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# OAR Box 

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### Document

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# 70 ) ll-B-4 4

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MIDWES TRESEARC H INSTITUT E TE-12>-'4' 4 Suit e 35 0 40 1 Harriso n Oak s Boulevar d Cary , Nort h Carolin a 2751 3 Telephon e (919 ) 677-024 9 FA X (919 ) 677-006 5

Date :
Subject :

From : To : Ma y

20 , 198 8 (Finalize dJun e 30 , 1988 ) Sit e Visit—Plan t AB C Chromiu m Electroplatin g NESHA P EP A Contrac t 68-02-3817 ; ES D Projec t 85/02 a MR I Projec t 7717- K Robi nBarke r 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 

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I

. Purpos e Th e purpos e o f thi s sit e visi t wa s t o gathe r backgroun dInformatio n o nth e us e o f th e trivalen t chromiu m proces s a s a replacemen t fo r th e hexavalen t chromiu

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

d Dat e Plan t AB C Southeaster nU.S . Januar y 18 , 198 8
III . Attendee s Plan t AB C
J . T . Gilbert , Finishin g Superintenden t Harshaw/Filtro l Partnershi p Thoma s Ferguson , Accoun t Manage r Midwes t Researc hInstitut e (MRI ) Robi nBarke r

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IV . Discussio n A meetin g wa s hel dwit hplan t personne l t o discus s th e trivalen t chromiu m platin g operatio na t Plan t ABC . Th e meetin g wa s followe db y a tou r o f th e platin g shop . A . Genera l Plan t AB C i s a jobshopspecializin g i ndecorativ e chromiu m platin g o f stor e shelvin g an

dsupplie s fo r departmen t store s suc ha s J . C . Penne y an dK-Mart . Ther e ar e tw o platin g line s a t Plan t ABC , a nautomati c an

da hand-operate dline . Th e automati c lin e i s operate dinfrequentl y durin g th e year . Th e hand-operate dlin e operate s 9 hours/day , 6 days/week , an d 5 0 weeks/year . B . Proces s Descriptio n Th e two trivalen t chromiu m platin g proces s line s use da t thi s facilit y fo r decorativ e chromiu m platin g ar e identica l inproces s configuratio n(sequence) . On e lin e i s equippe dwit ha hand-operate dhois t t o transfe r eac hrac k o f part s throug ha serie s o f tanks , an dth e othe r lin e i s equippe dwit ha nautomati c hoist . I t take s approximatel y 1 hou r fo r eac hrac k o f part s t o complet e th e platin g cycl e fo r bot hlines . Th e trivalen t chromiu

m proces s line s consis t o f th e followin g tank s i n series : (1 ) alkalin e soa k clean ; (2 ) wate r rinse ; (3 ) electroclean ; (4 ) two wate r rinses ; (5 ) hydrochlori c aci ddip ; (6 ) tw o wate r rinses ; (7 ) hydrochlori c aci ddip ; (8 ) electroclean ; (9 ) tw o wate r rinses ; (10 ) hydrochlori c aci ddip ; (11 ) wate r rinse ; (12 ) brigh t nicke l plating ; (13 ) fou r wate r rinses ; (14 ) trivalen t chromiu m plating ; (15 ) dri ptank ; (16 ) wate r rinse ; (17 ) causti c solution ; (18 ) wate r rinse ; an d(19 ) ho t wate r rinse . Ther e ar e two trivalen t chromiu m platin g tank s inth e hand-operate d line . Bot htank s ar e identica l i nsize . Eac htank i s 5. 0 meter s (m ) (16. 5 fee t [ft] ) long , 1. 1 m (3.7 5 ft ) wide , an

d2. 2 m (7. 2 ft ) dee pan

d hold s approximatel y

11,74 0 liter s (i)

(3,10 0 gallon s [gal] ) o f platin g solution . Eac hplatin g tan k hold s on e rac k o f part s a t a time . Eac hrac k remain s inth e platin g tank fo r 2. 0 minutes . Th e platin g thicknes s range s fro m 8 t o 1 0 mi month s o f a ninch . Th e norma l operatin g voltag e i s 1 3 volts , an

dth e amperag e i s 15,00 0 ampere s o f direc t current . Eac htank i s equippe dwit ha filtratio nsystem tha t constantl y

filter s th e platin g solution . Th e tank s ar e no t equippe dwit ha ventilatio nsystem ; however , durin g th e visi t no visibl e mistin g wa s observe da t the surfac e o f th e platin g solutions . Ther e i s on e trivalen t chromiu m platin g tank inth e automati c line . Th e tank i s approximatel y 3. 0 m (10. 0 ft ) long , 0. 8 m (2. 5 ft ) wide , an

d1. 7 m (5. 5 ft ) dee pan

dhold s 3,54 0 i

(93 5 gal ) o f platin g solution . Th e platin g tan k hold s fou r rack s o f part s o f a time . Th e norma l operatin g voltag e i s 1 3 volt s a t anamperag e rang e fro m 6,00 0 t o 7,00 0 amperes . Th e tank i s equippe dwit ha filtratio nsyste m tha t constantl y

filter s th e platin g solution . Th e tank i s no t equippe dwit ha

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ventilatio nsystem . Th e automati c lin e wa s no t operatin g a t th e time o f th e visit . Th e platin g solutio nuse dinal l thre e tank s i s Tri-Chrome ®L C Plus , manufacture db

y Harshaw/Filtro l Partnershi p(Harshaw) . Th e solution s containe dabou t 2 2 gram s pe r lite r ( 3 ounce s pe r gallon ) o f trivalen t chromium . Th e trivalen t chromiu m solutio ninus e a t Plan t AB C i s a first generatio nbat htha t operate s a t a lowe r temperatur e (21° C [70°F] ) tha n th e newe r trivalen t chromiu m bath s now

available . Thre e chiller s ar e use d t o coo l th e platin g solutio ni nth e thre e tanks . Sample s o f th e solutio n ar e sen t t o Harsha w

eac hmont hfo r chemica l analyse s t o ensur e th e bat h1 s runnin g a t it s prope r concentratio nan dt o identif y

th e leve l o f contaminants . Chemica l addition s ar e mad e t o th e bath s o na nampere-hou r basi s b y automati c ampere-hou r controller s connecte dt o th e rectifie r an d tank . Th e platin g solution s ar e purifie do na weekl y basi s t o remov e an

y contaminant s presen t i nth e solutions . Th e bath s ar e purifie db y addin g a proprietar y

compoundwhic hprecipitate s meta l contaminant s ou t o f th e bat h o r b y "dummying " th e bath . "Dummying " i s a electrolyti c proces s i nwhic h a nonproduc t par t i s place dinth e tank an dth e curren t densit y i s se t belo w o r abov e th e operatin g rang e o f trivalen t chromium . Th e meta l contaminant s i nth e bat hplat e ou t ont o th e part . Plan t personne l state d tha t routin e maintenanc e o f th e platin g solution s require dabou t 2 0 minute s pe r da y

wit hhexavalen t chromiu m an dincrease dt o 4 5 minute s pe r da y fo r trivalen t chromium . C . Cos t Dat a Th e chemica l cos t fo r th e hexavalen t chromiu m proces s wa s $0.015/f t , an

dth e chemica l cos t o f th e trivalen t chromiu m proces s 1 s currentl y

abou t $0.047/f t . Plan t personne l state dtha t sinc e trivalen t chromiu m ha s bee ninuse , reject s hav e decrease dfro m 1 0 percen t t o 0 percen t an

da 3 0 percen t increas e inoveral l productio nwa s observed . Th e plan t save s $27,00 0 a yea r o ntreatmen t chemical s fo r wastewate r treatmen t an

dsave d$10,00 0 o ntreatmen t equipmen t n o longe r require ddu e t o th e eliminatio no f th e hexavalen t chromiu m reductio nunits . Th e eliminatio no f th e colo r buffin g proces s (require dwit hth e hexavalen t chromiu m proces s t o trea t chromiu m stains ) reduce dequipmen t operatin g cost s b y $91,000/yr , an

dsave d$14,000/y r an d$8,000/y r inbuffin g pad s an dcompounds , respectively . Th e plan t als o save s $3,000/y r b y no t havin g t o replac e th e tin-lea danode s use dinhexavalen t chromiu m platin g an

d save s $10,000/y r b

y eliminatin g th e nee dfo r th e strippin g operatio ntha t wa s require dbecaus e o f poo r chrome throw experience dwit hth e hexavalen t chromiu m process . Th e tota l annua l saving s generate dfro m th e trivalen t chromiu m proces s i s $153,000/yr . Th e initia l conversio ncos t t o th e plan t wa s $118,480 . Tabl e 1 present s th e component s o f the capita l cos t fo r th e trivalen t chromiu m conversion . Al l cost s ar e in198 1 dollars .



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### V . Conclusio n Plan t AB C i s a medium-siz e captiv e sho pspecializin g i nstor e fixtures . Th e trivalen t chromiu m proces s ha s bee nsuccessfull y runnin g fo r 7 years . Th e plan t state dtha t th e trivalen t chromiu m proces s ha s allowe d the m t o stay competitiv e wit hothe r companie s becaus e i t ha s decrease dth e cos t t o runth e operation . Plan t personne l wer e ver y cooperativ e in supplyin g EPA

wit hth e cos t dat a an dtechnica l compariso no f bot h processes .



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TABL E 1 . CAPITA L COS T FO RTRIVALEN T CHROMIU

M CONVERSION

A T PLANT AB C Component s Cost , $ Equipmen t 1 . Arkl a chiller s (3 ) 27,594.8 4 2 . Anode s (170 ) 13,174.0 0 3 . Hanger s (170 ) 4,580.0 0 4 . Cooling coil s (5 ) 3,778.0 0 5 . Tank liner s (3 ) 3,000.0 0 6

. Ampere-hou rcontrolle rsystem s (3 ) 2,250.0 0 7

. Rectifier s (2 ) 39,600.0 0 Modificatio ncost s Trivalen t chromiu

m makeu psolutio n(3 ) 24,502.0 0 TOTAL 3 118,480.0 0

a Cost s wer e rounde dt o neares t $10.00 .



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