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OAR Box 1313 

Preppedby LaTeiaShed 

Document Number: 

10) l-B-3 

Docket Number: 

A-88-02 

Printed 6/12/2008 9:03:27AM Sheet 10 of 99 
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Date: February 25, 1985 

(Finalized April 2, 1985) 

A-88-02 

MIDWEST RESEARCH INSTITUTE 

•3T- o- 3 4505 Creedmoor Road 

Raleigh, N.C. 27612 

Telephone (919) 781-5750 

FINAL 

FILE OOP? 

Subject: Site Visit--Gibbs Plating Company 

Survey of Chromium Emission Sources—Chromium Plating 

EPA Contract 68-02-3817; ESED Project 85/02 

MRI Project 7711-L 

From: Barb Duletsky &u^-* 

To: Al Vervaert 

ESED/ISB/SSS (MD-13) 

U. S. Environmental Protection Agency 

Research Triangle Park, N.C. 27711 

I. Purpose 

The purpose of this site visit was twofold: (1) to gather 

background information on this chromium plating plant, and (2) to 

determine the suitability of this plant for chromium emissions testing. 

II. Place and Date 

Gibbs Plating Company 

5210 Hovis Road 

Charlotte, N.C. 28208 

(704) 392-7382 

December 20, 1984 

III. Attendees 

Gibbs Plating Company 

Ed Gibbs, President 

Doug Fairchild, Plant Manager 

U. S. Environmental Protection Agency (EPA) 

Al Vervaert, Lead Engineer 

Midwest Research Institute (MRI) 

Barb Duletsky 

IV. Discussion 

We arrived at 9:40 a.m. at the plant, where we were greeted by 

Messrs. Ed Gibbs and Doug Fairchild. The plant visit consisted of a 

discussion about chromium plating, followed by a guided tour of the 

facility. 

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Principal Laboratories 425 Volker Boulevard. Kansas City. Missouri 64110 
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A. General 

The Gibbs Plating Co. facility is an average-sized job shop involved 

in the hard chromium plating of items such as pump parts, textile manufacturing equipment parts, and other machinery components. Other 

operations performed at the plant include zinc barrel-plating, cadmium 

plating, copper plating, and chromating. There are 17 full-time employees 

working in the plant, one of whom is responsible for operating the 

chromium plating tank. About 25 percent of the company's total annual 

sales is a result of the chromium plating operations. 

The Gibbs Plating Co. moved to the facility we visited about a 

year ago. It had previously operated at another location in Charlotte, 

North Carolina. Over the past year, the company has installed electrical 

and plumbing fixtures, relocated several planting tanks from their 

previous location, and acquired a new automated zinc plating tank; 

however, the relocation is not complete. Presently, the plant operates 

1 shift/day, 5 days/week. 

B. Process Information 

1. Hard Chromium Plating. Currently, the company operates one 

hard chromium plating tank. The tank measures 6 feet (ft) in length, 

3 ft in width, 4 ft in depth, and holds about 450 gallons (gal) of 

plating solution. Another tank was expected to go on-line within the 

next 90 days. This second tank measures 21 ft in length, 3 ft in width, 

and 7 ft in depth. 

The plating solution consists of chromic acid (Cr03) in a concentration of 32 ounces/gallon (oz/gal). The acid is manufactured by 

Allied Chemical and supplied by M & T Chemical Company. Historically, 

the company has used between 12,000 and 15,000 pounds (lb) of dry chromic 

acid annually for this chromium plating tank. (Mr. Gibbs said that 

chromic acid consumption is a good indicator of the size of a chromium 

plating facility.) Sulfuric acid (H2S04) is used as a catalyst in the 

plating solution. It is used in the proportion of 1 part of sulfuric 

acid to 100 parts of chromic acid. Mr. Gibbs indicated that fluoride is 

not used as a chromium catalyst for hard chromium plating at this plant 

because of its tendency to corrode unp'rotected surfaces of steel parts 

that remain in the tank for several hours to obtain thicker deposits of 

chromium. A sample of the plating solution is tested weekly to ensure 

that the proper concentration of constituents is maintained. Mr. Gibbs 

noted that a plating tank can operate for as long as 20 years without 

needing to be emptied and cleaned, providing that the buildup of contaminants such as copper and iron in the tanks is avoided. 

The plating solution is normally maintained at 125°F. The 

temperature is regulated by both an electric heating system and a water 

cooling system. The plating tank is energized by a single transformer/ 

rectifier. Maximum operating voltage and current are 9 volts (V) and 
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3,000 amperes (amps), respectively. Typical jobs require that parts 

remain in the tank for 1 to 4 hours; however, some jobs may require that 

parts be plated as long as 24 hours. This type of job involves leaving 

parts in the tank overnight and occurs only about once a week. 

After being plated, the parts are rinsed over the top of the 

plating tank with water from a hose. This allows excess plating solution 

on the parts to drain back into the plating tank, thus reducing drag-out. 

("Drag-out" refers to the carry-over of plating solution with parts when 

they are transferred from one tank to another.) After the initial 

rinse, the parts are transferred to an adjacent rinse tank where they 

are submerged. After rinsing, the parts are air-dryed, buffed, and 

packed for shipment. 

2. Chromating. Gibbs Plating Co. operates a chromating tank but 

does not consider it to be a source of chromium emissions. The chromic 

acid solution in the tank is very dilute, containing only about 1 percent 

of the amount of chromic acid that is used in the hard chromium plating 

solution. Chromating is performed for coloring purposes only. There is 

no electric current in the tank, and the process is performed at room 

temperature. Because no mist is generated, there are no emissions to 

capture or control. 

3. Decorative Chromium Plating. This plant is not involved in 

decorative chromium plating, but Mr. Fairchild provided the following 

information based on his own experience. 

In decorative chromium plating, a thin layer of chromium (about 

0.01 mil) is applied over a nickel coated substrate to provide a bright, 

tarnish-resistant surface. Because the layer of chromium plate is very 

thin, parts only need to be in the chromic acid solution 10 to 30 minutes. 

Decorative platers usually process a high volume of parts and are likely 

to have automated lines. 

A variety of substrates can be chromium plated, but some of them 

require special pretreatment. For instance, aluminum parts must be 

plated with zinc before being plated with chromium because chromium does 

not adhere well to aluminum. Also, plastic parts require chemical 

pretreatment before they can be effectively chromium plated. Plastic is 

not conductive and, therefore, cannot attract chromium ions in the 

electrolytic solution. 

About half of the plating cycle time for plastic is spent rendering 

the parts conductive. Most of the plastic that is plated consists of 

acrylonitrile-butadiene-styrene (ABS). The butadiene is sensitive to 

solvent attack; therefore, the first step in plating plastic involves 

etching it in a strong chromic acid solution that is heated to 71°C 

(160°F). This etching leaves microscopic holes on the surface of the 

plastic part where the acid has dissolved the butadiene. The part is 

then treated with paladium, which is adsorbed in the holes on the surface. 

The paladium attracts nickel or copper molecules from an electroless 

solution, thereby forming a continuous, conductive surface. Subsequent 
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steps include electrolytic copper plating, electrolytic nickel plating, 

and then electrolytic chromium plating. 

In dipping plastic parts into the various solutions, the arrangement of the parts on the rack is critical. Because the plating 

temperatures are high, parts must be arranged in a way that does not 

apply stress in any direction so that warping does not occur. On the 

other hand, good contact must be achieved between the part surface and 

the rack so that the part can conduct electricity and, thus, attract 

metal ions from the electrolytic plating solutions. 

C. Pollution Control 

1. Emissions Control. Mist is generated in the hard chromium 

plating tank due to the evaporation of water and the formation of hydrogen 

gas on the surface of the cathodes (parts). The mist carries entrained 

hexavalent chromium (Cr+6) molecules as it escapes from the surface of 

the plating solution. There was visible misti'ng from the hard chromium 

tank during the plant visit but no visible misting from the chromating 

tank. 

There is nothing on or in the plating tanks to prevent misting. 

Although Mr. Gibbs is familiar with the use of polypropylene balls, and 

chemical foams to retard misting, neither is used at the plant because 

he does not consider either method to be very effective. The chemical 

that produces the foam layer is very expensive and causes a pitted 

appearance on the plated parts. Also, the agitation of the bath due to 

the bubbling of hydrogen gas from the surface of the cathodes is usually 

sufficient to displace a layer of balls or foam from around the cathodes. 

The hard chromium plating tank is equipped with a side-draft hood 

along one side. An induced draft fan is used to draw about 10,000 cubic 

feet/minute (ftVmin) of air across 18 square feet (ft2) of tank surface 

area and the through the hood. The fan is upstream of a Duall inclined, 

packed-bed fume scrubber. The scrubber collects chromium emissions when 

the mist impinges on the packed-bed plates. The control system, which 

includes the scrubber, ductwork, hood, and fan, was installed for about 

$14,000 and is shown in Figure 1. 

Water is recirculated continuously to flush the scrubber plates. 

When the chromium concentration in the water reaches a certain level, 

the water is drained and treated by an on-site effluent treatment system. 

The system is designed so that eventually the water will be emptied into 

the hard chromium plating tank, but the piping to accommodate this has 

not been installed yet. It is expected to be installed within the next 

90 days. 

Emissions from the second hard chromium plating tank that is to be 

installed will also be treated by a scrubber. These emissions will be 

ducted to the existing scrubber if the company determines that this 

scrubber can accommodate air flows from both tanks. Otherwise, a new 

scrubber will be designed and installed by either Duall or KCH. 

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TO ATflOSPHERE 

SCRUBBER 

HOLDING 

TANK 

TO EFFLUENT 

TREATMENT 

HARD CHROME PLATING TANK 

Figure 1. Control system on hard chrome plating tank. 

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2. Effluent Treatment. The company has permission to direct its 

effluent to the local, publicly-owned wastewater treatment plant. The 

company is in the process, however, of installing its own complete 

effluent treatment system. The system includes a sodium bisulfite tank 

for the reduction of hexavalent chromium in the chromium plating wastes 

to trivalent chromium. Other processes being installed for the, treatment 

of combined wastewater from the plant are a pH neutralization tank, a 

flocculation tank, a primary clarifier, and a sand filter. Mr. Fairchild 

is overseeing the installation of this system, which represents a total 

capital investment of about $100,000. 

Currently, sludge from the effluent treatment system is not 

considered to be hazardous, so it can be disposed of at a local sanitary 

landfill. However, because of the heavy metal content of the sludge, 

Mr. Gibbs expects this nonhazardous status to change soon. When the 

sludge is officially considered to be hazardous, it will have to be 

hauled to Pinewood, South Carolina, for disposal at a secure sanitary 

landfill. 

D. Conclusions 

The trip to Gibbs Plating Co. was very informative. Because of 

Mr. Gibbs' involvement with the American Electroplaters Society (AES) 

and the National Association of Metal Finishers (NAMF), he was able to 

supply information on the chromium plating industry in general. It was 

suggested that the project team attend the AES/EPA conference in Orlando, 

Florida, in January 1985 for more information on the industry. 

This plant is representative of other job shops performing hard 

chromium plating. Emissions from the plating tank were observed to be 

effectively drawn into the hood along the back edge. The fume scrubber 

was effective in collecting emissions, as evidenced by the clean exhaust 

stream. Inlet and outlet testing of the fume scrubber is feasible; 

however, a port would need to be installed at the inlet location and a 

stack would need to be constructed at the outlet location. Test data 

from this plant could be used to determine uncontrolled emissions from a 

typical hard chromium plating tank and the performance of a fume scrubber 

in controlling those emissions.