p. 1



# OAR Box 1313 Prepped byLaTeiaShed



### Document

Number: 

# 72 ) ll-B-4 6 Docket Number: 

# A-88-0 2

Printed 6/12/20089:03:30AM

Sheet 72 of 99P. 2 

# VIRIfg ) A-88-02 MIDWES TRESEARC H INSTITUT ! ^0 1 Harriso n Oak

s Bouteva ' Carv . N C 27? '



### Date : Ma y

20 , 198 8 " " J 

### ^f (Finalize dJun e 30 , 1988 ) Subject : Sit e Visit—Custo m Processin gCompany Chromiu m Electroplatin gNESHAP EPA Contrac t 68-02-3817 ; ES DProjec t 85/02 a MR I Projec t 7717- K 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 ogathe rbackgroundinformatio n o nth e us e o f trivalen t chromiu m proces s a s a replacemen t fo rthe hexavalen t chromiu

m proces s fo rdecorativ e electroplatin g(plating ) applications . II . Plac e an

dDat e Custom ProcessingCompany Surre t Driv e Pos t Offic e Box170 8 HighPoint , Nort hCarolin a2726 1 Decembe r7 , 198 7 III . Attendee s Custom Processing Butc hReddick , PlatingSuperviso r Harshaw/Filtro l Partnershi p(Harshaw ) RonRuzzy , Technica l Sale s Representativ e U . S . Environmenta l Protectio nAqenc y Andrew M . Smith , IS B Gai l Lacy , SDB

/P. 3

Midwes t Researc hInstitut e (MRI ) Robi nBarke r IV . Discussio n Custom Processin gCompany i s a jo bsho ptha t specialize s inchromium an dbras s platin go f furnitur e suc ha s lamps , chairs , andpedesta l feet . The plan t operate s 8 hours/day , 5 days/week . A . Genera l Th e trivalen t chromium proces s lin e ha s bee ni noperatio na t Custom Processingfo r approximatel y 9 years . Th e mai nreason s th e plan t switche d t o trivalen t chromium platin gwer e th e bette r coverag e an dthrowingpowe r o f the process , whic heliminate s the nee dfo r colo r buffing . I naddition , the plan t switche dt o trivalen t chromiu m becaus e o f concer nfo r the healt h o f it s employees . B . Proces s Descriptio n The trivalen t chromium platin glin e consist s o f a serie s o f tank s fo r cleanin gandplatin gth e parts . Th e platin glin e i s equippe dwit ha hand-operate dhois t tha t transfer s part s i nandou t o f th e followin g proces s tanks : (1 ) causti c soak ; (2 ) electroclean ; (3 ) tw o rinses ; (4 ) fou r brigh t nicke l baths ; (5 ) dragou t rinse ; (6 ) two countercurren t rinses ; (7 ) a bras s platin gbath ; (8 ) two rinses ; (9 ) a blac knicke l platingbath ; (10 ) a ho t wate r rinse ; (11 ) th e trivalen t chromiu m platin g bath ; (12 ) dragou t rinse ; (13 ) tw o countercurren t rinses ; an d(14 ) a ho t wate r rinse . Th e firs t si xstep s ar e essentiall y th e same fo r al l parts , an dthe remainin gstep s ar e determine db y th e typ e o f finis hdesired . Fo r instance , a par t tha t require s a chromium plat e woul dski pthe bras s an d blac knicke l platin gtank s an dg o directl y

t o th e trivalen t chromiu m tank followingth e rinsin gstep s afte r brigh t nicke l plating . Th e trivalen t chromium platin gtan ki s 1. 2 meter s (m ) (4. 0 fee t [ft] ) long , 1. 2 m

(4. 0 ft ) wide , an

d3. 0 m (10. 0 ft ) deep . Th e platin g tan khold s approximatel y 4,16 0 liter s (1,10 0 gallons ) o f plating solution . Th e trivalen t chromiu m platin gsolutio ni s Tri-Chrome L C Plu s manufacture db

y Harshaw/Filtro l Partnership . A produc t brochur e fo r Trichrome-L C Plu s i s attache dan dpresent s th e proces s operatin g parameter s fo r th e bath . Th e trivalen t chromium solutio ninus e a t Custom Processingi s a first-generatio nbat htha t operate s a t a lowe r temperatur e (21° C [~70°F] ) tha nth e newe r trivalen t chromium bath s now

available . A chille r wa s installe do nth e tankt o maintai nth e platin gsolutio nwithi n the operatin gtemperatur e range . Sample s o f th e solutio nar e sen t t o Harshaw eac hmont hfo r chemica l analyse s t o ensur e th e bat hi s maintaine d at it s prope r concentratio nan dt o identif y

th e leve l o f contaminants . Addition s ar e mad e t o th e bat hevery 1,00 0 ampere-hour s b y anautomati c ampere-hou r controlle r tha t i s connecte dt o th e rectifie r an dtank . The ampere-hou r controlle r cos t approximatel y $950 . A

purifyin gsolutio ni s addedperiodicall y

t o remov e an

y meta l contaminant s b y precipitation , an

d



### 52P. 4

the p Hi s als oroutinel y

checked . The tanki s no t equippe dwit ha filte r syste m t ofilte r th e bat hsolutio no r wit ha ventilatio nsystem becaus e mistingi s no t a problem wit hth e trivalen t chromiu m solutions . Plan t personne l state dtha t cost s associate dwit hwastewate r treatmen t ar e substantiall y lowe r fo r the trivalen t chromium proces s compare dt oth e hexavalen t chromium proces s becaus e th e hexavalen t chromiu m reductio ntank s ar e no t require dan dles s sludg e i s generate da s a resul t o f th e lowe r chromium concentratio ninthe trivalen t chromiu m baths . (The plan t recentl y installe da wastewate r treatmen t system an d saveda significan t amoun t o f mone y b y no t havingt oinstal l reductio n tank s an db y usin gsmalle r treatmen t tank s t ohandl e th e amoun t o f chromiu m wastewate r generate db y the process. ) I

naddition , compare dt o the hexavalen t chromium process , th e trivalen t chromium proces s reduce d the numbe r o f rejecte dparts . Plan t personne l als ostate dtha t an y reject s fro

m th e proces s ca nbe place ddirectl y bac kint oth e trivalen t chromiu m platin gtankfo r replating ; wit hth e hexavalen t chromiu m process , the ol dplat e hadt obe strippe dof f prio r t oreplating . Mor e thorough rinsingi s require dprio r t oan dfollowin gth e trivalen t chromiu m tankt o preven t contaminatio nan dremov e chloride s fro m the par t tha nwa s neede d for the hexavalen t chromiu m platin gtank . V . Conclusio n Custom Processin gi s a smal l jobshopspecializin ginelectroplatin g o f furniture . Th e trivalen t chromiu m proces s ha s bee nsuccessfull y runningfo r 9 year s wit hver y few problems . Th e larges t problem occurre d whe na plan t employe e mad e th e wron gadditio nt othe bat han dthe solutio n ha dt obe replaced . Th e plan t expresse da grea t dea l o f satisfactio nwit h the trivalen t chromiu m proces s becaus e o f the proces s improvement s an d saving s inwastewaste r treatmen t associate dwit hthe process . Attachmen t



### v 3P. 5 

# HARSHAWPLATINGPRODUCTS

OPERATIN GINSTRUCTION S HARSHA WTRI-CHROME " I C PLU S TRIVALEN T CHROMIU M PLATIN GPROCES S

INTRODUCTIO N Harsha wTRI-CHROME " L C i s a ne wtechnolcg 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 - r.o nee d t o reduc e toxi c hexavalen t chromium . Reduce d slucr e volume . 2 . No 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 the

- hig hplatin g spee d c f LC a t lowe r pH' s som e microcracfce d deposit s ca nb e detected . Thes e deposit s ca ngiv e t.h e aDDearanc e o f burninc . 5 . Ine formulatio nfo r bot. hdecorativ e and haze

fre e microcisccntir.uou s deposits . 6 . Improve d meta l distributio.**. : mor e unifor m thicknes s acros s curren t densities . Simplifie s rac k design . 7 . Tolerate s curren t interruption , sulfat e an d chlorid e drag-in . 3 . Bette r evaporatio n- reducin g cost . ? . Anode s wil l las t indefinitely . Harsha wTri-Chrom e ca n reolac e ccnventio.na i o r crocnetar y chromi c aci d base d electrolyte s '.vithou t chana e c f process ing sequences . Timin g sequence s c.ncresen t equiome.n 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 nfirs t ceneratio n trivalen t chromiums . 

# HARSHA WFILTROL ,-.2I Mor*

- • :'..':3 n. . " r*..-r ; i.\,r ; 7-i O • 

# Y.u y HARSHA WT K I-CHROM E I. C PLATIN GPROCES S

SOLUTIO NCOMPOSITIO N Mat_er_i a [

Tt. " AiU 1 i I i vi. * T i ! li t .i hi I i zt. ; I T C Kljljl l1 a

lto i rii i011 1 i um( Ci' - ) Ho ii c Ai: ii li lljhO j ) Rang e
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 m l/I
. 2.0-5. 0ml/1 , (2- 5 gal/100 0cjal ) i. O ml/1
. 20- 2Jg/I , (2.7-3. 0oz/gal ) 2 2 g/1
. ()0-6 5 ij/I , (
. J()/l
. Op t i IIIIIII I ( 5 )
. 5 oz/i- aI) (6. 5 /./vo l) (1 g aI/ I00 0 ) ( 2.'. ) oz/g aI)

OPKU/VIMN O CONDITION S I'l l2
. 3-2.' J .T--mp er aIur u i'. i Ilioil ui' ui i u nt DUIL S i t

y Aij i t at

io n Anoilui i Amni o I' Ui i u 11

1 Densit y Spe c i I i i : G i a vi I y1.20-1.2 4 2.5-2. 7 ( U0 - 1 1 0 ° F ) H 5 - ' J 0 " F UGO-1OU O A/m 2 (HO-10 0 ASF ) Mil d Ai r Ag i ta t io n Harsha wSpecia l Graphit e Maximu m5 4 0 A/m 2 (5 0 ASF ) 1.2 2



### * A * • 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" . Additien 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/ h-rai. ; c r eac. neigh t hour s c f accumulate d CDeraticn . Extensio no f th e foreaom a current-tim e relationship s wil l resul t i nimbalanc e c f th e solutio nand 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-cut . Al l addition s shoui 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 t.h e bat hand als o replace s chromiu mlos 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 n rate 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 yand 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 nmi.mu mvalu e o f 1.13 . A n additio n o 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 y0.3 1 units . I t i s creferre d t o mak e thi s additic. n =ubseauen t t o addition s c f T C Chrom e Adjuste r se e Specifi c Gravity) . Hig hconcentration s o f T C Additiv e ma yresui t mth e formatio nc f som e crystals , especiall yi f th e solutio n temperatur e i s low . Th e presenc e czcrystal s ma yresui 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 cos e a problem , th e affecte d equipmen t and anode s shoul d be remove d and cleane d (scrubbed) . Lo wconcentration s c f T C .Additiv e wil l reduc e conductivit yc f th e bat h resulti.na i.

nreduce d curren t o r th e nee d fc r increase d voltag e t o maintai n cathod e curren t density . TRI-CHRO.M E T C Additiv e i s a ligh t gree npowde r an d w i 8 1 tend t o dus t easilv . Prope r safet yprocedure s shoul c be use d whic har e suitabl e fo r th e handlin g c f powdere d materia l tha t ca norcduc e dustina .P. 8

Adjuste r TRI-CHROM E T C Chrom e Adjuste r i s use d t o replenis hth e chromium

plate d fro mth e solutio nan d i s adde d c n th 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 c f th e solu

tio n i n th 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 c f powdere d materia l tha t ca n produc e dusting . TC Stabilize r TRI-CHROM E T C Stabilize r form s a stabl e compoun d wit h th e chromiu m

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 chromiu msalt s especiall yi f th e solutio ni s unbalance d i nothe r respects , suc ha s hig hpH , an d 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 n th e rang e specified . TC Stabilize r i s consume d b ydrag-ou t an d electrolysis . Aconsumptio nrat e o f 100 0 m.L/100 0 amp-hour s '3 5 fi . 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 c 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 no t especiall y harmful , however , amount s greate r tha n1 0 -L/ L 1 2 gal/100 0 gal ) ma yresul t i n reduce d cove r and/c r haz y whit e patche s i n th e deposits . TC Regulato r i s consume d mainl ybyelectrolysi s an d shoul d b e adde d base d o n anaverag e consumptio nc f 15-5 0 mL (1- 2 f l oz ) pe r 130 0 am p hours . TC Correcto r TC Correcto r i s use d a t th e tim e c f make-up , : ...L/ L j gal/100 0 gal) . Furthe r addition s ma yb e require d msom e installation s bu t shoui d b e adde d onl vcnth e advic e o f a Harsha wReoresentative . Harsha wTC Zcr recto r heio s improve s throw . /P. 9

o H Cpti.mu moperatin 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 c 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 c nth 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 0. 1 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 meve r a perio d o f time . Becaus e c f 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 nstep 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 b

yadditio 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 , and the n addin 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 n whil e highe r temperature s wil l reduc e coverin g power . 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 n wit hHarsha wfo r appropriat e coolin g rec ommendation s i s suggested . Operatin g a t temperature s belo w3 0 ° F maycaus e precipitation . Heatin g abov e HO T wil l redissolv e precipitate . Cathod e Curren t Density. / ?latin a Rat e I t i s suggeste d tha t a n averag e cathod e curren t densit y o f 360-108 0 A/m 2 (30-10 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 an d -cooling capacity . Increasin g curren t densit ywil l resul t i n• decreasin g cathod e efficienc yresultin a 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 of additive s and oossibl ycver-heati.n g (requirin g addi

tiona l cooling) . I n extrem e case s wher e th e utmos tP.1 0

•*> - i n coverag e i s require d a s wel l a s uniformit yc 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 optimumconditicns , '6-1 0 u in._ ) c f chromiu mwil l b e deposite d pe r minut e a t 108 0 .A/m--

- '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 ni s t o insur e uniformit yc f meta l distributio n rathe r tha n t o sto p hig hcurren t densit yburning . Th e agitatio nshoul d b e mil d an d a s unifor ma s poss.ible . 'Se e Equipment ) To o muc hagitatio n result s i n a sligh t los s o f coverag e and to o littl e result s i n uneve n meta l distribution . Ai r Agitatio nshoul d b e turne d of f durin g idl e periods . SDecifi 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 mc f 1.18 . Operatio n o 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 n o 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 n i s allowe d t o eco l belo w27° C (80°F) . Warmin g th e solutio n t o operatin g temperature, ' 27-43 7 (30-110T• , wil l usuall y redissolv e th e crystals . (se e Equipment-Anodes ) Specifi c gravit yi s maintaine d byadditio n o f TC Additiv e foliowin g adjustmen t o f th e bat h(i f necessary ) wit hT C Chrom e Adjuster . Th e followin g tabl e proviae s fro m specifi c gravit yt o Baum e o f hydromete r i s available : conversio n i nth e even t nrormatio n

thi s tvo e Soecifi c Gravi

- d a um e .19 0 .20 0 .21 0 .22 0 .23 0 .24 0 2 4 2 5 2 6 :3. 1


# fp.1 1

SOLUTIO NMAINTENANC E Th e Tri-Chrom e solutio ni s maintaine d b yadditio no f TC 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 n give nshoui 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 , 2 2. 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 , ma y unbalanc e th e chromiu mcomple xrequirin g re-eiectrolysi 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 and sprea d cu 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 n t o insur e tha t th e tan k 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 tank one-hal f ful l wit hclea n cit ywater . Tur no nth e ai r agi

tatio nan d hea t th e solution

- t o 60-65° C (140-150°?) . Disconnec t hea t afte r reachin g thi s temperature . 2 ) 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 tan k may . dissolv e wit hdifficult yan d seriousl yaffec t prope r break-i n o f th e solution . Th e temperatur e o f th e solutio n wil l fal l durin g th e additio ndu e t o th e solutio n o f th e T C Additive . It ' wil l b e helpfu l t o rehea t th e solutio n t o 3 5 J C ,95'T ) t o facilitat e dissolvin g th e T C Additive . 5 ) Instal l anode s a t thi s tim e ''see Equipment-Anodes) . 6 i Fil l th e tan k t o abou t 55 % 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 2 5- 2 0 T (77- 8 6T) . Continu e / *P.1 2

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 n fo r 15-2 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 ad d 2. 0 Ml/ L (3. 0 gal/100 0 gal ) T C Regulator . Adjus t temoeratur e t o 29° C (85°F) . 9 ) Ad d 3 gal/130 0 gal . Hydrochlori c Aci d an d chec k p H afte r 3-1 0 hours . 10 ) Ad d 3 mL/ L ( 3 gal./100 0 gal. ) T C Corrector . 11 ) Inser t previousl ynicke l plate d corrugate d stee l dumm y cathodes . A

tota 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 . Ad d wate r t o th e workin g leve l a t thi s tim e an d begi nelectrolyzing . 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 shoui d b e performe d a t 108 0 A/m 2 (10 0 ASF ) usin g 0. 2 5-1. 0 amp/litr e (i- 4 amp/ga l ) fo r cn 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 n b e pu t int o operation . Defect s i nth e deposit , especiall ya t hig hcurren t densit yareas , canb e eliminate d byfurthe 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 contaminaticr . b yplating , ther e shoul d b e n o excessiv e buildu p Y:Z impuritie s unles s part s ar e frequentl ylos t frcmrack s c r i f post-nicke l rinsin g i s inadequate . I nsom e cases , electrolyti c purificatic nmayb e recommende d t c insur e tha t trac e element s ar e keo t withi nth e tolerabl e levels , a.n d thi s i s bes t achieve d b yplatin g periodicall yfc r a fewhour s a t 108-32 4 .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 mlevei s c f trac e element s whe n cresen t alon e and • show s tna t cccce r and zin c mus t b e maintaine d a t a lowlevel . /(I n oractice , 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 nan 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 nalon 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 nb e confuse dwit hnicke l o r iro ncontamin

ation . Poorl ymaintaine dsolutions , especiall y thos e deficien t i nT 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 nanalysi 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 n practic 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 . SvmDtom 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 and 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 cu t o n nicke l plate d corrugate d meta l cathode s a t lowcurren 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 , TC Purifie r wil l remov e coppe r a t th e sam e tim e a s othe r metalli c contaminants . /-*

-P. M

1 0 - Zin c - alH C zin c shaoe d plate d maximu m

0 .'J D contaminatio n di e castina s tha t the v • SvmDtom s g/ L ca noccu r esDeciall v canno t b e i n plant s platin g

whe npart s ar e s o full vcoDDer/nicke i

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 c f zin c contaminatio nsho wa whit e iridescen t stai n a t lowcurren t densit yarea s and 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 byplatin 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 - maximu m0.2 0 g/ L Som e nicke l contaminatio n i s found i nal l baths , du e t o drag-i n an d dissolutio n fromnicke l plate d part s los t fro mracks . Th e leve l o f nicke l contam inatio n i s foun d whe npost-nicke l rinsin g i s poo r o r part s retainin g nicke l solutio nar 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 an d iron . Symotom s Contaminatio n i s indicate d b ydar 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 t.hos e resultin g fro m iro ncontamination . 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 n combinatio n wit hiro nth e regio n belo wth e cut-of f become s golde n'se e Iron ) and t.h e mark s black . Remova l Nicke l plate s ou t ver yslowl yand i s no t normall y remove d whil e elatin g ou t zin c c r copper . Th e recommence d metho d c f remova l i s t o us e T C Furirier . 

## 53Iro n - maximu m0. 5 g/ L Iro n contaminatio nca n aris e i ntw o ways , b ydis

solutio n o f part s los t fro mrack s o r b ybipo'larit y effect s whe nusin g plai n unplate d stee l dummysheets . Tri-Chrom e i s toleran t t o iron , whic hwhe npresen t alon e ca nb e detecte d byth e golde nyello wstai n presen t belo wth e chromiu mcut-off . Symptom s Iro nalon e ca ncaus e brow nfluff ymark s a t mediu m curren t density , togethe r wit hobviou s iro ndep

ositio n(se e above ) i n ver 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 nextendin g cove r and 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 n no 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 of . T C Purifie r i s recommended . Lea d - maximu m0. 0 2 g/ L Lea d contaminatio n ma yaris e a s a consequenc e c f inadequat e cleanin g o f tank s whic hhav e bee nuse d fo r hexavalen t chromiu msolutions . Remova l o f lea d i s no t alway s complet e eve nwit hhydrochlori c aci d leachin g and 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 lowcurren 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 .

curren t tensitie s i s bes t remove d Remova 1 Lea d elate s ou t o f 108-21 6 A/ 2 b ythi s means . readil va t (10-2 0 ASF ) lo w

an d

/ /P.1 6

TROUBLESHOOTIN GSUMMAR Y Poo r Coverag e

ai r agitatio nto o hig h T C Additiv e c r specifi c gravity , to 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 n o f exces s T C Purifie r (dar k ban d ma yals o b e presen t a t chromium cut-off ) Depositio nRat e To o Lo w

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 low inadequat e ai r agitatio n ove 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 lo w lo wtemperatur e lo wanod e are a anode s covere d wit hcrystal s 7 . Crystallizatio n

solutio n to o col d (crystallize d salt s ma yb e sic wt o redissolve ) excessiv e evaporatio ndurin g idl e period s T C Additiv e tc o hig h Microcrack s Fai l t o Form

insufficien t chromiu mthicknes s crack s difficul t t o se e unles s th e tart s ar e coooe r elate d (Dubournel l Test ) /<- *Dar k Smudge s c nWor k Piece s metalli c contaminatio n lo wT C Regulato r lo wT 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 n Wor k

zin c contaminatio n drying-o no f nicke l solutio n du e t o excess ivel yho t nicke l solutio no r prolonge d dryin g incorrec t precleanin g prio r t o nicke l lea d contaminatio n hig hnon-pitte r i nnicke l solutio n hig hT C Regulato r microcracke d i n HC D are a du e t o excessiv e curren t IX . Adhesio nLos 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 TC'Additiv e lo w(i.e. , lowspecifi c gravity ) 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 b yaddin g T C Purifier . Th e precip

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

abl ythroug ha filte r precoate d wit hfilte r aid . Th e precipitate d fil mca n b e wipe d of f easil y and i s normall yfound onl yo nexcessivel y contaminate d solution s requirin g constan t T C Purifie r additions . E n UIPMEN T /anx s Th e tank linin g mus t b e o f plasti c (PVC , ABS , polyethyl

ene , c 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 hV

rigi d clasti c sheet , insurin g tha t th e fina l / «P.1 8

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 c 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 c f rigi d PVC b e place d c nth e tan k 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 . Bot hlea d and chromate s ar e undesirabl e contaminants . Scrappin g and leachin g wit hsodiummetabisulohit 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 . Anyfil m

lef t afte r thi s operatio nshoul d b e scrub

be d of f and th e tan k agai nleache d wit h1 % hydrochlori c acid . Anode s Existin g lead anode s mus t b e replace d b yspecia l graphit e anodes , fitte d wit htitaniu manod e hanger s speciall y designe d t o insur e soun d electrica l an d mechanica l contact . .Anode s an d hanger s ar e availabl e fro mHarshaw . Consultatio nwit hHarsha wi s recommende d fo r prope r installatio n o f anode s an d hangers . A s a genera l guide , th e tota l immerse 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 " : < 2 " '51 0 m

m x5 0 mm ) diamete r anod e ha s a maximu m effectiv e are a o f 1 ft 2 (0 . l.m 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-chrcmiu m

plate d t o avoi d possibl e coppe r contam inatio nand expose d bu s ba r shoul d b e shielded , fro m solutio nb

ya plasti c shiel d o r b ywrappi.ng 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 platm 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 n anod e life . Anode s shoul d b e inspecte d fc r a coatin g o r crystal s i f bat hcrystal

lizatio ni 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 ) 

# /7P.1 9

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 nbelo 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 n min 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 and 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 chromiu m 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 lowpressur e require d fo r prope r agitation , al l perforate d ai r line s mus t b e installe d leve l an d i n th e sam e plan e o r uneve n agitatio 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 nou 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 line(s ) abov e th e solutio nlevel . Cooling/Heatin a Becaus e th e proces s operate s a t temperature s c f 27-43° C (30-110°F ) som e heatin g i s necessary . Th e us e c f titaniu m coil s wit hboile r heatin g (controlle d b ythermostat ) 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 n shoul d no t b e "over-cooled " (beic 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 optimumcontro l o f solutio ncompositio na s maintenanc e addition s ar e bes t mad e c n a nampere-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 amoere-hou r mete r bysuitabl e correction s fo r tim e and current .

/ 

# 1P.2 0

. 0 - 

### Rectifier s Existing 6- 9 vol t rectifier s ar e suitabl e fo r som e in

stallations , depending on anod e area , cathod e area , anode-to-cathod e spacing , voltag e losse s inbu s bars , etc . , bu t fo r part s consistentl yrequiring ver ygoo d coverage , 9 t o 1 2 vol t rectifier s giv e mor e flexibility . Ventilatio n Althoughther e i s no toxi c chromi c aci d spra yemitte d b ythe Tri-Chrom e solution , th e gassin g at . the cathod e may , unde r certai n conditions , produc e a noverspray tha t mayb e objectionable . Fo r thi s reason , exhaus t ventilatio n i s recommended . Existin g ventilatio nfo r hexavalen t chromiu mbath s i s satisfactory . Filtratio n Tri-Chrome platin g solution s requirin g TC Purifie r addition s maycreat e enoughinsolubl e materia l i n the solutio n t o produc e a whit e fil mo nth e work . Filtratio n o f the solution , especiall ydurin g th e perio d immediatel y following T C Purifie r addition , maytherefor e be desir

able . Filter s constructe d o f material s suitabl e fo r us e wit hhighchlorid e nicke l solution s ar e satisfactory fo r us e wit hth e Tri-Chrome solution . The us e o f a n approve d typ e o f filte r ai d i s recommende d t o assis t i n removing the insolubl e material . Consulta

tion wit hHarshawfo r satisfactorytype s o f filte r aid s i s suggested . The residu e filtere d fro mthe Tri-Chrom e solutio nshoul d no t be subjecte d t o the actio n o f strong minera l acids ; noxiou s fume s ma yresul t i f thi s practic e i s followed . Se e separat e bulleti non the "Filtratio n o f Tri-Chrome Plating Solutions " fo r informatio no nfilte r siz e an d filtratio n techniques .

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