Annamalai, P.L.

Rajagopal, C.

Rajagopalan, K.S.

Ramakrishnan, V.

Subramanian, V.

IR@CECRI

CIOYDNMBNTOP INDIA. TIIB PATI"" M.a. 214, AOIMYA JACIAa •• _ MIl\))CA&aJTr,....'.ea..... t. ".dlndaD No. 141+11+1 Ita. J_ua~·J'. 1916Au'l 111 "' 11•• 1111 116'+/c~1I1S .... 13th J_,1975A III' • " pI..11f III. ,.~ April, 1978.............. - 130 p C XXXIII (7).:711+... B fIll (3:» .:z.188 XXXII!'(917Ian 1111,.. a 'I••11.- C 23 t 3/01." PROCIS8 POR OJI\OMAD !BAt.., err Zma8ARD'DB CAST IDe ALLOY1PCI' OCIlRGIIC* ...... 1011".OantOIL 0" IODWlInc a DOOIftU:L ...... 011'Rali .....1'1,. lev De1b1 -1, India" an ,In41&*"'lItere4 bocll' lDCorpon\ecl 1a4er 'berelbtratlO1l ot 1001eU•• ~t ( .at IXI ., 1160 '),PaICB: TWOaU,.I +Jj-14-1Thi. invention relat., to Il1provelllt-ntB in or r--lat·in, to chromate treatment of zinc and die cast zinc alloT-Hl therto it has been proposed tha t the I.:~!('ornatetr •• t~nt bath 18 an ae1dic aqueous solution of 801ubl~hexavalent chromium ~ompound + one or more activators.Th~ typical formUlat1r:n for chromatlng zinc 'anl1dlbl~ 1n11teraturf!'18 one o·t 180- 200 "I. p.l •. sodilllll or potll~~ t'. 41-, "chromate acidified with 6- 6., eel litre or concentratedsu1phur1c acid With Qtiw.tora 8uch a8 .t:luorlde, nltI·~t.·bora te t' ace ta te etc.'It:L .This 18 open to J!'« objection that ( .) oll"e creenchromate coatirJI haying the- hlgh~~ t corrosion resil!tan •• "!. not, Ir"oduce4 1n these bath. on zinc or z1ne cast alto1'and (h) lr1lUscent coatings hayinl pleasing appearance aNnot obta1"~~ .t ~8- cast ~1nQ al101·I ~1--4 -I -1- ITh~ o1j'>:rt or. 'ti.).8 pre •• at innntloD 11; to obviate.the•• disadvantages by produoing an o11ye green ~cat1D&wi tb the irld1eoent appearanoe.To these ends the iDTention oroadl1' oona1sts into:rmu.latin& a ohromate treatment bath oon'ta.1.n1ng 80-200BrIIIIl!f of potae81uDlor 80dium d1chrolllfil,te 5·...25 grams otaulphLIr10 a01d, 0.5-5 grams ot sod1u.mtlUI)r14e and 5-2'srems of sodium nitrate and 0.1 to 1 gra1Jlot wettlng ..... "per l1t~ of aolution to get an lr14i8oen" ,eUow or- 1l"141.080t oll"e green oolour.The following VP1oaJ. exaaple. are ginn tolUu.tra "e the 1Dn1Dt10D.Examil~ 1~,. % , •• 11]0 pl.a'e with _Will 1. _ken aDd plokl ...ill 20" chromio a01", at 80.0 tOl· 5 m.DIl•• to remOTe onl ••• ale on the .urface. Atter p1okl1D£. tbe speelJD1D 1.wuM4 in tap water aDd then ail,peeL 1n tbe 80lution OOD-tai.n1lDg 100 g,!1 ot po\&se1ulR diohromate. lC~ml/l ot .ul.phurl0 a014 (s.p.gr. 1.84) 1 &11 ot la~'l .ulpba'te all10.5 Sl'au/l! tre of .04J.wa fluoride tor 10 .eoonQ W Ie"U 011,.. &reel1lri41a •• at ohroaie ooat1lJ1&on 'tb8 .uf....Example lIt,_uk aUof (41.oaat-s1,llo a 1101)1 .peo!M1l 1-,1okle4 1n 20~ obroll1o &014 for al)ou1; 10 II1nuw8 a~ 80-0to reao" tbe 80al. on ~ .urtaoe. Uter p1okllnc. 1it.eapeo1_11 1111.. abed. 10 tap wat.r aM tbea d1pped 10 tU.01,,\100 oonta1ni.l:I.g 100 g/l ot pota8a1wa cU.obro_t.,10 aJ.1111i.lirea~r litre of .\1lptu~r10 &0.14(a.p_gr. 1.84).1 BI1 of O:rAB 1lB.llt aDd 0.5 grama/11 if" ot a041\lm fl"'ol'14ef .. 1 aiWAt. \0 ,-, &Ii 011,.. &.1".0 1ri41".D~ ob.rollA_... ,iAg on tbI au..•:faoe_3J 1- 4- / 4- /Example IIIMazak alloy co~~onent 18 oleaned in alkalineol.aner containing 6 g/l each of sodium h;.rdroxide ,andaocl1um Darbonate at 90-9S.C for ~ secondCiI, r.1nsad in~P wat.r, then dipped 1n solution containing 120 lv'l ofa04ium-d1ehrol11a-te, 12S/l of s"llphur10 aciel. 0.5 g/l ot.o4lum ~luoJ:'14. and 5 &/1 ot .odium nitrate for 20-·30a.oont_ to S.t an 1r1d18c.n't chromat. coat1J:lg on tb.aufao ••OOJli)&raU" Oorro81oo reeiaane. 1. g1Y.D J,n ~bl. 1•..J, lODea 200 &/1 at tiohrouh, 0071. OODO. BzIO., h'opr1'~174 rateDtea fGNUlatlODHour8 ot re81atano. tosalt apraJ5~ BaalD~-oast ~~no~__~1011nl26i+" 9'"12' "49t. oolourof ouo. •• "BUt.o. "bul ob.1I... Jo._l&n4 withooapoai'i.oM _o"i.oD" ill l1w.tuft au,wop1etoq: ._the 11l .'1e 2.~.7 .',Aal 908' a;4 NIl Vllt'd, -lu.... t aino alU't veat.d from 20 .,ooll,dea,,,. 60 •• ooa. al14 the 1tath Dot "~l'ni8bed ,froJiU7 .t 1. OOIWU1n.l.D'. ~ •• ~ f1&~. an aDOllt the_ to~ tJM 1M'o _tba.(p t 0)/ ++1+ I:&IW.I&aZLio'J:-'_._.._------'-------------------2.. 110-100 IP1. c11obrcaat:e l" • 00/1 00II0., sulpburl0 aolc1~•• (1) CODtalD1Dl 2.5 IPl.' .,., ,.041 .. a1va te. "I. (1) eon_uSa, 1,iPl 10-. , 4_ t1&aor14e... .l'Opit1etorlI. 'ateD''''Oolden ,.now' Daft "N7 or browD1\1terteHDoefila.Golden "llowDirty ,.n..Blul.b are7~Ir!41.oeDtyellowBlulab INTI.-141 .... ,,.uow.• •:. . , ,1,. M 011•• p'.. n ooat1D1 with 11'141._,.,,..MaN 1. obtaiDad ODbOtal .1no ud"cU.•••• t sino alloy Galik. tile OGaJO.1Uoa •. .... 't.oaH in 11teara_1'..I. !be oo.t of tAi. tr t i••saUar .00" of ..... , ••• ts. in 1.1 "(1ab1. I).Dated tbi. ttb da7 ot IG •• , 1171.'514-+1+1THE PATINT. ACT. 1910CO•• LaTB 'PBCDr:lC&T:lOK( Sectlon-10 )1. pnocKSS FOH COAI.ING ZINC AND DIE CAST ZDlCALLOY. FOR CmHOOION PROTECTION2. COUNCIL OF SCIENT IFIC AND INDUSTRIAL R&S'RARCBRafi Marg, New DeJhl-1, India, .in Indian re,l-atered body' incorporated under the reI1s1;ratl.on of Soc1etles Act (Act XXI of 186(».The (01]0,,1ng sppc1flcatl00 partl~lllarlydescr1bfl8 and ascertil1ns tbf! nat.ure of ttt1.1nvent10n and the mamer 1n whioh 1t 1s to beperformed : ..This is an invention by KUJIIn8.ttlthidal SilnthanaaRAJAGOPAI.AN t Palaniyappa AN NAMALA I , Mrs "FoNUSubramanyan, ~e lent.1sts , Chakrabarthl RJWAGOP1L•Senior Scientific Assistant and :Mrs V1JaJralakshll1Ran)4lkr1shnan , Senior Laboratory' ft"slsta"t .. an. from C~ntral Elect'roch~mteal n,. "l~a I'en 1nil t 1tute,Kara1.lrud1, Tamil Nadu- India- and IndianCitizens.14--1-/4-1 ~L'nti': .i.'h"el~tiun rlllal~es to process for thromate tren- .aJ-ylk\zinc alloy lilld relat,es to )fetal~ of zinc and die-eastr Iiniahi ng industry.IUtherto it has been proposed that ohromate tl'eatmentbath 1s tH. acidic aqveou8 80lut ion of soluble hexavalentchromium compound plull one or more acti..,ators.This is 0P&D to the objeotion that (a') l)live Irean ohromatecoating having the good corrosion resistance 1.8 not produced1n these baths on zinc or zinc dte-out alloy and (b) iride ..oent coatinga harins pleuing apl'" arance are lliot obtaine4 OD.die-·~.t sine alloy.The object of this invention ia to obvjate this disadvantageby producins an olive green or yellow coatins wiLh theiridiscent appearance having good con osion rEls:Lstance.The main finding i8 the formulation of a chrolllate t p'9.tmentbath containio& 80-200 grama of potassium or f;odium dlchro-mate, 5-2') grams of sulphuric Rr.-idO.'5-·~ gft,IIl~; I1f Rodium'fluoride and 5-25 ~rams of sodium ni t:rat e and IJ. 1 to , gramof wetting agent (sodium 1auryl aul, hate ...... ~dt.B. ~ perlitre or solutlon to get an iridescent yellow or iridescentolive green colour with good corro.ioto reststlUlce propertiea.The formulation givea an irideacent ulive grel9n or 'r' 1 lowooating having lood aorro.ion resistanoe and pl eaaio(£ ......,.oe.the present inventioD consiats of a process wl1i,~h coapr1a •• of,be 1ncorporati.on of a wetting agent and an at~t:1.Vll.tor in the~hromat. passivating solution, which makr• ~t pos.1bJ~ to1" a decorative and corrosion r.si.tance coatin,.71+-+1+1fb. tollow1aa t7p1oal exaapl •• are IiYen to 111u.trat.the In••a'iOD.h.,pl.' I1" x 1· sino pl.'. witb .t_ 1. takeD an4 pioJel.4 1n 20.'~ ~ .obrOll1c&014., so'e tor 5 a1nu' •• to 1''''''. oz14tt .oal. 011.the nrtaoe. Atter p10kllns. tbe .peo1•• n 1. "bH 1n tatv.'.r and tb.n Uppe4 :Lnthe .olu'lon ooni-.iD1na 100 &11 otpot .. nUll 41ob:toa&t. 10 al/l ot: Alphuno 80014(Bll'-sr 1.84)1 1/1 ot .041\111 1&11171.ulpba'. AD4 0.' .,au/11, re of .041.t180r14. tor 10 .eooD4a to I.' aD ir1d •• o.nt obroi1Me oo..'~08 'be .urt&oe.~Masak 61101' (a..-o.. ' lliao allo,) .peoiwil :L•. piokled :L1l,.IOJ' obl'OlIS.oaoi4 tor MOU' 10 iii.'.. a' 8,0'0 '0 I'dOye ,he- .Hal. ODtb. aart..... At'.1" p1oWaa. tbe .peoiMl1 1. wMb":LA 'ap v.'.r ... 'be. 41".4 :LA tbe 1I01u'ioll oouain:L .. 100 .:L.ot. ,. .... :l.ua Ai.broM'., 10 III "1' u,'tr. ot *lpbu~:1.o _i4(I,•., , .84), 1-'lot CBI, ........ 0.' 11'-../1:1.111'. ot .oti_... . ".. .f1uor14. tor 1 aiAU.'. '0 p, all olly. 11"•• 111n4.. 0.n' obro-.,. oo.'i.JIc. 08 tb. _rt •••__ ....In·,k.m...-Muak a11oJ' OC*POAut 1. 01..... 1a alkal1lM ol.lIAer.oatalAi ... , III eaob ot ao41u11bT4rox14. and .odlum carbo-~'e, a' 9~5:C. tor '0 .econda. ~ae4 :Ln'ap vater, thenti,,.. ia ao1u'101l oonta1n:Lnc 120 1/1 ot .otium· dichromate,11 .11 .f .ulpbuno 80:140.5 III ot a041wa tluoride and814-+'1+15 s11 aotiu. a.t,I' .... "or 20-30 NO.... •. _ .....~ i.~~'emt f.UOW ohro_t. coat1ACOIl 'he .1Irface.(a) The oorrosiun reaiatanee ot ohroJl&te apee1.eftll pua1Tate4 1nthe chromate .olut1on, d.veloped by u. 1. slYeR b.low, 1n COII-pari.on with unchromated zinc .p.o1men.. ComparatiY.oorros10n res1.tance 1a liv.n in table 1•••1aa.1vat1ng treatment Hour. ot rea:l.tano. toSalt 8pl'a¥ (1_ I1IC1)IW 1)1.'1_' lia M19',1. Hon. 26 10492. 95200 Spl ot 41ohroaa.....+ 6 81/1 Cono.,HiS04,. "A.h chrome -a If (chromat•• 01u- '5tlon manutactured and mark.tedby MI. A.hok Industri •• ,Bo._,the eompo.ition ot whiob i.not known).(80-200 I.p.l. diohromat.(pot....1W1 or .odium)5-25 1M aulphur:le &014 I0." to 5 IU ao41wa t11l0-1125rid. 5-25 pe. .041wa Ai-'rat. 0.1 to 1 sa w.tt1ns... nt (eTAB) (all 1Jl PfI. litr.)"49;(-.) Th. oolour ot' ollro.'. ..rtM. 'bu. obta1IlL.CS1. ooapar.4vith ooapo.1tiou •• n_tonH :I.A a'....' .r ... , Pl'Opl'1.to17_a'. :Ln"81. 2.qJ +4:'"; + IIJt..ll LE .iL------------------------._-,---SloMo. Pa.ssivating com"Poeit1on Zinc Die-cut; zinoa1"Lo 'I•.---------.-.~-. I" .._....,...._", --------- . .............__ ~ _ lll_. _1. 180-200 g.p.l. d1chromat. + 6 mlllCone., H2S04goldenyellow2. (1) containing 2.5 g.p.l.sodium nitrat.e. i nterfe-· ])1 I I:y gr.eyrf'ncefilm.). (1) conta.1n1ng 1 Spl sodiumfluoride." IJ4. Ash chrome -I (chromate !~fjlut1onmanufactured and marketed byMIs Ashok Industries, Bombay theoomposition of wh1.h 1. notknown) •golden Dark grelyyellow.bluish·arey.bluish arey,. (80-200 g.p.l. dichromate(potassium or sodium);-25 sma .ulphuric acid0.5 to 5 gms. sodium fluoride5-25 gma. sodium nitrate0.1 to 1 g'JI ....!"t.ting agent(CrAB) (all in gms/litre)olivegreeniridescent 011.,..g "'38"/iellow.-_._---------------------,-_._----------An olive green/yellow cQating wt~h iridescent appearvlc8.1sobtained on both ..inc and die-(.~.~t zinc alloy Wl11ke t,b.compositions mentioned in literature.l'b. J.nvention OOftsists 1n :f'orJDulat1ng a chrolllAte pUI,1Yat1nccompoa1tion for sine and die-osat zino alloys. whioh produoe. aDiridescent co.tine having good corrosion resi,st.ance.la14-4-1+1Ve cl&llm,-A prooes. tor coating .iDo and die - ca8t zlnoalloys for corroslon proteotlOD where1D the metal plec.1. dipped 1n a chromate bath, oharaoterised in that thebath compriees 8O-?OO gm••/lltre ot pot••• 1ua or sodlua41chroaate 5-25 g_./lltre of eul.phur1c a,oid, 0.5-5 ".../11tre of 8od1ua fluor1de, 5-25 .... !11tre of .odluaD.1trate and 0.1-1 pII./11 tre of a ..ttl!l8'agent auch ..• 041U11laurl1 suPba" ••Dated thi- 30th d., ot ))e-o •• ber, 1915.lt.-<.. r. k " ,. ·•·( I.M.S. MlJUJ[) -SOIBftIBT 'B It (P4TBll!B)oaUBClL or 8011.'11'10 a I.DUSTKIAL RBSKUOB."

Process for chromate treatment of zinc and die cast zinc alloy for corrosion protection.

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