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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 manufacturers Waste Minimization Assessment Centers (WMACs) were

established at selected universities and procedures were

adapted from the EPA Waste Minimization Opportunity Assessment Manual (EPA/625/7-88/003, July 1988). That document has been superseded by the Facility Pollution Prevention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. Aluminum 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 investigators and EPA’s National Risk Management Research Laboratory, 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.

Introduction

The amount of waste generated by industrial plants has become 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 manufacturing 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 participating plants. In addition, the project provides valuable experience for graduate and undergraduate students who participate

in the program, and a cleaner environment without more regulations and higher costs for manufacturers.

Pollution Prevention Assessment for a Metal Parts Coater

ENVIRONMENTAL

RESEARCH BRIEF

Harry W. Edwards*, Michael F. Kostrzewa*, Trevor Spika*,

and Gwen P. Looby**

* Colorado State University, Department of Mechanical Engineering ** University City Science Center, Philadelphia, PA

United States

Environmental Protection

Agency

National Risk Management

Research Laboratory

Cincinnati, OH 45268

Research and Development EPA/600/S-95/027 September 1995
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Methodology of Assessments

The pollution prevention opportunity assessments require several 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 supporting technological and economic information is developed. Finally, 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 conversion 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

rinse, 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 returned to the customer.

Chromate Conversion Coating

Only aluminum parts receive chromate conversion coatings.

The chemical solutions and rinses for chromating are integrated 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, caustic etch, two-tank counterflow rinse, tri-acid etch or desmut

(determined by the part and customer specifications), two-tank

counterflow rinse, yellow or clear chromic acid solution, twotank 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 customer.

Electrolytic Nickel Plating

Electrolytic nickel plating is performed on brass, copper, aluminum, 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 water 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 craneoperated line for large parts.

The process solutions used in each line are similar, but different 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 hydroxide sludge.

• Flow reducers are used on all flowing rinses to reduce water

consumption.

• Staged counter-flowing rinse tanks are used for more effective 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 opportunity reflect the savings achievable when implementing each

opportunity independently and do not reflect duplication of

savings that would result when the opportunities are implemented 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. Environmental Protection Agency. The EPA Project Officer was Emma

Lou George.

Aluminum

Parts

Aluminum

Parts

Parts

Stainless Steel,

Copper, Brass,

and Aluminum

Anodizing

Chromating

Nickel Plating

- Cleaning

- Anodizing

- Dyeing

- Sealing

- Rinsing

- Cleaning

- Chromating

- Etching

- Rinsing

- Cleaning

- Etching

- Plating

- Rinsing

Finished Parts

Finished Parts

Finished Parts

Cleaning

Freon

Figure1. Abbreviated process flow diagram for metal parts coating.
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BULK RATE

POSTAGE & FEES PAID

EPA

PERMIT No. G-35

United States

Environmental Protection Agency

National Risk Management Research Laboratory (G-72)

Cincinnati, OH 45268

Official Business

Penalty for Private Use

$300

EPA/600/S-95/027

Table 1. Summary of Current Waste Generation

Annual Quantity Annual Waste

Waste Generated Source of Waste Waste Management Method Generated (lb/yr) Management Cost*

Rinse water All process lines pH adjusted; sewered 62,700,00 $10,500

Chromium-containing wastewater Chromating and anodizing lines Chromium removed by ion exchange; 2,590,000 1,330

pH adjusted; sewered

Chromium-containing sludge Pretreatment of chromium-containing Shipped offsite to reclaimer 1,470 2,930

wastewater

Nickel-containing wastewater Nickel plating Nickel removed by ion exchange; 3,070,000 510

pH adjusted; sewered

Nickel-containing sludge Pretreatment of nickel-containing wastewater Shipped offsite to reclaimer 1,730 3,470

Waste Freon TFTM Vapor degreasing of parts Allowed to evaporate onsite 8,630 28,500

Waste 1,1,1-trichloroethane Miscellaneous cleaning jobs Shipped offsite for incineration 2,090 2,250

 *Includes waste treatment, disposal, and handling costs and applicable raw material costs.

Table 2. Summary of Recommended Pollution Prevention Opportunities

Annual Waste Reduction

Pollution Prevention Opportunity Waste Reduced Net Annual Implementation Simple

Quantity (lb/yr) Per Cent Savings Cost Payback (yr)

Replace Freon TFTM used in the vapor de- Waste Freon TFTM 8,630 100 $26,2001 $4,900 0.2

greaser with a nonhazardous cleaner and

post-clean rinse. The spent cleaner can be

regenerated onsite through vacuum distillation

and the waste post-clean rinse can be

sewered.

Replace the chromic acid cleaner in the Chromium-containing 1,180 80 2,940 0 0

electroless-plating hoist line with a less sludge

hazardous cleaner such as a phosphoric

acid cleaner. The current use of chromic acid

results in the generation of a chromium-containing sludge. The replacement cleaner can

be pH-adjusted onsite.

1Total annual savings have been reduced by an annual operating cost required for implementation.