SEPA
United States
Environmental Protection
Agency
National Risk Management
Research Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/S-95/027 September 1995
ENVIRONMENTAL
RESEARCH BRIEF
Pollution Prevention Assessment for a Metal Parts Coater
Harry W. Edwards*, Michael F. Kostrzewa*, Trevor Spika*,
and Gwen P. Looby**
Abstract
The U.S. Environmental Protection Agency (EPA) has funded
a pilot project to assist small and medium-size manufacturers
who want to minimize their generation of waste but who lack
the expertise to do so. In an effort to assist these manufactur-
ers Waste Minimization Assessment Centers (WMACs) were
established at selected universities and procedures were
adapted from the EPA Waste Minimization Opportunity As-
sessment Manual (EPA/625/7-88/003, July 1988). That docu-
ment has been superseded by the Facility Pollution Prevention
Guide (EPA/600/R-92/088, May 1992). The WMAC team at
Colorado State University performed an assessment at a plant
that applies corrosion resistant coatings to metal parts. Alumi-
num parts received from customers may be anodized or may
receive a chromate conversion coating. Brass, copper, steel,
and aluminum parts from customers are nickel plated—either
by electrolytic or electroless plating. The assessment team's
report, detailing findings and recommendations, indicated that
large quantities of wastewater and metal sludge are generated
by the plant and that significant cost savings could be achieved
through replacement of Freon used for degreasing.
This Research Brief was developed by the principal investiga-
tors and EPA's National Risk Management Research Labora-
tory, Cincinnati, OH, to announce key findings of an ongoing
research project that is fully documented in a separate report
of the same title available from University City Science Center.
Colorado State University, Department of Mechanical Engineering
University City Science Center, Philadelphia, PA
Introduction
The amount of waste generated by industrial plants has be-
come an increasingly costly problem for manufacturers and an
additional stress on the environment. One solution to the
problem of waste generation is to reduce or eliminate the
waste at its source.
University City Science Center (Philadelphia, PA) has begun a
pilot project to assist small and medium-size manufacturers
who want to minimize their generation of waste but who lack
the in-house expertise to do so. Under agreement with EPA's
National Risk Management Research Laboratory, the Science
Center has established three WMACs. This assessment was
done by engineering faculty and students at Colorado State
University's (Fort Collins) WMAC. The assessment teams have
considerable direct experience with process operations in manu-
facturing plants and also have the knowledge and skills needed
to minimize waste generation.
The pollution prevention opportunity assessments are done for
small and medium-size manufacturers at no out-of-pocket cost
to the client. To qualify for the assessment, each client must
fall within Standard Industrial Classification Code 20-39, have
gross annual sales not exceeding $75 million, employ no more
than 500 persons, and lack in-house expertise in pollution
prevention.
The potential benefits of the pilot project include minimization
of the amount of waste generated by manufacturers, and
reduction of waste treatment and disposal costs for participat-
ing plants. In addition, the project provides valuable experi-
ence for graduate and undergraduate students who participate
in the program, and a cleaner environment without more regu-
lations and higher costs for manufacturers.
*§& Printed on Recycled Paper
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Methodology of Assessments
The pollution prevention opportunity assessments require sev-
eral site visits to each client served. In general, the WMACs
follow the procedures outlined in the EPA Waste Minimization
Opportunity Assessment Manual (EPA/625/7-88/003, July 1988).
The WMAC staff locate the sources of waste in the plant and
identify the current disposal or treatment methods and their
associated costs. They then identify and analyze a variety of
ways to reduce or eliminate the waste. Specific measures to
achieve that goal are recommended and the essential support-
ing technological and economic information is developed. Fi-
nally, a confidential report that details the WMAC's findings
and recommendations (including cost savings, implementation
costs, and payback times) is prepared for each client.
Plant Background
This plant applies corrosion resistant coatings to metal parts. It
operates as a job shop and produces approximately 200,000
coated parts annually during 4550 hr/yr of operation.
Manufacturing Process
Coatings to provide protection or to enhance appearance are
applied to parts received from the plant's customers. Coating
processes used by this plant include anodizing, chromate con-
version coating, electrolytic nickel plating, and electroless nickel
plating. Each of these coating procedures is described below.
Anodizing
Anodizing is performed on aluminum parts only. Parts received
from customers are racked in aluminum or titanium racks. The
racks are immersed in a series of chemical solutions and rinse
water baths to generate an aluminum oxide coating on the
part's surfaces.
Three steps-- cleaning, anodizing, and dyeing- make up the
anodizing process. The cleaning process sequence consists of
an alkaline cleaner, a two-tank counterflow rinse, a caustic
etch, a second two-tank counterflow rinse, a desmut rinse, a
third two-tank counterflow rinse, and a final acid rinse. After the
cleaning process, the parts are soft- or hard-coat anodized in
sulfuric acid. Following anodizing, the parts either proceed to a
dyeing process or remain uncolored (clear). The baths that
make up the dyeing process are an agitated deionized water
rinsa, a two-tank counterflow deionized rinse, a dye tank, and
another two-tank counterflow deionized rinse.
Both the dyed parts and the clear parts are then immersed in a
sealing solution and rinsed in a two-tank counterflow rinse and
a heated deionized water rinse. The racks containing the parts
are then hung on bars to allow the parts to air dry. Dried parts
are removed from the racks, inspected, packaged, and re-
turned to the customer.
Chromate Conversion Coating
Only aluminum parts receive chromate conversion coatings.
The chemical solutions and rinses for chromating are inte-
grated with the anodizing solutions, and, therefore the
chromating process uses many of the same baths as the
anodizing process. The sequence of baths used for chromate
conversion is: alkaline cleaner, two-tank counterflow rinse, caus-
tic etch, two-tank counterflow rinse, tri-acid etch or desmut
(determined by the part and customer specifications), two-tank
counterilow rinse, yellow or clear chromic acid solution, two-
tank counterflow rinse, and deionized water rinse. Following
processing, the parts are allowed to dry and are removed from
the racks, inspected, packaged, and shipped back to the cus-
tomer.
Electrolytic Nickel Plating
Electrolytic nickel plating is performed on brass, copper, alumi-
num, and steel parts. However, this line is not used very often
and as a result generates very little waste. The treatment baths
used in the electrolytic nickel line are: caustic cleaner,
electrosoap, two-tank counterflow rinse, desmut, desmut
dragout, two-tank counterflow rinse, acid salt, hydrochloric acid,
nickel strike, three-tank counterflow rinse, nickel plating, nickel
dragout, two-tank counterflow rinse, and heated deionized wa-
ter rinse. The parts are allowed to air dry, inspected, packaged,
and shipped.
Electroless Nickel Plating
Most of the production in this plant is electroless nickel plating
of steel and aluminum parts. Five lines are used for nickel
plating: a hand-operated barrel plating line, a second line with
an overhead hoist, a third line dedicated to aluminum parts, a
fourth line dedicated to plating ice cube trays, and a crane-
operated line for large parts.
The process solutions used in each line are similar, but differ-
ent prep solutions are required for the different base metals
that are plated. In general, the sequence of preparation tanks
is: alkaline cleaner, electrolytic soap, two-tank counterflow rinse,
desmut, desmut dragout tank, two-tank counterflow rinse, acid
dip, two-tank counterflow rinse, acid salt, and a two-tank
counterflow rinse.
An abbreviated process flow diagram for the processes used in
this plant is shown in Figure 1.
Existing Waste Management Practices
This plant already has implemented the following techniques to
manage and minimize its wastes.
• Electrowinning is used to generate reusable nickel prior to
precipitation, thereby reducing the generation of nickel hy-
droxide sludge.
• Flow reducers are used on all flowing rinses to reduce water
consumption.
• Staged counter-flowing rinse tanks are used for more effec-
tive rinsing and to reduce water consumption.
Pollution Prevention Opportunities
The type of waste currently generated by the plant, the source
of the waste, the waste management method, the quantity of
the waste, and the annual waste management cost for each
waste stream identified are given in Table 1.
Table 2 shows the opportunities for pollution prevention that
the WMAC team recommended for the plant. The opportunity,
the type of waste, the possible waste reduction and associated
savings, and the implementation cost along with the simple
payback time are given in the table. The quantities of waste
currently generated by the plant and possible waste reduction
depend on the production level of the plant. All values should
be considered in that context.
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It should be noted that, in most cases, the economic savings of
the opportunities result from the need for less raw material and
from reduced present and future costs associated with waste
treatment and disposal. Other savings not quantifiable by this
study include a wide variety of possible future costs related to
changing emissions standards, liability, and employee health. It
also should be noted that the savings given for each opportu-
nity reflect the savings achievable when implementing each
opportunity independently and do not reflect duplication of
savings that would result when the opportunities are imple-
mented in a package.
This research brief summarizes a part of the work done under
Cooperative Agreement No. CR-814903 by the University City
Science Center under the sponsorship of the U.S. Environmen-
tal Protection Agency. The EPA Project Officer was Emma
Lou George.
Aluminum
Parts
Anodizing
- Cleaning
- Anodizing
- Dyeing
- Sealing
- Rinsing
Finished Parts
Aluminum
Parts
Chromating
- Cleaning
- Chromating
- Etching
- Rinsing
Finished Parts
Stainless Steel,
Copper, Brass,
and Aluminum
Parts
Nickel Plating
- Cleaning
- Etching
- Plating
- Rinsing
Freon
Cleaning
Finished Parts
Figuret. Abbreviated process flow diagram for metal parts coating.
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Table 1. Summary of Currant Waste Generation
Wasta Generated
Source of Waste
Waste Management Method
Annual Quantity Annual Waste
Generated (Ib/yr) Management Cost"
Rinse water
Chromium-containing wastewater
Chromium-containing sludgo
Nickel-containing wastewater
Nickel-containing sludge
Waste Freon TF™
Wasta 1,1,1-trichtoroettano
AH process lines
Chromatlng and anodizing lines
Pratreatment of chromium-containing
wastewater
Nickel plating
Pretreatment of nickel-containing wastewater
Vapor degreaslng of parts
Miscellaneous cleaning jobs
pH adjusted; sewered 62,700,00 $10,500
Chromium removed by Ion exchange; 2,590,000 1,330
pH adjusted; sewered
Shipped offsite.to reclaimer 1,470 2,930
Nickel removed by ion exchange; 3,070,000 510
pH adjusted; sewered
Shipped offsite to reclaimer 1,730 3,470
Allowed to evaporate onsite 8,630 28,500
Shipped offsite for Incineration 2,090 2,250
'Includes waste treatment, disposal, and handling costs and applicable raw material costs.
T*bl»2. Summary of Recommended Pollution Prevention Opportunities.
Annual Waste Reduction
Pollution Prevention Opportunity
Replace Freon TF™ used In the vapor de-
gtmser with a nonhazardous cleaner and
post -dean rinse, Thaspont cleaner can be
regenerated onsKa through vacuum distillation
»nd tfw waste post-dean rinse can be
sewered.
Replace the chromic add cleaner In the
etectrotoss-plating hoist Una with a less
hazardous cleaner such as a phosphoric
acid ctatnor. The current use of chromic add
results In the generation of a chromium-con-
talnlng sludge. The replacement cleaner can
be pH-adfustad onsite.
Waste Reduced
Quantity (Ib/yr) Percent
Waste Freon TF™ 8,630 100
Chromium-containing 1, 180 80
sludge
Net Annual Implementation tiimpie
Savings Cost Payback (yr)
$26,2001 $4,900 0.2
2,940 0 0
1 Total annual savings have been reduced by an annual operating cost required for implementation.
United States
Environmental Protection Agency
National Risk Management Research Laboratory (G-72)
Cincinnati, OH 45268
Official Business
Penalty for Private Use
$300
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
EPA/600/S-95/027
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