p.1 

OAR Box 1313 

Prepped by LaTeia Shed 

Document Number: 

72) ll-B-46 

Docket Number: 

A-88-02 

Printed 6/12/2008 9:03:30 AM Sheet 72 of 99 
P.2 

VIRIfg) 

A-88-02 

MIDWEST RESEARCH INSTITUT! 

^01 Harrison Oaks Bouteva' 

Carv. NC 27?' 

Date: May 20, 1988 ""

 J^f 

(Finalized June 30, 1988) 

Subject: Site Visit—Custom Processing Company 

Chromium Electroplating NESHAP 

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

MRI Project 7717-K 

From: Robin Barker 

To: Andrew M. Smith 

ESD/ISB/SSS (MD-13) 

U. S. Environmental Protection Agency 

Research Triangle Park, N.C. 27711 

I. Purpose 

The purpose of this site visit was to gather background information 

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

hexavalent chromium process for decorative electroplating (plating) 

applications. 

II. Place and Date 

Custom Processing Company 

Surret Drive 

Post Office Box 1708 

High Point, North Carolina 27261 

December 7, 1987 

III. Attendees 

Custom Processing 

Butch Reddick, Plating Supervisor 

Harshaw/Filtrol Partnership (Harshaw) 

Ron Ruzzy, Technical Sales Representative 

U. S. Environmental Protection Aqency 

Andrew M. Smith, ISB 

Gail Lacy, SDB 

/ 
P.3 

Midwest Research Institute (MRI) 

Robin Barker 

IV. Discussion 

Custom Processing Company is a job shop that specializes in chromium 

and brass plating of furniture such as lamps, chairs, and pedestal feet. 

The plant operates 8 hours/day, 5 days/week. 

A. General 

The trivalent chromium process line has been in operation at Custom 

Processing for approximately 9 years. The main reasons the plant switched 

to trivalent chromium plating were the better coverage and throwing power 

of the process, which eliminates the need for color buffing. In addition, 

the plant switched to trivalent chromium because of concern for the health 

of its employees. 

B. Process Description 

The trivalent chromium plating line consists of a series of tanks 

for cleaning and plating the parts. The plating line is equipped with a 

hand-operated hoist that transfers parts in and out of the following 

process tanks: (1) caustic soak; (2) electroclean; (3) two rinses; 

(4) four bright nickel baths; (5) dragout rinse; (6) two countercurrent 

rinses; (7) a brass plating bath; (8) two rinses; (9) a black nickel 

plating bath; (10) a hot water rinse; (11) the trivalent chromium plating 

bath; (12) dragout rinse; (13) two countercurrent rinses; and (14) a hot 

water rinse. The first six steps are essentially the same for all parts, 

and the remaining steps are determined by the type of finish desired. For 

instance, a part that requires a chromium plate would skip the brass and 

black nickel plating tanks and go directly to the trivalent chromium tank 

following the rinsing steps after bright nickel plating. 

The trivalent chromium plating tank is 1.2 meters (m) (4.0 feet 

[ft]) long, 1.2 m (4.0 ft) wide, and 3.0 m (10.0 ft) deep. The plating 

tank holds approximately 4,160 liters (1,100 gallons) of plating 

solution. The trivalent chromium plating solution is Tri-Chrome LC Plus 

manufactured by Harshaw/Filtrol Partnership. A product brochure for 

Trichrome-LC Plus is attached and presents the process operating 

parameters for the bath. The trivalent chromium solution in use at Custom 

Processing is a first-generation bath that operates at a lower temperature 

(21°C [~70°F]) than the newer trivalent chromium baths now available. A 

chiller was installed on the tank to maintain the plating solution within 

the operating temperature range. Samples of the solution are sent to 

Harshaw each month for chemical analyses to ensure the bath is maintained 

at its proper concentration and to identify the level of contaminants. 

Additions are made to the bath every 1,000 ampere-hours by an automatic 

ampere-hour controller that is connected to the rectifier and tank. The 

ampere-hour controller cost approximately $950. A purifying solution is 

added periodically to remove any metal contaminants by precipitation, and 

52 
P.4 

the pH is also routinely checked. The tank is not equipped with a filter 

system to filter the bath solution or with a ventilation system because 

misting is not a problem with the trivalent chromium solutions. 

Plant personnel stated that costs associated with wastewater 

treatment are substantially lower for the trivalent chromium process 

compared to the hexavalent chromium process because the hexavalent 

chromium reduction tanks are not required and less sludge is generated as 

a result of the lower chromium concentration in the trivalent chromium 

baths. (The plant recently installed a wastewater treatment system and 

saved a significant amount of money by not having to install reduction 

tanks and by using smaller treatment tanks to handle the amount of 

chromium wastewater generated by the process.) In addition, compared to 

the hexavalent chromium process, the trivalent chromium process reduced 

the number of rejected parts. Plant personnel also stated that any 

rejects from the process can be placed directly back into the trivalent 

chromium plating tank for replating; with the hexavalent chromium process, 

the old plate had to be stripped off prior to replating. More thorough 

rinsing is required prior to and following the trivalent chromium tank to 

prevent contamination and remove chlorides from the part than was needed 

for the hexavalent chromium plating tank. 

V. Conclusion 

Custom Processing is a small job shop specializing in electroplating 

of furniture. The trivalent chromium process has been successfully 

running for 9 years with very few problems. The largest problem occurred 

when a plant employee made the wrong addition to the bath and the solution 

had to be replaced. The plant expressed a great deal of satisfaction with 

the trivalent chromium process because of the process improvements and 

savings in wastewaster treatment associated with the process. 

Attachment 

v3 
P.5 

HARSHAW PLATING PRODUCTS 

OPERATING INSTRUCTIONS 

HARSHAW TRI-CHROME" IC PLUS 

TRIVALENT CHROMIUM 

PLATING PROCESS 

INTRODUCTION 

Harshaw TRI-CHROME" LC is a new technolcgy chromium 

plating process using no chromic acid and offering the 

following advantages: 

1. Reduced effluent problems - r.o need to reduce 

toxic hexavalent chromium. Reduced slucre 

volume. 

2. No toxic hexchromium - no mist suppressants 

needed. 

3. Improved covering power. 

4. Complete absence of "burning at high current 

density. 

Note: Due to the- high plating speed cf 

LC at lower pH's some microcracfced deposits 

can be detected. These deposits can give 

t.he aDDearance of burninc. 

5. Ine formulation for bot.h decorative and hazefree microcisccntir.uous deposits. 

6. Improved metal distributio.**.: more uniform 

thickness across current densities. Simplifies 

rack design. 

7. Tolerates current interruption, sulfate and 

chloride drag-in. 

3. Better evaporation - reducing cost. 

?. Anodes will last indefinitely. 

Harshaw Tri-Chrome can reolace ccnventio.nai or crocnetary 

chromic acid based electrolytes '.vithout chanae cf processing sequences. Timing sequences c.n cresent equiome.nt 

need little, if any, alteration. 

Harshaw Tri-Chrome LC will help provide a lighter color 

deoosit than first ceneration trivalent chromiums. 

HARSHAW FILTROL 

,-.2IM or*- • :'..':3 n . ." r*..-r; i.\,r; 7-i O • Y 
HARSHAW TK I-CHROME

.u I. y C PLATING PROCESS 

SOLUTION COMPOSITION 

Mat_er_i a [ 

Tt." AiU1 i I i vi.* 

T i! lit .ih i I i zt.; I 

T C Kljljll 1 al to i 

riii 0111 i um ( Ci ' - ) 

Hoi i c Ai:i il i lljhO j ) 

Range 

360-42 0 tj/l . (40-5 6 oz/gal ) 40 0 g/I . 

55-7 5 ij/I. (5.5-7. 5 'i/vol ) (> 5 ml /I . 

2.0-5. 0 ml/1 , (2- 5 gal/100 0 cjal ) i. O ml/1 . 

20- 2 J g/I , (2.7-3. 0 oz/gal ) 22 g/1 . 

()0-6 5 ij/I, (. J ()/l. 

Opt i IIIIIIII 

( 5 ) . 5 oz/i- a I ) 

(6. 5 /./vo l ) 

( 1 g a I / I 00 0 ) 

( 2 .'.) oz/g a I ) 

OPKU/VIMNO CONDITIONS 

I'll 2 . 3-2.'J 

.T--mpe r a I u r u 

i'.i I lioilu i'u i i un t DUILS i t y 

Aij i t a t io n 

Anoilui i 

Amnio I'U i iu 111 Density 

Spec i I i i: Gi av i I y 1.20-1.24 

2.5-2.7 

( U 0 - 1 1 0 ° F ) H 5 - 'J 0 " F 

UGO-1OUO A/m2 (HO-100 ASF) 

Mild Air Agi tat ion 

Harshaw Special Graphite 

Maximum 54 0 A/m2 (50 ASF) 

1.22 

*A *• 

b> 
P.7 

PROCESS CONTROL 

general 

All constituents should be maintained within the ranges' 

specified under "Solution Composition". Additiens cf 

all constituents should be made no less often than everv 

5 amp-hours/litre 20 A/h -rai.; cr eac.n eight hours 

cf accumulated CDeraticn. Extension of the foreaoma 

current-time relationships will result in imbalance 

cf the solution and the necessity to make large additions 

which will require additional electrolyzing to restore 

the bath to operating condition. .Addition schedules 

should be established for each installation to adjust 

for varying amounts of drag-cut. All additions shouid 

be made during or just preceding electrolysis. 

TC Additive 

TRI-CHROME TC Additive is used for makeup and replenishment. It provides conductivity to t.he bath and 

also replaces chromium lost through drag-out. TC Additive 

may dissolve with difficulty unless special precautions 

are used. Fast addition rates may result in the formation 

of wet lumps of additive which may not dissolve. The 

TC Additive is preferably distributed slowly and evenly 

over the surface of the solution, giving most of the 

material time to dissolve before further additions are 

made. Small frequent additions are therefore preferred. 

The concentration of TC Additive should be maintained 

by keeping the specific gravity of the solution at a 

nmi.mum value of 1.13. An addition of 22.5 g/L '3 oz/gal) 

cf TC Additive will raise the specific gravity approximately 0.31 units. It is creferred to make this additic.n 

=ubseauent to additions cf TC Chrome Adjuster see 

Specific Gravity). 

High concentrations of TC Additive may resuit m the 

formation cf some crystals, especially if the solution 

temperature is low. The presence cz crystals may resuit 

i.n plugged air agitation lines or coated anodes. The 

latter may result in reduced current. If the crystals 

cose a problem, the affected equipment and anodes should 

be removed and cleaned (scrubbed). Low concentrations 

cf TC .Additive will reduce conductivity cf the bath 

resulti.na i.n reduced current or the need fcr increased 

voltage to maintain cathode current density. 

TRI-CHRO.ME TC Additive is a light green powder and wi 81 

tend to dust easilv. Proper safety procedures shoulc 

be used which are suitable for the handling cf powdered 

material that can orcduce dustina. 
P.8 

Adjuster 

TRI-CHROME TC Chrome Adjuster is used to replenish the 

chromium plated from the solution and is added cn the 

basis of ampere-hours. TC Chrome .Adjuster must be distributed slowly and evenly cver the surface cf the solution in the same manner as TC .Additive discussed above. 

TC Chrome Adjuster will have a consumption rate of 225-240 

g/1000 amp-hours (8-12 oz/1000 A-h) and should be added 

at least after each eight hours of accumulated actual 

plating time. 

TRI-CHROME TC Chrome Adjuster is a dark green powder 

and will tend to dust easily. Proper safety procedures 

should be used which are suitable for the handling cf 

powdered material that can produce dusting. 

TC Stabilizer 

TRI-CHROME TC Stabilizer forms a stable compound with 

the chromium allowing it to plate out from the trivalent 

state. High concentration of TC Stabilizer may result 

in some precipitation of chromium salts especially if 

the solution is unbalanced in other respects, such as 

high pH, and high temperature. Low stabilizer reduces 

plating rate. It is therefore important that TC 

Stabilizer be maintained within the range specified. 

TC Stabilizer is consumed by drag-out and electrolysis. 

A consumption rate of 1000 m.L/1000 amp-hours '35 fi. 

oz/1000 A-h) may be used until a specific consumption 

rate for the individual installation can be established 

based cn analysis. 

TC Regulator 

TRI-CHROME TC Regulator functions to clear the deposit 

of dark smudges and provide satisfactory metal distribution. Low TC Regulator may result in dark smudges in 

the deposit and decrease chromium thickness in mid-current 

density areas. High concentrations are not especially 

harmful, however, amounts greater than 10 -L/L 12 

gal/1000 gal) may result in reduced cover and/cr hazy 

white patches in the deposits. 

TC Regulator is consumed mainly by electrolysis and 

should be added based on an average consumption cf 15-50 

mL (1-2 fl oz) per 1300 amp hours. 

TC Corrector 

TC Corrector is used at the time cf make-up, : ...L/L 

j gal/1000 gal). Further additions may be required 

m some installations but shouid be added onlv cn the 

advice of a Harshaw Reoresentative. Harshaw TC Zcrrector heios improves throw. / 
P.9 

oH 

Cpti.mum operating pH is in the range of 2.5-2.7 pH values 

between 2.3-2.9 can be used, however, at high pH •'2 . 9 • 

coverage is improved at the expense cf plating speed. 

pH should be measured with a pH meter fitted with a 

sleeve type calomel electrode (see Analytical Methods 

for measure of pH). Due to the dark color of the 

solution, most pH papers will produce unsatisfactory 

results and their use is not recommended. pH adjustments 

should be made cn the basis of 2 mL/L (2 gal/1000 gal) 

concentrated hydrochloric acid to lower the pH 0.1 units 

or 2 mL/L !2 gal/1000 gal) of concentrated ammonium 

hydroxide (Sp. Gr. 0.89) to raise the pH 0.1 units. 

Additions of hydrochloric acid or ammonia will initially 

produce large temporary changes in pH which will then 

reach equilibrium ever a period of time. Because cf 

this, pH cannot be accurately measured for about 3-12 

hours following an addition of acid or ammonia. 

pH adjustments should be limited to 0.2 pH units at 

one time. pH adjustments greater than 0.2 pH units 

are preferably made in steps over a period of several 

hours, e.g., a desired adjustment of 0.4 pH unit should 

be made by addition of enough hydrochloric acid (or 

ammonia) to change 0.2 pH unit, waiting several hours, 

and then adding the additional requirement. 

Temoerature 

Optimum temperature range is 80°-110°F. At lower temperatures there is some danger of crystallization while 

higher temperatures will reduce covering power. Cooling 

may be required when operating continuously at more 

than 0.5 amp/litre (2 amp/gal) (see Equipment-Cooling). 

Consultation with Harshaw for appropriate cooling recommendations is suggested. Operating at temperatures 

below 30 °F may cause precipitation. Heating above HO T 

will redissolve precipitate. 

Cathode Current Density./?latina Rate 

It is suggested that an average cathode current density 

of 360-1080 A/m2 (30-100 ASF) be used to provide a balance 

between consumption of additives, deposition rate, rectifier requirements and -cooling capacity. Increasing 

current density will result in • decreasing cathode 

efficiency resultina in increased covering power but 

at the same time decreasing deposition rate (especially 

in high current density areas), increasing consumption 

of additives and oossibly cver-heati.ng (requiring additional cooling). In extreme cases where the utmost 
P.10 

•*> -

in coverage is required as well as uniformity cf metal 

thickness, it may be advantageous to strike at higher 

current density," e.g., 1600-2100 A/m2 '150-200 ASF) 

for thirty seconds. 

Under optimum conditicns, '6-10 u in._) cf chromium will 

be deposited per minute at 1080 .A/m--- '100 ASF). Increasing current density will not significantly increase 

the plating rate due to a decrease in cathode efficiency. 

Air Agitation 

The role of air agitation is to insure uniformity cf 

metal distribution rather than to stop high current 

density burning. The agitation should be mild and as 

uniform as poss.ible. 'See Equipment) Too much agitation 

results in a slight loss of coverage and too little 

results in uneven metal distribution. 

Air Agitation should be turned off during idle periods. 

SDecific Gravity 

Specific Gravity should be measured with a suitable 

hydrometer (see Analysis Bulletin). The specific gravity 

of the solution should be maintained at a minimum cf 

1.18. Operation of the bath at specific gravity of 

1.22 will produce best results with greater tolerance 

to the effects of metallic impurities. Operation of 

the bath at specific gravity greater than 1.24 may result 

in some crystallization especially if the solution is 

allowed to ecol below 27°C (80°F). Warming the solution 

to operating temperature,' 27-437 (30-110T•, will usually 

redissolve the crystals. (see Equipment-Anodes) Specific 

gravity is maintained by addition of TC Additive foliowing 

adjustment of the bath (if necessary) with TC Chrome 

Adjuster. 

The following table proviaes 

from specific gravity to Baume 

of hydrometer is available: 

conversion 

in the event 

nrormation 

this tvoe 

Soecific Gravi- da ume 

.19 0 

.20 0 

.21 0 

.22 0 

.23 0 

.24 0 

24 

2 5 

26 

:3.1 

f 
p.11 

SOLUTION MAINTENANCE 

The Tri-Chrome solution is maintained by addition of 

TC Additive, TC Chrome Adjuster, TC Stabilizer, TC 

Regulator and control of pH as described under "Process 

Control". The information given shouid allow for near 

optimum performance for most installations. Occasionally, 

the solution should be analyzed and adjustments made 

to optimize the solution. 

Large additions of TC Additive, 2 2.5 g/L (3 oz/gal) 

or greater, TC Chrome Adjuster, 7.5 g/L (1 oz/gal) or 

greater, or smaller quantities if both are added, may 

unbalance the chromium complex requiring re-eiectrolysis 

(30-60 minutes) to avoid plate defects. To avoid reelectrolysis, additions should be broken up and spread 

cut over 2 4 operating hours, along with the regular 

maintenance additions. 

SOLUTION PREPARATION 

The sequence outlined below should be followed as closely 

as possible. Suitable precautions should be taken where 

noted to insure proper make-up and aging of the solution. 

1) Read "Equipment" section to insure that the tank 

has been cleaned out properly and the proper equipment is in place. 

2; Fill the properly prepared plating tank one-half 

full with clean city water. Turn on the air agitation and heat the solution- to 60-65°C (140-150°?). 

Disconnect heat after reaching this temperature. 

2) Add (1.3 oz/gal) 10 g/L 3oric Acid. Let mix until 

dissolved. 

4) Using air agitation, slowly add the Tri-Chrome 

TC Additive (400 g/L or 3.33 lbs/gal) making sure 

that the material is dissolving as fast as it is 

being added. (See Process Control-TC Additive) 

Undissolved material on the bottom of the tank 

may. dissolve with difficulty and seriously affect 

proper break-in of the solution. The temperature 

of the solution will fall during the addition due 

to the solution of the TC Additive. It' will be 

helpful to reheat the solution to 3 5JC ,95'T) to 

facilitate dissolving the TC Additive. 

5) Install anodes at this time ''see Equipment-Anodes). 

6i Fill the tank to about 55% of its final volume 

with cold water. At this time the solution temperature should be about 2 5-2 0 T (77-8 6T) . Continue 

/ * 
P.12 

to agitate the solution 'use mechanical agitation 

if necessary) to insure complete solution cf the 

TC Additive. It is preferred to agitate the solution for 15-24 hours to insure complete solution. 

7) With good agitation, add 6.5 -=./vol (65 mL/L cr 

6.5 gal/1000 gal) TC Stabilizer. Add TC Stabilizer 

only as fast as thorough mixing of previous additions of TC Stabilizer will allow to avoid localized high concentrations. 

8) Mix for a few minutes and add 2.0 Ml/L (3.0 gal/1000 

gal) TC Regulator. Adjust temoerature to 29°C 

(85°F). 

9) Add 3 gal/1300 gal. Hydrochloric Acid and check 

pH after 3-10 hours. 

10) Add 3 mL/L (3 gal./1000 gal.) TC Corrector. 

11) Insert previously nickel plated corrugated steel 

dummy cathodes. A total area of about 25-100m2/ 

1000 litres (1-4 ft2/100 gal) should be used. 

Add water to the working level at this time and 

begin electrolyzing. 

12) The solution must be electrolyzed at this point 

to complex bath constituents properly. Electrolysis 

shouid be performed at 1080 A/m2 (100 ASF) using 

0.2 5-1.0 amp/litre (i-4 amp/gal ) for cne hour at 

operating temperature. 

13) After the one hour electrolysis period, the solution 

can be put into operation. Defects in the deposit, 

especially at high current density areas, can be 

eliminated by further electrolysis. 

METALLIC CONTAMINATION 

Due to the very mild acidity of the solution (pH 2 .•3-2.9' 

and the continuous removal of trace metallic contaminaticr. 

by plating, there should be no excessive buildup Y:Z 

impurities unless parts are frequently lost frcm racks 

cr if post-nickel rinsing is inadequate. In some cases, 

electrolytic purificaticn may be recommended tc insure 

that trace elements are keot within the tolerable levels, 

a.nd this is best achieved by plating periodically fcr 

a few hours at 108-324 .A/m2 (15-45 ASF) using nickel 

plated corrugated steel cathodes. 

The information below gives a guide to maximum leveis 

cf trace elements when cresent alone and• shows tnat 

ccccer and zinc must be maintained at a low level. 

/( 
In oractice, contaminants are found together, and under 

these conditions may reinforce one another. For example, 

0.0 5 g/L zinc, 0.10 g/L iron and 0.01 g/L copper may 

well be more harmful than 0.20 g/L nickel alone, even 

though all elements are present within their tolerance 

limits. 

Occasional difficulties have arisen in practice due 

to siphoning of nickel solution along compressed air 

lines. To avoid this, air lines should be fitted with 

anti-siphon devices (e.g., the drilling of a small hole 

at the highest point). 

In cases of gross contamination, methods are available 

for removal of metallic impurities by precipitation 

with TC Purifier, (see Harshaw Plating Processes Bulletin, 

"Purification of Tri-Chrome Trivalent Chromium Plating 

Solutions".! 

Important Note: 

Imbalance in solution composition may lead to brown/black 

marks which can be confused with nickel or iron contamination. Poorly maintained solutions, especially those 

deficient in TC Stabilizer and/or TC Chrome Adjuster, 

or too high in pH or temperature, will also be more 

susceptible to the effects of metallic contamination. 

If an analysis is available, the solution should always 

be optimized before attributing the defect to metallic 

contamination. In many cases readjustment of the solution will cure the problem without use of TC Purifier. 

1. Copper - maximum 0.0 2 g/L 

This is rarely found in practice unless solution 

is allowed to come into contact with exposed copper 

structures (e.g., bus bars) or brass/copper parts 

are allowed to dissolve in the bath. 

SvmDtoms 

— --

First shown by a graying at high current density, 

extending to lower current densities as the concentration increases. At very high concentrations, 

mid-current density areas can appear black and 

exposed nickel is stained brown (by immersion plate 

of copper) . 

Removal 

If copper is the only contaminant it is best to 

plate cut on nickel plated corrugated metal cathodes 

at low current density of 108-324 A/m2, (15-45 

ASF). If other contaminants need to be removed, 

TC Purifier will remove copper at the same time 

as other metallic contaminants. 

/-*-
P.M 

10 -

Zinc -

alHC 

zinc 

shaoed 

plated 

maximum 0 .'J D 

contamination 

die castinas 

that thev 

• 

SvmDtoms 

g/L 

can occur 

esDeciallv 

cannot be 

in plants plating 

when parts are so 

fullv coDDer/nickei 

Low levels of zinc contamination result in a reduction in coverage and a characteristic sharp 

white edge at the chromium cut-off. (Normal TriChrome deposits have a diffuse blue/brown cut-off 

in low current density areas.) High levels cf 

zinc contamination show a white iridescent stain 

at low current density areas and this can spread 

into mid-current density regions in the presence 

of other contaminants. 

Removal 

If zinc is the only contaminant and is present 

at a low level it can best be removed by plating 

out as for copper. High levels of contamination 

usually require treatment with TC Purifier. 

Nickel - maximum 0.20 g/L 

Some nickel contamination is found in all baths, 

due to drag-in and dissolution from nickel plated 

parts lost from racks. The level of nickel contamination is found when post-nickel rinsing is poor 

or parts retaining nickel solution are processed. 

The presence of nickel tends to reduce the tolerance 

to other contaminants such as copper and iron. 

Symotoms 

Contamination is indicated by dark brown or black 

marks at mid-current densities. These tend to 

be streaky and sharp-edged, unlike t.hose resulting 

from iron contamination. Nickel contamination 

can also be recognized by the reduction in staining 

below the cut-off although coverage is not reduced 

as with zinc. In combination with iron the region 

below the cut-off becomes golden 'see Iron) and 

t.he marks black. 

Removal 

Nickel plates out very slowly and is not normally 

removed while elating out zinc cr copper. The 

recommenced method cf removal is to use TC Furirier. 

53 
Iron - maximum 0.5 g/L 

Iron contamination can arise in two ways, by dissolution of parts lost from racks or by bipo'larity 

effects when using plain unplated steel dummy sheets. 

Tri-Chrome is tolerant to iron, which when present 

alone can be detected by the golden yellow stain 

present below the chromium cut-off. 

Symptoms 

Iron alone can cause brown fluffy marks at medium 

current density, together with obvious iron deposition (see above) in very low current density 

areas. A small amount of iron (0.05-0.10 g/L) 

is beneficial in extending cover and minimizing 

the effects of slight zinc contamination. 

Removal 

Iron plates out slowly at 108-324 A/m2 (15-45 ASF) 

on nickel plated corrugated steel cathodes but 

care should be taken not to introduce iron by the 

use of unplated cathodes. For larger concentrations 

of iron the use of. TC Purifier is recommended. 

Lead - maximum 0.0 2 g/L 

Lead contamination may arise as a consequence cf 

inadequate cleaning of tanks which have been used 

for hexavalent chromium solutions. Removal of 

lead is not always complete even with hydrochloric 

acid leaching and lead contamination manifests 

itself usually after the first overnight standing 

period. 

Symptoms 

White patches in low current density areas, spreading 

around the back of parts as a white haze. Some 

high current density adhesion failure may also 

be noted when high levels of lead are present. 

current tensities 

is best removed 

Remova1 

Lead elates out 

of 108-216 A/2 

by this means. 

readilv at 

(10-20 ASF) 

low 

and 

/ / 
P.16 

TROUBLESHOOTING SUMMARY 

Poor Coverage 

air agitation too high 

TC Additive cr specific gravity, too low 

needs plating, if additions have just 

been made 

zinc contamination 

lead contamination 

temperature too high 

current density too low 

.nitrate contamination 

oxidation of excess TC Purifier (dark 

band may also be present at chromium 

cut-off) 

Deposition Rate Too Low 

pH too high 

TC Regulator too low 

TC Stabilizer too low 

TC Additive or specific gravity too low 

inadequate air agitation over vertical 

surfaces 

III. Non-Uniform .Metal Distribution 

air agitation too low or badly positioned 

air coil 

TC Regulator low 

poor rack design 

poor anode positioning 

IV. Poor Conductivity 

poor electrical connections 

TC Additive too low 

low temperature 

low anode area 

anodes covered with crystals 

7. Crystallization 

solution too cold (crystallized salts 

may be sicw to redissolve) 

excessive evaporation during idle periods 

TC Additive tco high 

Microcracks Fail to Form 

insufficient chromium thickness 

cracks difficult to see unless the tarts 

are coooer elated (Dubournell Test) 

/<- * 
Dark Smudges cn Work Pieces 

metallic contamination 

low TC Regulator 

low TC Stabilizer made worse if TC Additive 

and TC Chrome Adjuster are also low, 

e.g., by excessive dilution 

VIII. White Patches on Work 

zinc contamination 

drying-on of nickel solution due to excessively hot nickel solution or prolonged 

drying 

incorrect precleaning prior to nickel 

lead contamination 

high non-pitter in nickel solution 

high TC Regulator 

microcracked in HCD area due to excessive 

current 

IX. Adhesion Loss 

post nickel rinse contaminated with chromic 

acid 

lead contamination 

bipolarity during exit from nickel tank 

bipolarity during entrance to chromium 

tank 

inadequate nickel activation (re-chroming) 

current density too high 

TC'Additive low (i.e., low specific gravity) 

X. White Film on Work 

This is usually due to the presence of a precipitate formed by adding TC Purifier. The precipitate can best be removed by filtration, preferably through a filter precoated with filter 

aid. 

The precipitated film can be wiped off easily 

and is normally found only on excessively 

contaminated solutions requiring constant 

TC Purifier additions. 

E

nUIPMENT 

/anxs 

The tank lining must be of plastic (PVC, ABS, polyethylene, cr rubber. Lead-lined tanks must not be used. 

Existing lead-lined tanks can be converted by lining 

with V rigid clastic sheet, insuring that the final 

/ « 
P.18 

assembly is leak-proof. A less preferred alternative 

is to fit a flexible plastic liner, but this is not 

recommended due to the likelihood cf mechanical damage. 

If a flexible liner must be used, it is suggested that 

a sheet cf rigid PVC be placed cn the tank bottom, above 

the flexible liner, to minimize possible damage to the 

liner. 

Existing plastic or rubber tanks must be thoroughly 

cleaned to remove all traces of lead chromate which 

may be adhering to the tank walls. Both lead and 

chromates are undesirable contaminants. Scrapping and 

leaching with sodium metabisulohite solution are required 

to insure complete cleanliness. After cleaning, the 

lining should be leached with 5% hydrochloric acid before 

use. Any film left after this operation should be scrubbed off and the tank again leached with 1% hydrochloric 

acid. 

Anodes 

Existing lead anodes must be replaced by special graphite 

anodes, fitted with titanium anode hangers specially 

designed to insure sound electrical and mechanical 

contact. .Anodes and hangers are available from Harshaw. 

Consultation with Harshaw is recommended for proper 

installation of anodes and hangers. As a general guide, 

the total immersed anode area should be twice the cathode 

area and should be sufficient to allow for a maximum 

anode current density of 540 A/m2 (50 ASF). A nominal 

24" :< 2" '510 mm x 5 0 mm) diameter anode has a maximum 

effective area of 1 ft2 (0. l.m2 ) . The top of the anode 

should be at least 2.5 cm (one inch) below solution 

level. 

Copper anode rails or bus bars should be heavily 

nickel-chrcmium plated to avoid possible copper contamination and exposed bus bar should be shielded, from 

solution by a plastic shield or by wrappi.ng wit.h plastic 

waterproof tape, etc. 

Anodes should not be removed until at least 3 0 minutes 

after platmg stops as they may be saturated with electrclytically produced noxious compounds. 

Continuous use of extremely high anode current densities 

will significantly shorten anode life. Anodes should 

be inspected fcr a coating or crystals if bath crystallization is noted. Operation of the bath with coated 

anodes will in effect produce high anode current 

densities. see Specific Gravity) 

/7 
P.19 

Air Agitation 

Perforated plastic air lines must be installed to give 

uniform mild agitation below the cathode area. Oil-free 

air from a blower should be used. 

It should be kept in mind that the air agitation is 

used to provide solution movement over the surface of 

the cathode and is not used to improve limiting current 

density as, for example, in nickel plating. Too much 

air agitation may result in a reduction of chromium 

coverage whereas too little may result in non-uniform 

thickness. 

Air lines should be designed as for nickel plating 

(Harshaw Technical Bulletin-Installation of Air agitation 

Systems for Electroplating Solutions), however, the 

air pipes should be spaced 100-150mm (4-6 in.) apart, 

not over 150mm (6 in.). The number of pipes used should 

be sufficient to cover the anticipated cathode area 

above the pipes plus 75mm (3 in.) in each direction. 

Due to the low pressure required for proper agitation, 

all perforated air lines must be installed level and 

in the same plane or uneven agitation will result. 

Valves for each air pipe should be provided to adjust 

the air volume at the tank. To prevent the possibility 

of siphoning solution out of the tank, a siphon-break 

hole should be drilled at the highest point of the air 

line(s) above the solution level. 

Cooling/Heatina 

Because the process operates at temperatures cf 27-43°C 

(30-110°F) some heating is necessary. The use cf titanium 

coils with boiler heating (controlled by thermostat) 

is appropriate. In high production units with high 

square footages some cooling may be necessary. 

If external cooling is to be used, the circulating plating 

solution should not be "over-cooled" (beicw 75°F) due 

to crystallization of the plating solution. 

.Ampere-Hour Meter 

An ampere-hour meter is necessary for optimum control 

of solution composition as maintenance additions are 

best made cn an ampere-hour basis. In most automatic 

operations, the chromium ampere-hours can be related 

to the nickel amoere-hour meter by suitable corrections 

for time and current. 

/ 1 
P.20 

.0 -

Rectifiers 

Existing 6-9 volt rectifiers are suitable for some installations, depending on anode area, cathode area, 

anode-to-cathode spacing, voltage losses in bus bars, 

etc. , but for parts consistently requiring very good 

coverage, 9 to 12 volt rectifiers give more flexibility. 

Ventilation 

Although there is no toxic chromic acid spray emitted 

by the Tri-Chrome solution, the gassing at. the cathode 

may, under certain conditions, produce an overspray 

that may be objectionable. For this reason, exhaust 

ventilation is recommended. Existing ventilation for 

hexavalent chromium baths is satisfactory. 

Filtration 

Tri-Chrome plating solutions requiring TC Purifier 

additions may create enough insoluble material in the 

solution to produce a white film on the work. Filtration 

of the solution, especially during the period immediately 

following TC Purifier addition, may therefore be desirable. Filters constructed of materials suitable for 

use with high chloride nickel solutions are satisfactory 

for use with the Tri-Chrome solution. 

The use of an approved type of filter aid is recommended 

to assist in removing the insoluble material. Consultation with Harshaw for satisfactory types of filter aids 

is suggested. 

The residue filtered from the Tri-Chrome solution should 

not be subjected to the action of strong mineral acids; 

noxious fumes may result if this practice is followed. 

See separate bulletin on the "Filtration of Tri-Chrome 

Plating Solutions" for information on filter size and 

filtration techniques. 

These oata are oelieved io Oe accurate Dut are not guaranteed to oe so. 

Notnmg fierein snail Oe construed as suggesting tne use ot our product 

in violation of any laws, regulations or ngnts ot tnird parties. Buyer snouid 

evaluate suitaoiliry ana salety ot product tor buyer's use. We cannot 

assume liaoility for results tnat Buyer ootains witn our products since 

conditions are not unaer our comrol.