p.1 

OAR Box 1313 

Prepped by LaTeia Shed 

Document Number: 

70) ll-B-44 

Docket Number: 

A-88-02 

Printed 6/12/2008 9:03:30 AM Sheet 70 of 99 
MRI^J 

P.2 

MIDWEST RESEARCH INSTITUTE 

TE-12>-'4'4 Suite 350 

401 Harrison Oaks Boulevard 

Cary, North Carolina 27513 

Telephone (919) 677-0249 

FAX (919) 677-0065 

Date: 

Subject: 

From: 

To: 

May 20, 1988 

(Finalized June 30, 1988) 

Site Visit—Plant ABC 

Chromium Electroplating NESHAP 

EPA Contract 68-02-3817; ESD Project 85/02a 

MRI Project 7717-K 

Robin Barker 

Andrew M. Smith 

ESD/ISB/SSS (MD-13) 

U. S. Environmental Protection Agency 

Research Triangle Park, N.C. 27711 

r" 

CT 1661 8 ! NV! 

1 | ! 

i

l

TTT187 

^•* " *• — •' • < — • " ' * 

ll 

I . Purpose 

The purpose of this site visit was to gather background Information 

on the use of the trivalent chromium process as a replacement for the 

hexavalent chromium process for decorative electroplating (plating) 

applications. 

II. Place and Date 

Plant ABC 

Southeastern U.S. 

January 18, 1988 

III. Attendees 

Plant ABC 

J. T. Gilbert, Finishing Superintendent 

Harshaw/Filtrol Partnership 

Thomas Ferguson, Account Manager 

Midwest Research Institute (MRI) 

Robin Barker 

/ 
P.3 

IV. Discussion 

A meeting was held with plant personnel to discuss the trivalent 

chromium plating operation at Plant ABC. The meeting was followed by a 

tour of the plating shop. 

A. General 

Plant ABC is a job shop specializing in decorative chromium plating 

of store shelving and supplies for department stores such as J. C. Penney 

and K-Mart. There are two plating lines at Plant ABC, an automatic and a 

hand-operated line. The automatic line is operated infrequently during 

the year. The hand-operated line operates 9 hours/day, 6 days/week, and 

50 weeks/year. 

B. Process Description 

The two trivalent chromium plating process lines used at this 

facility for decorative chromium plating are identical in process 

configuration (sequence). One line is equipped with a hand-operated hoist 

to transfer each rack of parts through a series of tanks, and the other 

line is equipped with an automatic hoist. It takes approximately 1 hour 

for each rack of parts to complete the plating cycle for both lines. The 

trivalent chromium process lines consist of the following tanks in 

series: (1) alkaline soak clean; (2) water rinse; (3) electroclean; 

(4) two water rinses; (5) hydrochloric acid dip; (6) two water rinses; 

(7) hydrochloric acid dip; (8) electroclean; (9) two water rinses; 

(10) hydrochloric acid dip; (11) water rinse; (12) bright nickel plating; 

(13) four water rinses; (14) trivalent chromium plating; (15) drip tank; 

(16) water rinse; (17) caustic solution; (18) water rinse; and (19) hot 

water rinse. 

There are two trivalent chromium plating tanks in the hand-operated 

line. Both tanks are identical in size. Each tank is 5.0 meters (m) 

(16.5 feet [ft]) long, 1.1 m (3.75 ft) wide, and 2.2 m (7.2 ft) deep and 

holds approximately 11,740 liters (i) (3,100 gallons [gal]) of plating 

solution. Each plating tank holds one rack of parts at a time. Each rack 

remains in the plating tank for 2.0 minutes. The plating thickness ranges 

from 8 to 10 mi month s of an inch. The normal operating voltage is 

13 volts, and the amperage is 15,000 amperes of direct current. Each tank 

is equipped with a filtration system that constantly filters the plating 

solution. The tanks are not equipped with a ventilation system; however, 

during the visit no visible misting was observed at the surface of the 

plating solutions. 

There is one trivalent chromium plating tank in the automatic 

line. The tank is approximately 3.0 m (10.0 ft) long, 0.8 m (2.5 ft) 

wide, and 1.7 m (5.5 ft) deep and holds 3,540 i (935 gal) of plating 

solution. The plating tank holds four racks of parts of a time. The 

normal operating voltage is 13 volts at an amperage range from 6,000 to 

7,000 amperes. The tank is equipped with a filtration system that 

constantly filters the plating solution. The tank is not equipped with a 

«?• 
P.4 

ventilation system. The automatic line was not operating at the time of 

the visit. 

The plating solution used in all three tanks is Tri-Chrome® LC Plus, 

manufactured by Harshaw/Filtrol Partnership (Harshaw). The solutions 

contained about 22 grams per liter (3 ounces per gallon) of trivalent 

chromium. The trivalent chromium solution in use at Plant ABC is a firstgeneration bath that operates at a lower temperature (21°C [70°F]) than 

the newer trivalent chromium baths now available. Three chillers are used 

to cool the plating solution in the three tanks. Samples of the solution 

are sent to Harshaw each month for chemical analyses to ensure the bath 1s 

running at its proper concentration and to identify the level of 

contaminants. Chemical additions are made to the baths on an ampere-hour 

basis by automatic ampere-hour controllers connected to the rectifier and 

tank. The plating solutions are purified on a weekly basis to remove any 

contaminants present in the solutions. The baths are purified by adding a 

proprietary compound which precipitates metal contaminants out of the bath 

or by "dummying" the bath. "Dummying" is a electrolytic process in which 

a nonproduct part is placed in the tank and the current density is set 

below or above the operating range of trivalent chromium. The metal 

contaminants in the bath plate out onto the part. Plant personnel stated 

that routine maintenance of the plating solutions required about 

20 minutes per day with hexavalent chromium and increased to 45 minutes 

per day for trivalent chromium. 

C. Cost Data 

The chemical cost for the hexavalent chromium process was 

$0.015/ft , and the chemical cost of the trivalent chromium process 1s 

currently about $0.047/ft . Plant personnel stated that since trivalent 

chromium has been in use, rejects have decreased from 10 percent to 

0 percent and a 30 percent increase in overall production was observed. 

The plant saves $27,000 a year on treatment chemicals for wastewater 

treatment and saved $10,000 on treatment equipment no longer required due 

to the elimination of the hexavalent chromium reduction units. The 

elimination of the color buffing process (required with the hexavalent 

chromium process to treat chromium stains) reduced equipment operating 

costs by $91,000/yr, and saved $14,000/yr and $8,000/yr in buffing pads 

and compounds, respectively. The plant also saves $3,000/yr by not having 

to replace the tin-lead anodes used in hexavalent chromium plating and 

saves $10,000/yr by eliminating the need for the stripping operation that 

was required because of poor chrome throw experienced with the hexavalent 

chromium process. The total annual savings generated from the trivalent 

chromium process is $153,000/yr. 

The initial conversion cost to the plant was $118,480. Table 1 

presents the components of the capital cost for the trivalent chromium 

conversion. All costs are in 1981 dollars. 

^J 
P.5 

V. Conclusion 

Plant ABC is a medium-size captive shop specializing in store 

fixtures. The trivalent chromium process has been successfully running 

for 7 years. 

The plant stated that the trivalent chromium process has allowed 

them to stay competitive with other companies because it has decreased the 

cost to run the operation. Plant personnel were very cooperative in 

supplying EPA with the cost data and technical comparison of both 

processes. 

f 
P.6 

TABLE 1. CAPITAL COST FOR TRIVALENT CHROMIUM CONVERSION AT 

PLANT ABC 

Components Cost, $ 

Equipment 

1. Arkla chillers (3) 27,594.84 

2. Anodes (170) 13,174.00 

3. Hangers (170) 4,580.00 

4. Cooling coils (5) 3,778.00 

5. Tank liners (3) 3,000.00 

6. Ampere-hour controller systems (3) 2,250.00 

7. Rectifiers (2) 39,600.00 

Modification costs 

Trivalent chromium makeup solution (3) 24,502.00 

TOTAL3 118,480.00 

aCosts were rounded to nearest $10.00. 

o