resources; protection of water quality in public water systems;
remediation of contaminated sites, sediments and ground water; prevention and control of indoor air pollution; and restoration
of ecosystems. NRMRL collaborates with both public and private sector partners to foster technologies that reduce the
cost of compliance and to anticipate emerging problems. NRMRLs research provides solutions to environmental problems
by: developing and promoting technologies that protect and improve the environment; advancing scientific and engineering
information to support regulatory and policy decisions; and providing the technical support and information transfer to
ensure implementation of environmental regulations and strategies at the national, state, and community levels.
This publication has been produced as part of the Laboratory's strategic long-term research plan. It is published and made
available by EPA's Office of Research and Development to assist the user community and to link researchers with their
clients.
Hugh W. McKinnon, Director
National Risk Management Research Laboratory
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Preface
This capsule report provides an overview of the nickel plating emission and waste release issues within
the nickel plating industry. Emphasis will be placed on pollution prevention and control technology options.
It is the objective of this report to assist the metal finishing community and specifically, those involved with
nickel plating operations, with the management of environmental challenges that result from wastes that
are potentially generated by nickel plating. Both the electrodeposition and electroless deposition processes
for nickel plating have been profiled to examine resultant waste streams and potential releases.
Nickel plating practitioners are challenged with making a high-quality product that meets the needs of the
customer while being competitive within the market. Furthermore, nickel plating practitioners must deal
with environmental, regulatory, and technical requirements to protect human health and the environment.
This report serves as an advisory to nickel plating practitioners by providing technical information to
reduce environmental impacts and lower the liabilities associated with environmental releases.
IV
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Abstract
This capsule report, entitled "Nickel Plating: Industry Practices, Control Technologies, and Environmental
Management," was prepared under the direction of EPA's Office of Research and Development (ORD) to
assist the metal finishing community with the management of nickel plating environmental issues. Information
provided by this capsule report provides the rationale for developing the document, identifies the intended
user audience, and presents the framework for evaluating nickel plating management practices from case
studies that incorporate cost-effective solutions to solving persistent nickel plating problems.The capsule
report provides a current analysis of the nickel plating industry from a technical, economic, and regulatory
perspective.
This capsule report is organized into six chapters including recommendations.
• Chapter 1 provides an introduction and scope of the issue.
• Chapter 2 presents a profile of the nickel plating industry, including an overview of both the nickel
electro-deposition process and electroless nickel deposition process. Nickel plating is accomplished
by using a variety of chemical reagents in a rectified-direct current (electroplating) or via a chemical
reducing agent with no rectified current (electroless plating). Decorative and other engineered coatings
define the type of additives and formulations required by the plating practitioner. These formulations
and additives are included in this overview.
• Chapter 3 concentrates on the potential environmental releases from conventional operations within
the nickel plating industry. While some of these practices vary among authorized regulatory offices,
most apply to the nickel plating industry within the United States. Air emissions, wastewater releases,
and toxic and hazardous waste management issues are discussed in the context of worker safety and
environmental impacts.
• Chapter 4 addresses economic, technological, and regulatory factors.
• Chapter 5 applies pollution prevention and control technology options to environmental release issues.
• Chapters presents conclusions and recommendations, which include:
- Economically achievable pollution prevention and control technology options;
- Environmental compliance consistency;
- Continued research and development needs for reducing waste generation through process changes,
material substitution, water use reduction, metals recovery/recycle and bath life extension;
- Government-industry partnerships involving trade associations and professional organizations to
consider solutions to environmental problems;
- Long-term research and development planning by the industry to identify what is needed years from
now to enable companies to remain sustainable and competitive within a changing global economy.
Major Recommendations
This capsule report includes five major recommendations. The first recommendation is for facilities to
continue the conduct of environmental audits and pollution prevention opportunity assessments. These
tools have been very successful in assisting nickel-plating practitioners to identify where P2 and
environmental compliance can be accomplished. These tools help to establish baselines to provide for a
systematic approach for environmental decision-making. The second recommendation is to embrace
environmental management techniques and approaches that encourage a more comprehensive life-cycle
assessment; pollution prevention; environmental management systems that incorporate ISO 14000; and
environmental cost accounting, such as activity based costing. The third recommendation is to improve
production and reduce environmental impacts through enhanced technology transfer by government,
industry, academia, and trade associations. Several nickel-plating practitioner needs can be met with
technical and management information transferthrough case studies, reports, workshops, journal articles,
meetings, and newsletters. The fourth recommendation builds on the first three recommendations and
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calls for a continuation and enhancement of the existing EPA-lndustry partnerships for out-year planning
by promoting more competition in the global market while reducing environmental impacts and improving
productivity. The fifth recommendation is for government and industry to develop more efficient plating
solutions that utilize lower concentrations of nickel and produce lower levels of air emissions and other
releases. These five recommendations encourage the nickel-plating industry to use existing environmental
management tools and technologies, improve upon their environmental management and technology
base, seek competitive cost-effective environmental solutions using compliance through pollution prevention
approaches, and conduct joint government-industry research and development that targets specific industry
environmental issues.
VI
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Contents
Foreword iii
Preface iv
Abstract v
Major Recommendations v
Acknowledgments ix
1. Introduction 1
1.1 Objective 1
1.2 Scope 1
2. Nickel Plating Industry Profile 2
2.1 Industry Overview 2
2.2 Nickel Electrodeposition Processes 4
2.3 Electroless Nickel Deposition Process 7
3. Potential Environmental Releases from Production 12
3.1 Wastewater 12
3.2 Air Emissions 13
3.3 Toxic and Hazardous Wastes 13
3.4 Workerand Environmental Impacts 14
4. Economic, Technological, and Regulatory Factors that Influence the Resolution of
Nickel-related, Environmental Problems 15
4.1 Economic Factors 15
4.2 Federal, State, and Local Regulatory Factors 15
5. Integrating Best Management Practices and Control Technologies 17
5.1 Recovery, Recycle and Extended Bath Life 17
5.2 Surface Preparation of Substrate 20
5.3 Process Changes 22
5.4 Waste Reduction through Process Simulation 23
5.5 Life Cycle and Sustainability Considerations 23
5.6 Integrated Pollution Prevention/Control Technology Case Studies 23
5.7 Wastewater Pretreatment Options 25
5.7.1 Chemical Precipitation 25
5.7.2 Carbon Adsorption 25
5.8 Wastewater Control Technology 26
5.9 Air Emissions Control Technology 26
6. Conclusions and Recommendations 27
7. References 29
VII
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Figures
Figure 2.1 Metal finishing process flow diagram 3
Figure 2.2 Comparing electroplated to electroless nickel 7
Figure 5.1 Ion exchange flow diagram 19
Figure 5.2 Typical reverse osmosis system 20
Figure 5.3 Closed loop process flow diagram for bath life extension 21
Tables
Table 2.1 Constituent and Operating Conditions of Typical Nickel Plating Solutions 5
Table 2.2 Plating Problems and Potential Causes 6
Table 2.3 Typical Properties of Electroformed Nickel 6
Table 2.4 Typical Electroless Nickel Solution Constituents and Operating Parameters 8
Table 3.1 Metal Finishing Industry Waste Characteristics 12
Table 5.1 Comparison of Coating Performance of Conventionally Produced Panels
to Picklex®-Produced Panels 22
VIM
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Acknowledgments
This capsule report was developed for the U.S. Environmental Protection Agency (EPA), Sustainable
Technology Division in Cincinnati, Ohio, under Contract No. 68D70002, \Afork Assignment No. 3-06. David
Ferguson, Office of Research and Development (ORD), National Risk Management Research Laboratory
(NRMRL), Multimedia Technology Branch, coordinated the preparation of this report, and is the co-author
with Frank Altmayer, President of Scientific Control Laboratories, Inc., of Chicago, Illinois. Doug Grosse,
ORD, NRMRL, Technology Transfer Branch, coordinated and provided technical document review.
This publication is the result of the collaboration of many people within the metal finishing community. The
principal authors are Frank Altmayer of SCL, Inc., and David Ferguson of the EPA. James Bridges, Dean
High,Todd Lesousky, and Randy Patrick of Pacific Environmental Services (PES), Inc., provided technical
consultation, document production, and graphics support in the preparation of this document.
The cover design was created by John McCready, EPA,ORD, NRMRL, Technical Information Branch.
Photos are the courtesy of Leonhardt Plating Co., Cincinnati, Ohio. Electronic publishing and format
review were completed by Carol Legg, EPA,ORD, NRMRL, Technical Information Branch.
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1. Introduction
1.1 Objective
The purpose of this capsule report is to inform the metal
finishing community, stakeholders and decision makers,
including both industry and regulatory communities, about
the management of nickel plating environmental issues by
providing technical information and practical examples of
cost-effective, environmentally acceptable practices. The
capsule report's review of the nickel plating industry provides
an understanding of nickel plating uses, processes and
chemistry used by metal finishers. Metal finishers have the
opportunity to compare and contrast their own operation
and maintenance, source reduction, control technologies
and equipment with those presented in this capsule report.
Assessments of demonstrated performance for innovative
practices along with the regulatory and economic drivers
impacting the nickel plating industry are evaluated.
1.2 Scope
The updated National Metal Finishing Environmental R&D
Plan (EPA600/R-00/035) dated March 2000, identified nickel
plating emissions as one of the upcoming environmental
issues requiring additional research and development within
the metal finishing community. The U.S. Environmental
Protection Agency (EPA), working with stakeholders from
the private and public sectors, determined that producing
this capsule report will assist the metal finishing community
by identifying and evaluating releases from nickel plating
operations (both electrodeposited and electroless). The
scope of this capsule report includes a profile of the nickel
plating industry; pollution prevention and control technology
options; and economic, technological and regulatory
influences within the nickel plating industry. This capsule
report includes a description of the nickel plating industry,
current nickel plating management practices, and alternative
approaches for waste reducation and control technologies.
In addition, research opportunities are described which have
the potential to meet the regulatory and economic demands
for environmentally sound technology.
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2. Nickel Plating Industry Profile
2.1 Industry Overview
The nickel plating industry is part of the larger metal finishing
community in the United States. It consists of job shops
(independently owned plating businesses) and captive shops
(metal finishing operations contained in larger manufacturing
facilities).There are over 3,000 U.S. job shops that average
fewer than 50 employees each with annual sales of,
approximately, $5 million. Captive shops that support larger
manufacturing facilities can vary in size depending on their
role within the company. The metal finishing industry is
regulated for environmental protection and occupational
health and safety due to the nature of the processes and
materials required to satisfy industrial and public consumer
demand. Nearly all manufactured products require some
type of surface finishing. Consumers demand products that
have aesthetic appeal, will not deteriorate, and have
durability. The nickel plating industry provides a product that
improves appearance, slows or prevents corrosion, and
increases strength and resistance to wear for manufactured
parts and products.1
Most of the nickel plating industry is located in or near major
metropolitan areas and may generate air emissions, water
discharges, and solid wastes that add to overall pollution
concerns. Pollution abatement costs and expenditures for
the metal finishing industry comprise nearly 20% of its
budget. Industry representatives are working together with
government, trade associations, and professional
organizations to encourage technological advances that lead
to more efficient, cleaner production while reducing waste
generation and control costs.12
Nickel plating is most commonly applied through the
utilization of aqueous chemical reagents by means of
electroplating or via chemical reducing agent that is referred
to as electroless plating. Typical constituents of nickel
electroplating solutions include nickel sulfate (or nickel
sulfamate), nickel chloride, and boric acid, along with
inorganic or organic additives that modify the crystal
structure of the deposit. While a variety of formulations for
nickel plating exists, the Watts, Woods, and Sulfamate
processes comprise the majority of the formulations used
by the metal finishing industry. Figure 2.1 depicts a typical
metal finishing process.23
The types of additives used in nickel plating formulations
tend to be categorized by product specificity: decorative or
engineered coatings. Decorative nickel plating solutions
contain brightening additives that refine the grain structure
of the deposit and additives that modify the surface defects
of base parts.The latter additives are called leveling agents.
Engineered nickel plating formulations also tend to contain
additives for reducing stress, modifying hardness, or
modifying the ductility of the deposit.4
Additives may modify the nucleation and growth of crystals,
as they are formed on the cathode (part).They also correct
surface imperfections partially insulating regions that are
plating at faster rates. Additives account for the variation in
desired surface appearances ranging from dull to satin-like,
semi-bright, or full mirror bright. In many cases, the finish
requires no further polishing or buffing.5
Decorative Nickel Plating
When nickel is plated for aesthetic reasons, it is termed
"decorative" nickel plating. Decorative nickel finishes may
range from 2.5 to 50 microns of one or more layers of
electroplated nickel. In almost all decorative nickel plating
applications the nickel deposit is followed by the application
of a thin (0.1-0.5 microns) layer of chromium to enhance
the longterm appearance and abrasion resistance of the
finish. Decorative nickel plating is applied by electroplating
versus electroless plating technique. There are some
decorative nickel plating processes that yield a metal deposit
that is bright black or pearlescent in appearance. These
finishes are commonly used on components that match the
black color of surrounding surfaces or on parts that must be
non-reflective, such as antennae and camera parts.Typical
decorative nickel plating applications include consumer
products, such as toaster housings, automotive trim, writing
instruments, door hardware, shelving, lighting fixtures, and
appliance trim, such as handles and knobs.1
Engineered Nickel Plating
When the appearance of nickel is secondary to other
properties, such as low stress, high corrosion resistance,
modified magnetic property or increased wear resistance,
the deposited nickel is termed "engineered" nickel plating.
Engineered nickel plating is typically produced using either
electroplating or electroless plating methods, depending on
the desired property of the deposit. Typical engineered nickel
plating applications include computer connectors, oil drilling
components, valve components for highly corrosive liquids,
specialized cutting saws, disks in computer hard drives,
printing rolls, filtration screens, and mold production for
plastic injection molding. Nickel plating can also be used to
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Workpiece
Vapors/Mist
(To Exhaust
Scurhbers)
Process
Chemicals
Process
Bath
Spent Bath
Spent Metal Waste
Figure 2.1. Metal finishing process flow diagram.
Workpiece _
Chemical Drag-out
Workpiece
to Next Step
Rinse
System
Wastewater
Fresh Water
salvage improperly machined parts that would be costly to
scrap. Engineered nickel deposits are often used as an
underlayment for other metals. For example, gold, silver,
palladium, palladium-nickel, platinum, or rhodium plating is
applied over an underlayment of nickel that is
electrodeposited for the enhancement of corrosion
resistance, prevention of base metal diffusion into the
precious metal, enhanced appearance of the deposited
precious metal on the exterior surface, ductility of the
component, or reduced stress (porosity) of the component.6
Another form of engineered nickel electrodeposition is
electroforming.Electroforming is the deposition of a relatively
heavy thickness of metal over a disposable or re-usable
mandrel. The mandrel is separated from the nickel deposit,
thus, leaving the product. Economics often prohibit the
manufacture of electroformed products by other fabrication
methods. Such electroformed products include seamless
belts, compact disk (CD) stampers, mesh products for
batteries, filtration screens, printing screens, porous
electrodes, and molds for the production of a wide variety of
products, including interior plastic panels of automobiles,
automobile dashboards, reflector tail-lights and optical
lenses.6
Electroless Nickel Plating
Nickel coatings are also applied by electroless techniques.
Electroless plating was discovered in 1944 as a chemical
coating process that operates without electricity. The initial
nickel deposit is itself catalytic to the chemical reduction
process, with the deposition of nickel continuing until the
operator terminates the process. The terms "autocatalytic"
or "self-catalyzing" often refer to electroless nickel plating.
This process is applicable for conditions where uniform
thickness is critical; a nonconductor is being plated to prevent
electromagnetic interference; the material being coated has
low porosity and deposition in recesses is required.7
Electroless plating provides hardness, wear resistance and
corrosion resistance while maintaining solderability, a
diffusion barrier and the manipulation of magnetic properties.
The manipulation of magnetic properties is especially
important in computer hard drive manufacturing, since
electroless nickel can be plated with no magnetism or with
partial (controlled) magnetism. Similarly, the control of
magnetism plays a critical role in the re-manufacturing of
developer rolls which are a component of most recycle grade
printing cartridges in laser printers and copiers. Electroless
plating utilizes reducing agents to supply the electrons that
convert dissolved nickel ions back to nickel metal.The type
of reducing agent determines the type of nickel alloy
deposited by the process. For example, the use of sodium
hypophosphite (the most commonly used reducing agent
for electroless nickel plating) will produce a nickel alloy
containing approximately 2 to15% phosphorus. If dimethyl
amine borane is used as the reducing agent, the nickel
deposited is an alloy of nickel and boron, containing
approximately 0.6 to 5% boron. Other electroless plating
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process reducing agents for nickel include borohydride
compounds and hydrazine.17
Advantages of electroless nickel (EN) over electroplated
nickel include higher corrosion resistance, a very uniform
thickness overthe most complicated shapes, high as-plated
hardness, very high hardness after a heat treatment
procedure, high solderability and bondability, and control over
magnetic properties. Disadvantages of EN, compared with
electrodeposited nickel plating, include much higher cost (5
to 6 times as expensive to apply), a slower deposition rate
(0.25 to 0.5 microns an hour versus 10 to 400 microns an
hour, depending on formulation and agitation levels) and a
shorter bath life (months versus years). EN requires a higher
bath temperature (95°C versus 21 °C to 65°C) which may
produce more brittle deposits. EN also requires better
chemical control. As a rule, EN should not be considered a
substitute for electrodeposited nickel plating; rather, should
be used where the unique deposit characteristics or process
capabilities are an advantage in functional and engineering
applications.7
Other Nickel Plating Techniques
Nickel coatings can also be produced by techniques other
than electroplating or electroless plating including chemical
vapor deposition (CVD), physical vapor deposition (PVD),
high velocity oxygen fuels spraying (HVOF) and by plasma
spray methods, along with other vacuum technologies.7
2.2 Nickel Electrodeposition Processes
Electrodeposition or electroplating of nickel usually takes
place in a tank containing water and at least one salt of the
metal to be deposited.This metal salt (nickel) is dissolved in
the water producing ions. Nickel ions are positively charged;
whereby, each atom of metal loses two electrons, as the
salt is dissolved into the water. While nickel solution is
typically emerald green, the deposited nickel will be silver
or gray on the electroplated object. The nickel ions are free
to move about in the solution. The positive charge attracts
the nickel ions to the negatively charged cathode or the part
to be plated.The excess electrons on the negatively charged
part return to the outer orbit of the nickel ions producing
neutrally charged nickel metal atoms at the surface of the
part to be plated. This is the basic process of electroplating.
Typically, the electroplating solution also contains hydrogen
ions, as the pH of the solution approaches 4.These hydrogen
ions, also, are reduced to hydrogen gas, thus, reducing the
efficiency of the process from 100 to, approximately, 90 -
95%.1
The pH of the plating solution is an important control
parameter, since it can affect the appearance, efficiency,
and physical properties of the deposit. In general, lower pH
values produce more ductile deposits, while reducing the
efficiency of the process. Each process has an optimum
operating pH range. There are a number of nickel
electrodepostion processes in use today. The following
sections describe some of the more common processes
and solutions.
Watts Nickel Electroplating Process
The basic constituents for a Watts nickel plating solution
include: nickel sulfate (26 to 35 oz/gal, or 195 to 262 g/L) as
the primary source of nickel ions, nickel chloride (6 to 12
oz/gal or 45 to 90 g/L) as a secondary source of nickel ions
and for improved anode corrosion, boric acid (5 to 6.5 oz/
gal or 37.5 to 49 g/L) to stabilize the pH of the solution and
water. Boric acid also enhances the "whiteness" of deposit
and enhances the performance of the leveling agent. Nickel
sulfate and nickel chloride are nonvolatile, highly conductive
and soluble in water.1
Addition agents are added for hardness, leveling, anti-pitting,
and/or brightness. Solutions for decorative plating differwith
the types of addition agents employed to produce surfaces
that are bright, semi-bright, or satin. Addition agents for
brightening may be organic or inorganic. Trace amounts of
cadmium, for example, may be added to the Watts
formulation for producing a deposit of semi-bright to bright
appearance (without leveling). Addition agents for leveling
or anti-pitting are organic chemical compounds.1
In Watts decorative nickel plating processes, there are two
distinct classes of brighteners. Class I brighteners are
distinguished by the presence of an unsaturated carbon
bond and a sulfon group. Class I brighteners are mirror bright
when initially introduced and gradually become semi-bright
as the deposit thickens on the object. Examples of Class I
brighteners are benzene disulfonic acid, benzene trisulfonic
acid, naphthalene trisulfonic acid and benzene sulfonamides.
These brighteners infuse sulfur into the deposit. The added
sulfur causes the deposit to be less noble or more active
than pure nickel deposits or nickel brightened without sulfur.
The downside of adding these brighteners are a reduced
resistance to corrosion and embrittlement. However, when
combined in a two or more layer system, the less noble
nickel can provide galvanic corrosion protection to a more
noble layer of nickel (usually a semi-bright deposit containing
no sulfur); thereby dramatically increasing the overall
corrosion resistance of the nickel layer. Such two layer nickel
deposits are referred to in the industry as "duplex" nickel
plating. Such multiple layers are applied to parts used on
exterior automotive and marine applications, where high
resistance to salt corrosion is necessary.1
Class II brighteners are sulfur free, cationic organics with
unsaturated carbon bonds in either long chain (aliphatic) or
ring (aromatic) structures. These brighteners add a small
amount of carbon into the deposit and have a milder effect
(semi-bright) on the nickel deposit when used alone.
Examples of Class II brighteners are formaldehyde,
coumarin, ethylene cyanohydrin and butynediol. High
concentrations of Class II brighteners can yield highly
stressed deposits. Therefore, it is important to balance the
concentrations for low internal stressed, fully bright, ductile
deposits. Class II brighteners also act as leveling agents to
provide relatively smooth surfaces.This results in a product
that requires less end polishing and buffing.1
Leveling agents function in a similar mannerto brighteners,
but are much more aggressive to ensure surface perfection
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without peaks and valleys. The leveling agents (organic
compounds) are incorporated at a higher rate during the
peak of surface imperfections (moderately higher current
density areas); thereby, insulating the peaks slightly and
redirecting the current into the valleys. The valleys then
receive a greater amount of current than the peaks and the
overall deposit tends to be level.1
The broadest range of operating conditions for the Watts
nickel plating solution is a temperature range of 21 °C to 65°C,
a pH range between 1.5 and 4.5, a current density range
from 300 to 700 A/dm2 and air and/or mechanical agitation.
For specific applications, these conditions are controlled to
within more narrow windows of operation. Typically, the Watts
nickel plating solution is about 95% cathode current efficient.
The remaining 5% of the cathode current generally produces
hydrogen gas bubbles and causes the pH of the solution to
rise as the solution is spent. Some Watts bright nickel
solutions are available in "high speed" versions that contain
high concentrations of nickel salts, higher operating
temperatures and greater agitation.1
The Watts nickel plating solution may be operated without
addition agents, in which case a "dull," highly ductile deposit
is produced. Such a deposit can be used in both decorative
and engineered applications. High concentrations of any
organic additives in a Watts or sulfamate nickel plating
solution cause a dramatic increase in tensile orcompressive
(depending on the additive) stress in the nickel deposit.1
Sulfamate Nickel Plating Process
Electrodeposition of nickel for applications in the electronic
industry require more ductility and a lower level of porosity
than what is typically obtained from a Watts formulation.The
sulfamate nickel process is used to obtain such properties.
The sulfamate solution increases the process cost, as nickel
sulfamate is significantly more expensive than the sulfate
salt, but the sulfamate process offers lower internal stress,
higher purity, higher ductility, and a lower level of porosity.1
The sulfamate nickel plating process utilizes nickel sulfamate,
boric acid and in many applications, a small amount of either
nickel chloride, nickel bromide or magnesium chloride to
enhance anode corrosion and promote conductivity.These
halogen compounds increase tensile stress which is then
controlled by the addition of a small amount of stress-
reducing compound. An example of a common stress
reducing compound is saccharin.1 The primary function of
chloride, in both the Watts and sulfate nickel formulation, is
to improve anode corrosion, especially in solutions using
non-sulfurized anode materials. Magnesium chloride may
be used as an alternate source of nickel chloride for nickel
sulfamate plating solutions.The magnesium chloride has a
lesser tendency of increasing tensile stress in the nickel
deposit.1 Control of stress in nickel plating is extremely
important in electroforming operations, as high tensile or
compressive stresses tend to deform the electroformed part
resulting in poor replication of the mandrel. Ideally, the nickel
should have zero stress, which can be obtained using proper
operational controls or a combination of operational controls
and the use of stress modifying agents.1
Another common additive to sulfamate nickel plating
solutions is a wetting agent to reduce the pitting tendency.
Wetting agents lower the surface tension of the plating
solution to a range of 30 to 40 dynes/cm, reducing the
tendency of hydrogen gas bubbles to remain on the surface
of the part. These bubbles, eventually, will burst and produce
a pit on the plated part. Wetting agents are typically organic
soaps.1 Nickel sulfamate is non-volatile, highly conductive
and soluble in water. It is more soluble than nickel sulfate
and breaks down at the anode to form a beneficial, stress-
reducing compound. On the other hand, when using such
solutions without chlorides there is a tendency to create
anode polarization that will lead to unstable pH and result in
a decrease of nickel concentration in the solution.1 Boric
acid is an inexpensive pH buffer and tends to stabilize the
pH in the cathode film of all nickel plating solutions. Boric
acid has a limited solubility of about 7 oz/gal (52 g/L) at
65°C. To avoid roughness from boric acid crystals, the
crystals should not be added directly to the solution.
Additions should be made by hanging an anode bag
containing the crystals in the solution until they are
dissolved.1
General Operational Information for
Nickel Plating
Table 2.1 lists constituent and operating conditions of typical
nickel plating solutions.
Anodes/Anode Baskets
Anodes, bagging, and anode baskets are important parts
of the nickel plating process. In a well-operated nickel plating
process, anodes replace the nickel ions at about the same
rate as nickel ions are converted backto metal at the cathode.
There is a variety of anode materials available for nickel
plating. For high pH applications, nickel oxide or carbon
Table 2.1 Constituent and Operating Conditions of
Typical Nickel Plating Solutions1
Constituent and
Conditions
Nickel sulfate,
NiS04*7H20
Nickel chloride,
NiCI2*6H20
Nickel sulfamate,
Ni(NH2S03)2
Boric Acid, H3BO3
PH
Temperature
Current density,
A/m2 (A/ft2)
Plating Solutions
Watts
300 g/L
(40 oz/gal)
60 g/L
(8 oz/gal)
7.5 g/L
(5 oz/gal)
3.0-4.0
20°C to 60°C
430 (40)
Sulfamate
400 g/L
(60 oz/gal)
30 g/L
(4 oz/gal)
4.5
30°C to 60°C
430 (40)
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depolarized anodes function well. In Watts bright nickel
applications, sulfurized anode materials are most commonly
used. In most applications, bagging is either recommended
or required to prevent particle roughness. The purpose of
the bag is to filter residues that are created as the nickel
metal dissolves. Such residues consist of metallic
compounds and non-metallic impurities. Anode bags should
be durable, fit tightly, be correctly sized, and be made of
appropriate woven cotton, cotton flannel, Dynel®orDacron®
material. Double bagging in specialized applications is also
employed. Bags should be periodically inspected, emptied
of residuals and washed clean before reuse.1
Anode baskets are used to provide a higher economy and
to maintain a constant anode current density, since a full
basket will always have the same current density for a given
rectifier setting. Baskets should be kept full to prevent etching
of the titanium and be placed in a mannerforthetopsofthe
baskets to be above the solution level to prevent residues
from inside the bags from entering the plating solution.This
allows for easy inspection and material replacement.
Titanium baskets are preferred except in rarely used
fluoborate-based nickel plating solutions.1
Solution Agitation
Agitation (mixing) of the plating solution is necessary to
maintain optimum placement of the nickel deposit, prevent
anode/cathode polarization effects and improve coverage.
Inadequate levels of agitation can result in dull, burnt, pitted,
and streaky deposits. The Watts solution may be agitated
using air or mechanical means, such as recirculating pump,
moving cathode rod, oreductorsystems. Airagitation is most
commonly used in decorative bright nickel plating. Forthose
processes requiring air agitation, 2 to 3 cfm/ft2 of tank surface
area is recommended. However, many installations have
successfully switched to the use of eductors to avoid the air
emissions that air agitation tends to produce. The sulfamate
solution is most commonly agitated via mechanical means.1
Filtration
Filtration of bright nickel plating solutions is important for
obtaining a deposit that is free from roughness and has an
optimum brightness appearance. Continuous filtration at 2
to 3 turnovers per hour is desirable to maintain the optimal
deposit appearance. The filter pore size should be between
10 to 15 microns. Sufficient filtration surface area (media)
should be installed to allow for adequate design operation
of the filter. Typical design specification for cartridge filters
is one 12" cartridge filter per 50 gallons of solution.1
Nickel Plating Problems
Plating problems caused by pitting, poor adhesion, brittle
deposits, and rough deposits can result in rejects. Rejects
due to defects in plating can be costly, since rejected parts
must be either replaced or stripped and re-plated; effectively,
generating two or more times the waste beyond normal
operation. While there are many factors contributing to poor
performance, Table 2.2 lists the more typical ones.1
Inorganic contaminants can affect the nickel plating solution
causing undesirable appearances (dark deposits in low
Table 2.2. Plating Problems and Potential Causes1
Problem
Pitting
Poor Adhesion
Brittle Deposits
Rough Deposits
Potential Cause
pH too low, inadequate agitation, current
density too high, low wetting agent content,
organic contamination, copper contamination,
poor surface preparation
Poor cleaning/rinsing, hexavalent chromium,
contaminated pickling acid.
pH too high, organic contamination, high
sodium content, high chloride content.
Calcium contamination, torn anode bag, poor
filtration.
current density areas), poor adhesion and roughness.
Purification processes, such as carbon treatment and low
current density dummying (plating at very low current density
onto scrap steel sheets) are used to remove common
metallic and inorganic contaminants, such as copper and
zinc.
Barrel Nickel Plating
Since nickel plating solutions typically exhibit poorthrowing
power in comparison to other metal plating solutions, the
process and plating solution formulation requires
adjustments for barrel plating.Typically, barrel nickel plating
solutions use the Watts formulation with higher
concentrations of nickel sulfate and nickel chloride.1
Electroforming
Nickel electroforming is generally performed by the sulfamate
process due to economical advantages, high plating speeds,
and low internal stress. The Watts nickel plating solution is
used for electroforming of rotary printing screens. The typical
properties of electroformed nickel are shown in Table 2.3.1
Table 2.3. Typical Properties of Electroformed Nickel1
Property
Tensile Strength
(MN/m2)
Tensile Strength (psig x
103)
Elongation (%)
Hardness (VHN100)
Internal Stress (MN/m2)
Internal Stress (psig x
103)
Watts
345-4485
50-70
15-25
1 30-200
125-1 85 tens.
18-27
Sulfamate
415-620
60-90
10-25
170-230
0-55 tens.
0-8
Note: 1 Mega Newton/m2 (MN/m2) = 1 N/mm2 = 1 Mpa =
145 Pounds/in2 (psi)
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Other Nickel Plating Solutions
There are numerous nickel plating solution formulations,
including all-chloride and fluoborate-based solutions, which
may be employed in high-speed plating. In addition, there
are black nickel process solutions used in decorative
applications, including two formulations that bear special
mention called "strike" solutions. A nickel strike solution is
typically a very thin (usually, less than 2.5 microns) deposit
that is designed to activate (activation is the term used for
any process that removes oxides from the surface of metals)
and, simultaneously, deposit a thin film of relatively pure
nickel that readily accepts the final deposit(s) without loss
of adhesion. Nickel strike solutions are commonly employed
in processing metal alloys that yield poor adhesion due to
the presence of a chemically resistant oxide film that quickly
re-forms upon exposure to air. Examples of such metal alloys
include most stainless steel alloys, Monel®, Kovar®, Invar®
and other nickel-iron alloys. Nickel strikes are also employed
when processing hardened steel and tool steel alloys. Two
formulations of nickel strikes commonly found in the nickel
plating industry are the Wood's process solution and the
Sulfamate strike.1
Wood's Nickel Strike
The Wood's formulation employs a solution that has only
three ingredients: water, nickel chloride (225 g/L) and
hydrochloric acid (5 to 8% volume). Typically employed
current densities range from 1000-3000 A/dm2.The solution
is intentionally formulated to produce a large volume of
hydrogen gas.The hydrogen gas chemically reduces oxides
present on the metal surface while depositing a thin film of
nickel.1 The Wood's nickel strike may contain as much as
8% by volume hydrochloric acid, producing fumes and mists
which must be removed from the exhaust by a scrubber.
The solution is very corrosive and tends to corrode metal
components that are near the tank; often corroding the
building itself.1
Sulfamate Nickel Strike
This solution also contains only three ingredients: water,
sulfamic acid (150 g/L) and nickel sulfamate (320 g/L). The
sulfamate process solution is favored overthe Wood's nickel
formulation since it eliminates hydrochloric acid, which
generates fumes that pose worker health issues during
make-up and control of the process, along with the corrosion
problems.The sulfamate process does produce solution mist
that should be scrubbed from the exhaust.1
2.3 Electroless Nickel Deposition
Process
Electroless plating occurs without applying electric current,
utilizing an oxidation-reduction chemical reaction instead
(see Figure 2.2 for comparison with electrodeposition).The
electrons are supplied by a chemical reducing agent (sodium
hypophosphite, amine boranes, or hydrazine) dissolved in
the plating solution.The deposited nickel acts as a catalyst
forthe continuation of the chemical reaction until the plating
process is terminated by an operator.7
Electrodeposition
Mr + 2e- (Rectifier)
Electroless
Ni++ + 2e~ (Reducing agent) •
Figure 2.2. Comparing electroplated to electroless nickel.
Sodium Hypophosphite Reducing
Agent
The hypophosphite ion is known to be catalytically oxidized
on the object's surface to release hydride ions which are
available for reduction of nickel ions at the surface. The
products of this reaction are the nickel-phosphorus deposit,
phosphite ions, hydrogen ions and hydrogen gas. The
phosphorus is co-deposited with nickel to the extent of 1%
to 15% by weight.7
Sodium Borohydride/Amineborane
Reducing Agents
Sodium borohydride and amineborane are two other
reducing agents used in electroless nickel plating. If either
borohydride or an amineborane is used as a reducing agent
in place of hypophosphite, boron is co-deposited with nickel
in the range of 0.2 to 6% by weight.1
Alkaline versus Acid EN Formulations
The two types of EN solutions currently in use are acid and
alkaline solutions. These solutions are described in the
following paragraphs and Table 2.4.
Acid EN-Phos Solutions
Acid solutions with pH ranging from 4 to 5.5, are the most
commonly used EN plating solutions. Acid solution can be
utilized to deliver a broad range of nickel phosphorus alloys
ranging from low-phosphorus alloys (typically 2 to 6% P) to
medium-phosphorus alloys (typically 6 to 9% P) to high-
phosphorus alloys (9 to 15% P).The high-phosphorus alloys
are typically utilized in applications where the deposit must
be non-magnetic or highly corrosion resistant. Low- and mid-
range alloys are more readily heat treated to yield exceptional
hardness and wear resistance that approaches that of
chromium (Vickers Hardness Number 800 compared to 1000
for chromium).8
Typical ingredients of acidic EN solutions are nickel sulfate,
sodium hypophosphite, complexing agents, buffers and
stabilizing agents.The pH range for EN acid solutions should
be carefully controlled since the deposition rates below a
-------
Table 2.4 Typical Electroless Nickel Solution Constituents and Operating Parameters8
Electroless Bath
Acid Nickel
Alkaline Nickel
Temperature
77-93°C
(1 70-200°F)
26-95°C
(79-205°F)
PH
4.4-5.2
(for medium to
high P)
6.0-6.5
(for low P)
8.5-14
Deposition Rate
12.7-25.4
micrometers/hr
(0.25-0.7 mils/hr)
10-12.7
micrometers/hr
(0.25-0.5 mils/hr)
Metal Salts
Nickel sulfate
Nickel chloride
Nickel sulfate
Nickel chloride
Reducing Agents
Sodium
hypophosphite
Sodium
borohydride
Dimethylamine
borane (DMAS)
Sodium
borohydride
Sodium
hypophosphite
DMAB
Hydrazine
pH of 4 are too slow, and above 5.5 can cause the formation
of insoluble nickel compounds which can lead to
spontaneous decomposition of the solution.This occurence
can be extremely dangerous with large amounts of heat
and gas generated in a burst of energy, causing hot process
solution to be ejected from the tank. Precipitated nickel
compounds can also cause rough deposits.8
In an acidic EN plating process, the phosphorus content
decreases with an increasing pH.The phosphorus content
may also be affected by the temperature of the EN solution,
the concentration of the sodium hypophosphite and other
EN solution additives. The major change in phosphorus,
typically, comes from an increase or decrease in the pH or
chelate/additive(s) concentration and this change can affect
deposit properties. A decrease in pH will cause an increase
in phosphorus content resulting in changes in properties
that may decrease ferro-magnetism and decrease tensile
strength while, simultaneously, increasing wear resistance
and corrosion resistance. Manipulation of the pH to change
the phosphorus content in the deposit is typically not done.
Rather, solutions are formulated to deliverthe desired alloy
composition when operated within carefully controlled pH
windows.8
Alkaline EN-Phos Solutions
EN alkaline solutions yield nickel deposits with 3% to 7%
phosphorus. Alkaline EN solutions typically operate within
thepH range of 8to 10.ThepH is maintained by the addition
of ammonium hydroxide (NH4OH). However, there are a
number of alkaline EN solutions that do not use ammonium
hydroxide to control the pH.8
In the alkaline EN plating process the nickel deposition rate
and phosphorus content is not significantly affected by the
operating pH of the solution. Instead, the type and
concentration of chelate and additives present in the solution
determine the alloy composition when the process is
operated within a narrow pH range. A visual inspection of
the EN alkaline solution will indicate a need for adding
ammonium hydroxide when the solution changes color from
blue to green. The phosphorus content of the alloy is
controlled by the concentration of the reducing agent.8
Operating Temperatures of EN
Solutions
One of the most important factors affecting the nickel
deposition rate for EN hypophosphite solutions is
temperature. Alkaline EN processes are typically used for
obtaining conductive nickel films over nonconductors such
as plastics, since the process can be operated at relatively
low temperatures versus acidic EN processes. The alkaline
process can be operated at temperatures as low as 86°F
(30°C) or as high as 185°F (85°C). The acidic process
typically operates in the temperature range of 180 to 190°F
(82 to 88°C) in orderto take advantage of higher deposition
rates. Low temperature alkaline EN plating solutions may
contain ammonium citrate, a nickel complexing agent, to
prevent precipitation of nickel hydroxide at the lower
operating temperature.7
There is a concern that the solution may decompose with
the formation of nickel-phosphorus particles, as the
temperature of the EN acid solution increases. It is preferable
to use indirect heating of the EN acid solution. Hot water or
steam in heat exchangers or jacketed tanks are the most
common indirect heating techniques. For smaller tanks (5
to 100 gallon), electric immersion heaters are frequently
used. A low nickel deposition rate and a decreased EN acid
solution life can occur when the EN acid solution is held at
the operating temperature. Low EN acid solution loading
can cause a high usage of the reducing agent. A minimum
EN acid solution loading of 0.6 dm2/L (0.25ft2/gal) is
recommended.7
EN Deposition Rates
The nickel deposition rate for EN hypophosphite solutions
are most effective when controlling the pH, temperature,
and the concentrations of nickel and hypophosphite. This
requires the operator to keep the concentrations, pH, and
temperature at optimum levels with periodic analysis and
monitoring of the solution.7
-------
The nickel deposition rate from EN acid solutions can be
substantially increased by the presence of organic additives,
such as hydroxyacetate, succinate, acetate, propionate,
malate and lactate.The functions of these organic additives
are to increase the nickel deposition rate, stabilize the pH,
and form complex Ni++ ions. For EN alkaline solutions, the
nickel deposition rate can be increased, the pH stabilized
and the ion complexes formed with organic additives such
as citrate and pyrophosphate.This is particularly important
for EN alkaline solutions that require replenishing for several
nickel turnovers due to an increase in the phosphite ion
concentration. The precipitation of nickel salts and/or the
introduction of other unwanted particles from the chemicals
or atmosphere may provide the necessary conditions for
catalytic deposition. This condition causes nickel fallout, and
these highly active surfaces will spontaneously decompose
resulting in deposit roughness. Filtration (continuous or
periodic) of the EN solution is required to remove these
suspended solids.The filtration requires a 1 to 5 micron filter
and a pump displacement that can produce 5 solution
turnovers in a one-hour period.7
Binary alloys of nickel and phosphorus or nickel and boron
comprise the best known electroless deposits. The number
of metals that can be deposited by electroless means is
rather limited. The incorporation of additional metal elements
into the electroless deposits can be an important means of
enlarging the range of chemical, mechanical, magnetic and
other properties attainable.7
Ternary (three elements) and quaternary (4 elements) alloys
of nickel deposited from electroless solutions offer some
unique properties and applications. Notably, Ni-Co-P
deposits of varying compositions can be produced from
similar alkaline ammoniacal solutions. Ni-Co-P alloys can
be utilized to enhance the corrosion protection of an EN
system in similar fashion to "Duplex Nickel" electroplating.
The outer layer of Ni-Co-P is galvanically more active and
provides cathodic protection of the layer underneath which,
typically, is a Ni-P alloy. In essence, the underlayer Ni-P
becomes the cathode in the galvanic cell formed between
the two layers of alloys, while the Ni-Co-P alloy becomes
the anode.7 Ni-W-P alloys can be employed in applications
where the coating is subjected to high temperatures, as the
melting temperature of the alloy is much higherthan Ni-P7
Ni-Mo-P and Ni-Mo-B alloys can be utilized to control
magnetic properties. For example Mallory found that Ni-Mo-
P alloys typically are no harder in the plated condition when
compared to Ni-P alloys, but are harder after heat treatment.
Ni-Mo-B alloys were about 10% harder in Vickers hardness
readings than similar alloys without molybdenum and also
were harder after heat treatment than binary nickel-
molybdenum alloys.7 Even a small amount (1%) of copper
can improve ductility, brightness, and corrosion resistance.
The deposits are virtually non-magnetic, even at elevated
temperatures, and may be utilized on computer memory
disks, as a corrosion resistant, non-magnetic under-coat
for the outer magnetic deposit.7
Ni-P-Cu-Sb is a quaternary alloy, used for superior
resistance in marine environments (salt resistance). Ni-P-B
is a compromise between the best features of each binary
alloy process. The deposit is harder and more wear resistant
than Ni-P, and more corrosion resistant than Ni-B. Ni-Fe-B
alloys can be used in applications requiring specific levels
of ferro-magnetism. Ni-Pd alloys can be utilized in electronic
applications where a uniform thickness over a very complex
shape is necessary and electroplating the alloy can not yield
the desired uniformity.7
EN Containing Particulate Matter
More recently, the incorporation of PTFE (Teflon®) into
electroless nickel deposits has become available. Most
applications employ coating thicknesses of approximately
0.25 to 0.5 mil, with a preferred underlayer of pure electroless
nickel for added corrosion resistance. Typical electroless
nickel-PTFE composite coatings incorporate PTFE in the
range of 25% by volume, with focus on deposits having 18
to 25 volume percent. Contrary to the inclusion of wear
resistant particles (e.g., silicon carbide and diamond),
electroless nickel-PTFE composite coatings appear to be
limited to particles of 1 jj,m or smaller.7
The mechanics of composite electroless plating are different
from prevailing practices for conventional electroless plating.
Finely divided, solid particulate material is added to and
dispersed throughout the electroless plating solution. The
dispersed particles are not filtered out. The dispersion of
the particulate matter results in a new surface area loading
in the range of 100,000 cm2/L, which is 800 times greater
than the plating load generally acceptable in electroless
nickel plating.7
Uniformly dispersing micron or sub-micron particles provides
enhanced wear, abrasion resistance and/or lubricity of the
surfaces of base substrates. The adoption of such a coating
can yield ways of conserving both energy and natural
resources. The use of a composite electroless coating also
offers the benefit of reduced solution handling and waste
treatment problems, as well as reduced reliance on strategic
materials (e.g., chromium) for wear applications.7
Particles are suspended and prevented from coagulating
by means of "Particulate Matter Stabilizers" (PMS); patent
numbers: 4,997,686 and 5,145,517. These materials
(combinations of wetting agents) impart a zeta potential to
the particles and prevent plating on the particles by
maintaining solution stability. Not all particles require these
PMS materials.7 While a wide variety of particulate matter
can be co-deposited with EN, at present, commercial
composite electroless plating activities have been limited to
natural and synthetic (polycrystalline) diamond, silicon
carbide, aluminum oxide, fluoropolymers (PTFE) and
fluorinated carbon.7 The above information regarding EN
containing particulate matter can be obtained by referencing
the AESF Electroless Deposition Course materials, AESF,
12644 Research Parkway, Orlando, Florida.7
-------
Addition Agents for EN Processes
Additions of trace quantities of certain catalytic agents
("poisons"), in a narrow concentration range, will stabilize
EN solutions against general solution decomposition. Most
EN solutions use stabilizers such as lead acetate, lead
sulfide, thiosulfate, thiourea, molybdicacid, and thiocyanate
in low concentrations of a minimum/maximum number of 1
mg/L for lead acetate and a minimum/maximum range of 1
mg/L to 10 mg/L for molybdic acid. As with the use of all
stabilizers and additives, only demineralized or preferably
deionized water should be used for make-up and
replenishment of EN solutions. Water containing impurities
can only shorten the life of the EN solution and may also
affect the appearance of the nickel deposition. It is best to
rinse parts in counterflowing deionized water to reduce
impurities before implementing any EN solution process.7
Surface Treatment Prior to EN Plating
Provided that there is a chemically clean surface, metals
that are spontaneously deposited with nickel, when
immersed in an EN solution, are nickel, cobalt, iron,
aluminum (usually processed through a zincate treatment
prior to plating to enhance adhesion), zinc, titanium,
beryllium, and palladium. Plastics, ceramics, and silver
require catalytic activation and copper and copper alloys
may require galvanic initiation, ora thin nickel electrodeposit
(strike). Metals such as lead, cadmium, antimony, and
bismuth are normally incapable of direct EN deposition since
they are catalytic poisons. These metals can be EN
deposited by first applying a copper or nickel electrodeposit.7
Some typical activation procedures for surface treatment of
metals include the application of momentary cathodic
current, the application of palladium film, and the immersion
of the part in reducer solution such as dimethylamineborane
(DMAB).7 Copper and silver can be plated directly in EN-
boron processes.
For nonconductors, typical activation procedures require
immersion in a collodial palladium suspension, followed by
immersion in an "accelerating solution" that is comprised
mostly of hydrochloric acid. This is known as the "two-step"
process for activating plastics. A single-step process consists
of immersing suitably cleaned and etched plastic in a single
solution containing tin/palladium complexes and colloids
stabilized by excess stannous chloride in a hydrochloric acid
solution.7
Production and Maintenance of EN
Solutions
EN plating solution formulations can be found in the literature.
Some companies produce their own solution from basic
ingredients, but most companies utilize commercially
available solutions. Commercial EN solutions are produced
by blending concentrates supplied by the company selling
the formulation. The concentrates typically contain nickel
salt, complexing agents and stabilizers, hypophosphite, and
a pH adjuster.
Work load dictates the frequency of chemical replenishment,
but some degradation occurs even if the solution is not
utilized. For this reason, tanks should only be as large as
the load, minimally, requires. A "turnover" occurs when the
maintenance addition of nickel salt is equal to the original
concentration. For example, if the solution is initially made
up with 28 g/L of nickel sulfate, as the nickel alloy is being
used in the EN process, a "turnover" occurs when the total
amount of nickel sulfate added to the process overtime is
28 g/L. After a number of turnovers, the contaminants
(primarily the orthphosphite byproduct of the chemical
reaction) are so concentrated that the solution no longer
delivers an adequate deposition rate and the solution is taken
out of service and replaced. The number of turnovers
obtained from an EN process before the solution is no longer
usable depends upon careful control of contaminants,
solution loading, chemical concentrations, temperatures, and
filtration.7
Equipment is available for the selective removal of
contaminants such as ortho-phosphite from the EN process.
This equipment is based upon "electrodialysis" principles.
In installations where this technology has been used, the
EN solution has lasted more than a year without degradation
of the process. Also, a commercially available formulation
(Everon TM) that selectively precipitates the orthophosphite
from the EN solution, yields 60 to 150 turnovers before the
solution requires replacement. Installations that do not use
either of these life prolonging technologies can experience
between 4 and 14 turnovers before the EN solution is no
longer suitable for production use.7
Treatment of Spent EN Solutions
The spent solution must be treated to reduce the nickel
concentration to an acceptable level before it can be
discharged. Electroless nickel plating solutions employ
chelating agents to keep nickel ion activity at a controlled
concentration. Once the plating solution becomes "spent,"
it must be treated to reduce the dissolved nickel below
regulated limits.
Treatment methods include autocatalytic decomposition
which employs the following:
1. The room temperature solution is loaded with a high
surface area substrate. Steel wool is a cheap, readily
available, high surface area substrate.
2. The solution temperature is slowly raised and the level
of gassing is monitored. As gassing subsides, the
temperature is further increased until the boiling point
is approached. No further increase in temperature
beyond the boiling point is feasible.
3. Additional reducing agent is added in small amounts
until further additions result in no further gassing. At
this point, the dissolved nickel concentration has been
reduced to a concentration of about 5 to 50 ppm.
4. The remaining dissolved nickel is precipitated using
starch xanthate, DTC (pH>11), sodium hydrosulfite,
or sodium borohydride. Bench testing in the laboratory
10
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is typically used to discoverthe most effective of these
agents for the solution.7
Electroless nickel bearing wastes can also be treated utilizing
displacement of the nickel with calcium added as the oxide.
The treatment is rather time consuming, but is effective on
a variety of wastes. Either lime (calcium hydroxide) or sodium
hydroxide can be used to raise the pH to 12, prior to
treatment with calcium oxide. Numerous other treatment
schemes can be found in the literature.7
EN Plating Equipment
The plating tanks are usually fabricated of polypropolene or
passivated stainless steel to resist reaction with nitric acid
which is used to strip off nickel that is typically deposited
onto the tank surfaces over time. Disposable plastic liners
(15 to 30 mil polyvinyl chloride) can be used in tanks which
add additional chemical resistance and ease of waste
disposal, as less nitric acid is required to remove unwanted
nickel deposits on the tank walls. Parts with blind holes must
be fixtured to allow the escape of hydrogen gas that would
otherwise be trapped on the surface during the plating
reaction. Plastic or plastic-coated racks will help to reduce
the waste of nickel. Small parts may be plated in a rotating
plastic basket. Another plating set-up includes suspending
the part to be plated with a wire or hook. Whatever method
is used for providing the fixture or set-up, good solution
agitation and work piece movement are recommended and
the plating solution chemicals should be kept at near
optimum operational conditions.7
Surface Preparation
Metal parts are prepared for EN plating in very much the
same manner as forall electroplating, and it is perhaps more
critical that the part be clean. Cleaning usually involves the
part being soaked in a hot alkaline cleaner. After a rinse, the
part is subjected to electroclean-anodic or periodic reverse,
and rinsed again. The next step typically is immersion in a
dilute acid solution (sulfuric acid, 10% by volume is
commonly employed) before the part is double or triple
rinsed. This cleaning process should render the part ready
for EN plating. Aluminum parts are typically processed
through soak clean, rinse, electroclean, rinse, zincate dip,
rinse, acid dip (nitric), rinse, zincate dip, and rinse prior to
EN plating. Proper pretreatment cycle for each type of metal
to be plated is critical for proper adhesion.9
Modifying EN Hardness
While EN plating provides a harder deposit than
electrodeposited nickel, the hardness of nickel-phosphorus
deposits can be further increased from a Vickers hardness
of about 500 kp/mm2 to about 800 to 1000 kp/mm2 with the
application of a heat treatment. The heat treatment requires
the part be heated to 400°C for an hour. Lower treatment
temperatures and longertimes can be used as well, but the
ultimate hardness obtained is lower than 800 kp/mm2. The
resulting hardness is comparable to that of electroplated
hard chromium. It is the crystallization of the nickel and the
formation of a nickel phosphide (Ni3P) precipitate in the
coating by the heat treatment that produces dispersion
hardening. In general, heat treatment of a non-magnetic,
high-phosphorous EN deposit will re-introduce magnetism
into the deposit.710
Nickel-boron EN deposits are harderthan nickel-phosphorus
EN coatings in both the plated condition (650 to 700 VHN
compared to 500 to 600 VHN) and after heat treatment (1000
to 1200 VHN compared to 800 to 1000 VHN). However, the
EN-boron alloy deposited is notably more porous and does
not offer the same combination of corrosion resistance and
hardness as the EN-phosphorus alloys.7
EN-Boron (NiB) plating can be accomplished with reducing
agents to produce plated parts requiring a greater hardness,
wear resistance, wire bondability and solderability. Such
parts are used for automotive and jet engine applications.
Other NiB applications are for printed circuits, electrical
contacts, and electronic components. Electroless NiB plating
is a good example of the use of EN plating to take advantage
of one or more of the unique characteristics: exceptional
deposit thickness, deposit uniformity, low porosity,
solderability (if the boron content is below 1%), ability to
deposit directly on copper, silver and nonconductors, and
particular chemical, mechanical, or magnetic properties of
the deposit.6'7
EN-B processes are also available in alkaline and acidic
formulations. The alkaline process typically utilizes sodium
borohydride as the reducing agent, at a pH ranging from 12
to 14 and at a temperature of 90 to 95°C (195 to 205T).The
boron in the deposited alloy typically is in the 5 to 6% range.
The acidic-neutral EN-B process typically utilizes dimethyl
amine borane (DMAB) as the reducing agent. These
processes operate at pH levels of 4.8 to 7.5 and at
temperatures of 150 to 170°F (65 to 77°C).The deposit boron
content ranges from 0.1 to 4%.7
11
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3. Potential Environmental Releases from Production
3.1 Wastewater
Industrial wastewater is generated in all phases of
electrodeposition and electroless nickel plating processes.
The pretreatmentofthe part or product to be treated requires
the use of solvent baths, alkaline cleaning baths, vapor
degreasing, pickling baths, and a variety of spray rinses and
rinse baths. The process requires cooling water, boilers,
steam condensates, rinse water, and wash water. There are
spent plating bath solutions and cleaning solutions that are
contaminated with reducing agents, nickel compounds,
acids, alkalines, complexing agents, buffers, stabilizers, rate
promoters, organic additives, and other chemicals
depending on the process (seeTable 3.1). Wastewaters are
commonly treated with NaOH to neutralize and precipitate
residual nickel.3
The primary source of wastewater is from rinsing operations.
Most of the waste contaminants result from drag-out from
plating baths where plating solution remains in blind holes,
seams or other crevices that remain on the part. This solution
becomes the primary source of rinse water contamination.
Therefore, when examining primary locations to decrease
drag-out, an attempt to quantify the drag-out rate should be
made. If a process utilizing a nickel plating tank has a single
flowing rinse immediately after the plating operation, a
theoretical equation that assumes ideal mixing can be used
to estimate the drag-out rate. This calculation is as follows:3
Table 3.1. Metal Finishing Industry Waste Characteristics3
Waste
Alkali (hydroxide)
Acid (nitric, sulfuric,
hydrochloric, hydrofluoric)
Surfactants
Oil and Grease
Nickel oxide, nickel
hydroxide, and traces of
cadmium, zinc, nickel,
copper, other metals
Perchloroethylene,
trichloroethylene, other
solvents
Cyanide
Chromium
Water
Waste Stream
Wastewater
Wastewater
Wastewater
Wastewater
Plating bath, drag out, rinse
water, spent filters, sludge
Spent solvent (liquid or
sludge), air emissions
Spent plating bath, drag
out, rinse water, other
wastewater
Plating bath, drag out, rinse
water, sludge, other
wastewater, mist
Rinse water, drag out,
process bath, air emission
(evaporation), cooling
water, boiler blowdown
Process
Cleaning, etching
Cleaning, pickling, etching, bright dipping
Cleaning
Cleaning
Plating
Cleaning
Plating, tumbling, stripping, heat treating,
desmutting
Plating, chromating, etching
Various
Potential Hazards
Corrosivity
Corrosivity
Aquatic Toxicity
Aquatic Toxicity
Toxicity
Toxicity
Toxicity
Toxicity
12
-------
= (vr
rtw*c
/c
pb
where,
V.
pb
volume drag-out
volume flow rate in the rinse
concentration of contaminant in the rinse
concentration of the contaminant in the
process tank
In cases where mixing is far from ideal or a single rinse is
not in use, drag-out must be estimated using other methods.
One such method is to convert the first rinse to a non-flowing
rinse and monitoring the buildup of nickel overtime; then,
back-calculating the volume of nickel solution required to
achieve such a buildup of nickel in the stagnant rinse.3
A survey of 318 plating shops in the United States revealed
that an average of 160,000 L/day of water is discharged
from a typical plating shop. With an estimated 3,500 job
shops in the U.S. consuming 160,000 L/day, the total water
discharged by job shops alone would be over 145 billion
liters per year. With an average water and sewer cost of
$0.01/L, this represents about $1.45 billion per year forthe
electroplating industry. Therefore, reducing water usage and
reducing wastewateris a major environmental and financial
issue.11
3.2 Air Emissions
Air emissions from nickel plating operations are generated
in the form of mists during the process due to the evolution
of hydrogen and oxygen gas and acidic fumes from highly
acidic processes such as the Wood's nickel strike. Hydrogen
gas bubbles are formed in the process tanks on the surface
of the submerged part or on anodes and/or cathodes. These
gas bubbles rise through the plating solution and "burst"
upon reaching the surface escaping into the air forming a
mist. There are a number of factors that determine the rate
of gassing, including the temperature of the solution, the
current densities in the plating tank, the solution composition,
solution pH, the surface area of the parts being processed,
and the surface tension of the plating solution. Air sparging
can also result in emissions from the bursting of air bubbles
at the surface of the plating tank liquid. Usually, nickel plating
baths (other than strikes) have high cathode efficiencies,
so the generation of mist in nickel plating is minimal. Other
air emissions, such as volatile organic compounds (VOCs),
may be generated in preparing the part for plating from
degreasing, solvent cleaning, and open containers of
solvents. There also may be emissions from exhaust
ventilation, spills or leaks, and, especially, from stripping of
rejects. The most commonly used stripping solutions are
either nitric acid or sulfuric acid (used with direct current).
Cyanide-based nickel stripping solutions may also be used.
These solutions have a high temperature and are without
current. Air emissions from cyanide-based stripping solutions
may include ammonia from decomposition of cyanide.12
In addition to the atmospheric releases, nickel plating
operations also pose a hazard to workers from inhalation of
fugitive emissions. Emission factors for nickel electroplating
from the process tank are 0.63 grains/A-hr without a wet
scrubber or 6.7 x 10 ~6 grains/dscf. Worker exposure results
from the release of airborne aerosols containing soluble
nickel compounds, hydrochloric acid if a Wood's nickel strike
is utilized orsulfamicacid if a sulfamic acid strike is utilized.
Exposure can be reduced by adequate ventilation in the
work place and/or the use of respirators.12
Air emissions to the atmosphere from nickel plating
processes are becoming increasingly regulated in California
and may become regulated in a number of other states. The
nickel plating industry is faced with many legislative
regulations, and federal, state, regional, and local
environmental guidelines. The emission limits vary from
jurisdiction to jurisdiction, and it is the responsibility of the
plating shop ownerto determine which emission standards
are applicable. Consequently, many platers are unaware of
their compliance responsibilities. Government inspectors
from the various jurisdictions will help sort out the applicable
air emission regulatory requirements. Fortunately for nickel
platers, air emissions from nickel plating shops appear to
be a minor environmental concern to many regulatory
agencies.12
Nickel, as an air emission, has gained a lot of attention in
recent years. California has declared all nickel compounds
to be toxic air contaminants and considered carcinogenic.
Therefore, in California, all watersoluble nickel compounds
are listed as inhalable carcinogens and will be regulated
accordingly. There is controversy regarding the decision to
declare nickel and nickel compounds as carcinogenic. This
topic will be discussed in greater detail in the next section
regarding regulatory issues.12
3.3 Toxic and Hazardous Wastes
Most toxic and hazardous wastes are generated during the
cleaning part of the process. More specifically, surfactants
are used to remove oil and grease from spent EN solution,
nickel plating solution is contaminated beyond beneficial
reuse, and sludge that contains metals is formed as a result
of wastewater treatment. Absorbents, filters, filter cakes, still
bottoms, contaminated solvent, carbon, wipe rags, aisle
grates, and abrasives are generated solid wastes that are
potentially hazardous. Under the Resource Conversation
and Recovery Act (RCRA) (Code of Federal Regulations
[CFR], 40 CFR 261.21-261.24), the two types of hazardous
wastes are listed and characteristic waste. Although nickel
plating wastes are not included as listed RCRA wastes,
(except for F006 waste generated from wastewatertreatment
systems), some may be characteristic hazardous wastes.13
Wastes that exhibit toxic characteristics defined by the
presence of metal ions and other organic compounds, which
are eventually placed in a landfill, would likely leach
hazardous concentrations of these toxic constituents into
the environment. These constituents are subject to the
Toxicity Characteristic Leaching Procedure (TCLP). The
TCLP extracts the toxic constituents from a waste in a
13
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manner that simulates the leaching action which occurs
within a landfill.TheTCLP is ERA'S regulatory leachatetest.
Wastes must pass the leachate test before disposal in a
Class D landfill. Wastes that fail the TCLP must be handled
and discarded in a hazardous waste landfill to restrict
leaching into groundwater or surrounding soils. Generally,
tank residues from the nickel plating processes have to be
transported off-site fortreatment and disposal because they
are typically defined as characteristic hazardous wastes.13
3.4 Worker and Environmental Impacts
There are many soluble nickel compounds that pose adverse
human health and environmental impacts in the nickel plating
industry. Such compounds include nickel chloride, nickel
nitrate (produced in stripping of nickel in nitric acid), nickel
sulfamate, nickel carbonate (used in pH adjustment), and
nickel sulfate. Nickel chloride (CAS No. 7718-54-9) is an
odorless, monoclinic, green crystalline compound. Nickel
chloride (CI2Ni • 6H2O) is soluble in water, alcohol, and
ammonium hydroxide, and insoluble in ammonia. The
anhydrous compound is not used in the electroplating
industry. Nickel nitrate (CAS No. 13138-45-9) is an odorless,
green, deliquescent powder or crystalline substance,
commonly found in the hexahydrate form. Nickel nitrate (N2O6
• Ni 6H2O) is soluble in water, alcohol, and ammonium
hydroxide. Nickel sulfamate, H4N2NiO6S2, (CAS 13770-89-
3) is an odorless, green crystalline compound, that is most
often purchased by a plater in dissolved (in water) form.
Nickel carbonate, CNiO3, (CAS 3333-67-3) is an odorless,
pale green dusty powder that is only moderately soluble in
water but is commonly added to acidic nickel plating solutions
to raise the pH. Nickel sulfate (CAS No. 7786-81-4) is an
odorless, crystalline substance that commonly occurs in the
form of hexahydrate orheptahydrate crystals.The anhydrous
material is a yellow to green color, hexahydrate appears as
blue to pale-green, and the heptahydrate is green. Nickel
sulfate (NiSO4) is soluble in water in any form. The hexa-
and heptahydrous forms are also soluble in alcohol, while
anhydrous NiSO4 is insoluble in alcohol, acetone, and ether.14
The current Occupational Safety and Health Administration
(OSHA) permissible exposure limit (PEL) for soluble nickel
compounds is 1 milligram per cubic meter (mg/m3) of air as
an 8-hour, time-weighted average (TWA) concentration.This
PEL is referenced in 29 CFR 1910.1000, Table Z-1. The
exposure to soluble nickel compounds can occur through
inhalation, ingestion, and eyeorskin contact. Although nickel
compounds are not absorbed in sufficient concentration
through the skin to cause systemic toxicity, they are capable
of inducing contact dermatitis in sensitized individuals. Nickel
is also, relatively, non-toxic by ingestion. Positive findings in
many epidemiology studies attest to the potential human
carcinogenicity of nickel compounds. The American
Conference of Governmental Industrial Hygienists (ACGIH)
has assigned nickel a low threshold limit value (TLV) because
nickel compounds have been identified as suspected
carcinogens. Although there is a current debate about the
possibility of all nickel compounds being carcinogenic, the
general consensus in the industry is that there is no elevated
cancer risk when airborne levels are below the OSHA PEL.
EPA considers only nickel refinery dust, nickel subsulfide,
and nickel carbonyl to be carcinogenic. The California Air
Resources Board (GARB) in 1990 listed all nickel
compounds as toxic air contaminants under the state's "hot
spots" law. Therefore, soluble nickel is considered to be
carcinogenic. In animals, nickel is toxic to the kidneys,
cardiovascular, respiratory, and reproductive systems. In
humans, soluble nickel compounds can affect the
cardiovascular system, kidneys, and central nervous
system.15
Prevention and control methods for worker exposure include
process enclosure, local exhaust ventilation, general dilution
ventilation, elimination of airagitation system (often replaced
with eductor systems), and personal protective equipment.
Plating company owners whose employees are exposed to
soluble nickel compounds are required to implement medical
surveillance procedures.These procedures include medical
screening, replacement medical evaluation, periodic medical
evaluation, biological monitoring and termination medical
evaluation. Special precautions should be taken for personal
hygiene, workplace monitoring and measurement, storage
of soluble nickel compounds, and leaks or spills.
EPA requirements for emergency planning, reportable
quantities of hazardous releases, community right-to-know,
and hazardous waste management can change overtime.
At the time of this writing, soluble nickel compounds were
not subject to EPA emergency planning requirements under
Title III of SARA in 42 United States Code (USC) 11022.14
The reportable quantity for soluble nickel compounds is 100
pounds. If an amount equal to or greater than 100 pounds
of soluble nickel is released within a 24-hour period in a
mannerthat exposes persons outside of the facility, owners
are required to immediately notify the National Response
Center (800-424-8802) in accordance with 40 CFR 302.6.
In the event of any release (spilling, leaking, pumping,
pouring, emitting, emptying, discharging, injecting, escaping,
leaching, dumping, or disposing) into the environment,
owners must notify the proper federal, state and local
authorities, as required in 40 CFR 355.40.14 Nickel and nickel
compounds are on the Community-Right-To-Know List and
are subject to Toxic Release Inventory reporting to EPA.
Nickel and its compounds are also on the TSCA Inventory
list.14
14
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4. Economic, Technological, and Regulatory Factors that Influence the
Resolution of Nickel-related Environmental Problems
4.1 Economic Factors
There are a number of economic factors to consider
regarding nickel plating, pollution prevention, and control
technology forthe nickel plating industry.These factors may
differ from one facility to another but, in general, include the
level of government intervention, the size of the individual
companies, and the opportunities for reducing raw material
costs.
Government intervention usually occurs as regulations and
policies are enacted which govern the way industry
manufactures goods. Such factors include environmental
rules and regulations, labor policies and regulations,
transportation laws, local energy policies, and local
community resource systems, such as water and sewage.
Often, consideration of these factors determines the final
profit of the firm. According to Department of Commerce
estimates, over a fifth of a metal finishing company budget
is for pollution abatement and compliance requirements.2
The nickel plating industry in the United States is comprised
primarily of small businesses who strive to be competitive.
Nickel plating shops are not highly capitalized and cannot
afford to make major changes in processes unless the capital
payback is short-term. Investment in capital-intensive
projects for environmental compliance can compete with
those for improving profits. It is, therefore, necessary to
assure that profitability is compatible with environmental
improvement projects in both the short- and longterm. One
area for consideration is capital improvement projects that
reduce costs for pollution abatement and waste treatment
through recycling, resource recovery, and pollution
prevention.
The loss of raw materials associated with process operations
can result in five distinct cost items that need to be
considered in an economic evaluation targeted for reducing
environmental impacts:2
Replacement of raw material
Removal of product from the waste stream before
release
Disposal of unwanted materials from the waste stream
Replacement of water
Processing the wastewater
These same cost items are applicable to waste reduction,
recycle, and reuse opportunities. By eliminating the
discharge of process wastewaters by closing the loop, metal
finishers can eliminate the administrative costs and risks of
non-compliance, while reducing production costs and
enhancing public relations. Striving for efficiency and quality
will reduce the reject rate and related costs. It is reported
that electroplaters lose about 5% of production because of
rejects due primarily to improper process control.2
4.2 Federal, State, and Local
Regulatory Factors
The metal finishing industry is regulated under several
federal environmental laws:
• The Clean Water Act (CWA)
The Clean Air Act (CAA)
Resource Conservation and Recovery Act (RCRA)
Toxic Substances Control Act (TSCA)
Superfund Amendments and Reauthorization Act
(SARA)
Emergency Planning and Community Right-to Know
Act (EPCRA)
Comprehensive Emergency Response, Com-
pensation, and Liability Act (CERCLA or Superfund)16
In addition, the metal finishing industry must comply with
federal, state, and local regulations for occupational safety
and health, and transportation. Regulatory factors impact
technology choices and economic decisions that can provide
solutions to reducing wastes.
Water Discharges
Wastewaters from nickel plating operations are generally
discharged to the sewer provided that the effluent meets
the established categorical discharge limits (40 CFR part
433.13 regulates nickel at 3.98 mg/L daily maximum and
15
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2.38 mg/L monthly average). EPA has established national
"effluent guidelines" for the metal finishing industry.17
EPA regulations require permits of operators who discharge
directly to surface waters. This also includes water quality-
based limitations for all pollutants at concentration levels
that cause, have a reasonable potential to cause, or
contribute to an excursion above any state water quality
standard. Nickel plating operations that discharge directly
to a public sanitary sewer system do not require a National
Pollutant Discharge Elimination System (NPDES) permit but
are often required to obtain a surcharge permit from the
local publically owned treatment works (POTW).17
Most plating operations are regulated underthe Clean Water
Act pretreatment program. Underthe pretreatment program,
limitations are imposed on industrial users of a POTW
through a permit or agreement issued by the POTW. The
pretreatment regulations are found in Title 40 of the CFR,
Part 403. Nickel wastewaters are commonly treated with
sodium hydroxide, magnesium hydroxide, lime, or
combinations of these alkaline compounds to neutralize and
precipitate residual nickel concentrations to meet the
compliance limits. These wastewaters typically come from
acid pickling, stripping, cleaning and rinsing processes. Other
liquid wastes contain spent plating bath solutions (RCRA
F007, F008, F009) and sludges that contain metals (RCRA
F006). These wastes are commonly shipped off-site for
treatment, recycle, or disposal. A reduction of wastewater
through process changes, recycle, and/or on-site treatment
and reuse, is a target for the nickel industry.
Pretreatment requirements are enforceable by EPA, state,
and local pretreatment POTW authority.13
Air Discharges
Air emissions from nickel plating operations, typically, include
VOCs in the few cases where solvent degreasing is
performed or open containers of solvents are used. Other
sources are acid/alkali mists, particulates and vapors emitted
from process and plating baths, exhaust ventilation, spills,
and leaks.
Emissions to the atmosphere from stacks and other
ventilating systems are becoming increasingly regulated on
a local basis (California). It appears doubtful that air
emissions from nickel plating shops pose any significant
environmental impacts; however, controversy exists
concerning health risks and nickel emission impacts.12These
health impacts are currently under review.
Control of nickel emissions from nickel plating tanks may
include a mist eliminator or a scrubber. The cost of controls
to meet any air emission compliance requirements for nickel
tanks could impact competitiveness. The controversy first
raised in California, is the designation of soluble nickel as a
carcinogen.The California Air Resources Board (GARB) in
1990 listed all nickel compounds as toxic air contaminants
underthe state's "hot spots" law. Currently, no other state or
the federal EPA has declared soluble nickel to be a
carcinogen. The National Association of Metal Finishers
(NAMF) and the Metal Finishers Association of Southern
California (MFASC) have partnered with EPA and Health
Canada to perform a new risk assessment on soluble nickel
salts. The MFASC is hopeful that the designation of soluble
nickel compounds as a carcinogen will be reviewed in
California.15
Solid Wastes
The major concerns governing nickel plating solid waste
are related to industrial wastewater treatment sludges that
contain nickel, along with other heavy metals resulting from
electroplating operations (such as, copper, chromium, iron,
and lead).18 As previously mentioned, not all RCRA wastes
are listed wastes. Some are characteristic wastes by
definition in the RCRA Code, with the responsibility for
identifying the hazard being imposed upon the generator.
These wastes are accumulated in drums or specially
designed tank or roll-off boxes to be collected at appropriate
time intervals by recyclers and/or public or private disposal
operations. Characteristic waste must meet regulatory
leachate tests (TCI_P SPLP) before final disposal in a landfill.
If the solid waste fails the TCLP, the waste is restricted from
disposal in a municipal waste landfill. Many platers prefer
having others collect and dispose of their solid and
hazardous wastes.18
While most nickel-containing wastes are not RCRA listed
wastes, they are included on the "California List" of metal-
containing wastes that were prohibited from land disposal
at specified concentrations by the 1984 RCRA Amendments.
It is, therefore, necessary to treat aqueous nickel wastes by
chemical precipitation to convert the toxic constituents into
an insoluble form. There are a few metal plating shops that
are located near a centralized waste treatment facility for
metals recovery and treatment.18
Metal finishing facilities that generate small quantities of
RCRA hazardous waste can reduce or eliminate many
regulatory requirements, waste handling expenses and other
liabilities by implementing low-cost waste reduction
alternatives. While the federal regulations institute baseline
requirements, compliance also requires adherence to
additional state requirements. In some instances, state
requirements can be more stringent than federal laws.
Wastes from most facilities in the nickel plating industry are
regulated underthe CAA, CWA, and RCRA.TSCA, SARA,
EPCRA, and CERCLA are much less likely to affect the
nickel plating industry if the facility is in compliance with the
CAA, CWA, and RCRA. It is important to recognize the
applicability of these federal environmental regulations for
wastes being generated at a specific facility and understand
the options and alternatives for compliance. Most federal
environmental regulations are managed through state
regulatory agencies, with states implementing pollution
prevention (P2) regulatory integration programs. State P2
programs are evolving from technical assistance to
integration of P2 into state environmental activities, such as
enforcement, inspection, and rule-making.The next section
of this report addresses P2 options.18
16
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5. Integrating Best Management Practices and Control Technologies
Environmental solutions forthe nickel plating industry include
the reduction and control of wastes generated by the industry.
This waste reduction and control approach integrates the
concepts of pollution prevention and waste management
control technologies. The Pollution Prevention Act of 1990
reinforces EPA's "Environmental Management Options
Hierarchy" which assigns the highest priority to preventing
pollution through source reduction, reuse, and/or closed-
loop recycling. Pollution prevention focuses on product and
process changes that reduce the volume and toxicity of
production wastes and the reduction of end-product wastes
during the product lifecycle. When waste cannot be reduced
by pollution prevention methods, the preferred alternatives
are recovery/reuse/recycle of the process materials during
the lifecycle of the product. Where prevention and/or
recycling are not feasible, waste treatment followed by
authorized disposal is required to achieve environmental
compliance. "End-of-pipe" approaches were the earlier
methods for achieving environmental compliance, controlling
releases and environmental clean-up. These approaches
not only can be expensive, they often transferred pollution
from one media to another. Today's trend is to integrate the
best practices and technologies available to meet the goals
of industry and regulatory agencies.
This report presents pollution prevention and end-of-pipe
control technology options in addressing the environmental
issues affecting the nickel plating industry. This practical
approach allows the nickel plating community to determine
the best options for managing pollution. The nickel plating
industry uses numerous chemical processes. There are
technical, cost, and regulatory limitations to consider on a
process-by-process and facility-by-facility basis. While it is
important to recognize the differences and similarities of
waste management approaches, the desired outcome for
the individual nickel plater is to be competitive and compliant
while producing high quality products. In most cases, there
will be waste disposal concerns for the producer and
consumer. Therefore, all waste management options should
be considered in addressing the environmental issues of
the nickel plating industry.
5.1 Recovery, Recycle and Extended
Bath Life
The most common P2 option for nickel plating being
implemented today is reusing the drag-out rinsewater.This
involves using the tank water where the parts have been
rinsed (before the parts are rinsed in a flowing-water rinse),
to replace the process tank water lost through evaporation.
This reuse of drag-out rinsewater reduces chemical loss.
Other waste rinsewater P2 alternatives include:
Operate equipment to reduce drag-out;
Increase solution temperature;
Lower the concentration of plating bath constituents;
Use an air knife to reduce, drag-out from the process;
Reduce speed of product withdrawal to allow for
drainage time;
Use surfactants to lower solution surface tension;
Position part properly on rack for maximum drainage;
Use multiple rinse tanks in countercurrent series;
Use fog nozzles and sprays for rinsing simple work
pieces;
When still-rinsing, recycle rinsewater upstream (re-
use the water elsewhere upstream in the process line);
Use automatic flow instrumentation to control flow rate;
Reuse rinsewater when possible;
Increase rinsing efficiency by agitating rinse bath.3'18'19
P2 alternatives for work cleaning wastes are:
Reduce cleaning frequency when possible;
Design process and equipment to minimize surface
area of exposed process liquid;
Record cleaning costs as a separate item;
Convert from a batch process to a continuous process;
Maximize dedication of process equipment;
Avoid unnecessary clean-ups;
Operate equipment to inhibit fouling;
Minimize residue buildup during operation;
Minimize the amount of cleaning solution used;
Recycle cleaning solution by filtering solids from used
solution;
17
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Substitute cleaning system with a proprietary process
("Bio-Clean") that bio-degrades the oil, generating
almost no oily waste.35
P2 alternatives for waste treatment include:
Install a sludge dewatering system;
Improve operating practices;
Install a metal recovery system;
Segregate waste streams to facilitate treatment and
recovery of metals;
Use the most efficient precipitating agents;
Return spent process solutions such as strippers and
EN plating solutions to the manufacturer for
recycling.35
There are a variety of technologies that are used within the
nickel plating industry to separate plating chemicals from
rinsewaters, or to concentrate the chemicals for ease of
recycle/reuse. The six most commonly used technologies
are:
1. Electrowinning
2. Atmospheric Evaporation
3. Vacuum Evaporation
4. Ion Exchange
5. Reverse Osmosis
6. Electrodialysis
Electrowinning involves placing two electrodes (insoluble
anode and cathode) in a solution containing ions, where
there occurs a movement of ions toward the charged
electrodes. Dissolved metals in the electrolyte are reduced
and deposited on the cathode. The deposited metal is
removed by mechanical or chemical means and either
reused as anode material or sent off-site for processing or
disposal. Electrowinning is used to recover valuable common
metals for recovery/reuse or to reduce the amount of
inexpensive metals for treatment and disposal. This
technology is most often applied for gross metal recovery
from concentrated solutions. The combination of ion
exchange and electrowinning has a much higher potential
metal recovery efficiency than electrowinning from a drag-
out rinse. Nickel recovery using ion exchange is possible,
but it requires de-acidification of the regenerant and close
control of pH; thus, it is not commonly performed.3520
Electrowinning is inexpensive to operate and not labor-
intensive. Energy costs comprise only a small part of the
total operating costs. The system utilizes an inert anode that
is very costly to replace, if damaged. The relative low cost
of nickel in today's market compared to the cost of recovery
should be considered in evaluating this technology for
recovery of nickel.3520
Atmospheric evaporation is used to concentrate liquid plating
wastes priorto treatment/storage/disposal.This technology
reduces the amount of waste and consequently lowers costs
for transportation, treatment, storage and disposal.
Atmospheric evaporation is the most widely used method
for chemical recovery in the plating industry. An evaporator
is a device that evaporates water to the atmosphere and
incorporates a pump for moving the solution, blowerto move
the air, heat source, mixing chamber for mixing the solution
and air and mist eliminator to remove any entrained liquid
from the exhaust air stream. The capital and operating costs
can be relatively low in some installations in arid climates.3520
Vacuum evaporation systems are relatively complex and
more expensive than the simpler atmospheric evaporation
systems. The vacuum evaporator is a distilling device that
vaporizes water at low temperature when placed under a
vacuum. Vacuum evaporators can be employed for
recovering nickel plating solutions, if foaming problems are
resolved. At least one supplier of vacuum evaporators has
resolved the foaming problem using thin film evaporative
methods. Vacuum evaporators consume high quantities of
energy, making the technology less competitive on an
operational cost basis.3520
Ion exchange is a chemical reaction recovery technology
that is especially applicable to dilute rinsewaters. It involves
exchange of the ions from a plating solution with similarly
charged ion attached to an immobile solid particle, such as
an ion exchange resin.The resins are typically contained in
vessels (columns), and the exchange occurs when the
solution is passed through these columns. A simple diagram
illustrating the use of the ion exchange method is presented
in Figure 5.1.3'5'20'21
Ion exchange is not practical for process solutions that are
more concentrated than the ion exchange regenerate;
therefore, this technology does not work well for
concentrated drag-out solutions. The capital and operating
costs can be relatively high for the benefits received from
nickel chemicals.21
Reverse osmosis (RO) is a membrane separation technique
applicable to dilute streams. RO is used primarily to separate
water from a feed stream containing inorganic ions. The
purity of the recovered water is relatively high and the water
is generally suitable for recycling. Osmosis occurs when a
semi-permeable membrane separates two solutions of
different dissolved-solids concentration. Pure water
(permeate) will flow through the membrane into the
concentrated solution, while rejected ions (brine) are retained
behind the membrane. RO occurs when pressure is applied
to the more concentrated solution to reverse the normal
osmotic flow, with the pure water forced through the semi-
permeable membrane into a less concentrated solution.The
purified stream that passes through the membrane is called
permeate; the concentrated stream retained by the
membrane is called concentrate. Chemical recovery by RO
is usually not practical for highly concentrated, oxidative
solutions, due to fouling. A RO system is relatively
inexpensive to construct and operate for the benefits
18
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,Drag-ln.
,Drag-Out_
..Drag-Out..
..Drag-Out.
Process
Bath
De-Acidification
via
Acid
Sorption
Rinse
Tank
1
Rinse
Tank
2
Selected Regenerates
Ion
Exchange
System
Purified Rinse Water (Low IDS)
Make-up
Water
Waste Acid
Regenerates
Wastewater
Treatment
Figure 5.1. Ion exchange flow diagram.
received from nickel recovery. Using a spiral wound cellulose
acetate membrane, a number of successful RO systems
are in operation for bright nickel, nickel sulfamate, and Watts
nickel plating baths. A typical RO application is shown in
Figure 5.2.3>16>20
After minimizing water use by rinsewater reduction or reuse
and metal recycling, the focus for P2 is on extended bath
life. An appropriate method to conserve water and conserve
chemicals while maintaining bath life is a closed-loop plating
bath recycling system. Figure 5.3 shows how a closed-loop
plating bath recycling system can be arranged to extend
bath life.3'16'20
Another method to extend nickel plating baths is to remove
contaminants, such as grease, oil, organic impurities from
proprietary additives, and unwanted metals from the nickel
baths. The most common treatment technologies used are
electrolytic treatment (dummying), batch metal precipitation,
and batch adsorption. Electrolytic treatment is particularly
effective forthe removal of copper, zinc, and excess organic
impurities. Metal precipitation at high pH is used for the
removal of impurities, such as aluminum and iron. Carbon
adsorption is an effective method for removing specific
organic contaminants from nickel plating baths. Plating bath
contamination occurs most commonly when parts fall into
the tank and from bare areas (areas not designed to be
plated, such as the inside of tubing) exposed to the solution
during the plating process.Therefore, it is importantto assure
that the parts are properly attached to the racks while in
process.3'20
Water used for evaporation loss can be a major source of
contaminants. Therefore, de-ionized water should be used
for solution make-up. Continuous or batch filtration through
activated carbon is recommended to eliminate
decomposition products and minor levels of oils and greases
that may be dragged into the baths. These purification
methods can be combined for greater contamination
removal. Removing contaminants to extend bath life can
reduce costs by reducing process chemicals, energy usage,
quantities of wastes fortreatment/disposal and the potential
19
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Surface
Evaporation
Drag-Out
Make-Up
Water
Second Rinse
Parts
Permeate Recycle
To Waste
Treatment
Concentrate Recycle
Figure 5.2. Typical reverse osmosis system.
for noncompliance. Plating bath solution maintenance has
become a greater priority to plating shops for extending bath
life and improving the operating efficiency and effectiveness
of a plating solution.320
5.2 Surface Preparation of Substrate
Surface finishing involves direct atom-to-atom bonding
between a basis material (such as steel, aluminum, brass,
or plastics) and a metal or organic surface top coating that
provides the desired material performance and/or
appearance properties. Multi-step surface preparation
processes remove oils, particulate materials, old coatings,
corrosion products, residual cutting fluids, brazing residuals,
smut, pickling acid residuals, cleaner residuals, etc. The
surface preparation process removes contaminants,
preserves the cleaned surface, and/or modifies the surface
for the next coating. It is common for surfaces to undergo
more than 10 finishing steps that include degreasing and
cleaning (for oil removal and descaling), etching, desmutting,
pickling, plating, and rinsing. These baths ultimately are
exhausted due to depletion of chemical reagents or buildup
of impurities and are a major waste stream.9
The volume of hazardous/toxic waste streams produced
from metal surface finishing operations is significant. Most
of these result from blowdown of the ventilation air scrubber
and from tank dumping. Therefore, reducing the number of
tanks (surface area) needed for production could significantly
20
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Work Flow
Product-
,Drag-Out
"I"
I
I
,Drag-Out
j Fresh
j JWater purified Water
Recycle
M.k.upni.t,no^lut,.n»
T ,,
Plating
Tank
-^ ••
^ V'
Rinse
Tank
••
^ TX
Rinse
Tank
«••
^ T r
Rinse
Tank
^-—^
Regenerated
Solution
Storage
Legend
Normal
Operation
Regeneration
Figure 5.3. Closed loop process flow diagram for bath life extension.
Ion
Exchange
Column
Filter Residual to
Waste Management
System
Regeneration
Acid Supply
reduce the amount of these wastes. Decreasing gas
evolution from the baths (e.g., the hydrogen gas formed
during acid pickling) also reduces wastes since bath gassing
causes mist formation. Lower operational temperatures also
reduce discharges by reducing impurities carried into the
process with make-up water.9
The elimination of surface processing steps is favored by
manufacturers to reduce processing costs, waste
production, and energy consumption. With this objective in
mind, International Chemical Products, Inc. (ICR Huntsville,
Alabama), has introduced Picklex®as a no-waste surface-
finishing agent designed to provide a nearly one-step metal
surface preparation operation for metal finishing operations.
In a study sponsored by EPA, Picklex® provided metal
surface cleaning, pickling, conversion coating, and priming
using a process simply consisting of degreasing, one dip-
step, one rinse, and final processing. Due to the large number
of surface-finishing operations, the potential forsizable waste
and cost reductions by using Picklex®is significant.Therefore,
EPA's National Risk Management Research Laboratory
(NRMRL) performed an assessment of the efficacy of
Picklex® in major polluting surface-finishing operations.22
Surface coatings on treated test panels were evaluated by
common techniques including: tape adhesion, salt fog
corrosion resistance, hardness, burnishing, bending, impact
adhesion, and microscopic examination. Most of these
evaluation procedures were standard tests performed in
accordance with ASTM practices. The test conditions, test
data, and detailed process descriptions are available in the
referenced report entitled, "Use of Picklex® as a Cost
Effective Metal Treatment."22
Conventional Treatments versus
Picklex®
Table 5.1 compares the test results for conventional to
Picklex® coatings on contaminated (oxidized) and non-
contaminated substrates. Although none of the processes
was optimized for maximum properties, the results indicate
that, in most cases, Picklex®-pretreated and/or conversion
coated panels, performed as well as or slightly better than
conventionally pretreated panels. However, Picklex® may not
be applicable to all systems. For example, it may not be
acceptable as a pretreatment for electroless nickel-coated
materials when bending of the parts occurs due to lack of
adhesion of the plate. Picklex® was not tested on the nickel
plating process. Individual testing of substrates should be
conducted prior to use. Picklex® appears to be a viable
alternative to conventional pretreatments for aluminum
substrates. Unlike conventional processes, steel and
aluminum can be treated with Picklex,® simultaneously.
Picklex® appears to offer an advantage overthe conventional
process with respect to top coat adhesion because it
21
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Table 5.1 . Comparison of Coating Performance of Conventionally Produced Panels to Picklex®-Produced Panels
Coating
Powder Top
coat on
Aluminum
Powder Top
Coat on Steel
Hard
Chromium
Electrolytic
Zinc on Steel
ENi on Steel
Alodine®
Tape Adhesion
Equivalent*"',
good on
contaminated and
noncontaminated-
surfaces
Equivalent*"',
good on
contaminated and
noncontaminated-
surfaces
Equivalent*"',
good on
contaminated and
noncontaminated-
surfaces
Contaminated,
conventional
failed
Contaminated,
Picklex® failed
NA
Bend
Equivalent*"',
passed, no
peeling/flaking
Equivalent*"',
passed, no
peeling/flaking
Equivalent*"',
passed, no
peeling/flaking
Equivalent*"',
passed, no
peeling/flaking
Equivalent*"',
passed, no
peeling/flaking
NA*b>
Burnishing
NA*b>
NA*b>
Equivalent*"',
passed
Picklex® failed
lifting, passed
blisters and
peeling
Both passed
blisters and
peeling; only
contaminated,
conventional
passed lifting
NA*b>
Impact Adhesion
Equivalent*"'
Conventional
slightly better
than Picklex®
Equivalent*"'
Picklex® much
better on
contaminated,
equivalent on
noncontaminated
Equivalent*"',
good
NA*b>
Hardness
NA*b>
NA*b>
Equivalent*"',
good on
contaminated and
noncontaminated
NA*b'
Equivalent*"',
good
NA*b>
Corrosion
Resistance
Equivalent*"'
Equivalent*"'
Conventional
slightly better
Equivalent*"',
marginal
Equivalent*"',
marginal
Equivalent** both
need CrCC for
excellent
performance
*"' Conventional and Picklex®-pretreated panels provided the same coating performance.
NA = Not applicable
provided equivalent mechanical strength with fewer steps
along with reducing waste production.22
EPA test results suggest that Picklex® can provide an
effective, one-step metal surface preparation operation for
many metal finishing operations. Hence, based on these
limited screening test results, Picklex® appears to effectively
avoid the production and use of certain hazardous/toxic
chemicals in surface finishing operations, such as pickling
acids, metal salt phosphatizing solutions, hot alkaline baths
and gas mists from electro-cleaning. It appears not to
exhaust readily, even when processing heavily corroded
surfaces.22
5.3 Process Changes
Changes can be made in the production process through
improved operation and maintenance procedures, material
substitutions, or changes in equipment that will reduce waste
generation. Operating the plating line more efficiently can
reduce waste generation and is usually inexpensive to
implement. Instituting standard operating procedures and
optimizing the use of raw materials can increase overall
efficiency. An evaluation of all current operating practices
will provide an opportunity to identify waste generating
activities. In many cases, simple operational changes can
reduce waste generation. Areas to target for waste reduction
may be identified by following the raw material flow from
receiving, through process, and as finished products leave
the facility through shipping and/or releases.23
A strict maintenance program that stresses corrective and
preventative maintenance can reduce waste generation
caused by equipment failure. Assuring that all employees
are properly trained for operating and maintaining equipment,
process materials and managing waste materials is key to
increasing efficiency. Well-written, practical guidance
manuals coupled with hands-on training and interaction
between employees and supervisors are necessary for
communicating this ongoing process.23
Material substitution is a more difficult means for reducing
waste generation because it may require product
reformulation with a less hazardous or non-hazardous
material, that may adversely impact quality. In the United
22
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States there is increasing pressure to make products that
contain less hazardous materials. This pressure is coming
from both regulatory agencies with more stringent
regulations on hazardous substances and wastes and from
consumers looking for safer, more environmentally friendly
products. Due to the proprietary nature of product
formulations, specific examples are limited. Examples
include using water-based cleaning systems instead of
solvent, and replacing chlorinated solvents with non-
chlorinated solvents. Adding more holes to a product or
designing product shape for better drainage or easier
shipping may also reduce waste and costs. Redesigning a
fixture to allow better escape of gases generated on the
plating surface may reduce the waste of plating chemicals.23
Modifying process equipment can be a very cost-effective
method for reducing waste generation within the nickel
plating industry. A number of technologies and equipment
have already been discussed in this section for recovery of
chemicals, recycling,and extended bath life. The
incorporation of such equipment will reduce waste and
improve operational efficiency. Improving parts draining
before and after cleaning and improving reactor design are
two examples of process modification.23
5.4 Waste Reduction through Process
Simulation
Process simulation is a general methodology for designing
or modifying processes to reduce their environmental
signature. In traditional manufacturing process design,
attention is focused primarily on minimizing cost while the
environmental impact of a process is often overlooked,
resulting in large quantities of generated waste materials.
By using process simulation techniques and models, it is
possible to modify a process to reduce the generation of
wastes and their environmental impact while reducing cost
resulting in a more "sustainable" process. Most decorative
nickel electroplating processes are similar in design and
operation. Technologies such as ion exchange, reverse
osmosis, and electrowinning are similar in design and
operation. A model of these technologies with the typical
electroplating process can be simulated to determine the
optimum technology to use for a specific operation. This is
true for determining operating modifications within a specific
nickel plating operation without actually expending capital
in a trial and error approach. Software products are available
for other industries, such as the chemical and
pharmaceutical industries to identify inputs and wastes
throughout the operation. The nickel plating industry should
consider the development of a computer-based tool to
facilitate user input of desired qualities and determine
environmental considerations along with process
optimization. The advantage of process simulation for nickel
platers is being able to consider optimization and waste
reduction options by using a model prior to any capital
expenditure for modification.
5.5 Life Cycle and Sustainability
Considerations
Environmental decision making is benefitted through life
cycle and sustainability considerations for a holistic approach
to envision environmental impacts beyond the facility gates.
While the major focus of environmental impacts occurs within
the manufacturing stage for nickel platers, life-cycle
assessment (LCA) utilizes a comprehensive approach by
analyzing the entire product life cycle. This approach is
comprised of four stages: 1) raw materials acquisition; 2)
manufacturing; 3) use/reuse/maintenance; and, 4) recycle/
waste management. LCA is a systematic method for
identifying, evaluating, and minimizing the environmental
consequences of resource usage and environmental
releases associated with a product, process, or package.
LCA evaluates the mass, energy inputs, and product outputs
for an industrial system in an effort to identify their possible
environmental significance. The life-cycle impact
assessment goes beyond the unit operation to encompass
a cradle-to-grave perspective. The purpose of using LCA is
to avoid shifting pollution from one media to another or from
one life cycle stage to another.18
LCA can benefit companies that want to strategically
evaluate their position on environmental impacts in reference
to the rest of the industry. The life cycle concept can be
employed for any product, process or design activity. LCA
can be used as a screening tool to help the user determine
if impacts occur outside the facility when an improvement is
made to the product or process inside the facility.There are
several methods, computer programs and models for
addressing environmental impacts using LCA principles.
These "tools" encourage more informed environmental
decision making and can be applied for cost-benefit analysis.
5.6 Integrated Pollution Prevention/
Control Technology Case Studies
Pollution prevention success case studies are increasing
with the nickel industry's increased environmental awareness
and pursuit of improved operational efficiency. Four case
studies are presented as examples of incorporating sound
cost effective pollution prevention techniques into nickel
plating operations.
Case Study 124
Poly Coatings of Sarasota, Florida, is a family business with
12 employees that specializes in electroless nickel, Poly-
Ond, and electrodeposited (sulfamate) nickel plating. Poly-
Ond is a teflon-impregnated electroless nickel plating
solution used in plastic molds for dry lubricity. The company
plates a variety of items for many industries, including firing
devices for missiles and airbags, molds for injection and
blow molding, wear components for sealing devices and
other small, high-value components. The company has
several established specialized areas of high-quality
electroless nickel plating applied in thicknesses ranging from
0.000050 to 0.005 of an inch. The bath chemistry that Poly
Coatings has used for more than a decade is Nitec 75, a
high-speed, mid-phosphorus product manufactured by
Heatbath Corporation of Springfield, Massachusetts.
23
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The company's success in pollution prevention is a result of
carefully choosing high quality raw materials and operating
the facility at peak efficiency. Mr. Bernie Zapatha, owner and
president of the company, supports environmental
excellence by reducing odors and waste, and treating waste
with effective control technologies. Two fume scrubbers
eliminate odors and particulate releases. Rinsewaters do
not leave the facility.The plating system is 100% closed loop;
therefore, the only wastes leaving the facility are solids which
are disposed of in 55-gallon drums. The objective of waste
reduction and careful waste management was to be exempt
from RCRA permitting.The facility owner used to plate with
other metals, however, decided to focus exclusively on nickel
plating by installing high-quality systems for Poly-Ond,
electroless nickel, and sulfamate nickel. The elimination of
chromates, flouridesand cyanides made the task of meeting
compliance much easier. Choosing vendors who provide
high-quality materials and making good housekeeping a
priority eliminated many of the operational problems
common to nickel plating. Maximum quality is maintained
along the plating line. As an example of operational quality,
the company seldom plates in the same tanks (manufactured
from sheets of polypropylene and free of interior welds) two
days in a row. At the end of each workday, workers filter and
pump the chemicals into an adjacent tank and clean the
tank that has been used for that day. The following morning,
a 50% nitric acid solution is used to passivate the tanks and
heaters and dissolve the contaminants. The nitric acid is
removed in about five hours, with the tank, again, ready for
service. This company has provided experienced, well-
trained, quality conscious employees who support the
concept environmental stewardship.
Case Study 225
Thomas Industries, located in Hopkinsville, Kentucky,
recycles 12,000 gallons of rinsewater per shift while
recovering nickel and brass from its plating operation. The
company's goals are to exceed all environmental, health
and safety regulations in orderto support its reputation as a
high-quality producer of a complete line of lighting products.
These products include chandeliers, wall sconces, flush
mounts, and flourescent, recessed and outdoor lighting. Of
special concern forThomas Industries in operating its plating
facility was managing heavy metals in the process stream.
The company chose Pollution Application Systems of
Hillsborough, North Carolina, to provide the necessary
equipment for recycling chemicals and rinsewaters. The
water reduction occurs through exponential dilution (extra
counterflow rinses), reducing water use up to 90%, while
improving the overall rinsing process. Once water needs
are reduced, plating baths are recovered using standard
atmospheric evaporation. Due to the low level of water
needed for the operation, the amount of evaporation is
decreased, reducing plating bath contamination. Energy
requirements for converting waterto steam are reduced due
to lower water use. After conventional solids removal, electro-
coagulation technology allows for the removal of an
additional 90% of the heavy metals.
Due to the high recovery of nickel and brass, the volume of
solid waste (after dewatering) has been reduced by 90%.
Dewatering is performed using a plate-and-frame filter press.
The company is preparing for the next step to recover and
recycle rinsewater from its parts washer and paint
pretreatment line. This systematic approach to P2 and
pollution control will reduce the facility's waste burden to a
very manageable level requiring periodic disposal of reduced
amounts of alkaline cleaners, spent acids and filtration
backwash from the brass and nickel process tanks. The
equipment installed on the plating machine required three
weeks to install and another month of adjustment to achieve
its present performance.
Case Study 326
C.J. Saporito Corporation (CJS), located in Cicero, Illinois,
offers a variety of metal finishing processes for electronic,
aircraft, and commercial applications. Electroless nickel
finishes are an integral part of the business CJS has built
achieving a reputation for quality and reliability. Training is
an important component of the CJS management approach
that expands the theoretical and practical knowledge base
in electroless nickel plating within the company's operation.
CJS currently offers semi-bright and bright mid-phosphorus
and teflon co-deposited electroless nickel finishes.
Production is carried out in tanks ranging from 180 to 500
gallons, designed to process a wide variety of configurations
and load sizes. CJS experienced the traditional waste
generation of electroless nickel plating which led to the
investigation of a new electroless nickel technology that
offers extended bath life and process stability by allowing
for the precipitation and removal of the undesirable
orthophosphite byproduct.
Using a 180 gallon tank, CJS began the regenerative
electroless nickel process plating a variety of base metals
in both rack and barrel modes. CJS obtained 10 to 12 metal
turnovers (MTO) of bath life from the regenerative electroless
nickel solution, as compared to 6 to 8 MTO from the
traditional electroless nickel solution.The bath performance
exceeded current specifications. After proving the
fundamental capability of the process. CJS scaled up the
process by adding a 500-gallon tank; with positive results.
CJS installed the equipment and put 680 gallons of the
regenerative electroless process into production. The
contents (200 gallons) from the 500-gallon tank were
combined with the entire 180-gallon tank and analyzed after
adding 93 g/liter orthophosphite. This concentration was
used to determine the quantity of precipitating agent needed.
The treatment of the regenerative electroless nickel solution
yielded successful results. The process removed 68.1% of
orthophosphite with minimal retention of nickel and
hypophosphite on the filter cake. Recovery of the nickel and
hypophosphite can be achieved by circulating deionized
water through the cake. This wash solution can either be
used to replace evaporative losses or added to the treated
solution prior to adjustment. If necessary, further washing
of the filter cake can be carried out to lowerthe nickel content
sufficiently to meet federal, state, and/or local regulatory
requirements for a non-hazardous waste. The electroless
nickel plating operation at CJS has increased production
time and become more efficient and profitable through the
24
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implementation of the regenerative electroless nickel
process.
Case Study 427
Fin-Clair Corporation plates nearly 40 million seat belt
assemblies each year at its facility in Knoxville, Tennessee.
Fin-Clair tested four bright nickel plating process solutions
(PPS) and index-based plating baths to provide good leveling
and extremely bright deposits at various deposit thicknesses.
The process included a total reclaim of the baths with rinses
flowing back into the tank. There is no evaporation or ion
exchange used, and the process has no drag-out.
Recognizing that PPS-based brightener systems commonly
have problems with buildup of degradation products, and
each system suffered from buildup of inorganic products
such as chloride, the company expected inconsistent plating.
Fin-Clair preferred the brightness and ductility of the PPS
bath but realized that PPS solution and performance
deteriorates with use and causes a buildup that results in a
loss of ductility and an overall reduction in brightness and
leveling.
In an effort to correct the PPS solution problem, the Fin-
Clair switched to a non-PPS, non-index system that was
low in chloride, the Enthone-OMI Ultra-Lite 2000 bright nickel
plating system.The new system was installed in the duplex
nickel/chromium hoist line in the company's St. Louis,
Missouri, facility and resulted in better performance without
the previous PPS solution problems. The new system was,
consequently installed for both lines in the Knoxville facility.
The two main reasons for the conversion were the deposit's
low stress and excellent ductility. The process is designed
for an air-agitated rack plating operation.The low stress and
excellent receptivity make it ideal for plating complex-shaped
parts, such as seat belt assemblies and wheelchair parts.
The duplex bright nickel line has four semi-bright nickel
stations, three bright nickel stations, and one trivalent
chromium tank. Rinses before and after the nickel and
chromium plating tanks are deionized water, generated from
wastewater treatment. Other generated rinses are fresh
water and exit sprays used on most of the rinses to reduce
drag-out. After the final deionized water rinse, parts are dried
using a forced-air dryer.
Fin-Clair is enjoying low maintenance of the plating bath
and excellent performance. The only item added beyond the
maintenance and carrier is the wetting agent which lowers
the surface tension and provides limited detergent action in
the nickel solution for pit-free deposits. Since there was no
buildup with the non-PPS, non-indexing nickel system (the
original reason to switch solutions), Fin-Clair could "close
the loop" and enjoy reuse of rinsewater after treatment
through a vacuum distillation unit designed and built by the
company. The nickel concentrate is pumped from the bottom
of the unit and filtered through heavy carbon before being
added, as needed, to the plating tank. The last time Fin-
Clair used landfill disposal was in 1985.
5.7 Wastewater Pretreatment Options
Typical pretreatment technology options for nickel plating
wastewater streams are chemical precipitation and activated
carbon adsorption. Section 2.1 of the Standard Handbook
of Hazardous Waste Treatment and Disposal indicates that
implementation of industrial pretreatment standards by EPA
and various states could very well affect hazardous waste
generation.13
5.7.1 Chemical Precipitation
In many cases, metal-bearing wastes contain several
constituents at high concentrations. Treatment of spent
plating, cleaning, and pickling baths by precipitation often
requires special design and operating conditions. More cost-
effective treatment may be achieved if wastes are
segregated. This is particularly true with wastes that contain
cyanide and hexavalent chromium. Segregation of cyanide
and hexavalent chromium will allow pretreatment of smaller
waste streams requiring smaller tanks and chemical feed
equipment, as well as reduced chemical usage for pH
adjustment. Jar testing is recommended to compare
alternative precipitation processes.Therefore, custom design
is the best treatment procedure for the process waste
stream.13
Either lime, magnesium hydroxide, caustic, or a blend of
these alkaline compounds can be used as the source of
hydroxide ions for precipitation of metal hydroxides.
Advantages and disadvantages of each of these reagents
should be considered in the selection of a system for a
particular application. For example, caustic is more
expensive than lime, but the cost of chemical feed systems
for lime slurry can be substantially more expensive than for
caustic. Lime and magnesium hydroxide tend to reduce
sludge leachability and break metal complexes that may be
present in the wastewater stream.13
Among the more common complexing agents encountered
in metal-bearing wastes are ammonia, cyanide, and
ethylenediaminetetraacetic acid (EDTA).There are a number
of treatment procedures for complexed metal-bearing wastes
by chemical precipitation and reduction. Most of these
complexed wastes contain copper, nickel, zinc, silver, tin
and lead. A treatment method that has been investigated
and reported to be effective for certain nickel complexes is
precipitation at high pH (11.6 to 12.5) utilizing lime. The
drastic increase in pH is believed to prompt a shift in the
complex dissociation equilibrium to produce uncomplexed
metal ions which can then be precipitated.13
5.7.2 Carbon Adsorption
Sometimes it is necessary to pretreat a wastewater stream
prior to discharge to a POTW. Activated carbon adsorption
is occasionally used to remove contaminants (usually
organic compounds) from such streams. Most carbon-
adsorption systems use granular activated carbon (GAG)
in flowthrough column reactors. Since the adsorption process
is reversible, it is common to remove the adsorbed
contaminants and regenerate the carbon for reuse. It is
important to determine if carbon adsorption can produce
25
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an effluent of acceptable quality and price for a specific
process. For additional assistance for specific waste
management applications, consult with an engineering
consulting firm, professional trade association, and/or a
major activated carbon manufacturer.13
5.8 Wastewater Control Technology
Wastewater is generated in the nickel plating industry as a
byproduct of:
1. Process tank rinses
2. Servicing filters
3. Clean-up of equipment and floor spills
These sources of wastewater are also the primary targets
for source reduction, recovery, recycle and reuse. Most of
the emphasis on recovery technology has been on
rinsewater since it constitutes the majority of the flow leaving
an operation and necessitates expensive treatment. Bath
dumps are generally of low volume and occur infrequently.
Often bath dumps are collected and transported by a waste
service provider for final treatment and disposal, but more
and more baths are being treated on-site for regeneration
and reuse of the bath chemicals. Floor spills include both
accidental and intentional waste sources, such as tank
overflows, drips from workpieces, leaking tanks or pipes,
chemical spills, salt encrustations, washdown water and oil
drips-spills from equipment during the operation, transport
and handling. Floor spills are managed by the application of
good housekeeping, maintenance and operating practices,
combined with appropriate operatortraining.13
Wastewater treatment following P2 and recovery/recycle/
reuse options can be accomplished using one of five general
approaches:
On-site treatment system
On-site treatment using a mobile treatment system
Pretreatment followed by discharge to POTW
Off-site treatment by a centralized waste treatment
facility
Transport of wastewater to an off-site treatment/
disposal facility
Maintaining and operating an on-site treatment facility can
be labor intensive and expensive and is usually not a good
option for small nickel plating companies. A mobile system
can also be expensive for a small plater. Mobile systems
are generally used for infrequent site clean-up requirements
and are not commonly used by nickel platers. Pretreatment
followed by discharge to a POTW is a wastewater control
option for many platers who are also active in recovery/
recycle programs. Off-site treatment by a centralized waste
treatment facility works when several platers are located in
the same vicinity, usually in large metropolitan industrial
areas. A typical option for most small waste generators is
storing the hazardous waste in accordance with RCRA
requirements until it is economically sound to have the waste
transported to an off-site treatment and disposal facility.13
5.9 Air Emissions Control Technology
Air emissions are created when hydrogen gas (H2) is
produced in the electroplating or EN plating process with
air bubbles from air agitation systems in these processes
escaping and carrying some of the nickel plating solution
with each release. Emissions escape from the blind holes
of parts being plated and during the chemical process of
the nickel deposition at the surface of the part. Capturing
these emissions with hoods or a general ventilation system
and routing them to a wet scrubber is the most common
control technology for nickel plating air emissions. If the rest
of the United States follows the lead of California and its
regulation declaring all soluble nickel compounds to be
carcinogenic, it will be necessary for all nickel platers to
install High Efficiency Particulate Air (HEPA) filters to control
emissions from small, medium, and large plating tanks. Since
most new tanks are not designed with ventilation systems
and the HEPA filters work best in combination with a scrubber
or mist eliminator, the estimated cost for achieving
compliance could range from about $20,000 to $140,000
per tank, depending on the size of the tank and design of
the facility.12
26
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6. Conclusions and Recommendations
In summary, this capsule report has compiled information
from reports, articles, books, guides, web sites, and manuals
that address nickel plating emission issues, pollution
prevention, and control technologies. The report's primary
purpose is to assist the metal finishing community in the
management of nickel plating environmental issues by
providing technical information and practical examples of
cost-effective, environmentally acceptable practices. The
nickel plating industry is described as part of the larger metal
finishing industry in the United States, sharing similar
problems and solutions. The technical descriptions provided
in this report focused on both the nickel electrodeposition
process and the electroless nickel deposition processes.
Special attention was given to incorporating issues and
factors to the processes regarding environmental releases,
costs, technology, and environmental regulations. Life-cycle
stages of source reduction, recycle/recovery, pretreatment,
treatment, and control technologies were integrated into
considering environmental management options.
Nickel plating practitioners are constantly making decisions
that affect their production and processes. One of the
purposes of this report was to provide a viable reference for
making informed choices. It is recommended that decision-
makers within the nickel plating community embrace the
opportunity for partnerships in solving shared technical
problems and coordinating difficult environmental issues.
Partnerships with professional and trade associations
encourage industry professionals in meeting these
challenges. The National Metal Finishing Resource Center
(NMFRC), http://www.nmfrc.org; American Electroplaters
and Surface Finishers Society, Inc.(AESF), http://
www.aesf.org; and National Association of Metal Finishers
(NAMF), http://www.namf.org are examples of metal finishing
organizations where partnerships are working. EPA offers a
number of hotlines and web sites regarding environmental
information. EPA's Small Business Ombudsman Office
(OSBO), http://www.epa.gov/sbo addresses small business
issues, problems, and needs. The "Small Business
Ombudsman Update" provides EPA web pages and hotlines,
the status of high visibility actions, and a variety of assistance
references including state contacts.
It is recommended that individuals engaged in nickel plating
consider integration of their options for environmental
compliance when determining a practice for their specific
facility. This requires the nickel plater to gather information,
analyze the data regarding facility needs and consider all of
the factors before making an informed decision.The plating
shop owner/operator best knows his or her facility and
processes and, therefore, should be able to make the
appropriate decision.The information and examples provided
herein were designed to help support decisions. By
integrating pollution prevention and control technology
options to meet the challenges of economic and regulatory
drivers, the decision-maker can take advantage of all the
tools available and avoid concentrating on a single approach,
or following examples not tailored for their facility. Generic
environmental solutions should be used only for generic
environmental problems. Most nickel plating small-shop
problems are site-specific and require site-specific solutions.
Approaches should be tailored to meet the individual nickel
plater's needs. Partnerships make good business sense,
but the responsibility for environmental compliance and
business success remains with the plating shop owner/
operator.
Major environmental issues:
Economically achievable pollution prevention and
control technology options are needed to meet
changing regulations.
The playing field for environmental compliance
between jurisdictions needs to be leveled within the
United States and globally.
Continued research and development are needed to
develop and transfer technology to reduce waste
generation through process changes, material
substitution, water use reduction, metals recovery/
recycle, bath life extension.
Continued government-industrial partnerships are
needed with trade and professional organizations and
environmental groups to jointly consider regulatory
limits and solutions to environmental problems.
Long-term research and development planning by the
industry should attempt to identify what is needed 5
years and 10 years from now to enable companies to
address environmental issues while remaining
competitive within a global economy.
Major recommendations:
Facilities should continue to conduct environmental
audits and pollution prevention opportunity
assessments for identifying where P2 and compliance
can be accomplished.
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Industry must continue to pursue approaches that
encourage life-cycle assessment, ISO 14000,
pollution prevention, and activity-based costing.
Government, industry, trade and professional
associations and academia should enhance
technology transferthat meets the needs of the nickel
plating practitioner to improve production and reduce
environmental impacts.
EPA and industry should continue to enhance
partnerships for out-year planning with specific goals
to be more competitive on the global market, while
reducing environmental impacts and improving
production.
More efficient plating solutions need to be developed
that utilize lower concentrations of nickel in the
electroplating and EN plating processes and produce
lower levels (preferably zero levels) of air emissions.
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7. References
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