Workshop Practice Series 11 - Electroplating

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WORKSHOP PRACTICE SERIES "Onl Argus Books He.JI TrPc1tmpnt

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11. Electroplating The techniques of depositing a thin metallic layer on dn object lor decoration, corrosion protection. electrical conductivity, wedr resistance and so on have been known for many years but have been developed and improved to a remarkable extent in the second hali of this century. This book sets out to discuss the principles and practice of those forms of plating most suited to the amateur and small workshop. using relatively simpl and inexpensive equipment to procluce results virtually uncletectable lrom work carried out by major plating concerns. Jack Poyner, a professional involved in all forms of plating for many years, is also a keen model engineer able to recognise the dividing line between what his average fellow enthusiast would consider practical and worthwhile and what is really better leit to experts in the field. The result is a really useful and practical book which will be of value to both dmateur and light industrial users in many diverse fields. ISBN 0-85242-862 -6

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Contents Chap'''' ,

IntrOduction and princip'H 0/ electroplating

Chap'''' 2

Chap'",3 Chapter 4

Chaptet 5

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Chap'''' 6

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Chap'",8

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Th, el.,nlng of 'he s"bSl,ata Th" "Kt,olyle

EIKtrofOfming and .'ecuopl.ting 0" non..:(lnducto"

EIKt,ol,," .'ea,opll,ing An example and Ihe c;:on,ide.atlorl 0'

.'ectroplating Chapte,9 I"de~

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Th" electrical Supply The e'eo;lropia ling lank

The finishing of aluminium and ill.llor-

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CHAPTER 1

Introduction and Principles of Electroplating Present d.... electropl,tlng h.. become I _II -utabli,he
In the ..,Iv dr(a 01 electroplating the indulllry 1It'"1'd with wooden VIIS. D,e.

lIen"."o.., •• perienee .nd

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thumb' method. 01 pfocess control.

Ove, the yea,. _

m,,,.t finIshes heve

been Int.odu"d. Automatic pll"t has been dflveloped 10 copt! with the in_

c.eased volume 01 parts to be finished Bnd 10 oonlrol Ihe DroceSl, ensu';"1I a

conlllm quality 0 1 linish. Inc'eased use. o f metellllee', .II,nI8.1.leel) Ind vlI.ioot plas,lee h,,,. beeo SHn in the m8~inll 01 tquipment for thlll finishing shop.

Pr_m dav finllh,,,,, shops off". I WIde end "."ed r.nge of finishing 1"0-

.......,.; ion end g •• pl"ing. high spIed sellICt..... pleling •• nodlli"glrKI electropla,ing on at ... mini ... m. Vlriol!. electrolell fi"i.h .. cov....... ide •• nge of en· ginee.ing .eq... iremenl •. Various alloy plallog. . . . carried OI.JI •• u<:h II ~Id eob.lt ..... hich gi..... herd thickness of gold. There II aiM! b.a.. plallrlg for elll(;' I.oplellng safety pin •• ,nd components

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which hive varioul r... bllers bonded 10 Ihem. Over the IISI fift .... yea.s developmenl hat beln carried OIl! on Ihe plating 01 plastics.. The lechnolog.,. of primed boa.ds in lhe elect.onif;$ ind ... strv 1111 added impel .... to IlIe developm&nl aod many ptasl~ can be lIICCusfull.,. elae"opllled. Wtlll Ihe vlrious processes involved In elect,oplating aod c ... r.. nt req ... iremenll of lIealtll and safety, 'ppropriate preca ... tionl must be ... nde,' taken to avoid Icxidenll and redu"., pol. IUlion of IlIe environment. These ... deall with In one of the following chap· tell. Wilh mOll of Ih a processas ... sed in model englneerinlllhere i. ready·made eq ... ipmenl $Old on the marlce!., obvio .... lumpl.. being lalh.., milling aod drill. ing mldlin.., alonll .... lh Ihe material •. m~all and plallle • . I" CQmpa.ison, wilh Ih. eleclfoplating proc-M Ih ••• i. verv little choice av.ilab'- on the market. Ipa" from UIS for electroplating. This is d .... to Ill ... limited "N 11 compared to Ihe machining Ind fabricatinll oper. ations in model .nllineering and in small worklhoPt' lIen..ally. Th. Olh.r main ,e..on, ho_"" •• is Ihe deg,.e o f avail,bllity 01 the chem l.

cal • . Cenain chemicalS Ire ,.st.lettd. and ,.,Iricllons Ire pl..:ed on th.m in ",nlit. The electrical eq"ipm.nl needed can be adapted from othe, so.."':.. - electrical t.1I eq ... ipm.nt. Avom~erl. Or bauerv charg... or larll. capacity electrica l cell,. If desired I pe •• man.nl rig can be made. Thi. I, uMf ... ' for I comin",0"5 vol"m. of componenll Ihel hay. to be f,ni.hed . A wiring dia· gllm i. inCluded in the chapl.r on the supply of current. Wilh ,egard 10 the lanks req ... i •• d.Thi, is depend.m on the lile o f Ihe compo, nent to be .11CI.oplaled. A uIII ... IIII. I, Ihe 5 litr. plastic ice c.e.m conla iner. Thell are ... ,.f... 1for mOlt pre·If.llmenl Ind elect.opllting 501 ... lion •. For ..... rm or hot 501 ... lion5 • ..... y • • nd m.an. of heatinll the SQiution may be conlldered. .... 1;11 IS fish lank heat ..... or. it "',1"111 a lIatnl'" steel or mild 51eel tank, • 11" ring or electrle h01 plale may be used Chemical glass beakers mede 0 1 heat· rllilling IIlall may be ... sed and Cln be h.ated on an .Iectrle hot plate or oYer. e... nlln boJrnerwith .....itabl••tend and ga ... te. Thi. 8<\ ... ipment c.n be pur · chased" most laborltory eq ... lpmeot .... ppli •••. The mod.1 engine.r mUSI dec:id40 on .... hll .ile Ind volumeof compon.nll he wanll to elect,oplate, .nd .... hlll.nllh •• h ..... Ints 10 ... SI. These points w illll.ve 10 be conlidered. """'ether he Wlnll a ",dlmenlary Of 1 more .... bsllnlial.1ee!fopl"inll facility. The Olh.. relev.nl lectOfl.re the space eVlllllbl., COII,II<>d the conveni.nce of "sing Ih. 8<\ ... Ipmenl. For example. con.idering one fin· ilh 10' IImll., sile componenll and I lIeedy vol ... m •. it .... ould .uffice to hlv, I .imple facility 01 en alkali cl.a"er•• plc~le made of diluted Kid . .... Ith e rln .. tank conteinlnll cold .... lIer or p.ele,ably r... nning .... ater. It co ... ld be made even

.Impler lor c.r1ain compon.nts by g'v, lng lhem a $COlI' with .brHive pOWder, Ihen rinsinll In cold ....el... Aftar these pretrHtmenll, lhe com· ponents Ir. electrOplated '" ......,.tev.. lIIectrolyte is dIoHn. For In e/ectricallUpp!y a 12 YOIt bit IIrv, or a battery chllg.r of 12 volt. or 6 VO!II. may be used. AI the othar a"!reme. for varied com· ponents and IlIga volume. one could UII In .Iaborall line of pr'lfellm.m and rinse \Inks, wilh a line 01 electro· plllinll "nh all combined wllh the c ... stom·b ... ilt rectifier.. healer, and .gilllion. The cost oflhi ..... o ... ld be con· ,iderlb le. and Ihere wo ... ld be Ill. prob· lem 0 1 dispoling 01 eftl .... nt .nd tpenl chemical •. PftINClPlES Of ELECTROPlA.nNG

The fundamental la_ ol.lect,opl.ting are bllsed on Faraday'. two la-. TkeM lilt.'· (1)

(2)

The weighl of melll d.poaited IS prOpOr1ionaJ to the quantIty 01 electriCity passed. For the same quantity 0 1 elec' lricity. The waight of metal de· posited i. propor1lonal to ill electrO-Chemical eq ... ivlleot.

TheN two 1__ need • liule expla· nallon to ... ndersllnd their implicatIons. Thi. is best provided by definIng Ihe un;IS.ln I..... 1.lhe_lIhllwll.lngraml Of ounces and the q .... ntily of .Iect,icity is in coulombs ..... hich Is .mpsla) x time lse«lnds) It!. Thereto..... is ptoponionallo I x I. In lew 2, the electro":hemical eq ... iv.· '.1"11 i. defined as the weight an el.ment .... ill ,eplac. or combine .... ilh eighl p.r11 by weight of oxygen in a reection . The vllency is defined 11 Ihe number

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EIect.olY'. A o;onducting medium for mOlt electro· plllling. An IIqUoroUI 100ulion wilh water·soluble chemicllls of Ihe m'lat 10 be deposiled. These chemical. dllsolve in _Ier Ind fo.m ionl which lCquire 11 posilive $ o< neglllive 6ch,rgt.

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Is en Ilom. Or etoml. wt>!ch "'ve g,ined

losl electron, IInd in consequenoa carry 11 polilive (!) o< 6ch,rge. The posilive chlrged ion I. called , CJllion, which .. d iseh,rgoed " tha cathode, The negltive charged ion il call&d en aniOll. wh.ch i. diacl1argtcl It the Inode. 0<

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The use of the te.m p.H will be men· tioned In th. book In VlnOUI chapte.,. Th' definilion of th' te.m p.H it defined liS the log to the baSil 10 oflhll concan· trelion of the hyd'ogen Ion. Of p.H • tog ,oIH+I. In elecl.Oplallnll il i. uI&d to d.lln, Ihe acidily or alkalinity o l an el.,;t.olvte. In prllctical le.ms 8 p.H of I 10 6 I. acidic ; p.H 7 is neutrlll ; Ind p.H 8 10 14 is .1~lIline . A good e~lImple of neu t.,1 tol · ulion is pure W.tl' whic h i, p.H 7.

InMt. o.lnsoluble .no
tha anode olllllt partlculllr metal, wIlich thus r&duca. the concentration 01 the mltallic ion In solulion, causing an im· bal,ne. in the elect.olyte. The olher l.,;to. aflected by In inert .node is Ihe p.H; thl' will change and Ifleet Ihe efficiency li>d phYlieel chlfecteristics of the electroplated deposil. The mlin elecltoplllt'no procel." Ullng lnen llnodll$ I.e chromium elecl'09lall (decor"ive and lIard ). u.ing I,ed .nodl• • end gold elec· t.oplating, alklline and acid elec!.olvtes respectively.

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CURRENT DENSITY Thi. term is defined a. the amounl of cu".nl (limp') pe. unilarel of cathode (componenl l, usullllv e~p.ass&d as .mounll of CUffent ,amps) pII' squa.s foot o. aquare decimet .... abbravill1ed . ... f. or 11 dml. The firll Ihing thet must be known lbout th. electroplating electrolvte il the preferred cur .. nl density .ange. Thi. v,.lu wilh ellCh elocl.olvte. Tha second considaralion i. Ihe tolal sur· laca lIfea olthe components you a.6 go· I"g 10 electroplale. The third Ihing 10 con,ide r;' the shape of Ihe comPOnenl o. components and it s position ,,, .e· IlIion 10 Iha anode, in Ihe lan k.

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The tinge 01 cu"ant density will be givan for Iha electrolvtes In Iha ch.ple. 0" elecl.olvtes. The measurema"t o f Ihfl surfaca arN o l lhe componenlslo be "lac:· Iropllled require .n elemenlary k"owl&dge of mensu.al;O
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31. MOll components Ire shaped ill a comb, .... lion of Ihe IisllId shapes. o. appro~j ",,"ng ID Ihese shapes. SO ul'''I,ng Ihe .pp.oprillte form·

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be obI"..-d 10 achieve. good pllll'ed appell.nce WIt" the requillte t!'l,dlne". In 011'1 •• words, It il nol .blOlulely nacosur)' 10 be ace ... •

011"1 high current dflnsil\l area mav be moved 10 one alde of lI>a ~mponent. 0< the bonom high w ..... t densilY ..e. may haV1l I "'ob/)t, " IUIIICt>ed. wh ich take$ the excess current. Fo. the low

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current dens'ty area the anode is bent

obialn Ihe corroct elewoplaled al·

Or a sub-anode attached nep, •• the .'"a

f&eland thickness.

wmponenls. end position 10 11'1,

of the component. Another method Is 10 redL>C
the elllC'l'OpI"'~ {tOnk IH! explained by • dia"

for eleclfopl'ling The~ met/>oclll'f. bosed on the an of

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The .h.pe of the component. Or Inodn can gram .

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Fig. 4 shaWl In electroplatong 'ank w"h enodes lInd 11 ~lI'hode !Wspendtd in The elect.olvte. Th" ~8lhode i, so Ihaped Ihat it h1l5 "US labelled h'gh current densnv lInd low current den,i'v. In elec · I'opl"ing Ih" component wnh,n Ihe IInge of Ihe currenl densilV la. the Plr' lieul., el«iroIVl" 'hG wmponent may Nove I coa'M. 'ough depol'l bu,1'II in Ih' h'gh current density ,rel Ind Intll 0' no depOsol ,n the low CUfflfl1 dens,ty • r... To Impro ... the depoln V'fOOUI m"ans If. pos"bll. The Inodl in front

CHAPTER 2

The Electrical Supply

elec:t.opllling. and WI\h • bulld·up of I(IlIpe,ienCllhey w>1I not be too d,ffICult

to eccomphll'l. However. mOSI ~ompanenlS are of. srraighlfofWlrd shape and will electroplale qune well when luspended in a bath. The olhe' Imparl.nl shapes in electroplaling are blind holll5. These p'ove difficull, leaY,ng 11"nl .round Ihe hole The best waV 10 ,tdu~e this ploblem ,. to filllh" hole w'th Wlx Or sim,l.!Jr mlle,i.l; IhlS will ,n .ffect "OP eleo;tropllll ' ing in th. holl. but w-II .edtJGe the staining effect On Ih' rompanent.

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Met.,s I .. mllnlv electrodeposiled bV the action of In electrical CUffenl. Direcl current IOC) I. l"lnlilll for electro· dlposition. Alle,nating curren, (AC) will not deposil mel.I •. However, th ..1 Irl vlI,iltiOJll on IlIlrnlting ,yslams which Ire slill bting developed. These methods g,ve .....ooth.. IInd denser metal depotll .nd Ire used in ~in lpe<;:illised engineering applications . The mlin conlideration for an eleclrl. ClI supplV in ,h. workshop 0, lighl In· gin..';ng lacihtv will be derived from the normallingle ph... AC supplV. The supply volllgel. immalerial. as I transformer I. uled to ronvert it 10 • working AC O!J'PUt. The Ir.ns1~, Ihould givllhe chlflICIeristics .. follo_ '

CHOICE Of' OUTPUT VOLTAGE Ona mllin continuous winding tapped al 4,6,9,10 and 12 YOlll, capable of giving a subllanllel ~Ufflnl of !Jp to 10 Imp. continuoul.

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RECT1f1CATION OF THE CURRENT OF TlfE AC SUPPL V The /undion of 11>1 'ect,tier is 10 convarl Ihe AC CUff"" from tl>l l,an.IOfme. 10 DC CUffenl. Rectil .... Cln be 01 the solid

lI.te Ylfietv, diodes etc., 0' Ihl older copper o~lde or selenium typet. Alo de."ibed in chapler one, Fara· d'V'1 L,w Sl81es Ihat the mall 01 el · ement. In Ihis CilS8 m"ll deposited, is directlv p.opoftionallO the quanti,v of electrical ch.rge. coulombs or (.mPS x lecon,",l. The .ectifie. should be ,uit· eble 101" rectifying 12 voll •• nd ~lIing 12 .mps withoul htolling .ff«;t. and be of Ih. double W'VltyPII giving lull wa"" rectilicaTion. thus giving' ...sonably ,mooth OC output. VARlA8LE RESISTANCE The nexl illm 10 comple" ths package of elllCl,ical equipment i. I varilble ... ,illenee. This usually ronli," of a ro\.Iry Iwn~h sel 011 I halNesisl,ng board. Fo. high lImPII'ege lhe varillble ...illlnee board is often mlde 01 melal 0' .Ilfe. Set in'o tha board are b,ass lIud •• rranged in a ~,,~Ia, with Islid,ng conlle! with I hlndl' m.dI 01 bflu. Aft.nged .nd connectad behind the lIud. are coils of metallic wire, Ylrying In .Ila Ind sh~ptI 10 p'oduce differsnt rlli.tlnces 10 obtain the dllired amptlr· .g• • The vlri.ble ,..illlnee i. Ihan COnflicted up with In Immele. and ... olt· matef to permit ronvenienl monlloring

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An ideel smell electropl.ting elact,j·

nltCled up with a vollme"" ammeler and variable resistance. The home beneeve. 6 volt output. use thi, for normal llea,opl.,. 11>11. A 6 voll control unit must be made IS • Mparat. item ••,the. on its own chHSis or in ils 0Wll metlll bolt. If m.c:le in ils own bo~. do nollorgello prOVIde .c:Iequale venlilallon, as quile I 101 of hell is generated wIlen using m ... imum

eIIl supplv cen be Ht up UI'"g' battery Ch'f~ on ill own. 0' bettl!f "ill con-

The 12 volt unit un .Iso be made IS.

of the ampt.ege and voUage r.,ding •. ~~~

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IAg.61. On lome mod •• n oo.,dl,lnl,.ad 01. ,liding I;I)rltact on bl... ,Iudt • , .. i$' ence wire I, uted, with ~ • • nd ,witch.t inltrlperled. which ... pr,Sled down fOf u.. delired Imper· Ig'. Thi. i. when JO amps or mOre .eqUlled, end by placlr>g the coil. in ~r· ,JI.llAltead 01 M,i.., I,.. hut is gene.· ,ted '1Ih, coils for Ihe high amperlge.

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.. ' ",pa"ta Itlm il dn"ld. but If you hava Inoogh loom Insldl thl battlry Chlfgll casing. you ean flltha COnl.ol Itlm.lnto thIS. Thin, whin thl Unil i, 0Ieded ... battlry ch •• glr, w,nd Ikct polllmllomlllf knob to fTMlI!mum vohs, maklng ..... thlll 11'11 one .mp meter is shOf1I1d 001 us'ng IhI 5 Imp switch, and you "1 ,e.dy 10 ch••g•. Should you m.ke the control unit IS. sapa.ata item, .. m.mbat 10 connect the ehaui, o. metal casa to tha matsl case o. chaUit of tha battary cha.ge •. F.g. 8 shows thl ci'cuit dl.gr.m which is vlry IImple. The potentJomlt.r is corlOectlld ac.oss tha ootput of lhe battary cha.ge., numbe.1Id 1 and 2 on the diltg.am, and the slidlng .. m 3 taps off the voltlog. I f .equ"IId,.mI is shown on th. voltmlllf

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11 you are electroplating a compon.nt thal .equi••• mo .. than one smp, then th. one .mp .mmete. must be .honlld oot by (IO$'ng the 5 .mp switch S.W. The higher .mpe"gl can then be teld on tne ch.rgar unil'. inllmal ammate •. When you "";sh to electroplata a small

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component 'equiflng than one amp, lu.n th' pOtantiomlte. right down 10 uto put minim ... m voltage In thl cir· cuit, open thl SWItch S ,W.. and with ll'Ie .nodes ami componlnll (cathodes) .I••.,ty in thl electrolytl, connect the control unit OOlput to the
(O.veysellypet hive bottn used by the Ivtho.). The simplest way of supplying 11 cu.· ,ent fa. elect.opllling is I 12 or 6 volt battery connactlldln .er'" with 10 am·

mile. and switch. The limitflion of this llthet the bll!lIry ha. 10 be .eo(:h~.ged .fter I period of time, depending of C(\une on thelmperag. d.awn.

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CHAPTER 3

Table 1 Recommended Malerial for Tan~s N°' Zinc N"2 Zinc

The Electroplating Tank

Dull N ickel Semi.brighl Nickel Dull Copper Sem;· bright Copper

Tho electroplating tBnk, VDI, or bsth,

whatever ;t is called, contains the "IIIC' trolyte. However. other pans o f the process Ilove 10 be considered, such as

cleaning end rinse lanu. The electroplating and cleaning tanks BrS the most imponant, because U'e)' hold corrosive solutions of chemicals. The rinse tanks. as their name suggests. arS merely suitable v9ssels containing plain waler.

(2)

The main pOints 10 consider are Ihe

materials. Ihe const ruction, the Size. end if requiting to be healed. This app-

lies to bolh cln";"g and electroplating tanks. TakIng Ihe points in order:MATERIALS

Most chemical solulions are either add Or alkaline. The only neu tral substances, i.e .. p.H 7.0, lire usuelly organic solven(s (used in the Initial cleaning) and waler. Lisl ing the cleaning solutions and electrolytes used in various chapters with the relevant materialS will illuslrate what can and cannOt be used fQr a par· ticular sQlution (see Table ' I.

NOTES REGARDING TABLE , (' I Where plastics 8re mentioned, the

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most usual are polythene a nd polypropylene. These plastics come under various trademarkS. and can all be used. Good u · amplllS of these are half and one gallon ice cream canons. Oiher good plastic containers for tanks are cut·down 2.5 li lre Chemical containers o. len gallon carboys. Using mild Or stainless sleellanh has Ihe edvanlage that they can be healed easily wilh a gas ring . They elso have more rigidity. especially when heated. This applies to tha alkaline clean8n. Pyrex· type glass is quoted be· C8Use it is heat resistant. When it is In Ihe form 01 chemislry lebore· tory squat beakers it can be healed Qn an electric hotplale or a Bunsen burner. CustQm· made plastic tanks cen be purchased from elec· troplating supply hous.es. Small plastic tanks Can be heated by low watlage aquaria plastic· covered haalers. For larger vol· uma tankS, varying Siled watlage of siHea sheathed beaters up to 2KW. or stainless steel or tilanium immersion heaters 01 similar wan· 8ge, can be used.

Ti, Alumrnium Anodise

Electrolytes Plastic. propylena Iype Pyrex glass, stainless steel Mild S!eel, Plastic. propylene type Pyrex glass, stainless steel Plaslic, propylene type, Pyrex gla ss PlaSlie/rubber lined sleel, Pyrex Plaslic, propylene type. Pyrex glass. stainless sleel. stainless steal. Plaslle/rubber rned sleel Mild sleel, Plastic, propylene type, Pyrex glass, slainless steel Plastic, propylene type. Pyre~ glass, Lead·!ined

Remar~s

Mildlyacid, e electrolyte Alkaline

M 'ldlyacidic

Acidic Alkaline Acidic

Pretreatment SOlutions N°' Soak Cleaner NG l A Electrolytic Cleaner N°2 Cleaner Aluminium N° , Hydrochloric Acid Pidle N°' A Hydrochloric Acid Pic~le N"2 Sulphu ric Acid Pickle N"3 Pickle Aluminium N"4 Slight Dip N"5 Bright Dip Aluminium Zincate Dip

All this group mild steel Plsstic, propylene Pyrex glass. slalniou steel All this group PlastiC. propylene typa, Pyrex glass Stainless sl eel

All Alkaline N°'A Mild Stoal can be used lor Anode and Cathode All Highly Acidic

Eanhenware (glaledl

Plastic. propylene type. Pyrex glass, stainless steel

Highly Alkaline

"

, ,.

, ' --~~~------------~.~'~

TANK CONSTfl UCTION

In the construction of electroplil!lng .nd ~".ninlllanks lor professional finill"",,, ShOPI, 11111&1 and most plastic link. ,., med. by moulding, end these ••• pul ' ch...d Iccordmg 10 \h, " l e .nd vol. ume requited. Som. plfStic tan t>. weld,d, SUCh" poly!hene Ind poly. p.opylenll. Be <:lllIlullo check tll.1 Ihese tin'" h'V8 no ,....,.. h i, good p.-.:Iice 10 fill ,"-m wllh Wile, ,nd allow to Ital>(l fot 11 dllV. 10 .... il any 1111" .p-

'01

pear. For metal 'snh thlt h8" 8 been welded Il'Ie S8mt1 checkmg for leak, Ipplies. For stl,nl"ss ,,"'tenks mike lu" 11 good lIt dipl .nd pickl ••. A typical Ulnk i. iIIu.I,"ed IInd th, fol·

Iowing numbers rei". 10 the' shown 1<1 Fig 10:

"

13'

,.,

-'--i-;-----+,~

Inlullled holder. for .node IInd

ea,hode bar •. usually m.d, 0' porcel"n Or pllSlie.. 11 the link i. .... de 01 Sleel. theW holders Ihen kHP anodll and o;alhodll ba,. In.ul.ted. These ,r. boiled or screwed onlo the lI.nge5. for plulic. the lank matedal providel in.ulllion. Th" .node ,nd o;alhode bar • . ulU.11y .... d" of copper or brass. typical d,emel" .. being I,(o;n. ~n . to Iln, end l'hin .. depending on Ih" size of Ih" lank ,nd Ih" weighl of Ih" .noda Ih"ywill h,v" 10 sup-

"'It

1>,

t)

""rt. Anode. These o;an be .h.... l. drilled

and hooked. or hooIIltd .node• . M,k" .u .. Ih" hooua.. OUI of lha eleclrolyte. Thl fim. or Ih" tlange ..ound Ihe lOP o f Ih" lank. ;,ulfllul/or hand· ling .nd affi.ing Ih" hold"'l 10. Ih. anode and CIIlhCHk bars. end

'"

holde" for the v.nou. heater. and agilallon eqUIpment. This is Ihe CIIlhode. Or compOnent to be electroplated. It can .ithe. be wired on Wilh eopp"r wir" o. alu· minium will 'or pleting 0' anodiling_ Th" CGmpO<>I'Inl o;an be jigged or hooked. A "1fIfu! method for small compon"nts is 10 pr«lean and spread Iham oul on. piece 0/ "8inles$ ItHI mesh shaped lika. busket, wilh I wire or hook through Ihe middlelfig . 12). Ah". Ipe IUrf_ 01 lhe meah. lhe b,sI
"

Thl Cllco.olelion Of Ihl voluml of I lank i' :Voluml lV) in gallons with Ihl dimensions ln inc:he,. V _ IInglh. width x hlight cu -,"ch.. 276.5 (Inches). V _ IIngth K width ~ height cu -felt 0.18 I. V In liv..

""''11 100al volume to lhe mU5Ured hlighl of Ihe lenk. The .etual volume il to Ih' height of tha IOlution. If agitation of the elaclrolyt81 i, needed Ilh,. depending on whit t',Ipe of finish II required) two methodl are luggUlld :· (11

121

"

Fo< nic:lcel and copper Ilacllolyt... .. _11 " !he anodiling . !hev Cln be aglllled by an ,Iactrit; ~dle 1I",er sitUlled 11 Ihe tide of Ihe tlnk. A good method ilia pllce Iplalllc pIpe Illhe bonom olthe link. WIth small hole. drilled in. Anached 10 thl •• by means of a nll.ible pipe. i. I regulaled compressed air lOurCI. When I" I. pened "'r()IJgh the pipes. Ihi. glv.. I

bubbling action. which agl"t.. thl 101I,Ilion. Care - regulate well. ar it wIll froth .nd bubble

,I"

CHAPTER 4

0 .....

Ho usekeepin g with electroplating prOCll-l llnh (1)

(2)

m

141 IS) 161

Alwa .... remOVI Ihe anode and cethodl bar •. and dean down by Nbbing WIth SCQIJring powder. Scotchbrite or dOlh . Rinse in will< and rel>l_. Check all elactricel contact. on the tenk for he". If hOI. make lure Ihat a beller COnnlClion i. Obt.ined. (Heat dissl' pate. the current). Mak. lure III the sOlutions ere up 10 the requirld volume. If nOllhey a.elopped up wllh clean wale'. or distilled or daioni"d weler. Makl sura III Ihl anodH ..I cleln, and thl eonllct. 10 thl Inodl ba. a'l cl. .n. In all Ihl" lreas Ihl currlnt denSIty will v.ry if Ihere i. I bed CCH'IlIct. Ensur. III 'aetifier alact.icll con· tact5 a .. claln. Removl Ihl anode. and rinse whIn thl Ilact.olyte Is nOI in USI. Cove. th, ellctrolytes with lids whIn nOl In u...

The Cleaning of the Substrate The mOlt imponanl p ..t of thl lIact.o· pl aling P'OCI.. i. Ihl preperatlon and cleaning 01 the substrala. i.e. Ihe SUrfacl of the componlm prior 10 Ihe elact.o· plating Op!lrallon. This Plrt of the p.ocess delefminl' the appearlnce Ind the adhesion Ollhl electroplateops a vlpour clean is used in cUllom-buil\ tan.. (:On-

taining haloglnated hY
....... linl Sootk a.. .....

Thi' cI"nlng solulion Cln be used for

"

III f.rrou. m.tll., eoppe. Ind its III~. It ,.mOVH Ih. IUI trKH of g.ease aMI oillnd ,Hidual poIi.h compouMls f,om lhe! componetttl. No.l Alkllin. Cl ...... ' Mak. up :· SodIum Hydrfll.ida 6ol. pe. gallon 40 grms. pe. lit •• . Sodium Cartxw.ra 40.1 . pe. gellon 25 g.m • . per 1i1.1. Sodium Tri.iUCiI,a 4oz.pe. gal1o" 25 grms. per lit.e. Thi. can be m.dl up w llh w ellr 10 thl 'UQuirttd volum •. Carl must be lakan wilh sod,um hyd.o~,dl which,s vlry al· kalina; glo~H .nd gogglas must be usttd. Th. cll.n,. ,. used 'I ,tempe.lturl of betwN" 6O'C Ind 8(f(:, (14O'F 10 176'f). fOl II"ous m.lals it .. besl 10 usa Ihllemperalurl of 80'(:. 11 is .ecom· mended 10 un IIIHI conl., ... r for Iha eI ••".,. Th. «lmpo~IS.,,, imm".StId Irom two 10 I.n minutls. fo •• SfICOnd SIIga CIa.net o. EIf1c. It()/yTHl Cle.ne. Ihl lbove blJlh can be used . It can be used in Ihe lam" tlnll wh.n m.dl of 11111. I1 is conside.ed good praclice lo pilei lWO links in tan · dem, the fi
"

ova. thlsurfac. Ollhl cathodl. i_I. Ihl compon,nl. th' IIIrface of which Is "ICrubbed" by Ih' hydn.gen gls Ind Ihi, in conllqu.1IOI IfflClS I clean.ng action Fo. copPl< and it. IlIoys Ihl same p.ocedU'1 Is used IS for Ih... f.....ous mllall. bullhelompe.alu•• usedil6O'C (14O'f), th' low.. Ind of Ihl Ilmpera· lurl r,ngl. The CUHent d ... nsity i, .150 10WI. a t 5 a, • .f. (O.SIIldm'), for a pe.lod 01 tw,ntv 10 fo rty slconds. To finish off Ih •• pi" o f till cycle for Dolh farrou. mal..ials lInd coppe. Ind copper alloy. Ih l pola, ity is .evlrsed. 1.1. Ih. component made anodk and cleaned fOf I furthl' \on teConds allh. ,a",. CUHlnl dln,itlH IS fOf flrrOUS • nd coppe •• nd coppe. Illoys respect· ively. Th...emov •• I ttny amount of mllll. 111Il0l giving I clean and ICIIVI surfKI. Alkali", CI.. n.. fo< Aluminiu m ,nd Zinc DlI Clltlng l Thlse 1<1 cll.ned in • Iow '1~11i Cllanl •• wh;eh g,vl •• dull. f.osty .p. pellrallOllo Ih. componlnts but off,,, a good cll,n .u.lac. p.ior to electroplel' ;ng Of anodIsing.

No. 2 Alklllnl CI..nl. Mak. up:' SodIum hrd,oxidl 31». pe. g.lIon 2Og.ml. pe. lil'e. Sodium c.t,boII,,11 40.1. per g.lIon 2Sg.m • . PIt hlfl. Th. eI.....,.. " used .t a lamplfllu •• 01 6O'C /14O'"F). Howev.., il can be used" • IOWlr Ilmpe'alu'l if. ,eduction in Ih. !tO$ty appea •• nee i. desired. Thl im· me
""""

Th. nll
Mike up: · Conct/n/fllr/ld

Hydrochloric

Acid

31511.oz.200 mls. Wirer ma.dcl up 10 one gallon (0' 200m1 in 0111 lit,,) . This pidcll is used a\ .oom IlITtpe,,· tU'I . The .ecommlndadlank 10 uM is of plllttc, usually polyp.opylene, Of gl.u. 11 I 11. .1 link i. used. it mull be lined w ith rubbe. Of plestic.1t i, p'ller.bl. to hlvlllid onwhan nol in uM beClUM of Ih, fumH, which will cauM ,ulling 01 11111 objects In clOSI p.o~imity. Thl prOCedU'1 for making up is 10 hili flll lh l lank w ilh cold waler. Ihln pour In the measu.ed volume of conclnt.aled hydrochloric acid slowly. Tak. ca'l 10 un glov.s, goggl ... s Ind ov... II •• nd carry oul in an open Spacl. Aft .. the Kid illS bIIn eddttd, makl up 10 Ihl fl· qui.td volume. Tilt! ,.action of hyd.o· Chlo
Pie.,.,

To malll up an Inhibt"ted IIlI mlkl up 10' Ihe h~drochlo.ic pidcll Is used w"h 0.5'4 by _ighl H.x,m,nl ad. dition . No .HA) Pickle 0.80>:. pe. galJon o. Sg.ml. PlO' hlrl of Hlxaminl. TlIa flIU!! 01 adding thl Hlx.minl will be Ihe 'Imov,1 ol lh. teel, by Ih. pickl •. bul lh ••t! will be no action of Ihe pickle on lhl cll an mllll surfacl. In o lhe. wo.ds, Ihlaction o f Iha pielll, will ceasl Whin Ihe seall het been 'a· movld . NOTE -Ihil inhibited plckll e.n only be utell on flfrous mltlrials. No. 2 PiclIl. Sulphuric kId Pickl•. Ma~e

up:· Conctml,.,1rI Su/phunc Acid 9fl.oz. !Y.;

m,.

W., ...hIt.).m.de up 10 onl gallon (SSml in

0lIl

Thl uml mlll".1 " used for Ih. lanu IS in No.1 Pickle . Thl procedU'1 10' m.king up Ihe pidll i•• Iso IhlUml 11 No. 1 Pickll, bu l lotk. ca.. with lul· phuric lcid - use goggles, glovH .nd oVlrllll. as Ihis is co.rosivl. and wh.n addld 10 wale. Ihe lemperatu'l of the 'Olulion .isos ropidly, so stir contlnu · ou.ly whill.lowIy .ddingthlacid. (SII lhl difflrlnCI with No.1 Pickll whlll no h." i'glnefllttd) . Aft .. cooling, Ihl pickll i. ready fOf uu. It il used 11 room l.mpe.lIIu'l.nd used bolh 10. i.on and liNt ,nd COpPl< and brill. Fo. normal 5Cl11 removal. OnllO Iou. m,nutH imm ... "ion liml i•• equired . No. 3 Pickle Aluminium and AJluys PI·eIIll. Maka up:Concentrated Nitric Acid 2SOmls.

3911 ,01

Sodium FIIIOr/de 1.SoI. 10grm•. Wa'" m.cle up 10 one gellon 12SOm1 in OMli"e). Thi. i.used 81a picklalo•• Iuminium. or 10' da'lmoWng "",n, in aluminlom .11oyI. and gen,,.lIy imlNrls a cl.. n

surlae.. The b-II(h ~n be mllde up In e gl/l51 o. plestic link. La. polyp.opylenl. To mltl op Ihe pickle. hatl fill the lint with water. add the mlllo.1d amoont of cO~nt'3ted nitric acid to 'hi werlr. slowly. continuou,ly slirring. Next add tha sodium lIuoriM and Illr Will ontit dio.solYed. Finally. mlk. up '0 the •• qoirod \IOluma wilh wat ... CARE with ni,fic 3cld. being corrosiv.; use glov ... gogglal.nd 0 ....,11 •. Th. pic:kJe i$ uH
Nitne

Acid

3011.0 •.

185mll. Concentrated Hydrochlorit: Acid 0.511.01. 15m1s. Warer 5OIl.o,z. JOOmII. IMaking one gallon or onl li(ra re· lpecI;lIaly). Tha lint cln be m.cle of gins. pla'lic. potyl/l_, P.V.C" or I good qU31ity "ainl....teel loch as 317512 glide. To mlk. up the Drlght dip, th, w3ter 1I poured In (ha tank..nd the COrocent'31ed .olphoric acid Iddad slowly. stirring coot inuou.ly; witch for ollerheating. The lolouon illlllowed to cool to room tamper3t U,.. The mtlaSllred amount 01 concen'flted nitric ,cid i. eddad. lIi •• ring contInuously. then the measu.ed

26

amount 01 corocent.ated hydrochloric acid .cIded, It i. good pey must be fm· merH
For Brlllht Dippi ng of Alu minium No. 5 Dip. M ••• up:· Conc.rrfraferi PtrosplK>rit: Acid 15."ll.o,z. 44Om1 •. Hydrogan Perox;do 120 lIolumes) O. UfI.o,z. "mlL W.f .... O.73f1.Q.r.21ml •. Tha IOlution i. operal~ &I I tempers· (ur. 019O"C 119!i' f). The link uH
phospho.ic acid Ind hydrogon peroxide arl corro.' .... therefore gJOVH. gogglos and oVflfatls must be WOM. The alu· minlum componan'. lIa immlrsed from ten IICOnds to ona minUle. depending on the btightnlll required and the perticular Iluminium aUoy being dipped. Imm.cli"lly ,Itar dipping th. eomponen,. ,ra rlnlled in cold wlter 10 removl traces ollha dip. OUllinad in this chapter aral number 01 chemical elealling methods. Thlse give I chBm~lIy claan wrlace. prior to electroplating. whid> is thoeideals/tuation. Howeva •• vllious ph~ic.rrl methods can be used with Or in IOml CIIII in· .tead of chlmi~1 cle.nlng. We! seouring powder. Scotchbfitl ped. and wi,. wool can be uMd on compon"nl$, Hpacially copper or DII" OnH. Th"se CIIl than be rinsed lod di· ractly alectroplated, or put throogh the lIarious chemic,rrl etesning p.oc...... G.it or wet Dlesling I. an excellenl mathod of deeoing COmponlnll. es· peclllly caS( i.on, Cllt componanl. o' healllly rulled "eet articles. Com· ponants cl..nad thil way ~n be directly alectroplated. In the caSI of casl componants. thi. reduCH tha lilk of occluded cleaf'HIl$ IllChing out alta, electroplating. AfI" the .ollllnt clesn process. I! dal' Ired. clrtain aress which m_V not nettd to be Ilectroplated m.y be 'masked off. This I. carried out by uling muking tape. PVC. O. simil., plaslic llpe. O. 'lIopping off' lacqu"l. The$ll "1 lac· quell m3de 01 synthelic IHinl. auch IS polyu."h.ne lIamish. They III peinted on .nd allOwed to dry. It I, best to use a tllpe or lacque. commensur8t" with tha hotte.t pen 01 the electropl3t;ng pro-

cen or Ih, masking m_v Dllak down during p
"

,

12'

'" '"

The preflrred cI..n is I gill, or wel bllIl. prior to electroplating. To Ilect'oplate eithlr of tha acid coppers I minimum 01 I /llIh 01 oil!>er 01 the nidell mull be de· posited. Fo. tin Ilectlopla(iog. to 13cilita'l $Olda.lng. it la recommended that , flash of nicl
"

N

~

SUBSTRATE MATERIAL

Solvent

N° ' Soak

N" ,A

Clean

Cleaner

EleC1rolylic Cleaner

N" Alkaline Cleaner Alum inium

N' ,

N° 1A Hydrcx:hloric Hydrochloric

Acid Pickle

"Id

+Hexllmine

N" Sulphuric Acid Pickle

IRON

V..

V..

V"

Yesor lA or2 Yes or 1 or 2 Yes or 1 or lA

STEEL

V..

V"

V"

YesorlAor2 Yes or 1 or 2 Vesor1 or lA

Vu

V..

Optional

IAONfSTEELl1 ) CASTINGS

V..

V"

V"

ALUMINIUM lit AllOYS

Vu

HIGH

TENSilE STEEL

V"

-

BRASS

V..

V..

Oplional

COPPER

V..

V..

Optional

BRONZE

V..

V"

Optional

NICKEL SILVER

V..

V"

Optional

CONTINUATION

Yes or lA, 2

Yesorl , 2

Yes or lA, 2

Yes or

V"

-

Pickle Aluminium

Yes " lA

1. 2 Vesor' , lA

V"

OlECA5TING

ZINC

-

N"

V"

Yes or 2 Yes or 2 Yes Of 2 Yes or 2

V"

-

Ves or 1 Yesor 1

Vasar 1 Yes or 1

CHAPTER 5

The Electrolyte The term elec;lrolyte i, delloed .. thil eond ucu"lI medium lor mOl' elect.o-

pl'ling processes. The mOl' common 91ectrolyta i. IIn IIqUflOU. IOlut lon w it h

......

•

A good eK,mpla of Ihi. is Ihe dipping of , ; """I in ac:idk copper .1,11· rHul1I in an Immersion

water ..oluble chemical •• When I CUr-

rent i. allowed 10 flow through the .alution vi. Ihe anode and CiOlhode, • deposilion of metlll ooeurt " \h8 cathode. The l1ecuolyt", v.ry in p.H

is:&~

_

end mav ~ Kid,,, solution., neutral.nd

01 rJlJ" _ ~v"l _ NmJ·1lrig1ll nlclce/. r .... bo:>Ir;, """~'Ied Wlrh bIu, plUiV.rfd. rt.. ~or;, .,."fOI1I....:J _rh "",~I>""hr NC/t;e/ from r.... ,1..

dpm'_ ill lion

~, ...

1C,

;(.*_

elkali ... lIOIu\ions..

The elecl.olyte mUll conl.i" the di.lolved Hit of the melllla b.- d'p<"iled. The lilt' dissolve in wlte. end form lonl. For eumple. copper lulph&'e di,· solved in wale. form. Cl,j·~ + SO--, the Ion. of eu' • IInd 50.--. Generally. the more complex the ion, the more effICient, ,nd , much tmootllar deposit o llh, m.~1 ooeurs. Mot' pro'es,iornol electfolytH .r. of the c:y.nide ion. which is compte"... di.· li~ from the ,imple ion of co~r 1... 1. ph" • . The mein rflasOn why CVlnide electrolyte. are commonly 1,114<:1 11 Ih.I w;Ih I eomple .. ion, Ihe Ictual COnlanl of Ihe metal In Ihe ion I, re llliYl ly low compared 10 • limple ion. ,nd Ihi. r. "reil Ihe form&lion olln immertion depolil when Ih eIIllIodt i. pi~ In Ihe eleclroIyte, whim eIIn CoIU .. problems Wilh IIdltMion.

30

<", is:.

'"

cop per Iulphate electrol yte 200gmlllilre G"'fl BOgml of coppor. Coming 10 more practie&1 I.,.,.,. lor electrOlylfl. Ihe mosl common ..e Ihe ones uNd 10r linc pilling, in their vlri()I.IS form •. The one Ihat I h''''' uNd, 'nd is considered rellonably ... fe lor 1,1. . In ,workshOj) or g ..ege . i. a l ine chloride bath. ZINC ctllOftiDE BATtt This i, , .Imple .Iectrolyte to u. . .nd m.inl,in ,nd h.. Ih I(Iv,nllgtl of &leeI'opt";ng on dilflCUh m'tals, aud! ..

CoIII or m.lle.bl. ilon. 11 i. OpItl'atad &I room IImperalure. Ih."lo
;1:.

Zinc Ch/o,;dtl3oI; pe. g.lIon 2Og.ms pe. iit ••. Ammonium Chlrmd. 200. pe. gllllon 120grm. per hue. To make up OM g,lIon 01 electrolyte Idd ,i~ pinls of liP wI, a. 10 Ihe pl .. I;ng link, Ihen Idd 1he 200. of .mmonium chlo.ide, $Iirrlng w,ll until complelely diuolved. In .nOlhe. com,ine •• pu t two pinl& of Wlrm liP Wile •• Ind ,dd 30•. of zinc chloride. slirring until di'soIved. Pour the two pint, Inlo Ihe ,i .. pints al.eady in !he pIIoling link ,od mi~ well.

TlIfIlIOlUlion i, now ready for UM. It is ,dvi .. bl. 10 mark Ih. on. g.lIon leval. Or whallv.. volume you use, OOlhe out· ,Ide 01 Ihe tank wilh , walerp.oof marke. pen . .., Ihat as Ihe level o f the link lall. thr()l.lgh avaporation 0' d.ag ()1.11 il tin be lOPped up Iglin. I1 you eIIn keep. lid on I". IInk....t>ef1 nOl ,n uM Ihi. will m'fllmise .... lpo •• IIog.oo pr....""1 dustl,ni"" iflto Ih.l4Iulion. Oper&ting Condition. Th. link i, conneaed up 10 1"'1 power supply. Ihe po"live connecled to Ihe ,n· od... In this eIIse piecH ol ll<>e 4in. ~ 3in .• Or perfor.ted zi<>e Ih"l Sin. ~ 600. boughl from you. 10<:11 ironmongefl. Pre-d •• n Ihe componentl, lOO 'mmene in !he el&<:trQlVle. Tu.n Ih. cur.enl on, ,nd rotgul&te 10 Ihe """lOt you

"

require whhin the current density ronge test paper in the electrolyte for a couple of seconds, and note thal the strip befor the electrolyte. For this electrolyte the platIng current tween 6 and 7 ch a nges colour. M2 t~h this colour to one of the numbered col· should 00 ootween ours either si de of the ~entre strip. and 14.4 a.s.1. to 28.8 a.s.f. the number that matches is the p.H o f or 1.S4 aldm' to 3.1.,dm'. The electrolyte is operaled ~t rOOm the solution. The p.H can also be measured by ona of a numoor of p. H temperature 15',2O"C. At 14.4 ~.,.I. the zinG depOsited will 00 mete rs and ponab\e p.H 'sticks' avail· Iloolin. or 25 microns. at a plating time able on tho ma,ket. These ~ary in pr,ca, and the ponable p.H Slkks are reason· of 83 minutes. At 28.8 a.s.1. a depOsit of 0.001 in. or 25 ablv priced between ( 40 and £130. To obtain a satisfactory deposit in mic'ons is 42 minutas. Using the lower end of Ihe currenl most electrolytes it is necessary to ·elec· density r.nge for electroplaling will troplate the electrolyta In'. This is done give a finer, more even depOsit 01 zinc . by hanging 8 pieco of scrap steel in the The faster the deposition. the more un· solution, and. using a current within the even and coarse the deposit becomes. current de nsity range. leave it electro· OccasIonally It may be necessary to pl ating for about one hour . This electro· electroplate a component of small area, lyses the solution, and ta kes out some such as a small washer Or pin. The cur· of tho impurities. Howe ver. 10 ta ke out rent ou tput may 00 tOO large at the low· impuritie'!l as e speci fic o peration. tho ItSt range of the supply. In thIS ",se, electrolyte Is plated oul a t a very low hang a piace 01 steel plate or twO pieces current. Tllis induces the impurities to of plate Irobbersl each side of tile com· deposit out l,rst on the scra p piece. then pOnent. This will InGf8ase the surface the no. mal me tal of the electrolyte is dearaa to correspOnd with the electroplat· posited. ing current, and thus bring it into the current density range. The robbers will ZINC HYDROXIDE 8ATH also carry out a second lunction by re· This is an al kaline zinc electrolyte made moving the high current density, giving up with sodium hydro~ ide. Thi, chemi· a more \!Ven and smooth appearance. cal is e ~tremely caustic. and care must be e~ercised when using it GOGgles, i.e. prevent "burning". gloves and overalls must 00 worn when handling, and also koep away from The p.H of the electroplating solutio n The optimum is between p.H:I to p.H 4. children and animals. Whe n nOI in use it but the solution performs quite well up is kept in 8 tightly closed pl astic or glass to p.H 1. Strip papers can 00 used to jar, bec ause it ta~es in water f'om the at· check Ihe p.H. These can be purchased mosphere and decomposes to SOdium from chemical su p ply houses and large carbonate end water. The formulation of the electrolyte is:· electroplating equipment suppliers. Atwavs koep the test papers we ll 5-8aled Zinc O~ide 1.00>: per gallon 6grms per wllen not in use. To use the papers you litre will 508 tll el they ara numbered I - 14, Sodium Hydroxide 9.Ooz per Gellon universal type, and thal between the 55grms per litre numbers 6 and 7 Is I strip. Immerse the De~trin 1% ad dition by weight.

"

To ma ke up the solution add the weighed ·out amount of sodium hydro~· ide (9,00>:.) to ai~ pints of water and ati, until diSSOlved. Ne >:.) and stir until dis50lved. The last to be added IS the de~lfin. Th is is stirred in until dissolved . The volume is then made up to one gal· Ion with water, and the electrolyte is ready for use. OOt. as mentioned in the previous zinc electrolyte, it must be 'plated out" oofore it i, usable. For this solu lion the 'platinG out' requirements a re O.2amps for 12 hours with a piece 01 steel 2in. ~ 2in.

ammonium chloride to the SOlution 8t the rate 2 to 40z. per ga llon . For No.2 zinc electrolyte 0.250z. of linG o~ide and lto 1.50!. of sodium hVdro~ide pe, gal . Ion of solution. FA ULT Electrolyte appears to be a rusty

colour .. REA SON Iron from the components

being electroplated is di~solved inlO the solution. REMEDY For No.1 zinc electrolyte add 50 millilitres of hydrogen paro~ ide. st" welt and leave to 58l1le. When settled, carefully decanl of/ the clear solution.

Operating Conditions FAUL TThe deposit is patchy. The same con ditions apply 8S lor the REA SON The pre·trealment clean ;s prev ious !lnC chloride electrolyte. The faulty. eleclfoplating currsnt density range i$ REMEDY Strip the deposit off to the between metal by immersing the component In 2 and 20 a.s.I. or 0.2a 'dm' to 2.0a, dm~. 30% sulph uric acid 0' 15% hydrochloric The electrolyce is operated 81 room ecid untll ,11 the zinc is removed. Go te mperBlure 15' - 20'C. bad th,ough the p re·treatment, and ,e· a eing al kaline p.H 12 - 14, Ihe conltol plate. of the p.H is not needed with this sol· CARE A small amount of hyd,-ogen gas ution. is given oH, so ma ke sure the area IS well ven tIlated. Using sulphuric or hydro· GENERAL FAULTS IN ZINC chloric add. goggles and gloves must ELECTROPLATING be wOrn. FA UL TThe deposit is rough or COar5-8 in te>
nenl. To .educe the Kt .... deposit, e 'pauiYe' I.ye •• usually of ch.om,um ion •. i• • pplied. This .educe. tM lietiviTY, hence p.oIonginll the lile of the depos't .nd enhenc,nll thl .nli. corto,ive p.operties. Fo. the diffe.ent colourinll' th. b3ths ..e m.de up IS lollows:' Black M.k, up Ammonium Mo/ybd". 40>:.

per II.UOn. 25grms pe. ""e. C«N:.nrr.ted Ammonl. 1.880 S.G) 6 fluid oz. pe. gallon. 375ml,. pe. lot ••. W.,..-Io mlk. up to '1I.11on (0' litr.). Le.v. tha eomponenl In the IOlut,on unt,1 th. desirBd sh.d. I, obt.lned. for d •• p bllld.s, h.allh. IOlul'On. bUI nole Ih ' ammonia w\ll lume and lIiv. olf • '''onll smell, Ih ••• fo.e it mutt be w.1I .... ntillted o. done outdoors. In both cases, wh.n IIM COI.ect coloo. ;. obt.ined •• inse in cold w.t .... ttHIn in hOt w"e'. and lelve to h..den olf the leye •. 00 not touch the colou.ed surfac. until h •• dened.

Brown M.k, up Double Nick.1 S,II, O.5oz. pe. 1I.1l0n 311'mS pa' "t ••. COP{H' Sulpllat. 0.5o.r. par lIallon 3grml per lit ••. Pot.mum Clllonte 0.5o.r. pe. 1I.llon 3grms pe. litra. UM Ih.lOlution al6O"C. "",th In Int •• • medlat. scr.tch-bfulhinll to even outlh. colou •. W.Minll off imp.O'I.' Ihe colour Nor. Potassium Chlo •• le i. e powerful oxidisinll Ig.nt, and Ihe pow. d., mull be kept in • well SIOppe/Bd cont.lne •.

we,

81ue Colou. (P,uivata) M.ke up Sodium OH;/!romlte 0.8o.r. pe. g.11on Sg.ml pe. litre. COfI(;"''''Ied Nitric Acid 3.2 fluid al. pe.

1I.1I0n 2OmJ •• per "tr • . D,uol.... the sodium dichrom.le In ooe IIt.e of Wile •• then add Ihe nlt.ic add car.lully. "i"lnll well in .Iowly The balh ;. ope.. ted at room lemper •• tu.e. Th, immersion time \ 0 to 20 seconds. IrId ...... nt CoIoo r (Pauivete) Mate up Sodium Dichrom't' l00.r. pe. 1I.llon 6Og.ml pe.lit.a C~ntr.red Sulphurit Add 0.511uid oz. pe. 1I.llon 3.Omls. pe. litr. 011101\1. tM sodium dichromat. in th. voluma r~uired. th.n add tM< con· e.nt.ated lulphu.ie acid slowly and ca.elully. Itl.ring continuoosly. Th. baTh i. ope.atad .t .OOm tamper.lu ••. Tha imm ...ion Ilm. is 8to 10 lOCOnd, CARE WiTh nItric acid Ind sulphu.ie acid, IIlov•• , 1101111181 .nd ov...1I1 mUll beWOfn. Th' Iln !WO formulations ' .. pU" pnsiv"a coatinll'•• nd It. left for 24 hoofl la hltden off belo •• funh..- 1,1111. Afta. hafCMning off th.y CIOn be plinted if requ ired. Th" combinl!ion 01 l ine. pluiv"e Ind pllnt olf... llood CO" .0slon '.Iilllnce 10./0"01,11 malals. NICKEL ELECmOLYTES

Nickel off.r. llood corrosion r,"i,"nce whon ,IKt'OpI.,ed on bolh let/oul and non-Ietfoo, ma'.I, .uch as copper .nd .110.... of copper. 1lMI mec.hlnitm of nickel. copper .nd tin .Iectropl.ting 11 thlt """ d
This;' dilllnct f.om th. mech.ni.m 01 tlM IInc .lectrOpI.t., which 11 I... nobl. ,h.n steet, .nd in COnseqU.nClt,", "'"

becomes cathodic ""'th!he zinc dislOl\I· ir>g i.e. lICfiflCi.1. A good .11 round nick" .lectroIyt. is " lollows :.

w.tt'. Nickel 38.50z.pe. gallon 240g.ms pe.lil ••. Nk:kal CII/on"de 7.2oz.pe. 1I.llon 45grms per "Ita. Boric Acid 4.80 •. pe, 1IIIIon 3()g.ml per lil, • . To mike up tM< ,Iecuolyt •. w.rm up three qUlrte .. o ltM< 'tOluma 01 w.ter. Idd The w.illhed .mount 01 n,cIt;.lsul· ph"., sti, .•nd WI.m until dissolved . Then add tha weillhed Imount 01 nick.1 chloride. r.pelt until d'ssolved. Finally. ,dd the bo.ic acid, which willt.ke tima to dissolv•. AIt.r '"lh, chemicals Ira in IOlulion, maka UP 10 th. required 't01. ume with W.I .... Th .. p.H thould be checked by wh.t· ...... mean •. papefl O. p.H meter. Tha p.H Ihould be 3_5. It is recommlnded th.t th;. soIUI;On be 'plat.d oot' I1 • Iow curr.nt with tom. scrap lleel pllla IImilar to Th" No.2 zinc alectrolyt., Till . will .emov. th. diSSOlved Imputitias in Ih. nickll Nickel

Sulphlla

alec!ric he.,er ;. und. 1lMI ev."nT clantlTY .. ~' is from 10 •.•.1.104O . ..... or l .oa.dm 104.0. dm' Thi. i, as pr.viously m.ntloned. The pan 01 tM ,.nga chosen il dependant on th. shape of Iha companlnl and the t.~lu.e of th. daposit required. Th. low •• tha Current danSlTy Th. lin •• the daposit. Thi, ,lectrolyt. w ill dapo.il:. 0.OOOlin.(2.5microns) 11 lOa.'" in 15 minutes or o.OOOlin.(2.5micron.) at lOII ... 1. in 5 minUles. Thil electrolyt. gl_ a llood dull 10ft dePOSlI which will polilh up to I hlllh IUllrl. III p.opetli •• 11 •• not lI.eatly Iffected by I wide ch.ng. In p.H, tarn. peratu.a Ind balance 01 ch.mical com. position In tha bath. Wh.n this deposit i, ov.r"lectro_ pI.ted w'lh decorative chrome illllves. plea,inll dull chromo effect. IImilar to the finish on mic.om.t..-. Ind simil•• tool • .

Seml·8rllilht Nickel EIac!.olytl Thl. Is baNd on I Wail's Formulllion with tha .ddition of an orllanic b.illhT· en ••. ulll. Sulphltl 38.~.pe. lIallon Nick" The anod •• uMd in Ihis electrolyte 240g.m. per litre . ..I 41n. ,,4in .•'11lI 01 pure n,cIt;.1. Thelll Nocllel Chloride 7.2oz.pe< ".1I0n 45g.ms can be Obtained Irom .Iectroplatlng PIf'ille .upply hou,,". Thi •• izl 'pproMim" •• BorIC AcId 4.80z..per "lIl1on 3()grm. pe. to tha .nodes uMd on Hull c.J1 Appa •• li"a. 811,1,. How ....... for. 1"lIa Nt·Up bas_ Saccll.n"n. 0.32oz.pe. 1I.,IOn 2.Ogrms keled nlckal.hot o. hoolt;ed Inodes may pe.lit.a. be used. buttha.. eln be •• pens;"'e. Th, alectrolyt. IS m.da up .. for Ihe The ope .. tinll t.mpe.atu.a for this prevloul nick.1 eleclrolyt. (Wall.), but el.c1tolyt. Is 5O'C 113O'FI. with th. addilion at Th. end 01 the Thl hea,inll m.y be accomplished by waillhed .mounl of sacch,"ne. Thil is vllious method •. If • "ainless steel con.tantly "irrBd wh.n wa.m, unlll dis· COntlina. is used, I 1111 ring i. placed IOlvad. Th .. d.ssolulion may t.ka some underneath, If th. con",in.. is Pyrex lime because SI (h~.in.I'I'IOI.-.rv ..,1111.15 o. pI.stic, Ihln.n aqu.rium TYpe ubi • •

"

The ..me current deflsity .anges apply lor Ihi. I. for the ptIYious electrolyte. u ~II uthe IImperllu<8 .ange Thi. llectrolyte wIll depoSit :O.OOOlin (25 micron.) II 10 a .s.f. in 18 minUllSOt 0 .0001in 12.5 ml(fonll at 30 a.s.f In 8 mlnules . Wilh Ih,.. elec1rolyte. ag'I81ion i, recommended , it ha. by sli"ing or com · pr"Hd air bubbled IhrOl.lgh Iha Sol· utlon. FAULTS IN NICKEL ELECTROPLA nNG FAUL r PIttIng of d.posit. REASON Acldlly of soIulion 100 high . nick.1 conll"llow, boric acid 100 low. REMEDY Adlust p.H 10 between J.nd 5. Adjust p.H Wllh aqueous solulion of 10dium hydro.ide until between Ihe I;mltt. Add lm. per gallon of nlCkalsul· phall. Add 0.501. per gallon of borIC lCid . FAUL T NOI enough coverllge of Ihe

componenl. REASON Electrolyte I8mpe.alure loo low. or low currenl denlity. REMEDY l~reaH electrolyta tempera· tU<8 10 5O'C - 55'C. lncrene currenl den· • ity. FAULT Poor .dhellon 01 Ihe nickel 10

lhe componenl • • nd may be of bumt appe... ~ . REASON Poor pte·deaning of Ihe componenl. Too hIgh p .H (alkllinity). Too high amlnl density. REMEDY Strip off lhe nickel pllte. depending wheth" 18
"

;ngly. and conSlantly Shrred a"d checked. CARE - Wilh aqueou.lOdium hydro.'de and hydrochloric: and .ulphurlC acid., gloves and goggles MUST bewom . Nickel depolltS from bolh elect.olytes can be buffed or polilhed 10 • good IU'I<8. It mull be remermberld Ihal .n enO""flCI on Ihe th,ck...,ss muSI be mlde for poli,hi"9. COPPER ELECTROLYTE Tha mOll u"d Ileclrolytes of copper Ife Ihe CYlnide copper and Ihe acid copper. The main distInction between Ihe two Ilectrolytes i, Ihll Ihe cyanide copper c.n be used 10 deposil coppe. on bolh ferroua and non·f8
O....dm·IO 3.08Idm·. Tl\is ,lectrolyte will deposil :· O.ooolin_ 12.5 micronl) al 10..s.f in 12 minUles. O.oool ln . {2.5 microns) 1I 201 ..... if! 6 m inutes. Allltllion is recommended at lhe lOP end of Ihe currenl density range . Pure copper may be used for Ihe .nodes. AI lIig h current densilies Ihere i. a rilk 01 the anodes polarising. with a reduction In Ih' currlnl. The recommended .n· odes lor Icid copper elactrolytes ale th e ph01phorrled IYpe. These are purified copper uling. process of ramoving the impuritie. 01 0><\'98n ""ith pho.phoric ICld in the anode making slage. The electrolyte is ope.alad It I templrllu,a of JO"C (86"F). For Ihin depO.1t1 01 copper 11 CIf! be used at room lem~IU". The h,"Mr lemperature of JO"C gIves • smoother depOSIt of

."",.,.

..... 1.Brighl Coppe< Elecuolyte M.ke up :Copper SulphBte 320L pet IIllIon 200grml pet litre. Con~lIntra/ed Sulphur;'; Acid 1.40z. per gallon 27 mls per IlIre. Thlourell pinch O.OOSgrms per liue . Welfmg Agent IT_pal} one drop Iml per lilre. The electrolyte is mllde up the ume 11 Ihe dull ecid copper, bul wilh lower concentration of sulphUric acid. BefOfe the bllh is mfde up 10 ill final volume, the Ihlour,. and wetting agenl ....e ~. After making up 10 lhe final volumelhe elect.olyte is ready IOf uH, N.B. "'" Ihi!)Urn al 0.005 grml- un be raglldad 11 I ' pinch'. The electrolyte lIIould be opereled al 23'C (14' F) for Ihe beSl resultl. Allow.r lIrnperelUre Ih. IXIppar depOsil I, In. brighl. The electrolyte will depO.lt :·

O,OOOlin , (2.5micron') al 10e.•.1. in 12 mInute.. O.OOOl in. (2.5micronll 1\ 2O •. s.!. in 1 m inutes. Agltalion I1 recommended 8
Oflhe

, 10 Ihat rlCommended lor Ihe electro' Iyte. Thl, fault mey be a combinllion 01 Ihe two lea sons, 10 ... ilh 11 small re ductlon In currenl density, end Incr""

"

on .empereture.•he depO.iI

01 copper

will be uti,factory. FAULT F.II in CUff,nl. and riu In "0'"

.ge. and. bleck Him formed on 'he an-

odn. REASON Lact of lulphuric acid ,n the SQlution. REMEDY Add dilule .ulphuric acid in smell .mounts untilthl anode 10sltS its black film. FA ULT Poor coverege of thl compo-

nent. REASON Poor pre-clnning or leek of sulphuric ecid. REMEDY Slrip Ihe COPP81. (10 bad< 'h rough ' he cycle of pre-cle.ning Ind re·plele. Add e .mell amount of dilu te • ulphur;c acid. If .he faullls cauted by a combinat,on of th' two r"'sonl. then add th' ,ulphuric fCld first. FA UL TNodular Or ,plky depo.'!.

eleclrolyla with un·

;;;"h. filler paper o. TIN ELECTROLYTES

nn depollted from "n electrolY'es i. used for pre"nf1ling corrosion on both non·ferrous .nd ferroUI metel ••• nd il Ilso u.ed '0 f"cill"" Ih" SQlderlng of compOnln,.. In some cases illl ultld as 'decorll..... finilh. The pollssium lIannall eleclrolY'e producel a depoli, of tin thal I, colou· red light grey, mitt in eppear.nee. bUI can be buffed to. Ill",.." finl.h. Thi' i,a good all roond e'eclrolyte for use IS an anli~ffOllon f1nl.h on "HI. Or for use on bo,h I ' HI and bra.. for soldering purpoMl. Thl ma~e up i ... follo_:· Potltllum Stennlla ElactrolY'a PoIISllum Sumnar. 1Sol. per gallon 95

"

grms. par li"", PoIassium Hydro)Cidfl20~ per glllon 12 grml. pe. lit.". To make up theelecl.olyte ttl'H qu a rters of 'he yoluma of distilled Or de· Ionised water is wlrmtd up in the bath. The weighld amount 01 pot.allium "snnete il added 10 Ihe w arm Wile •• and "i ..ed continuoully until di,· solved. NeKI, the w eighed a mount of potassium hydrOKide 11 added. and I1I ..td un,lI dissolved. CARE- with POl· allium hydroKide la IIrO,"", Ilklli) gloves. 1I001lles and overelll mUll be worn. After the chemical. are dissolved. lhe eleclrotyte 1I made up to the final ume wilh dillllled Or de-ionised w.'er. Thaelect.olyl e is now rlady fo. ule. but il i. r.,.;ommended ,h.t soma Krap pieces of Ileel o. copper are wi rld up lAd connacted up to the calhodtt. and 'he electroryle 'plated in' .t medium currant d e n,ity fo. " bauI one to 'wo hours. The .nod" used In 'hi. procesl are pu.e tin .nodes. usually in Ihe form 01 II,bs 'hll can be CllIIO tha ruqu;.1d lile. The elecl,olyte i. operaled 11 I ,em· pe.alure betw&en 6O"C and 8O'C. (14O"F and I76"F). No ellilll10n I. required. The el-.;uolyte will deposil :- O.oool;n. (2.Smicronl) at 10..1.1. In 10 minutn. O.ooolln. 12.5micronl) at 21la.I.I. In 6 minutes. The current denlity il between 10..•.1.•nd 408.1.1. U.Oaldm' and 4.081 dm"). The p. H of 'he solution i. highly Ilka· line. and Itays alkalin,. Whe n opetlting Ihi, solution it mUlt be remembered Ihlt It is best Ihll befota electroplating. I piece 01 Ktlp mlteri.1 (ItHII. i. con· nKled 10 Ihe cathode bar in tha fllecI'O' Iyte. The eleclrical ,upply is .witched on. and th' anodes .ta placed in the eleclrotyte. and connecced 10 the ,node bar. The K.ap pi8(:e should Slafl being

\/0'.

e lect.opllled Immtdlately, Al lhe seme time a.the se.ap PIece i. elecl.oplating. wi" Or hook the companentt 10 be elec. Iroplaled to 'he calhode ba •. This is car. rild Oul w i'h th' current s w ilched on . Th is procedure p. oduces an ;.idescent gold coloured film on 'heanodes. w hich is pen 01 the mechanism of llIe electroplating process. Mode.a la Currenl den_ l ity II used on Ihe scrap piece. FAULTS WITH STANNATEnN ELECTlIOPlAn NG FA UL T Elect.olyl e works sluggishly.

a nd th. anodes Ira I grey colou., REASON Initial currenl denllty lOO low to form Ihe corfKllilm. FrH patnsium hyd.o.ideloo low. REMEDY Remova anodes one 11 a timl. a nd r'p lace tham in Ihe elect.olyte . Somet,me. a llighl increlU In (he rent density is benefICIa .. Add O.50l. pe' gallon o f po"uium hydrOXIde.

cu.-

FAUL T Th, solution turnl I slighlly pink

colou,. with I spongy tIn depollt. REASON A build up of POlalllum "snn"eln the solution. REMEDY Add I smlll amount of hyd.o. gen peroxide dropwise. Ind SI .. until the pink ooloor diuppeefl. SI"p lhe tIn ciePOSlt. pre-de"n. and re-pia. . . I1er .dding the hydrOgen peroxide.

FA UL T Anodes coye.ed in a bllck Iilm. .nd currlft' drops oH REASON The InOO.. have become polarised. and become cove.ed in tin o.ide. u ..... lly b.ooghl ,bout by too high Cllrrent denllty. REMEDY Reduce currenl d ensity. Remoye Inodu one" I 'ime. and ICOur Ihe .nodes with. sIIH brush until the fIlm is .emoved. R,pI_. until III the snodes h,ve bMn scoured.

"

CHAPTER 6

Electroforming and Electroplating on Non-conductors ELECTROFORMING

The most common metals deposited

Elec'uoforminll " • p.oc;eSll 01 electroplll"ntl1h1t I. used in the manulac\ure

in electroforming". copper and nickel.

of int,ice'. components Ih".re difficult

\h, proc;e.... n(! sometimes Ihe moat ._pen.,ve, i, \h. mllnd.el. which i. th. shaped material \h. metal i. deposited

to I,b';';"e or machine. 11 is an idoll method la< m.klng c;QmponenlS 10 tight lolerenen.oo dimensions.

:Th~,';';';;'~':';;"' of metal deposited ;, I more Ihan conventional

;

(.nythin; from 0.0121n.

Ho_,. 1Il0l moSI essential pll" of

~.

M'I>I:l
ego.iH. .1 Dispoubl. M.ndrels. Thue

'f' • type

of mandr..1 Ih81

A m",,/d mMJ. from " m.~1 I>y ./«;t,,:>forming..., In 11 wckmg d'e .1I0wo~ 1I 10 W uH
\

An IKl mple 0/. cl'opMlf>I.

m.ndr~ m.~

'rom low m"lmp (JOIn' alloy. N(I1. ,,,.. in"",

mw/lied in 10' e H'Klng Pe ..".,,, Windows, and COMHI<:""II'N CI'_ b8r

cannot be eHtr&eted by pulling OUI 01 the ,'eClrolo,m. due 10 being either I bend. o. hiving smaller dim,msion. at th' ,nd • • Th, mate",' used cen be Pe,speH. low melting ,lIays. (Celrobend. CellO' cestl. end some gredes of WaH. All these m,t"i." cen be melted 0, diuo"'-d in IOIven ... The e55enlial piece of equip' menl fa' thi, mllnd.eI;' I mould to cell in. However. with Perspex Ihi. i. usullly machined to shape. IInd nol moulded. b). Pe,manem Mandrels. TheM lI'e u,ulllly made of ,,"nlell ".el 01 nickel electroplated Ileel. Sometlml1 certain plaslics are used.

These mand.els lI'e e"t'lIC1eble by pull · ing on a press. Other forms of aleet.olorming .. , qune ueeful. such es building up worn ,hllhs, 0' ,hllhs \hlt hlJYl been meeh · inod down 100 fll'. Small moulds can be mllde for ..... ,. 00. other processes, by milking I ''P' lica. elearoforming, .amoving Ih, raplice .nd seuing the elec!.ofOfm in I blocking die. Thl, mould can be ulld 10_ making' quantiry 01 componentl. From • mould liklthi. ilems can be made .nd UMd on, lor , xllmpla, modal boat • . The two elect'olytel used In el&et'o' lorm ing are coppe, and nickel.

"

Th. copPe' .I.,;trolyt. is th. dull eo~ Ii.t~ In th. dlapler on electro·

"'~

Co~

El«'lrofOfmln9 Electrolyt. Make up;· Copper Sulphal' Crysla/. 320.<.per gallon 200grms per litre. Concenlratfd Sulphuric Acid 4.Sfl.oz per gellon ]Oml. per !iUOit. A Imlll Imount of phanol dissol"ed up In wal" can be added. This gi"e. graln·fellnlng propenle. to the electrolyte. The current density is between 10..1.1. - 201 .•. /. 1.0a.dm' - 2.0a.'dm'. The OJ)8rltong temperatu,a is 3O'C.

!86"fl For nidel, the Dull Wltt's electrolyte can be ulUld. but a good elect.ofonning electrolyte la one fOfmulaled as follows :-

Nickel Electroformong Electrolyte Mllkeup: · N,,;k.t Su/pMmala n~. per glllon 450grms pe. hl.e. &wr: Add Soz.pe. gallon ]0 grms per I,tn>. The um. !ank can be u5eCI as 10f t"dull nickel, and ma~ up t"- samOit. with the n,ekel .... Iphamate dissolved firsl. Ihen th. boric .cid Idded and dissolved and made up 10 the final volume. The p.H i. 4.0. To reduce p. H 8dd sui· phemic acid. To increase p.H add am · monil O.880SG. Howe"e •. being stable. it usu.lly ... yl 11 about p. H 4.0. The soIullon IS oper81ed et 45'(:-SO"C (ll3'"F - 12O'FI. with 19'1allon if POSI' Ible. depending on the thicknen required. The cu ..... t denlllty is between 10..• .1 -SOl .•.! 1.0.dm'-S.Oadm'.

. -F'... " -,-? ;...: ........ ________ _-.;J._ .,

.......

~-- ~""---

-,,-;,:,."

/'

A simple example o f .Iectrolormingl.

I funnel Ihaped component. Sea

I~­

u,,,'3Ind,1I. Figure 14 is me assembly lor ,1«'1,0IOfmlng tha shape. The mandril ia macla wrth insert. \lIUewadl. if moulded. from low melting point IIIOYI. If made from Per5pe~, the ho," are d.iI1ed and tap ped. P"lpe~ windows are affixed al each and, the hanger attached. and th' ,r," that ara conducting are 'stopped olf' with molten 'Clamea' wax, o. Ilmll.. material.

If low melting ,lIoys ..a uNd. lhe pretreltment 11 a light cle.n WIth scou,ing powder or Scotdlbrile. then a dip in the alkaline cleaner and electrolytic cleane._ but the electrolytic deaner " opltOnal. The mandrel f;g is rinsed on wlter Ind Immersed in the particular elearolytl. Ind gfown to thtI required thickn.... 11 Pe .. pel< is used. thit it mlde con· ducti"e with either. layer 0 1 aqueous grlphite. 0'. preferably. sllver·IOlded conductive paint. whic'" i, p,lnted on the .urface of the Perapex, m,' inp 'uti the conlaet lor Ihe hanglflg bar I1 well

rn.nd", Wllh "'~tH" window and a/hods /HI, _"«10Id _1d/'rI"" with ctMducfi"fl si/wT tyifll. {No" ",. {»in. OIl I'" ItdoIJ. r". of ,htt pho/Of1t1ph 'he

,An ex,mpI, ol.n eIect",·lomti"fl .-od /lot> '-hi. r"" ngh • ...

_.0Id.

OOM«f'fItI /H, 01 ~ Doff.,... ;,," eIect",fo<....-J .n.p.s. in lit.. a ... , ~ and lid electro-fDnnMI it> si_

P,awI

11

-------

.. "

"

ElECT"AOPLATING NON . CON~UCTORS

Included in this section is Ihe electroplating 01 aluminium. This is n01 strictly a non electricel conductor, but neve'" Ihelen it will nOI electroplate like conveOlionat metals. Ana, going through tha lisled precleaning cycle lor aluminium, as in chlptet Iou., lincale solUlion is required. This is made up as follows:·

llneale SOlution Make up:· SQdium Hydroxide 701n. per gallon 440 grms. per litre. Zinc Oxide 130l. pe'gallon 87 9rms. per IIt'e. The solution ;s made up in hall Ihe volume 0Iw8te., adding the sodium hy" droxide slowly. and slirring conl;nu. oUlly. Aftef dlssolv;ng the sodium hydroxide, aod While still warm, add the

r-------------~~

A" e"~mple "f ,JeclrDplarl"fI 0" .lumi"i1. uti/iSM z,,,,,.r, JOlu· Iron, loIlowf
painted. The conductive SutfaC6 is al· lowed to dry, ~nd is immers&cl in the particular el&<:lrolyte, end grown la Ihe required thickness. I1 nickel·plated st&£ll or SUlinless steel mendrels are used, i,e, permanenl man" drels, the .."me procedure lor cleaning aa for low melting painlllloy mand'els is fOllowed. and growing i! the same. Ahe, growIng, Ihe wa" and windows are removed, and depending On what Ihe mlndrells made of, il is e"'ractad by Ihe following processes. Low melting III/oy. This is melled. either in an oven, o. hot oH unlil the aUoy Ilows oul. Pe,Spa". The mandrel is immaf'!led in I solvent Such as warm Genklene unlil

.

dissolved up. It mey also be eXlracted by holding Ihe elec{rofo.m snd pulling OUI the Persptl" mandrel. Nickal-plared s/&£II or Slainless slooI. This is e"'racted the same as Perspex, putling lrom the wide end. PoinU t o 'emember on e lectroforming (1) If 8 18rge quantity o f al&<:l,olorms ara required, slainless steel mandrels are more economical. (21 Wilh permanent mandrals (extra<:tabb.l), Ihe511 can only be used on el&<:lrolorms that have shapes Ihal can make Ihem axtreclable. (3) A small d.aughl 8ngle should be included on permanent mandrels 10 aid extraction.

A mOiJld
"".irised

/cuded

1.led.

~Inr,

.i_

(fIsin li.

wtln

and "ecrrop.

zinc o~;de, stirring unti! dissolved. Make up to the final volume and aUow to cool. The solution i. tllen ready for use. Idaal containers are Pyre~, glass Or plut~. Thll solution is uslld at room \emPllr~!Ure .

To imprOlie \he deposit. that is to make a mOra even deposil, a small amount of ferric chloride crystals (a large pinch, approximatllly O.5grms PIIr litrel and 5 grms of Rochelle salt are addlld. However. tile aulhor has found the original formula satisfactory for most finishes on aluminium. The immersion time is between len and thlr1y seconds. After "nsing in watar Ihe aluminium should have a grey apPllarance. While still wet from the rinse, im· men;e in either of the nickal elactrolVles to deposit approximataly 0.0002in. 0.0003in .• remove, and rinse, and Irans· fer to any other electrolVl8 you would like 88the finish. This is \I useful aid to soldering on alu · minium. either all over Or selectiVflly. with the lid of masking. The process is as mentioned, bUI after depositing nickel, the final finish i. a deposition of tin O.OOO31n. epproxim,uely . This finish is ideal for applying solder. Non-conductors ere usuaUy classed as plastics and caramics, but these can be electroplatlld when they have been made electricaUy conductive. In industry the classic of electroplat· ing non-conductors is the process in the electronics industry of 'plating through

hole" on printed circuits. Briefly, this is wllen the COPPII' dad plastic is driUad. The holes through the middle have plas· tic faces. This has to be sensiti$8d wilh various chemicals, such as stannous Chloride. then palladium chloride. to make tile surface conducive to a layer of copper from an alectroless copper 601· uti on. After rinsing. the leyer of copper is built up in the holes with high throw electrolVlic copper, followed by 8 tint lead electroplate. A simpler method for electroplating on non·conductors was mentioned in the lI!ectroforming section. namely aQu, eous graphite and silver·loaded paint. Silv8r·jo~d8d paint can be purchaslld 'rom paint or chemical supply houses. and comes in quite a few formulal ions. Some can be painlad On and air dried. Some can be fired, or even be put on with 8 silk scree n process. For ceramics, the firlld·on variety is usefuf. After firing. the surfaca Can lIither be elllClrolVlic plaled. provrded Ihere is a contact for the current. or elac· troless plated wilh nIckel, COPPllr, gold or even tin . An idea for making decorative jewellery is 10 dry leaves from trees or use clean seashells, paint with silver. loaded paint. air dry, and bright copper electroplate to 0.001 in. Also moulded epoxy figures Or busts can be made in 8 similar wav and this is an inexpensive means of making ornam ents.

CHAPTER 7

Electroless Electroplating The r&8son for the tWe ollhis chapter is Ihat tha deposition of metals can be car· rilld OUI without using an electrical current. No electrical equipment is in· volvlld in the actual electro·deposition. It is somatimes referred to as chemical plating, because the chemicals in the formUlation effect the metallic depo· sil ion. The main consti tuents of the solu tions ar8 an aqueous solution of the chemical containing the metal to be de-posited. and an equeous solulion containing a chemical .lIducing agent . These Can be mi~ed together to form the pl,,;ng solulion, but before any depo· sition takM plaCfl, a catalyst must be present. In this process the COmponent is the catalyst. No anodes are used. !t is merely a tank containing the electroloss 50lution, wilh 0. wilhout agiTation, set 10 tile cOrr8CI temperature, with the component immersed in the solution. The most popu!ar and usolul e!ectro· less solution is for depositing nickel. Usually this is depositlld 8S an alloy of nickel and phosphorus. appro~imately 12% phosphoru$.

ElECTROlESS NICKEL Make up:· Nickel Chloride Crystals. 5 Ol. per gallon 30grms pe. litre.

Sodium Hypophosphire 1.5 - 1.60. per gallon 1Ogrms per litre. Sodium Acetate Crystals Sol. PIIr gallon !;O grms per litre. The Sodium hypophoaphiTe is the re· ducing agent in the $Olul ion. The best method for using Ihis SOIUlion is 10 make up a solution of the nickel chloride and keep in one glass bottle, and make up a solution of th e sodium hypo' phosphite and !:IOdium hydroxyacetale tOGether. • nd keep in anOlher glass bo"le. These can be stock solutions. When required. enough volume Is mi~1Id to plate the componant. The ideal container W plate with Ihis !:IOlu tion is 8 heat rasiatant glass bea ker, healed by a Bunsen burner, lIas ring or electriC hot plate. Thll oPllrating temperature for this solUl ion i, 88'C - 94' C flSS"f - 200'F) . Some agIt ation is required. bulan oc· casional sh8ke of the 'Nirlld CQmponent will release the bubbles of hydrogen that collect On tha component as ~ prod· uct of the .eduction process. The deposilion rale for the solution at 88"C (lSS' F) is:. O.OOO6in. (IS microns) in sil<1y minUles. However. to mainlain this rate of de· position, small addilions of the stoc~

solullon. of niCkel cllloride . nd tile todium lIypopllolpllne wllh lOdium lIydfo>
n..

Tile eleclropll1rnlil lupply lIoule. of. Itrr In e Kcellenl ranlile of elecl roless nickel •.

Ferroul mal.ls ean be plated In thl, solutIon a fte r Ihl pre-<:Iean fiiled in ch'pter four. Coppe' and its alloys ean .Iso be pl'led, but, being no~talytic, nMd to be touched w ilh iron or .Iu· mlnium wife 10 .UI., the plallllg oper· a lion. AlumInIum ean be pI.ted direct WIth Ihis solulion, no zincale dip being

TIN ElECTROlfSS PlATING The followlrtg two formul.e are uHful for pulling' thin Ilyer of lin oyer ferroul metlland coppel.nd ill.lloys. Oeposili"g ti" o. copper by IlIi. m"lIod makes it useful for solderirtg, espec.. lly on prinled ~.cun., whanl Ihlle .. no common co"necllon '0' elK· trolytoc ti" 11e<:t.Opllli"liI

-.

Th' ",-"llu rlilCaI p' 0p8rties of Ihe pllllng .., Inleo"ting. As plaled il has , IIlfdneu of 500 V.P. N. By heallreallng up 10 4OO"C the h..dness ean be inerea.ed 10 900 V.P.N . The appearance of lhe dePOSIt ean va'V from dull 10 semi· brlglll melll.

An D.~ 0' mild ~wI ~"n, roI.o<1lO1eu ndM "u.fId. This depos,t wilt 11''' .,. ...... I_".,,_..u ,''' WI''''' o"IHJ cornPOl....~ 110', •• _ corn"I........, rIHJ sh."..

•

For d.positl"lI on eopptf ,r>d tu .lIoys EllCtroleu TI" M,k,up: · Stannous Chloride 1.60z per g.11on lOa.m. pe. litre T/'rjoorllll 13.60z per g.lIo" 85grml per lil'lI. COflC/ln!r,ted Hydrochloric: /Wld 2.311.02 per 1iI.lIo" ISm1. pe. litre. W"lIrto makll up Ihll volume. The soh.llio" i. uled 11. tempeflturll of 5O"C ,t22"F). Thll ululllmme •• ion timl i. fiYII min· ules. Notl : thil formula ia patented, For. quiek pra-<:Iun on prinlad dr· eu;ts, giYI a li"ht rubbing wilh a Ilurry of scouring powder, rinM. Ind immer50 in IlIe lolut;on .

For immllrsion coating tin 0" IUtel, IhIIlollow ing solutio" i. used. For d.po..;tinll on Iron and . ,N1 EIKtroleu tin for i.on , r>d dNl Make up:· Stllnnou.f Sulplt-alll 0.24ol per "allon l.5grml per lilll. Conc/Inrrlled Sulphuric Acid 0 14n.0J! pe. gallon 4m1. per lilrl. Wllllno make up the voluml. UM Ihe pre--dean for steel as set out in <;hapter foo •• then immerse i" the IIn soh.I\io" 81 I temperlh."e of Il2"C

"8O"Fl,

The time of immlrsion will YI'V WIth thl 'Urlace co"ditio" o . ttlll mlteril1. Thi. could be between one Ind le" minulH. Cofltli"ers for immll ..io" tin plall"" ..I hel l·resiSlant gl ass. or plastic con· IIiners, usu ally polytllene o. propyll"l. Fo, these conlainftrs Ihe aqullia 1111111. cln be used. The Ihickness o f deposit from electro· less Iln solution is Ihin. CARE with the aci ds used - glovel, gagglH a nd overalls musl be w o'''. Tile electrollss tin solution for copper being ralhe, solid, w he" heali"g I.om cold some 'bumping' w ill tak8 pilei<, un· tilthe solid chemicals ara d isSOIYed.

,

..

"

An Example and the Consideration of Electroplating All the chlJPters dea!! wllk IJO la' lIava been set down in • kind of logical ... quence 01 tile processes of 818(:"0918'ing. So, IIl$uming Ih. IV8'fge ••..cI•• ;, Itarti"9 on • smell loCale . end may be 11 model eng'nHr, he Or Ih' Win .. to eleeifopl.ilt I bitch of ,milt campo"e"". TakIng Ihe hub cups of • ,",,11 IrK-

tion engine

11

en ."empt.,. The

The .... XI pan oltheope.alion isto calcullte IlIe surf.ce • .,tll of the cornpon.nll 10 be electroplated. This Un be dont f.om the di"9fllrnl. 0. the pans menuted by hand. Either way il is the .. me. To cal\:ul"e,he .rea ohlle hub cups ;1) Fo, "'11'. di, thurea in,.>' _ 22 x 9'

-, "-

- 0.99 Iq in

sion. set DuI In Fig.15. 2) T,king ci I"(:um fe renee x height 01", '" n. The component. hev, bun mach o 2" K' x height reedy lor electroplating, efte. bei"; 510red in e dry ere •. In Olher words, IlIefa;. no heavy 1..,.leee .u.t.

'i,

2a x K ." . Tot.1 a'ea i, _ (0.99 _ '" . ~sqln . . Both inside and outside Fo'lourhubcaps K13.68sqln.

,I

r--- ---- --, ,, I'

,

OU.,.mv. 0"

............ _DS .. ~ '

•

Remembtfl"ll on. $qu ... loot _ 144 $qulralnch... TlM Ilm. IOf thl Ilee1roplatl"ll for nielel - 18 minUles. TIll lime for Ihe .Iact.oplltong 10' copper _ 60 mlnut". ISM ch.pta. livel . Th.t compl".. Ih'lhlO.eli~1 pert of Iha eleel,opllling p,oce.., .nd now come. the p'8Cl1c11 pe ... . Th. hub cap. are buffed to the deslted lus!te with a mop O. Olher polishing 1001 . Attar polishing. Ih. compon.nts • r. immefled In an organIC solvlnt. e .g . white .pirit. for live mlnullI. th.n wiped with. rag ",.ked In tha Ipirit. The componenll are thin .ir dried. They .ra th en hung vi. one of the sm,lI KreW hole. on copper wire 1I the requlfed length to fit the dapth of the cleaner•• nd the elec· \folyll. Aher wiring. lmmer.. b.ck in Ihe whila fpillt 10f thirty MConds .• nd .lIow to air dry . Thl. i. to m.ke 'ure the.e Ife no flng,r m.rU. Being m.de 01 mild .teel. Ih' cl"nlng cycla i. . . lollow •• from tha tlble. in ch. pte. four.

111

50

Immern in alk'line SO.k cleane • 11 8O"C 117f1"F)lo. th," minUIII.

121

,. """"

e

'"

components hive Ihe I hape and dimen.

ined 10 11 good surface lini.l>, end .re

pan 01 Iha rectifie •. Thi. gIves a cathodic clean.lWatch 10. glSllng on the eomponen1l, Ihi. glves.n indicallon of tha cloning eHeeI) Afte. one minute, rev .... the p0larity, i.•. connecl lhe poa.l iva reel,lier clip 10 the eomponenll and anodic cion IOf .bout ten sec:onds. Aft.. the alkali cleaning. rlnu in cold water fOf thirty wo;onds .nd !tansler to No. 1 0' No. 2 pickll, imme'te lor one minute 11 .oom lemperetu ... R,nte in cold wale. 10' thirty seconds.

The hub ~pt; boting m.
CHAPTER 8

Immer.. In .Ikallne .Iect.olytlc clll"" ., 8O"C 07frFl. Ior one minutl. Wllh 1"- compolWll't1l con· necled to lhe ~Ihoda negl1ive

e

Conneel lhl reeli!;e. 10 Ihe nielal tank. positiv. $10 the nickotl .nodH. calhoda neol1ive, 10 Ihe cathode be,. ChICk the circuit by switching on Ihl reelifie. on sm.1I adjustment of currenl. and dip Ihl clip Irom the cathode blI. into Ihe aleel.olytl. 11 curranl rlading i. obtained, thl circui l i.,he correct polarity • Wtlh Ihe eleelrolyte 81 tha .equi.ed tempe."ur, 01 5O"C l \3O'FJ and Ihe .ec· tifler III to approximately one ampe.e. connect the wired componenl. to Iha cathode ber. immersing in Ihe eleelroIyte 11 Ihe lime time. Afte. Ih e com· ponents hava been wired onto the cathode ba. Ihe currenl il .dJusled 10 0.95 Or 1.0 .mpe.e•. Tha comp.essed.i. agitalion I•• djusted 10 •• steady bubbling action. thIn left 1o. eighteen minutll to lleeI.oplate. WhIn Ihis lime hnelapHd. Ihlwi.ed componenlS ..1 removed .nd ,inHd in cold watar. Whilti they 1'8 ,inling conf1.l'Cl Ihe 'eelllie. to Ihe copper eleel.olytl IlhI same procedure IS 1o. the nickll electrolyta). The cirC\lIt polarity it ehedted ( _ nickel electrolyte). With thl eleel'oIytl I1lhe r&qui.ed temperllU,e 01 23'C

e

"

(74"Fj. end the fectili .. set el one Imp. Ihe _fed componenll Ife 'l'Il'Iove
4 ). Fo. Ittlppi"i! nlckellrom I lu mlnlum. Imm.... in SO% equeous nitfie acid. o. concentrated nllric ecid at room I.mperature, unlillha nlcklll dllposil is di', solved off the Iluminium,

CON$lOEAA noNS IN

5). Fo • • t rlpplng enodlll.

ElEC'TAOPLA nNG

som.

Thil i. by way of Illn.1 word on 01 thl espects mentioned. but not elaborl' ted on in verious ch,pI ... ollll4 book. M.ntion is mede of slripping the llee. Uopl"e
-.

Two pertl W4ler. by "olum• . The ".ipper is use
e

"

the stripper thl $Ubstrate will ..ert to diuol"l.way. 2). for " ripping COpper depr;>li1a trom IIHI I nd eoppe • • nd its 1110.,...

Use Ihe recommended nickel ,tripper. INot).

3). For "ripping 01 copper with nick. 1 undlrccNrt. Use the recommended niclel Strlppe •. (Noli-

The loIlowlng .alulion can be used; . Meke up ;Ccncenlref«/ .ulphurit: K,d. 1611 ,01 loomls pe. ti" • . PoreuJUm FIIJOF'cH. 6 01_ 40grms pe. litr,. W'fer. to mlk. up I gellon (to mek, 1 Iilr'.1 The SOlution Is mad. up by adding wale, tQ e h.1I r..ist ant glass Or pl..tic tank 1pc>lylhen, Iype). The sulphuric acid il Idded ,lowly. Ind stirred con. tinuously. All,. lhe Idditlon ollh. Kid. add the potelllum fluo.rd., slIrrrng con . linuously until dllSOl"rtd. Allow to COOl to .oom tl'll'lperature. Adjust to linll "01. ume wi!h W81er. Use Ihe stripper It room temper.lu... Allow the com . pc>nen15 to '''nd In Ih. ''';PP'' untIl the anodise i, d,llolvtrd off. The info, . mat ion on stripping d.fedive Inodi .. in chapter nine i, IIill rele~enl, but e separe" .Uipper mey be needed, especielly WIth dyed pen" which would colour the !he lnodise pre-trutment This glvtrl e choice.

6). Fo r Itrlpplnt tin trom steel end c:GpJl4f Ind Its ello.,... The lollowing lOIution C4n be used:Meke up:· CopPlr sulphete errsfe/s. 6 Ol, per gal· Ion 50grms per litre. Concentrated sulphuric e"id. 1611.0:.pI. glllon loomls per lit ... Water. to meke up 1 gellon Ho make 1 lit ..), The solulion is used et room tampe'l' ture. All tha listed IItippers can be used in plntic con"i.,..,. lik, pOlylhllne. CARE w ith sulphufic Ind nitr~ Kidl, both .rI corro.i~a. Use goggl •• , glovtr$ Ind OVllralls. Add acid to water. nOI ylce· versa. Watr;h fo. h"1 generated by the f41Ci;On. After .ach Plft 01 the pro' cessing. i,l. belween 1114 cleaners. pickle, bright dip. .ndthe electrolytes. 1

cold wit.. rinse must be carried out Thi' cleans the component.. end stops the .Netion, and pr_nil C4rrv-over 01 the solutions, thus pr_nting conllmi_ nllion. All of the lormuletion. hive I~c!uded ,1I\h' cyanides end chromic ,cld. They hay. "-en mentioned in Ihlle~t. but the '8Ison lor excluding the.. elect.olyles. auch .. silve, end gold. 11 because they COnllln cyanide. You might be eble 10 purd>.SI !h.m from th' VI"OUI IUpply housel. but td>eduleCfIss. In Industrlel .Ieclroplet· ing mendatory ,egul8110ns apply. and thl haurd, with chromium ,Iect.oplet· Ing, wh.n ClIrrirtd out in In un'l9ullled ..... cen be verv con,id..ebl • .

USEFUL INFORMATION To convert ' Fto"C To convert"C to "F To convert ounc.. pergtllon 10 gramm.. per 1i1re To conveft gramm.. pe. lilreto ouncet per glnon To cony.rt "uid ounces 10 millilt".. o. CC Nickel Sulphete CryStalS Nickel Chloride Sodium Hyd.o)(id. (Caustic Sod.t Potassium HydroHide lCaustic Potuh l Sodium Carbonata (Sode Ash) Concentrated Sulphuric Acid (SG 1.841 Concentrlied Nitric Acid S.G 11.36) Hydrochloric Acid Copper Sulphate C~tal. Hydrogen P.. o~J.de

{Temp "F -32) H'I. (Temp "C" -If) + 32 multiply by 6.25 mUltiply by O. 16 muluply by 28.35 formule NiS04 eH.O NiCI.6H.o NoOH

KO"

N •• C03

H.S0 4 HN03

"Cl

CuSO.5H.O

",0,

,

""'" "', ,

CHAPTER 9

The Finishing of Aluminium and its Alloys 1"",

The linllhlng of Ilumlnlum can be 8Ceompli,tu,d by e ilh •• an anodising p,o-

laver is dependent on liml, Thl InOdI,. ing proee.. Iccele rlt.. Iha lime and cess 0( I conllltf'SiOtl coating. allO giv.. a denser unblOk"n 11";'. 01 The MIOdi,ing ~U. Thl. a1n be oxidl, whICh enhanc:a till p.opetIies 01 divided inlO 11II).ptOCflnes:_ Iluminiu m againsl oo.,o,ion.ln Ihl .ul. phu ric acid process il .dd, a mordlm layer which can be used for Ihe dyemg SUlPHURIC ANODISE AND CHROMIC 0<' colOUring o f aluminium. Ho_er AOOAHODlSE for colOUring lhe maIn IUenl;al i, t~ Sulphuric ~d _nodi .. i. the mote p•..,_ h.v" a good laver of alumin;um oxide. lio;al PfOC'" for th. ,mlteu•• nd mode l Mlgnified 1000 .. thl laver w ould loo k englnee., Most g ..des 01 ,Iurninil,lrn likl Fig. 16. lOO aluminium alloys GIn be anodiHd Thl impOrt.nt ch"lCIerilllc$ are Ihl by rhlt proc,," ; the pur., Iha alu~"tfi layer and Ihl pOrI . izl. Thl mi nium the bene. the 81lodiMd film. Ih.ckness of the bl"'I' I.ver i, p.o. The 1I1.10UI aluminium alloy COnportlonll 10 Ihl voltage. The pore.lzl Is l tituenll. I.• . silicon .nd m'nglnase, dependem on Ihl conclnlralion of Ihe lend 10 'M'td the process o f Ih • •no. Iltctrolytl iMllphuric KId). !h" Ilactro. dind film, elll'I" in the pn",re.lment Or Iytl IImpe"lur. and Ihe applied cur. the actual,nodl,lng. rent. MOll labric"ionl from 0. Two faclors emergl whiCh make lor a 8l
I"",

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tl

Solution Prep • •l1lon To make up an anodising bath a 111891 o. , polythene Iype DIUlic link i, .ecommended A good link 10' domg small componlnts il • IlIge icl crllm conIImar. These havI. tlpacity of about 1 gallon 14.5 lilrll). Hall fHl Ihe tlnk with distilled or de.on."d waler, .nd th.n slowly add lna necesury voluml of sui. phu.ie acid. constanily stirr ing. CAREI Tha aCId must be added to Ihl wlte. and not vice ver~. h I1 adviUble 10 wl .. prOlectivl gloves and ufllY glasses. Altar allowing Ihl IOlution to cool Ihl volume 11 coulded by Ihl addilion of mar. di,tolled wate •. An I .. ample of Ihl dilution i, as foIIOW' :10*4 volume IOlution for h"d .nodi.ing. 450 m's per 4.5 16 flu.d al. per gallon.

"t"•.

0'

12% volume IOlutlon lor general anodiSIng. S40 ml. per 4.5 lit.... 19.2 fluid oz. per glllon. For else Ind convlnilnce balllIV acid .old 11 g ...g .. ~n be used. This i, of I d ilu tion of 33"<0 of sulphuric acid In distillld Wit... IpproMimlte specific grl~lly 0 1 1.275/1.280. If Ihl balllry aeid i, dilulid 1 volume 10 2.0 volumes 01 dislollad wlt"r. Ihi,

would g,vI • 10"1. ,ulphu"c .cid concemration. li the Iunery acid I, dilulld 1 voluml 10 1.5 volumas of dj'lllIad w ...., Ih" would giVfl I 12"4 Mllphuric .clll Con· cenlrllion. For. g.lIon 10lUllon the dllulion i. 3 p,nts of bl"lry acid 10 4"., p.nll 01 dis· 1.llad wallf. giving I total of 7"., p,nts lotal volum". JUSI undar Ihl g.lIon. If measuring1n "I". or ml •. the dilullon IS 2 lit". or 2000 mll. to 3 litres o. 3000 mls .. giving I t01l1 volume of Slit..s Or 5000 mll .• which i, jU$! ov,. the 4.5 htres; Ih' equivallnllO a gallon. Sen lng up 01 th, anodll lng la nk AIt" th, required volume of IOlulion 01 lulphu.ic: Kill i. midi up (IIIher 10% or 12%) !wO piec". of cllln sh..tlead 1'1 pl.~ed down two oppo.ite sodll of Ihe tlnk. TheM "I bent OVIf the lap Olthl tank 10 po'lil.on lhem and to mak'll>Im conVflnient to connect to thl llectric.1 supplV ThIS/! a.. Ihe cathode.. The anode bar i. pllced down the m.ddle • and the componlntl to be anodised are connectld to this. Thau.ual WIV to con· IIecI Ihl aluminium components for Inodismg i. 10 Jig them in a I.lln.um made .prung jig. The.. come in differ' enl sh.paslor variouI components. but are a>cpanliVIIO buy To1anium rod Ind

-.- ,, ,

fig. 17

small "«Id bit can bt' pur~h8Sed for makinglhlM jig •. fh_CIOn be used 10' ,nodi.,ng I la.ge Quan tIty o f ,imlll' components, which would p.oya the

mOlt ""onomlcal way of processin"

,k",rn.

Generally tha U51 01 al umlnum Wire IS

Ihe most II~Qnomjc.1 for Imall Quan . tities. and it Cln be bought In VI"OU' d"

amete, ,iled 'eel, 01 va'V'ng stiffn .... Lengths are CUI .Iightly IO!'lg8' I han re_

quired and coil\ld over a bar of "",'11 or wood so 11,,1 some tension i, obllioad. The component i, wired up u11nll' con-

venoent hole. or I PlrI of Ihe surface ,h" will 50!1CUre 11 good electrical conlKl . TI>e Will il then twisted 10 .n.... '. I rigid

contact. Tt,,, 'e51 of the componen" I',

wired lhe sama. if vou •• e anod .. ing I batch Or I sel of component • • The wired components should hlng Ipp.o_i. ma,ety midway in ,he elllCtfolyll, ..,,,th an allowll'ICfI Q<1 \h, wire for " ' .ching it on the lnode bat. Th wir.. lie then sn.pped off.o thlt I
"

, I I

.-

surface Irea 10 be 'nodll8
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, , ,

/ /

well .. makinll i, easier Ind ne~ter to w". onto lh. anode bar. Wilh the components wired up • •he power II switched on and edjust9d to the rlquired <;!.IlIent density lor anodis· inll.'t illhen leh for Ihe required lime 10 obl"n the 'lKIuired thic~ness 01 anodise. To enhellCtl and improve . he qu ality of anodised finish. ag italion is ,ecom· me nded. bUI good quali.y anodise ean be oblaln9d in still bOlhs. To a g itate the electrolyte a plutlc pipe wilh holes dtlll9d in is connected 10 a flexible pipe (Fig. I 7f. end In tu,n conneclftd to a rellu. laled compressor. Thi, wHl blow air inlO .h, 'Iectrolyte cau'lnll movement by bubbllnll. Ca,e must be &J
fit. " s..t.d".". ..'_

~, .

Sealing of the Anodised FIlm 11 desi.ed the anodised film can be selled. Thi. P'OC. .I in 'ffKt "Ill over ,lie pOf, .. tes of ,lie g.own aluminium oxide. Thil i. broughlabotJ' by an il\(:rease in lemperature in I sealanl. wh~h in· c.ease. the volume Ind swelll Ihe",1 wallland close. the po •••. The seal In' il UIUllty boilinll deionised w.'er" tempere,ureol l OO de· g"" C for • pe.iod 01 20 mlnu t... I, la best dOn, In • 11.1nlen steel container. An altern"ive is 10 boil pure deion;ud water In I ,"inl .....eel conlliner with • lid. and IUlpend Ihe Inodiud a"iele in ,he .. um gl~en o H for 30 mlnu, ... The ..,led "tieles Ire li ken out end al· lowed '0 dry In Ihe air. Or In I convenient

ov.n. THE DYEING OF ANODISED ALUMINIUM

The mljorlty 01 Iluminium 1110'(1 when anodised h.ve In Ippearence of nllurel aluminium or '"Iver' c(>lOl.l'. Some allo'(l conUrln alloy con,muanll luch .. mang,...,....!rcon. magnesium and copper. If the.. materials are pr,""nt between 5%-8%. ,hey produce a coIor. t.on o l lhe ..IOdised him. Th. colore"on varies from a brown for mangan,"", for silicon Ind mag ...... um I bluish g.ey.

and for eopper In o"nge yellow To obelin I consistent ,.p.odOKible uniform colour, the easiest and most ,",nomal wily ia to use an orlllnic dye tllat i. soluble in waler. To obtain the re· qui.ed sha de of colou. y",oua con· c,nt.ations of 'he dyes have to be used. A guide is between I IIrm.pe. li,re 10 100,ms pe. lit ... O.1SoB.pe. gallon '0 1.60z•. pe. glllon. This concent.ation will plso yary wilh colou •. ()pe<.rinll Conditlon. lor Dy. Tlnk, The id ul tank 10' dyeing should be made 01 good quolity ,"inle u l ' lel . Austlnlt;C grade 320S17. Howeva •. most plaSlic 0' glass tan~s can also be used. but they will 811 .equlre hel1lnll to BpplOK'mately 40 - SO deg" " C. 104 122 deg ..... F. The dyl is welglled ou, ~.dlng to the concentration. Ind added '0 hall the yolume of hot w"er conllined in .he dye link. The solution i. agillled by,,"" ong O. by air agitl1ion f.om I 'egula,9d comP'I$$OI. This il continued until all Ihe dye h.. dissolved and no partlC .... remain in wspension. Suspended pi.· 1~les of dye are the m.in Clull of " ..ab on thedyed wrl~ of ,he com· ponents. Aher dissolullon of ,lie dye. the solulion i, made up 10 wo.~inll vof·

ume. end H'e desir&g IICtoSS I bar 01 meud o. pll"k; Ind totelly immersed in the elyl, preflf.bly with egltallon for the requi.ed time. The time. beinll dependenl on Ihe inten,ity of the colour. I1 usullly between 5 and 15 minutM. lo mllntainlhl con.iller\CV 01 colour for .ubtequet\t batehH 01 componlf'l\S, the condilion. ollemperature and liml must be closely adhlred

•.

, A flow p.oc.ss chIn

A point to remember is thet the Inodlsed film letl 115 In eleeui. cllly insullting surfece, .0 if Ihl contltCl moVH, the conducting IUrface under tlM wire ;nth' electrolyte i. 1011. Tlte consequ'nce 01 this iSlhlltlMgrowth of anodised r;lm .IOP., bUI Ihe worst pin 01 this action I, thatttle resi.lance" thlt poinl inc.ease,lhe he"ingef_ fact. ceu";ng Ifo";on 011 thl su.· I~.

Id

10' Ih' v.rlous process" In Inodl.ing is shown In Rg.

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Poinllto .emember 10f good practice in the Inodising process are:-

1')

Ibl

FIg . 19

Tho.ough clllninll in th, p.etr8lltmenl CYCII, Ind the complete removll of lI.elSllnd .mut I.om Ihe compOr'lenta. omlin, fnd mlintain, a good electricel contKC be1V>elnthe wire on the component end the enode blr.

ldj

After the Inodill pan of Ihe pi'oeelS, the components Ir, r. moved 1ft .. switching 011 It the rectifier. and quickly rinsed In cold Wller, then quic:kJy imm,rMd ,ithe. in IIM dye bath or lhe HII· ing tlnk Ilor nllu.I' enodill). At nO lime should Ihl In.odiced mm be allowed 10 dry. To do 110 would givl I PlInlll closurl of the pore lrel, Ind hlnce rest.ict Ihe ing._ ollhe dye. A good method of checking InO· dill is to UII I tHt meler IAvo type) set On D.e. Iow vOltagl. and

",I 10 rnilllnce. Lightly pan thl mell' probe. across thl lurf&Cl. Any ,'ee. with no 8nodi .. will conduct. which will ceu.e I delteclion On the meter. A simp'l check 10. I ..eled surface 011 MtU'I' Inodill i. 10 moisten. IOny .... of the surfIC', Ind touch th, IUrface with In Indelible pencil. If Ihe IU', face i. thin wiped cleen. leaving no trac. of Ihe colour of Ihe pencil.

(el

the IUrf_ het ,,"n sl1islacto.ily SIlled. lo strip delective Inodise f.om ,0mpOnentl. ttle wi.ed ~om­ ponenlS ."Immersed'n Ihellkall Cl...... for • few minutel. "nsed in cold wlter, Imm •• sed 'nlhe ni_ t.ic &CId IIOlulio" fo •• few minut.., rinsed and ,,·enodised. In o ther word •. blek th.ough the pretreatments.

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V.I.ncy V.".bI.,ellsIIJ'lCe VOlumes (links)

w.""ij

up

Ziocale Zinc elect.oIytes

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30,31,32

Index

Ag,'-lion Alk.lin;ly AllefMIi"ij CV"e<11 (AC) Am~~

Amphou.

A""', Anod'H

AnodiH electrol.,.,. Amon A.... Atomi.; weight Atom.

BI1tery j12 and 6 voll) Sa1tlry chalg" Bright dip. C.thode Celion CI..ne .. Coppe.llect.oIytel CooJlomb$ CUlfe<1t denlity Dj.ect current (DC) i)ye,nglenodiH'

"" "", , 54, 55, 56, 51 55

",

10,12

,

" ",

15.16.17

"" ,

36.37,42

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ElectfO Chlmkel Equivlllnt IECE) 4O,41,42,4J Elect.ofo.mlng Eleet.ol... .1 tclfOoP I"i ng 47. 48, 49 Eleet.ol.,.,.

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Faraday.' 1._ FI.lday (unil) Gl...

l~lt .ni~i"ijl

Heate.. '00

Mlnd"ls Masking off Mouldl Nickel elect.olytes Non-eondueto.

""

Pickles PI.lties Potenliomete.

Rectifi"

,, "

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40,41

34. 35, 42 45.46

" " " " " " 2S

18, 19, 20

Sulingl.oodiH' 51"1 (,"inlesl end mildl Solvenls (o'genkl St.lpPtllt

52. 53

Tsnks Tin .llet.olyte.

38,39

20

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