p. 1



# OAR Box 

# 1313 Prepped byLaTeiaShed



### Document

Number: 

# 7DII-B-4 5 Docket Number: 

# A-88-0 2

Printed 6/12/20089:03:30AM

Sheet 71 of 99P. 2

* f 

# MR U A-88-0 2

gH* % MIDWES T RESEARC HINSTITU T 

## PB HX-6-MS -:-..e: = *m^^n p -0 1 Harriso nOak s Boutev** ' " ^ Carv . N C27= *



# - M ^ Date : Ma y

20 , 198 8 - - - - •«•;-*-• - (Finalize dJun e 30 , 1988 ) j *'• * Subject : Sit e Visit—Swai m Metals , Inc . 1 .— • Chromium

Electroplatin gNESHA P i(f : ! EPA Contrac t 68-02-3817 ; ES DProjec t 85/dii j MR I Projec t 7717- Kil l 

## 1 1661 8 1 NV

f :';.,.. \

_ . _—-»*i'n', ! 

# i l \ 8 HJL^ i From : Robi nBarke r To : Andre w

M . Smit h ESD/ISB/SS S (MD-13 ) U . S . Environmenta l Protectio nAgenc y Researc hTriangl e Park , N.C . 2771 1 I . Purpos e Th e purpos e o f thi s sit e visi t wa s t o gathe r backgroundinformatio n onth e us e o f th e trivalen t chromiu m proces s a s a replacemen t fo r the hexavalen t chromium proces s fo r decorativ e electroplatin g(plating ) applications . II . Plac e andDat e Swai m Metals , Incorporate d Pos t Offic e Box710 2 HighPoint , Nort hCarolin a 2726 4 (919 ) 889-353 5 Decembe r 7 , 198 7 III . Attendee s Swai m Metals , Incorporate d(Swaim ) Philli pT . Swaim , Presiden t Harshaw/Filtro l Partnershi p(Harshaw ) RonRuzzy , Technica l Sale s Representativ e U . S . Environmenta l Protectio nAqenc y (EPA ) Andre w M . Smith , IS B Gai l Lacy , SD B

/P. 3

Midwes t Researc hInstitut e (MRI ) Robi nBarke r IV . Discussio n Th e visi t bega nwit ha tou r o f th e manufacturin gandplatin g facility , whic hwa s followe db y a meetin gwit hplan t personne l t odiscus s th e operatio no f th e trivalen t chromiu m process . A . Genera l Swai m i s a captiv e sho ptha t manufacture s furnitur e sucha s tables , lamps , etc . Th e platin gsho pi s use dt oelectroplat e bot hbras s and chromiu m o nfurniture . Th e platin gshopoperate s 1 0 hour s pe r day , 4 day s pe r week . B . Proces s Descriptio n Eac hpar t i s fabricate dina serie s o f proces s step s includin g sanding , grinding , bending , an dpolishing . Th e part s ar e the nracke dan d electroplated . A

hand-operate dhois t i s use dt otransfe r part s throug h th e platin gprocess . Th e trivalen t chromiu m proces s lin e consist s o f a serie s o f 1 2 tank s containin gvariou s solution s tha t ar e use dfo r cleanin g an delectroplatin gth e part . Th e trivalen t chromiu m proces s sequenc e i s a s follows : alkalin e soak , electroclean , rinse , aci ddip , rinse , brigh t nickel , tw

orinses , trivalen t chromiu m electroplate , andthre e rinses . Th e firs t fou r proces s step s ar e performe dtwic e t oensur e tha t th e par t i s adequatel y

cleane dprio r t oelectroplating . Th e same proces s lin e als o i s use dt oplat e brass . Th e bras s tanki s situate dprio r t oth e trivalen t chromiu m tankand , dependin gonwhic hplatin gtanki s required , th e othe r platin gtanki s skippe dinth e proces s line . Followin gplating , eac hpar t i s spraye dwit hlacque r an doven-bake dbefor e packagin gfo r shipment . Th e trivalen t chromiu m platin gtanki s 1. 2 meter s (m ) (4. 0 fee t [ft] ) long , 1. 4 m

(4. 5 ft ) wide , an

d3. 0 m (1 0 ft ) dee pan

dhold s approximatel y

5,68 0 liter s (1,50 0 gallons ) o f platin gsolution . Th e platin gtankhold s on e rac ko f parts . Eac hrac ki s plate dfo r 3 minutes . Th e amoun t o f curren t an dvoltag e varie s wit hth e typ e o f part s plated . Th e platin gtanki s no t equippe dwit ha ventilatio n system . Th e platin groo m i s ventilated , whic hprovide s adequat e ventila tionfo r th e trivalen t chromiu m platin gtank . A t th e time o f th e visit , novisibl e mistin gwa s eviden t acros s the surfac e o f th e solution . Th e trivalen t chromiu m proces s ha s bee nuse da t th e plan t fo r approximatel y

1 0 year s withou t an y majo r problems . Th e trivalen t chromiu m solutio ni s Tri-Chrome LCPlu s manufacture db y Harshaw/Filtro l Partner ship . ( A

produc t informatio nbrochur e i s attache dandpresent s the typica l operatin gparameter s fo r th e bath. ) Th e platin gsolutio ni s coole db y a uniqu e coolin gsystem tha t plan t personne l fabricate dfro m an ic e machine . Th e bat hsolutio ni s occasionall y filtered , an

da sampl e o f the solutio ni s sen t onc e a mont ht oHarshaw 1 s la bfo r chemica l analyse s



## ZP. 4

t odetermin e wha t adjustment s ar e necessary t omaintai nth e bat hwithi n it s operatin grange . Th e bat hnormall y canbe maintaine db y makin g periodi c adjustment s t oth e solutio ncomposition . Th e bat hi s maintaine d b y additio no f TC-Additive , TC-Chrom e Adjustor , TC-Stabilizer , TC-Regulator , an

dcontro l o f th e pH . The bat hmay als orequir e purifica tio ndu e t ometa l contamination . Meta l contaminant s ar e remove dfro m the bat hb y "dummying " the solutio no r b y addingTC-Purifier , whic hresult s in precipitatio no f metals . I f TC-Purifie r i s adde dt oth e bath , th e solu tio ni s filtere dt oremov e th e metals . "Dummying " o f the solutio ni s a n electrolyti c purificatio nprocess . A non-produc t par t i s place dinthe tank , an dthe curren t densit y i s se t at 10 8 t o32 4 ampere s pe r squar e mete r (1 5 t o4 5 ampere s pe r squar e foot) , whic hresult s inth e meta l contaminan t platingou t o f th e bat hont othe part . A representativ e o f Harshaw visit s the plan t onc e ever y 3 t o4 week s t oadjus t th e bat ht oit s norma l operatin grange . Mr . Ruzz y o f Harshaw

informe dEPA

an dMR I personne l tha t the chemica l analysi s an dpurificatio nproces s ar e standard service s offere dt oal l Harsha w customers . Mr . Swai m

indicate dtha t th e trivalen t chromiu m proces s had increase dproductivit y b y 3 0 t o4 0 percen t ove r the hexavalen t chromiu m proces s b

y allowinganincreas e inth e numbe r o f part s containe doneach rac kan db y decreasin grejects . Th e numbe r o f reject s ha s decrease dfro m th e 1 0 t o1 5 percen t tha t th e plan t hadexperience dwit hhexavalen t chromiu m proces s t oapproximatel y 0 percen t wit hthe trivalen t chromiu m process . Mr . Swai m

als oindicate dthat , du e t othe increas e i nproduc tivit y an dthe decreas e i nrejects , the trivalen t chromiu m proces s cos t the plan t les s t oruntha nth e hexavalen t chromiu m process . V . Conclusio n Swai m Metals , Inc. , ha s bee nsuccessfu l at operatin gthei r trivalen t chromiu m proces s fo r 1 0 years . Mr . Swai m ha s agreedt osuppl y EPA wit h mor e detaile dinformatio nan dcos t dat a onthe trivalen t chromiu m proces s a s wel l a s the hexavalen t chromiu m proces s i f the informatio ni s availabl e throughthe company' s accountin gsystem . Attachmen t

•- 3P. 5

.-.ttaicnrnent 

# HARSHAWPLATINGPRODUCTS

OPERATIN GINSTRUCTION S HARSHAWTRI-CHROME ^ L C PLU S TRIVALEN T CHROMIU M PLATIN GPROCES S
INTRODUCTIO N Harsha wTRI-CHROME ^ L C i s a ne wtechnolog ychromiu m platin g proces s usin g n o chromi c aci d and offerin g th e followin g advantages : 1 . Reduce d effluen t problem s - n o nee d t o reduc e toxi c hexavalen t chromium . Reduce d sludg e volume . 2 . N o toxi c hexchromiu m- n o mis t suppressant s needed . 3 . Improve d coverin g power . 4 . Complet e absenc e o f "burnin g a t hig hcurren t density . Note : Du e t o th e hig hplatin g spee d o f L C a t lowe r pH' s som e microcracke d deposit s ca n b e detected . Thes e deposit s ca ngiv e th e appearanc e o f burning . 5 . On e formulatio n fo r bot hdecorativ e and haze

fre e microdiscontinuou s deposits . 6 . Improve d meta l distribution : mor e unifor m thicknes s acros s curren t densities . Simplifie s rac k design . 7 . Tolerate s curren t interruption , sulfat e and chlorid e drag-in . 8 . Bette r evaporatio n- reducin g cost . 9 . Anode s wil l las t indefinitely . Harsha wTri-Chrom e ca n replac e conventiona l o r proprietar y chromi c aci d base d electrolyte s withou t chang e c f process ing sequences . Timin g sequence s c npresen t equipmen t nee d little , i f any, alteration . Harsha wTri-Chrom e L C wil l hel p provid e a lighte r colo r deoosi t tha n firs t creneratio n trivalen t chromiums . 

# HARSHAW/FILTRO L

- •• •- •:.:• FILTRO L-*---"SHI P •3C*CC CHAGRI N BOULEVAR D •CLEVELAND

. OHIO-J-.'2-

. ••2'6 i 292-92 C 

# f.<! " IIAUSIIAW'I' U1-CHROM E[, C PLATIN GPROCES S

SOLUTIO NCOMPOSITIO N Mate r ia l
'l' C Acit' li t

i v e 'I'i. : Sta b i 1 i ze r 'l' C Regulato r Chroin ium(C r

•"*- * ) liori c Aci d(113BO3 ) Rang e 360-42 0cj/r
. (48-5 6 oz/gal ) 40 0 g/I , 55-7 5 cj/i
. . (5.5-7. 5 %/vo l) 6 5 ml/ L 2.0-5. 0ml/I
. (2- 5 cjal/100 0gal ) i. O ml/ L 20-2 3 cj/i
. (2.7-3. 0oz/gal ) 2 2 cj/l
. 60-6 5 g/I
. 6 3 cj/1
. Op t imu m (53. 3 oz/ga l ) (6. 5 i/vo l ) ( J cja'l/ l 0 0 0 ) (2 . l J oz/ga l )

OPERATUK ] CONDITION S (8 1 2 . 3-2.' J .Temperatur e Cathod e Curren t Densit y A< j i t a t i o n Anode s Anod e Curren t Densit y Specifi c Gravit y1.20-1.2 4 2.5-2. 7 (80-110°F ) U5-90° F 860-108 0 A/m 2 (80-10 0 ASE ) Mil d Ai r Agitatio n Harsha wSpecia l Graphit e Maximu m54 0 A/m 2 (5 0 ASF ) 1.2 2

< * • b >P. 7

PROCES S CONTRO L 

### Genera l Al l constituent s shoul d b e maintaine d withi nth e ranges ' specifie d unde r "Solutio n Composition" . Addition s c f al l constituent s shoul d b e mad e n o les s ofte ntha never v 5 amp-hours/litr e (2 0 A/ hgal. ) o r eac heigh t hour s o f accumulate d operation . Extensio no f th e foregoin g current-tim e relationship s wil l resul t i nimbalanc e o f th e solutio nan d th e necessit yt o mak e larg e addition s whic hwil l requir e additiona l electrolyzin g t o restor e th e bat ht o operatin g condition . .Additio n schedule s shoul d b e establishe d fo r eac hinstallatio nt o adjus t fo r varyin g amount s o f drag-out . Al l addition s shoul d b e mad e durin g o r jus t precedin g electrolysis . T C Additiv e TRI-CHROM E T C Additiv e i s use d fo r makeu p and replen

ishment . I t provide s conductivit yt o th e bat hand als o replace s chromiu m los t throug hdrag-out . T C Additiv e ma ydissolv e wit hdifficult yunles s specia l precaution s ar e used . Fas t additio nrate s ma yresul t i nth e formatio n o f we t lump s o f additiv e whic hma yno t dissolve . Th e T C Additiv e i s preferabl ydistribute d slowl yan d evenl y ove r th e surfac e o f th e solution , givin g mos t o f th e materia l tim e t o dissolv e befor e furthe r addition s ar e made . Smal l frequen t addition s ar e therefor e preferred . Th e concentratio no f T C Additiv e shoul d b e maintaine d b ykeepin g th e specifi c gravit yo f th e solutio na t a minimumvalu e o f 1.18 . An additio no f 22. 5 g/ L ( 3 oz/gal ) c f T C Additiv e wil l rais e th e specifi c gravit yapproxi

matel y0.0 1 units . I t i s preferre d t o mak e thi s additio n subsequen t t o addition s o f T C Chrom e Adjuste r (se e Specifi c Gravity) . Highconcentration s o f T C Additiv e ma yresui t i n th e formatio n o f som e crystals , especiall yi f th e solutio n temperatur e i s low . Th e presenc e c f crystal s ma yresul t i n plugge d ai r agitatio nline s o r coate d anodes . Th e latte r ma yresul t i n reduce d current . I f th e crystal s pos e a problem , th e affecte d equipmen t an d anode s shoul d b e remove d an d cleane d (scrubbed) . Lo wconcentration s o f T C Additiv e wil l reduc e conductivit yo f th e bat h resultin g i nreduce d curren t o r th e nee d fo r increase d voltag e t o maintai n cathod e curren t density . TRI-CHROM E T C Additiv e i s a ligh t gree npowde r an d wii l tend t o dus t easily . Prope r safet yprocedure s shoul d b e use d whic har e suitabl e fo r th e handlin g c f powdere d materia l tha t ca n produc e dusting .P. 8

T C Chrom e Adjuste r TRI-CHROM E T C Chrom e Adjuste r i s use d t o replenis hth e chromiumplate d fro mth e solutio nand i s adde d o nth e basi s o f "ampere-hours . T C Chrom e Adjuste r mus t b e dis

tribute d slowl yan d evenl ycve r th e surfac e o f th e solu

tio n i nth e sam e manne r a s T C Additiv e discusse d above . T C Chrom e Adjuste r wil l hav e a consumptio nrat e o f 225-24 0 g/100 0 amp-hour s (8-1 2 oz/100 0 A-h ) an d shoul d b e adde d a t leas t afte r eac heigh t hour s o f accumulate d actua l platin g time . TRI-CHROM E T C Chrom e Adjuste r i s a dar k gree npowde r and wil l ten d t o dus t easily . Prope r safet yprocedure s shoul d b e use d whic har e suitabl e fo r th e handlin g o f powdere d materia l tha t ca n produc e dusting . T C Stabilize r TRI-CHROM E T C Stabilize r form s a stabl e compoun d wit h th e chromium

allowin g i t t o plat e ou t fro mth e trivalen t state . Hig hconcentratio n o f T C Stabilize r ma yresul t i n som e precipitatio no f chromiumsalt s especiall yi f th e solutio ni s unbalance d i nothe r respects , suc ha s hig hpH , and hig htemperature . Lo wstabilize r reduce s platin g rate . I t i s therefor e importan t tha t T C Stabilize r b e maintaine d withi nth e rang e specified . T C Stabilize r i s consume d b ydrag-ou t an d electrolysis . Aconsumptio n rat e o f 100 0 mL/lOO O amp-hour s (3 5 fl . oz/100 0 A-h ) ma yb e use d unti l a specifi c consumptio n rat e fo r th e individua l installatio nca nb e establishe d base d o n analysis . T C Regulato r TRI-CHROM E T C Regulato r function s t o clea r th e deposi t o f dar k smudge s an d provid e satisfactor ymeta l distribu

tion . Lo wT C Regulato r ma yresul t i ndar k smudge s i n th e deposi t and decreas e chromiumthicknes s i nmid-curren t densit yareas . Hig hconcentration s ar e not . especiall y harmful , however , amount s greate r tha n1 0 mL/ L i 1 0 gal/100 0 gal ) ma yresul t i nreduce d cove r and/o r haz y whit e patche s i nth e deposits . T C Regulato r i s consume d mainl yb yelectrolysi s an d shoul d b e adde d base d o na naverag e consumptio nc f 25-5 0 m L (1- 2 f l oz ) pe r 100 0 am p hours . T C Correcto r T C Correcto r i s use d a t th e tim e o f make-up , 3 mL/ L ( 3 gal/100 0 gal) . Furthe r addition s ma yb e require d i n som e installation s bu t shoul d b e adde d onl yo nth e advic e o f a Harsha wRepresentative . Harsha wT C Cor

recto r helD S improve s throw . /P. 9

p H Optimu m

operatin g p H i s i nth e rang e o f 2.5-2. 7 p H value s betwee n2.3-2. 9 ca n b e used , however , a t hig hp H (2.9 ) coverag e i s improve d a t th e expens e o f platin g speed . p H shoul d b e measure d wit ha p H mete r fitte d wit ha sleev e typ e calome l electrod e (se e Analytica l .Method s fo r measur e o f pH) . Du e t o th e dar k colo r o f th e solution , mos t p H paper s wil l produc e unsatisfactor y result s an d thei r us e i s no t recommended . p H adjustment s shoul d b e mad e o n th e basi s o f 2 mL/ L ( 2 gal/100 0 gal ) concentrate d hydrochlori c aci d t o lowe r th e p H O. i unit s o r 2 mL/ L ( 2 gal/100 0 gal ) o f concentrate d ammoniu m hydroxid e (Sp . Gr . 0.89 ) t o rais e th e p H 0. 1 units . Addition s o f hydrochlori c aci d o r ammoni a wil l initiall y produc e larg e temporar ychange s i np H whic hwil l the n reac hequilibriu m ove r a perio d o f time . 3ecaus e of ' this , p H canno t b e accuratel ymeasure d fo r abou t 3-1 2 hour s followin g a n additio n o f aci d o r ammonia . p H adjustment s shoul d b e limite d t o 0. 2 p H unit s a t on e time . p H adjustment s greate r tha n0. 2 p H unit s ar e preferabl ymad e i n step s ove r a perio d o f severa l hours , e.g. , a desire d adjustmen t o f 0. 4 p H uni t shoul d b e mad e byadditio n o f enoug hhydrochlori c aci d (o r ammonia ) t o chang e 0. 2 p H unit , waitin g severa l hours , an d the naddin g th e additiona l requirement . Temoeratur e

- Optimu m

temperatur e rang e i s 80°-110°F . A t lowe r tempera
ture s ther e i s som e dange r o f crystallizatio nwhil e highe r temperature s wil l reduc e coverin g cower . Coolin g ma yb e require d whe noperatin g continuousl ya t mor e tha n 0. 5 amp/litr e ( 2 amp/gal ) (se e Equipment-Cooling) . Consultatio nwit hHarsha wfo r appropriat e coolin g rec ommendation s i s suggested . Operatin g a t temperature s belo w80° F ma ycaus e precipitation . Heatin g abov e 110 J F wil l redissolv e precipitate . Cathod e Curren t Density/Platin g Rat e I t i s suggeste d tha t a naverag e cathod e curren t densit y o f 860-108 0 A/m 2 (80-10 0 ASF ) b e use d t o provid e a balanc e betwee n consumptio no f additives , depositio nrate , recti

fie r requirement s and coolin g capacity . Increasin g curren t densit ywil l resul t i ndecreasin g cathod e efficienc yresultin g i n increase d coverin g powe r bu t a t th e sam e tim e decreasin g depositio nrat e (especiall y i n hig hcurren t densit yareas) , increasin g consumptio n o f additive s an

d possibl yover-heatin g (requirin g addi

tiona l cooling) . I n extrem e case s wher e th e utmos t 

# tP.1 0

- o i n coverag e i s require d a s wel l a s uniformit yo f meta l thickness , i t ma yb e advantageou s t o strik e a t highe r curren t density, * e.g. , 1600-210 0 A/m 2 (150-20 0 ASF ) fo r thirt yseconds . Unde r optimu mconditions , (6-1 0 u in. ) o f chromiumwil l b e deposite d pe r minut e a t 108 0 A/m 2 (10 0 ASF) . In
creasin g curren t densit ywil l no t significantl yincreas e th e platin g rat e du e t o a decreas e i ncathod e efficiency . Ai r Agitatio n Th e rol e o f ai r agitatio n i s t o insur e uniformit yo f meta l distributio nrathe r tha n t o sto p hig hcurren t densit yburning . Th e agitatio n shoul d b e mil d an d a s unifor m

a s possible . (Se e Equipment ) To o muc hagitatio n result s i n a sligh t los s o f coverag e an d to o littl e result s i n uneve n meta l distribution . Ai r Agitatio n shoul d b e turne d of f durin g idl e periods . Specifi c Gravit y Specifi c Gravit yshoul d b e measure d wit ha suitabl e hydromete r (se e Analysi s Bulletin) . Th e specifi c gravit y o f th e solutio n shoul d b e maintaine d a t a minimu mo f 1.18 . Operatio no f th e bat ha t specifi c gravit yo f 1.2 2 wil l produc e bes t result s wit hgreate r toleranc e t o th e effect s o f metalli c impurities . Operatio no f th e bat ha t specifi c gravit ygreate r tha n1.2 4 ma yresul t i n som e crystallizatio n especiall yi f th e solutio ni s allowe d t o coo l belo w27° C (80°F) . Warmin g th e solutio n t o operatin g temperature,'27-43° C (30-iiO°F; , wil l usuall y redissolv e th e crystals . (se e Equipment-Anodes ) Specifi c gravit yi s maintaine d byadditio no f TC Additiv e followin g adjustmen t o f th e bat h(i f necessary ) wit hT C Chrom e Adjuster . Th e followin g tabl e provide s conversio ninformatio n fro mspecifi c gravit yt o Baum e i nth e even t thi s typ e o f hydromete r i s available : Specifi c Gravit y'Baum e 1.19 0 23. 2 1.20 0 24. 2 1.21 0 25. 2 1.22 0 26. 2 1.23 0 27. 1 1.24 0 29. 1p.1 1

SOLUTIO NMAINTENANC E Th e Tri-Chrom e solutio n i s maintaine d byadditio no f T C Additive , T C Chrom e Adjuster , T C Stabilizer , T C Regulato r an d contro l o f p H a s describe d unde r "Proces s Control" . Th e informatio ngive nshoul d allo wfo r nea r optimumperformanc e fo r mos t installations . Occasionally , th e solutio n shoul d b e analyze d an d adjustment s mad e t o optimiz e th e solution . Larg e addition s o f T C Additive , 22. 5 g/ L ( 3 oz/gal ) o r greater , T C Chrom e Adjuster , 7. 5 g/ L ( 1 oz/gal ) o r greater , o r smalle r quantitie s i f bot har e added , may . unbalanc e th e chromiu mcomple xrequirin g re-electrolysi s (30-6 0 minutes ) t o avoi d plat e defects . T o avoi d re electrolysis , addition s shoul d b e broke nup an d sprea d ou t ove r 2 4 operatin g hours , alon g wit hth e regula r maintenanc e additions . SOLUTIO NPREPARATIO N Th e sequenc e outline d belo wshoul d b e followe d a s closel y a s possible . Suitabl e precaution s shoul d b e take nwher e note d t o insur e prope r make-u p an d agin g o f th e solution . 1 ) Rea d "Equipment " sectio nt o insur e tha t th e tank ha s bee n cleane d ou t properl yan d th e prope r equip

men t i s i n place . 2 ) Fil l th e properl yprepare d platin g tan k one-hal f ful l wit hclea n cit ywater . Tur no nth e ai r agi

tatio nan d hea t th e solutio nt o 60-65° C (140-150°F) . Disconnec t hea t afte r reachin g thi s temperature . 3 ) Ad d (1. 3 oz/gal ) 1 0 g/ L 3ori c Acid . Le t mi xunti l dissolved . 4 ) Usin g ai r agitation , slowl yad d th e Tri-Chrom e T C Additiv e (40 0 g/ L o r 3.3 3 lbs/gal ) makin g sur e tha t th e materia l i s dissolvin g a s fas t a s i t i s bein g added . (Se e Proces s Control-T C Additive ) Undissolve d materia l o n . th e botto mo f th e tank ma ydissolv e wit hdifficult yan d seriousl yaffec t prope r break-i no f th e solution . Th e temperatur e o f th e solutio nwil l fal l durin g th e additio ndu e t o th e solutio no f th e T C Additive . It ' wil l b e helpfu l t o rehea t th e solutio nt o 35° C (95°? ) t o facilitat e dissolvin g th e T C Additive . 5 ) Instal l anode s a t thi s tim e (se e Equipment-Anodes) . 6 ) Fil l th e tan k t o abou t 35 % o f it s fina l volum e wit hcol d water . A t thi s tim e th e solutio n temper
atur e shoul d b e abou t 25-30° C (77-86°F) . Continu e 

## /DP.1 2

- 3 - t o agitat e th e solutio n(us e mechanica l agitatio n i f necessary ) t o insur e complet e solutio nc f th e T C Additive . I t i s preferre d t o agitat e th e solu

tio nfo r 16-2 4 hour s t o insur e complet e solution . 7 ) Wit hgoo d agitation , add 6. 5 %/vo l (6 5 mL/ L c r 6. 5 gal/100 0 gal ) T C Stabilizer . Ad d T C Stabilize r onl ya s fas t a s thoroug hmixin g o f previou s addi

tion s o f T C Stabilize r wil l allo wt o avoi d local

ize d hig hconcentrations . 8 ) Mi xfo r a fe wminute s and add 3. 0 Ml/ L (3. 0 gal/100 0 gal ) T C Regulator . Adjus t temperatur e t o 29° C (85°F) . 9 ) Add 3 gal/iOO O gal . Hydrochlori c Aci d and chec k p H afte r 8-1 0 hours . 10 ) Add 3 mL/ L ( 3 gal./100 0 gal. ) T C Corrector . 11 ) Inser t previousl ynicke l plate d corrugate d stee l dummycathodes . Atota l are a o f abou t 25-100m 2 / 100 0 litre s (1- 4 ft 2 /10 0 gal ) shoul d b e used . Add wate r t o th e workin g leve l a t thi s tim e and begi n electrolyzing . 12 ) Th e solutio nmus t b e electrolyze d a t thi s poin t t o comple xbat hconstituent s properly . Electrolysi s should " b e performe d a t 108 0 A/m 2 (10 0 ASF ) usin g 0.25-1. 0 amp/litr e (1- 4 amp/gal ) fo r on e hou r a t operatin g temperature . 13 ) Afte r th e on e hou r electrolysi s period , th e solutio n ca nb e pu t int o operation . Defect s i nth e deposit , especiall ya t hig hcurren t densit yareas , ca nb e eliminate d b yfurthe r electrolysis . METALLI C CONTAMINATIO N Du e t o th e ver ymil d acidit yo f th e solutio n(p H 2.3-2.9 ) and th e continuou s remova l o f trac e metalli c contaminatio n byplating , ther e shoul d b e n o excessiv e buildu p o f impuritie s unles s part s ar e frequentl ylos t fro mrack s o r i f post-nicke l rinsin g i s inadequate . I nsom e cases , electrolyti c purificatio n ma yb e recommende d t o insur e tha t trac e element s ar e kep t withi n th e tolerabl e levels , and thi s i s bes t achieve d b yplatin g periodicall yfo r a fewhour s a t 108-324 A/m 2 (15-4 5 ASF ) usin g nicke l plate d corrugate d stee l cathodes . Th e informatio n belo wgive s a guid e t o maximu mlevel s o f trac e element s whe n presen t alon e and

- show s tha t coppe r and zin c mus t b e maintaine d a t a lowlevel . / /- q-

I n practice , contaminant s ar e foun d together , an d unde r thes e condition s ma yreinforc e on e another . Fo r example , 0.0 5 g/ L zinc , 0.1 0 g/ L iro n an d 0.0 1 g/ L coppe r ma y wel l b e mor e harmfu l tha n0.2 0 g/ L nicke l alone , eve n thoug hal l element s ar e presen t withi nthei r toleranc e limits . Occasiona l difficultie s hav e arise ni npractic e du e t o siphonin g o f nicke l solutio n alon g compresse d ai r lines . T o avoi d this , ai r line s shoul d b e fitte d wit h anti-sipho ndevice s (e.g. , th e drillin g o f a smal l hol e a t th e highes t point) . I n case s o f gros s contamination , method s ar e availabl e fo r remova l o f metalli c impuritie s byprecipitatio n wit hT C Purifier , (se e Harsha wPlatin g Processe s Bulletin , "Purificatio n o f Tri-Chrom e Trivalen t Chromiu mPlatin g Solutions" . ) Importan t Note : Imbalanc e i nsolutio n compositio nma ylea d t o brown/blac k mark s whic hca n b e confuse d wit hnicke l o r iro ncontamin

ation . Poorl ymaintaine d solutions , especiall ythos e deficien t i n T C Stabilize r and/o r T C Chrom e Adjuster , o r to o hig hi n p H o r temperature , wil l als o b e mor e susceptibl e t o th e effect s o f metalli c contamination . I f a n analysi s i s available , th e solutio nshoul d alway s b e optimize d befor e attributin g th e defec t t o metalli c contamination . I n man ycase s readjustmen t o f th e solu

tio n wil l cur e th e proble mwithou t us e o f T C Purifier . 1 . Coppe r - maximu m0. 0 2 g/ L Thi s i s rarel yfoun d i npractic e unles s solutio n i s allowe d t o com e int o contac t wit hexpose d coppe r structure s (e.g. , bu s bars ) o r brass/coppe r part s ar e allowe d t o dissolv e i n th e bath . Symptom s Firs t shown b

ya grayin g a t hig hcurren t density , extendin g t o lowe r curren t densitie s a s th e con centratio n increases . A t ver yhig hconcentrations , mid-curren t densit yarea s ca n appea r blac k an d expose d nicke l i s staine d brow n (b yimmersio nplat e o f copper) . Remova l I f coppe r i s th e onl ycontaminan t i t i s bes t t o plat e ou t o n nicke l plate d corrugate d meta l cathode s a t lo wcurren t densit yo f 108-32 4 A/m 2 , (15-4 5 ASF) . I f othe r contaminant s nee d t o b e removed , T C Purifie r wil l remov e coppe r a t th e sam e tim e a s othe r metalli c contaminants . 

## • OP. M

1 0 - Zin c - maximum0. 0 5 g/ L Zin c contaminatio n ca n occu r i nplant s platin g zin c di e casting s especiall ywhe npart s ar e s o shape d tha t the ycanno t b e full ycopper/nicke i plated . Symptom s Lo wlevel s o f zin c contaminatio nresul t i na re ductio n i n coverag e an d a characteristi c shar p whit e edg e a t th e chromiu mcut-off . (Norma l Tri

Chrom e deposit s hav e a diffus e blue/brow ncut-of f i n lowcurren t densit yareas. ) Hig hlevel s o f zin c contaminatio nsho wa whit e iridescen t stai n a t lo wcurren t densit yarea s an d thi s ca nsprea d int o mid-curren t densit yregion s i nth e presenc e o f othe r contaminants . Remova l I f zin c i s th e onl ycontaminan t and i s presen t a t a lo wleve l i t ca nbes t b e remove d b yplatin g ou t a s fo r copper . Hig hlevel s o f contaminatio n usuall yrequir e treatmen t wit hT C Purifier . Nicke l - maximum0.2 0 g/ L Som e nicke l contaminatio n i s foun d i nal l baths , du e t o drag-i n and dissolutio nfromnicke l plate d part s los t fromracks . Th e leve l o f nicke l contam
inatio ni s found whe n post-nicke l rinsin g i s poo r o r part s retainin g nicke l solutio n ar e processed . Th e presenc e o f nicke l tend s t o reduc e th e toleranc e t o othe r contaminant s suc ha s coppe r and iron . Symotom s Contaminatio n i s indicate d bydar k brow no r blac k mark s a t mid-curren t densities . Thes e tend t o b e streakyand sharp-edged , unlik e thos e resultin g fro miro n contamination . Nicke l contaminatio n ca n als o b e recognize d byth e reductio ni nstainin g belo wth e cut-of f althoug hcoverag e i s no t reduce d a s wit hzinc . I ncombinatio n wit hiro nth e regio n belo wth e cut-of f become s golde n(se e Iron ) and th e mark s black . Remova l Nicke l plate s ou t ver yslowl yan d i s no t normall y remove d whil e platin g ou t zin c o r copper . Th e recommende d metho d o f remova l i s t o us e T C Purifier . 

## A ?P.1 5

- 1 1

Iro n- maximu m

0. 5 g/ L Iro n contaminatio n ca n aris e i n tw o ways , b ydis

solutio n o f part s los t fro mrack s o r bybipolarit y effect s whe n "usin g plai nunplate d stee l dummysheets . Tri-Chrom e i s toleran t t o iron , whic hwhe npresen t alon e ca n b e detecte d b yth e golde nyello wstai n presen t belo wth e chromiumcut-off . Symptom s Iro n alon e ca n caus e brow nfluff ymark s a t medium curren t density , togethe r wit hobviou s iro ndep

ositio n (se e above ) i nver ylo wcurren t densit y areas . Asmal l amoun t o f iro n(0.05-0.1 0 g/L ) i s beneficia l i n extendin g cove r an d minimizin g th e effect s o f sligh t zin c contamination . Remova l Iro nplate s ou t slowl ya t 108-32 4 A/m 2 (15-4 5 ASF ) o n nicke l plate d corrugate d stee l cathode s bu t car e shoul d b e take nno t t o introduc e iro nb yth e us e o f unplate d cathodes . Fo r large r concentration s o f iro nth e us e o f T C Purifie r i s recommended . Lea d - maximu m0. 0 2 g/ L Lea d contaminatio nma yaris e a s a consequenc e o f inadequat e cleanin g o f tank s whic hhav e bee nuse d fo r hexavalen t chromiumsolutions . Remova l o f lea d i s no t alway s complet e eve nwit hhydrochlori c aci d leachin g an d lea d contaminatio nmanifest s itsel f usuall yafte r th e firs t overnigh t standin g period . Symptom s Whit e patche s i n lo wcurren t densit yareas , spreadin g aroun d th e bac k o f part s a s a whit e haze . Som e hig hcurren t densit yadhesio nfailur e ma yals o b e note d whe nhig hlevel s o f lea d ar e present . Remova l Lea d elate s ou t readil ya t lo wcurren t densitie s o f 108-21 6 A/ 2 (10-2 0 ASF ) an d i s bes t remove d bythi s means . 

# /fP.1 6

TROUBLESHOOTIN GSUMMAR Y Poo r Coverag e

cut-off ) II . Depositio n Rat e To o Lo w

ai r agitatio nto o hig h T C Additiv e o r specifi c gravit yto o low need s plating , i f addition s hav e jus t bee n mad e zin c contaminatio n lea d contaminatio n temperatur e to o hig h curren t densit yto o lo w nitrat e contaminatio n oxidatio no f exces s T C Purifie r (dar k ban d ma yals o b e presen t a t chromium

p H to o hig h T C Regulato r to o lo w T C Stabilize r to o lo w T C Additiv e o r specifi c gravit yto o lo w inadequat e ai r agitatio nove r vertica l surface s III . Non-Unifor m.Meta l Distributio n

ai r agitatio nto o lo wo r badl ypositione d ai r coi l T C Regulato r low poo r rac k desig n poo r anod e positionin g IV . Poo r Conductivit y

poo r electrica l connection s T C Additiv e to o low lo wtemperatur e lo wanod e are a anode s covere d wit hcrystal s V . Crystallizatio n

solutio nto o col d (crystallize d salt s ma yb e slo wt o redissolve ) excessiv e evaporatio ndurin g idl e period s T C Additiv e to o hig h VI . Microcrack s Fai l t o For m

insufficien t chromiumthicknes s crack s difficul t t o se e unles s th e part s ar e coppe r plate d (Dubpurnel l Test ) 

# /sP.1 7

VII . Dar k Smudge s o n Wor k Piece s

metalli c contaminatio n lowT C Regulato r lowT C Stabilize r mad e wors e i f T C Additiv e and T C Chrom e .adjuste r ar e als o low , e.g. , byexcessiv e dilutio n VIII . Whit e Patche s o nWor k

zin c contaminatio n drying-o n o f nicke l solutio n du e t o excess ivel yho t nicke l solutio n o r prolonge d dryin g incorrec t precleanin g prio r t o nicke l lead contaminatio n hig hnon-pitte r i nnicke l solutio n hig hT C Regulato r microcracke d i nHC D are a du e t o excessiv e curren t IX . Adhesio n Los s

pos t nicke l rins e contaminate d wit hchromi c aci d lea d contaminatio n bipolarit ydurin g exi t fro mnicke l tan k bipolarit ydurin g entranc e t o chromiu m tan k inadequat e nicke l activatio n(re-chroming ) curren t densit yto o hig h T C Additiv e lo w(i.e. , lowspecifi c gravit y X . Whit e Fil mo nWor k

Thi s i s usuall ydu e t o th e presenc e o f a precip

itat e forme d byaddin g T C Purifier . Th e precip

itat e ca nbes t b e remove d byfiltration , prefer

abl ythroug ha filte r precoate d wit hfilte r aid . Th e precipitate d fil mca nb e wipe d of f easil y and i s normall yfoun d onl yo nexcessivel y contaminate d solution s requirin g constan t T C Purifie r additions . EQUIP.MEN

T Tank s Th e tan k linin g mus t b e o f plasti c (PVC , ABS , polyethyl

ene , o r rubber . Lead-line d tank s mus t no t b e used . Existin g lead-line d tank s ca n b e converte d b ylinin g wit h-s " rigi d plasti c sheet , insurin g tha t th e fina l 

## / £- 1 4 -

assembl yi s leak-proof . Ales s preferre d alternativ e i s t o fi t a flexibl e plasti c liner , bu t thi s i s no t recommende d du e t o th e likelihoo d o f mechanica l damage . I f a flexibl e line r mus t b e used , i t i s suggeste d tha t a shee t o f rigi d PVC b e place d o nth e tank bottom , abov e th e flexibl e liner , t o minimiz e possibl e damag e t o th e liner . . Existin g plasti c o r rubbe r tank s mus t b e thoroughl y cleane d t o remov e al l trace s o f lea d chromat e whic h ma yb e adherin g t o th e tan k walls . 3ot hlea d an d chromate s ar e undesirabl e contaminants . Scrappin g and leachin g wit hsodiummetabisulphit e solutio nar e require d t o insur e complet e cleanliness . Afte r cleaning , th e linin g shoul d b e leache d wit h5 % hydrochlori c aci d befor e use . An yfil mlef t afte r thi s operatio nshoul d b e scrub

be d of f and th e tank agai nleache d wit h1 % hydrochlori c acid . Anode s Existin g lea d anode s mus t b e replace d byspecia l graphit e anodes , fitte d wit htitaniu manod e hanger s speciall y designe d t o insur e soun d electrica l and mechanica l contact . Anode s and hanger s ar e availabl e fro mHarshaw . Consultatio nwit hHarsha wi s recommende d fo r prope r installatio no f anode s an d hangers . A s a genera l guide , th e tota l i.mmerse d anod e are a shoul d b e twic e th e cathod e are a an d shoul d b e sufficien t t o allo wfo r a maximu m anod e curren t densit yo f 54 0 A/m 2 (5 0 ASF) . Anomina l 24 " x2 " (61 0 m

mx5 0 mm ) diamete r anod e ha s a maximu m ef f ectiv e are a o f I ft 2 (0.1m 2 ) . Th e to p o f th e anod e shoul d b e a t leas t 2. 5 c m(on e inch ) belo wsolutio n level . Coppe r anod e rail s o r bu s bar s shoul d b e heavil y nickel-chromiu m

plate d t o avoi d possibl e coppe r contam
inatio nan d expose d bu s ba r shoul d b e shielded , fro m solutio n bya plasti c shiel d o r b ywrappin g wit hplasti c waterproo f tape , etc . Anode s shoul d no t b e remove d unti l a t leas t 3 0 minute s afte r platin g stop s a s the yma yb e saturate d wit helectrc

lyticall yproduce d noxiou s compounds . Continuou s us e o f extremel yhig hanod e curren t densitie s wil l significantl yshorte nanod e life . Anode s shoul d b e inspecte d fo r a coatin g o r crystal s i f bat hcrystal

lizatio n i s noted . Operatio n o f th e bat hwit hcoate d anode s wil l i n effec t produc e hig hanod e curren t densities . (se e Specifi c Gravity )

' /P.1 9

- J. 3 - Ai r Agitatio n Perforate d plasti c ai r line s mus t b e installe d t o giv e unifor mmil d agitatio n belo wth e cathod e area . Oil-fre e ai r fro m

a blowe r shoul d b e used . I t shoul d b e kep t i nmin d tha t th e ai r agitatio ni s use d t o provid e solutio nmovemen t ove r th e surfac e o f th e cathod e an d i s no t use d t o improv e limitin g curren t densit yas , fo r example , i n nicke l plating . To o muc h ai r agitatio nma yresul t i na reductio no f chromium coverag e wherea s to o littl e ma yresul t i nnon-unifor m thickness . Ai r line s shoul d b e designe d a s fo r nicke l platin g (Harsha wTechnica l Bulletin-Installatio no f Ai r agitatio n System s fo r Electroplatin g Solutions) , however , th e ai r pipe s shoul d b e space d 100-150mm(4- 6 in. ) apart , no t ove r 150m

m ( 6 in.) . Th e numbe r o f pipe s use d shoul d b e sufficien t t o cove r th e anticipate d cathod e are a abov e th e pipe s plu s 75m m( 3 in. ) i neac hdirection . Du e t o th e lo wpressur e require d fo r prope r agitation , al l perforate d ai r line s mus t b e installe d leve l and i n th e sam e plan e o r uneve nagitatio nwil l result . Valve s fo r eac hai r pip e shoul d b e provide d t o adjus t th e ai r volum e a t th e tank . T o preven t th e possibilit y o f siphonin g solutio n ou t o f th e tank , a siphon-brea k hol e shoul d b e drille d a t th e highes t poin t o f th e ai r iine(s ) abov e th e solutio n level . Cooling/Heatin g Becaus e th e proces s operate s a t temperature s c f 27-43° C ;80-110°F ) som e heatin g i s necessary . Th e us e o f titanium coil s wit hboile r heatin g (controlle d bythermostat ) i s appropriate . I n hig hproductio nunit s wit hhig h squar e footage s som e coolin g ma yb e necessary . I f externa l coolin g i s t o b e used , th e circulatin g platin g solutio nshoul d no t b e "over-cooled " (belo w75°F ) du e t o crystallizatio no f th e platin g solution . Ampere-Hou r Mete r A n ampere-hou r mete r i s necessar yfo r optimu mcontro l c f solutio n compositio na s maintenanc e addition s ar e bes t mad e o n a n ampere-hou r basis . I nmos t automati c operations , th e chromiumampere-hour s ca nb e relate d t o th e nicke l ampere-hou r mete r bysuitabl e correction s fo r tim e an d current .

/ /1 6 -

Rectifier s Existin g 6- 9 vol t rectifier s ar e suitabl e fo r som e in

stallations , dependin g .o n anod e area , cathod e area , anode-to-cathod e spacing , voltag e losse s i nbu s bars , etc. , bu t fo r part s consistentl yrequirin g ver ygoo d coverage , 9 t o 1 2 vol t rectifier s giv e mor e flexibility . Ventilatio n Althoug hther e i s n o toxi c chromi c aci d spra yemitte d b yth e Tri-Chrom e solution , th e gassin g a t th e cathod e may , unde r certai nconditions , produc e a noverspra y tha t ma yb e objectionable . Fo r thi s reason , exhaus t ventilatio ni s recommended . Existin g ventilatio nfo r hexavalen t chromiu mbath s i s satisfactory . Filtratio n Tri-Chrom e platin g solution s requirin g T C Purifie r addition s ma ycreat e enoug hinsolubl e materia l i nth e solutio nt o produc e a whit e fil mo nth e work . Filtratio n o f th e solution , especiall ydurin g th e perio d immediatel y followin g T C Purifie r addition , ma ytherefor e b e desir

able . Filter s constructe d o f material s suitabl e fo r us e wit hhig hchlorid e nicke l solution s ar e satisfactor y fo r us e wit hth e Tri-Chrom e solution . Th e us e o f a napprove d typ e o f filte r ai d i s recommende d t o assis t i n removin g th e insolubl e material . Consulta

tio n wit hHarsha wfo r satisfactor ytype s o f filte r aid s i s suggested . Th e residu e filtere d fro mth e Tri-Chrom e solutio nshoul d no t b e subjecte d t o th e actio n o f stron g minera l acids ; noxiou s fume s ma yresul t i f thi s practic e i s followed . Se e separat e bulleti no nth e "Filtratio no f Tri-Chrom e Platin g Solutions " fo r informatio no nfilte r siz e and filtratio ntechniques .

These dat a are Believed i o D e accurat e Du : are no

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tDuyerootam s wit h ou rproducts since condition s are no

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# / ?