CA1145653A - Solution and method for selectively stripping alloys containing nickel with gold, phosphorous or chromium from stainless steel and related nickel base alloys - Google Patents
Solution and method for selectively stripping alloys containing nickel with gold, phosphorous or chromium from stainless steel and related nickel base alloysInfo
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- CA1145653A CA1145653A CA000373803A CA373803A CA1145653A CA 1145653 A CA1145653 A CA 1145653A CA 000373803 A CA000373803 A CA 000373803A CA 373803 A CA373803 A CA 373803A CA 1145653 A CA1145653 A CA 1145653A
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Abstract
A B S T R A C T
Improved solutions are provided for selectively stripping alloys containing nickel with gold, phosphorous or chromium from substrates formed from alloys containing iron with chromium and in some instances nickel, or nickel rich, chromium bearing alloys, some of which also contain iron. These solutions comprise concentrated nitric acid, at least one chloride salt, an organic corrosion inhibitor and optionally, an organic surface active agent. An improved method utilizing the solutions of the invention is also provided and facilitates stripping of these alloys in substantially reduced time, without degradation of the underlying substrate.
Improved solutions are provided for selectively stripping alloys containing nickel with gold, phosphorous or chromium from substrates formed from alloys containing iron with chromium and in some instances nickel, or nickel rich, chromium bearing alloys, some of which also contain iron. These solutions comprise concentrated nitric acid, at least one chloride salt, an organic corrosion inhibitor and optionally, an organic surface active agent. An improved method utilizing the solutions of the invention is also provided and facilitates stripping of these alloys in substantially reduced time, without degradation of the underlying substrate.
Description
SOLUllON AND MT:rHOD ~R SEl,RCllVELY STNIPPING ALLOYS
CON ï'AININC NICK~L WITII GOI,I), I'IIOSPIIOROUS OR CHROMIUM
PROM STI~INLESS ST~:EL ANI) REI A ï ED Nl(~Kl~L BASE ALLOYS
ackground The invention relates to chemical removal of alloys eontnining nickel with gold, phosphorous or chromium from stflinless steel or nickel base alloy substrates.
i More particu]rlrly, tl)e invention relates to selective stripping of A gold/nickel, niekeVphosphorous or nickel/chromillm alloy from substr~tes whiell are formed from 300 or 400 series Stninlc~s Stcels or niekel rieh, ehromiurn bcaring alloys, such as llastelloy, Ineonel or equivalent alloys.
Alloys of golc3 and niekel, which typically rnnge from between 70% to 80% gold nnci 18% to 30% niekel nre conventionnlly utilized as a brnze to join substrates, such ns ferrous nnd niekcl alloys in applications requiring struetural strength, yet resistnnce to cxtrctnc hent. (::old/nickel brn7.ing alloys hflve a melting point in exce.;s of 1000 F (537.8 C), nnd ar~ npplied in vnrying thieknesses by melting n paste or pre-formc(3 scglncllt with flux. In some applications, alloys of niel:cl ((~7% to 85~f) nnd ~ ospllorous (3~. to 15%) are used, eithcr as brnzing alloyt; or coatings. Nickel/cllrolllium nlloys may bc nE-plicd as a flame sprny, or plnslnn srlny, coatingr. I~clll~vnl, or "stripping", wllich is required to ¦ diSaSSell~blC ol' illSpC(!t pRl'tS nltlle'~ or colltc(l with such nlloys is prefernbly accomplislled t)y chcmicnl tecl~ lllcs, ratllor tllall l)y rehenting.
I WllilC tllC pre.qellt illVClltiOI~ i.S tlOt limitc(l to nny pnrticulnr application ¦ employin~r l~rll%il)g or corltillg nlloy~c:, citl~cr Or gol(l/nickcl, niekcl/pi~osphorous or nickel/ellrolllilln~, it Ls, however, Illo!;t prerclnl-ly nn(l n(lvflllta~cously utilizcd to seleetivcly strip sucll bra:zing nlloys whcll uscd to join segments of internal compolle-lts Or jct cngilles. For exnrnp]e, gold/nickel bra7ing alloys are used to secure nirfoil vnnes in stators uscd in thc turt ine section of a jet engine. These are stntionmy parts, downstream of the colnbustion chamber, which are exposed 1.
~r~lfle mc~ks , .
~' 11'~5~i53 I .
to extrenlely higll temperatures and stress. Ilowever, mandatory maintenMnce and inspection procedures require that such components are routinely removed, either for inspection or replacement. While it is necessary to selectively strip the gold/nickel nlloy from these components, it must be done in A manner which will not adversely effect, or degrnde, the substrflte alloys from which the stators or other components flre formed. I ypic~lly, fllloys of iron with chromium and in some instflnccs nickel, nnd nickel rich, chromium bearing alloys, some of wllich fllso cont~ iron, nrc use(l to m(lke such compollellts; for exarrlple, Stainless Steel, I-lastelloy, Incmlel or cquivnlerlt nlloys.
Fllrtllermore, the time requiled to complete stripping of the brazing alloy fronl jet engitlc cornponerlîs, in purlicul)lr, is of grent importance, in view of the fact th~t the nil craft mny l)e out of service durillg such procedures.
rrior m t techlli(llles for chclllicnlly stripping gold/nickel brHzing al~oys, for exarnple, involve rncthods cmployillg n .scries of step.s un~l vurious chclmic~l solutions. In ordcr to remove sllfficicnt l-ra7illg alloy, n substnlltial arnount of time was re(~uired, typicully ns m~lcll ns ~ to 18 days. Ilowever, with use of ultrasonic ~gitatioll, this timc co~lkl bc red~lced to 3 to 5 dnys.
l~lntherltlore, prior nrt techni(llles pre~ t disn(lvnlltnges due to employing citller sul~slantinl ~mo~ t~q of el(!ctl ic cllll~ent, or use of aq~leous solutions containing cynnides, nnd/or nitro-s~li)stitutc(l nromntic coml)ounds and chelàting a¢~nts, will~ tlle resulling toxicity ~Ind ellvironmentnl problcrns. Finally, prior art methods usllnlly re(lllire(l operlllioll nt clevllted tempernturcs, typic~lly rnn~ing flol~ 100 to 18S~ ~37.8 to 85~
l~xelnplnry of prior nrt tccllni(l~lcs for rcmoval of brnzirlg ulloys containing goki are those set forth in U. S. rnterlts No. 3,819,494 and No. 3,958,984.
llowcvel, the methods provided in nccordflllce with these pfltents involve the aforementiolled disadvantages, p~rticularly with regard to use of cyanides, ~nd are extremely slow in comparisoll to thc preserlt invention.
Anotller conventionully avflilnble gold/nickel braze stripping solution con-tnins concentruted nitric acid~ with copper, iron mld sodium chlorides. Not 1145~53 orlly is its actiorl very slow, in compurison witll the present invention, but pitting and degradation of the sub.strate nlloy is a problem, pQrticularly with longer exposure times. 1 he substantially longer exposure required for removal of the braze by prior art solutions renders the substrate much more susceptible to nttack on the St~inless Steel alloys, with resultant pitting, "smutting" or degrada-tion caused by intergranular nttack.
In accordunce with the prescnt invenlion, an improved solution is provided, which, used hy itself in preferred embodiments, is ~ully operable to strip gold/nickel, ni( kel/phosphorous or nicl<cl/chrolnium alloys from substrntes formed from 30U ~nd 40(~ series Stninlcss Steels, ~lustelloys, Inconels and eguivRlent alloys. Thc novel solution of tlle invclllion, nnd melllod provided for utilizing the snme to strip tllese bruzin~ or couting alloys, is opernble to remove the alloy in substlllltilllly less timc lh~n is possihle witll prior flrt techlliques or solutions, und witllout adversely effcctillg or dcgradirlg thc undcrlying substrate.
I`he novel SOIUt;OI1 nnd mcthod Or tlle invcntion haVe pnrticulflr utility for selectively stri~pill~ gold/nickel hrn7.inF nlk)ys uscd in jct engines~ wherc minimnl time and avc)icl~lncc of degrn(lll tion of tlle underlying substrnte is of utmo~st importnn~e nnd ctitic~llity.
'rhe hnproved solutions of thc invenlion provide n wide rnnge of operational utility, particulllrly witll respect to telllperlllurc Or trclltmcnt h~lths, or sprays, which while prefclnbly operal-lc nt nmt)icnt tempcrlJtllres~ mu<,t also be cnpQble of opcrntion nt higller tclnpelatures. I`his is purticulnrly udvnntu~eous t~ecnuse it pcrmits use of ultlnsonic ugitntion which tends to rnisc tlle tcmperature, ùs a result of the convcrsion of electricnl to n~cchullicnl ene Summ~ry of the Invention In ùccordance witll tlle present invention, an improved solution is provided for selectively ~stripping alloys containing nickel with gold, phosphorous or chromium from substrates formed from alloys~ containing iron with chromium and in some in~stunces nickel, or nickel rich, chromium bearing alloys such as 1~ ' r~ 3 l~astelloys, Inconel or qu:ivalent alloys. The improved solu-tion contains concentLated nitric acid, chloride ions sup-plied Erom one or more chloride salts, an organic corrosion inhibitor effective to inhibit degradation of the substrate and, preferably, an organic surface ac-tive agent, cGmpatible with and effective to reduce the surface tension of the solu-tion and, preferably contributing additional corrosion in-hibition.
The organic corrosion inhibitor may be an acetylenic al-]0 cohol, preferably 2-butyne 1,4 diol, ethoxylated butyne 1,4 diol or propargyl alcohol, and the organic surface active agent may be a polye-thoxylated arnine or diamine, preferably polyoxyethylene cocamine, po1.yoxyethylene soyaamine, polyoxy-ethylene oleylamine, polyoxycthylene octadecylamine or N,N',N'-polyoxyethylene ~15)-N-tallow 1,3 diaminopropane.
In accordance with the invention, a method is provided for stripping nickel contai.ning alloys with gold, phosphorous or chromium comprising application of an improved solution of the invention to a coated substrate formed of an alloy con-taining iron with chromium and in some instances nickel, or nickel rich, chLomium bearing alloy, such as llastell.oy, Inconel or equivalent all.oys. Appl.ication is, ~refcl-ably, by immersion or spray.in~, w:ith r~moval. oE ~I-e brli%in(3 or coati.llg all.oy completc!d withi.n tll)OUt 2 ~O 24 hours, at ~I t.(~ perclture of 70 to .l30F (21.1 to 24.4C). 'rhe me~hod may further includc exposure of Ille ';UbS~L~ allcl/or solu~ion to agi-tation, ei-ther mechallical or, pl-efcrably~ ultl-ason:ic, in orde~r to fu:rther increase the s~r.ipping speed.
In accordance with the present invention, gold/nickel, nickel/phosphorous or nickel/chromium alloys may be selec-tively strlpped from substrates utilized in structural com-ponents of jet engines more efficiently than possible using prior art materials or techniques, but without degradation of the substrate alloy.
Accordingly, it is an object of the invention to provide an improved solution for selectively stripping gold/nickel, nickel/phosphorous or nickel/chromium alloys, in particular, from substrates preferably formed from 300 to 400 series r ,.
31 l'~S~S3 - ~a -Stainless Steels or l~astelloy, Inconel or equivalent alloys over .....................................................
11~5~3 n wide range of opcralillg pfllnllletcrs, pnrticulArly tempcra~ure uncl eoneentration of chloride ions, witllout adverse effect upon or degr~d~ltion of the substrate, in subst~ntihlly le~s time than is preselltly possible utilizing prior art solutions or techniques.
It is an object of the illVClltiOIl to provide an improved method for seleetively stripping such alloys, which is particularly adaptable to removal thereoî from interllal components of jet engines and the like, and is capable of ~eeornplishing stripping witllout degrn-Jntiorl of the substrute nlloys and in su~
stantially less timc thnn eonventionally possil)le.
It is n furtller objeet of lhe illVCIlliOII to provide an improved solution I alld method for seleetively stripping suell alloys which, either with or witllout meehanieul or ultrasonie agi~ation, are enpnble of effeeting stripping in sub-stalltially less time thnn eonvelltion~llly possible.
~ t is yel nnotllcr objeet of tlle illVC!lltiOII to provide n sol(ltioll and method for seleetivcly strippirlg sueh nlloys, wlliell fn( ilitnte subse(ltlcnt reeovery of the gold, phosphorotls, ehrl)lllilllll ulld/or ni( I;el colllpollellts~ usinF corlventionnl re-eovery leelllliqlle ;.
It is vcl n fulther ohjeet Of tlle invelllioll to provide nn ilnproved solution nnd Inell~ocl r~"~ scle( tivcly stl il-pillg sllell nllovs wlliell po~:e~ n eommereinlly ndvnlltngeo~ls wi(lc rallge ,r Opel'ntiOnnl (!npal)ilitieS, pllrti('lllfll'ly ns to time nnd telllperalure, Ull(l wl~ich nvokl il~ oxcity~ ellvirolllllelltlll disposnl"lnd pollution disa~lvalltllgcs involvccl in usc Of cyalli(lcs, ~In(l whicll dt) llOt require use of IllUItipl(? soluliolls or trentlncllls"ls in lllc pl ior IlI't.
I)e~cription of Preferred l~mbodiments Ulld thc l~est Mod~ for CerryinF Out the Irlvention In a(colciallee witll preferred elllbo(3illlents of tllc present invention, a novel solution is providcd whicll hns utilily for stripping alloys eontaining niekel with gold, ph()sphorous or chromium, prcfcrn~)ly gold/nickel or niekel/phosphorous ~lloys, from suhstriltes formcd from alloys corrtnining iron with ehromium and in some instanccs nickel, or nickel ricll, chlolnium bcAring allays, some of whieh fllso conklill iroll. 1 his novel strippinE~ sollltio n has heen foulld to cause little, if any, degradatioll of the substr~lte, particularly with regal-i to intergrnnular ,,_ I
11~5~i53 attack of 410 Stainless Steel. l`hcrcfore, it is particularly useful to remove gold/nickel or nickel/phosphorous braze or eoating from eritical struetural eom-ponents which are subjected to high levels of tempernture and/or stress.
It is, however, fully within the purview of the invention that the substrate from whieh the alloy is stripped, or removed, is not a limiting faetor. Likewise, the eonfigurfltion, shape or size of a component from which these alloys can be removed in aceordance witll the invention is not limited. ~lowever, the configura-tion, shape or size of the substr~te may effcet the time or partieular manner of applieation of the improved solutions of the invention, QS will be readily apparent to one skilled in the nrt.
It has been found that the irnproved solutions and method of the invention can be uscd Witll pclrticular advantnge to remove gold/nickel alloys from substrates formed of Stninle~ Steel, prcfernbly 3no or 400 series Stainless ~teels, Hastelloy, Ineonel or equivl31(?nt flllOyS~ llowever, it is fully within the purview of the invention thnt other rclnted higl)-temperture nickel-contuining alloys, such as niekel/phos~horolls or nickel/chromium nlloys, wllich rrlny be used either as a coating or n brn7.c in higll-tempcr~lturc npr)lications, enn nlso be effeetively stripped fronl sllcll substratcs. I`helerorc, it is to be undcrstood that referenee herein to "golcJ/nickcl nlloys" nlso includcs ~sucll otller niekcl-eontflining alloys, pHrtieularly nickel/pllosphololls or nicl~el/(!luomium nlloys.
In one prefcrred crnbodirn(!nt, nn improved solution of the invention is eomprised of eoncelltrrltcd nitrie ncid, chloride ions froln nt least one salt, an orgnnic COl'l'O~;iOIl illhibi~ol which iS effectivc to inhibit degrsdation of the substl ate from whil h thc gold/nickel rllloy is removed, and an organic surface active agellt whicll is compfltiblc with ulld cffcctive to reduce the surfaee tension of the solution and, prefelat)ly contributcs additional corrosion inhibition.
Preferably, nitric aeid having eoncentr~tion ranging from between about 40% to 72~-, by weiglit, in ~queous solution is` utilized. Nitric acid having a eoncentration less tllfln nbout 40~, while functional, gcnerally produces a rate 11 .
llqS653 I!
~!
of brfl7c remoYFIl wllich is unacceptably slow. Use of nitric acid in a concentration of less than nhollt 40% in nqueous solution is also undesirable, because the increased water content tends to le~sen passivity, particularly of substrates made of Stainless Steel alloys, and increases the likelihood Or adverse effects on the substrate or degradation of the substrate alloy. Nitric acid above about 72%, by weight, can be used, but it is normally unavailable in quantity or commercial grades.
In accordance with the invention, a working solution is preferably prepared by ndrnixture of the other components to the concentrated nitric acid, on the basis of grarns pcr liter of nitric ncid.
lloride iOllS are provided in the improved solution of the invention from at least one chloride salt and, preferably, an inorganic chloride salt such as alkali metal chloridcs, particularly pota~ssium chloride, ferric chloride, calcium chloride, nic-kel chloride, magnesium chloride, aluminum chloride, or combinations thereof. The totnl chloride ion concerltratioll shoukl be at least 3.75 grams per liter of concenttute(i nitric ncid nn(l prcrcrnbly rnnges l etween about 3.75 to 90 grams E)el liter nlld, morc prefernl)ly bctween 15 to 27.5 grnms per liter.
In one embodimcnt Or thc inventioll, chloridc ions nre provlded from pota~qium clllol idc nn(l rcrri cllloride"lsc(l in comt)irlntion. 'I`he potassium fell ic iOn collcentrntioll cn(~h sllolll(l l~c nt Icll~;t ~.75 frrnms pcr liter of con-celltrntc(l nilric nci(l nn(l prcfcrnl)ly mny rnr)~c l)ctwcen nbollt 3.75 to fi0 grQms per liter nn(l~ most pl(~rerllt)ly, be~ween nl)nut 7.5 to hr~ ~rnms per liter. It is fully withirl thc purvicw of the invcntioll thllt potassiunl nll(l/or ferric ion can also be supplied froln potnssiurrl nn(l/or fcrric snlts other thall chloride salts;
for e~ample, from potn~ium nitrute, potn.ssiulll iodnte, potassium sulfate, potas-sium metaphospllate, potassium periodlltc, potassium selenate, potassium citrate, potassium tartrate or ferric nitrate, ferric sulfate or ferric phosphate, respec-tively.
Potas~siu~rl chloride is most preferably used in accordance with the inven-tion, because of its greater solubility characteristics, which allow it to provide higher levels of chloride ion in solution than other chloride salts, for example, sodium chloride. Furthermore, it is believed that the presence of potassium ions in the solutions of the invention enhance the solubility of gold, as the braze is stripped from the substrate.
It is also preferled to use ferric chloride as a source of chloride ions, most preferably in conjunction with potas-sium chloride. It is believed that ferric ion may benefic-ially function as a secondary oxidizer, in addition to nitric acid, the primary oxidizing agent. Furthermore, it is be-lieved that the presence of ferric ions in the working solu-tions of the invention may further accelerate stripping of the brazing al]oy, by acting as an electrical coupling acJent to establish an electromotive force which contributes to removal of the brazing alloy.
It has been found that the use of hydrochloric acid, particularly as a sole source of chloride ions, is undesir-able and results in a stripping solution which is inoperable in accordance with the present invention. Although a go]d/
nickel brazing alloy can be stripped using hydrochloric acid as the source of chloride ion, the substrate alloy is sub-jected to severe attack and degt-aclation. Accordingly, sub-stantial amounts of lly(ll-ochlo3ic ~cid should bc avoidcd in the improved stripping solu~ions of the invention, although it may be pe3rnlssible to in~orE~orate mlnor amoun~s to Lhe extent that its presence docs not adversely effcct or de-grade the substrate alloy.
Copper chloride has been found to cause problems, par-ticularly with pitting of the substrate alloy, which is believed to result from the galvanic effect of the presence of copper ions and ferric metal. Accordingly, the presence of copper ions, particularly in the form of copper chloride, in the improved solutions of the invention should be avoided, although its presence may be tolerated if it does not ad-versely effect or degrade the substrate alloy.
The organic corrosion inhibitors used in the strippingsolutions of the invention may be acetylenic alcohols and, preferably, 2-butyne 1,4 diol, ethoxylated ........
`'t, 1.1~}5~53 butyne 1,~ diol or propargyl nlcohol. rl`he organic corrosion inhibitor must be effective to inllibit degrndation of the substrate by the stripping solutions of the inventiorl, in view of the fact that they contain strong oxidizing agents.
Preferably, the orgnnic corrosion inhibitor is provided in a concentration ranging from about 1 to 30 grams per liter, based on the amount of nitric acid, and, most preferably, between about I to 3 grams per liter. The corrosion inhibitors are believed to contribute not only to the operability of the stripping solution in substantially reduced times of exposllre, without degradation or adverse effect upon the substrnte, but they also allow for operation over a wider range of ternperature and concentration of chloride ion.
In nccordnnce with the invention, an organic surface active agent which is compatiblc with the working solution nnd effective to reduce surfflce tension and, prefernbly contribute additionnl corrosion inhibition, is provided in the working solution, prefernbly in a conccntrntioll rnnging from about 1 to 30 grams per liter, bused upon the nmolltlt of nitric ncid pre~sent, and, most pr~ferably, in a concentlntion rnnging flom nbollt 1.0 to 3.0 grnms per liter. Preferably, a polyethoxylntecl nmine or dinmillc, for example polyoxycthylene cocoamine, polyoxyethylelle soynnmille, polyoxyethylenc oleylaminc, polyoxyethy1cne octa-decylnllline or N,N',N'-polyoxyetllylelle (15)-N-tnllow 1,3 dinminopropane, mny be utilized flS the orgnnic sulfnce ~ICtiVC ngcnt. Not only do these surface active agents appenl ~o mnil-tnin thc solubility of thc corrosion inhibitor, but they also appenl to huve n syncrgistic cfre( t, in collll)inQtion with the organic corrosion inhibitor, to provide improved protcction ngQirlSt intergrnllulnr attack or degrada-tion of the substrate alloys.
accordance with the method of the present invention a working solution of nny of th(~ preferred embodiments is prepared and applicd to the substrate, in fl manller which fncilitates physicnl removal of the products of the gold/nickel alloy from tlle alea of tlle surface of the bra7ed ~or coated substrate. Preferably, thc substrnle is imlllerscd in9 or sprnyed with, a working solution of the ,. , I
1, _9_ invcntion at n te-npcrature ranging bctween about 50 to 130E (10 to 54.4C), and, prefer~bly, between about 70 to 115 F (21.1 to 46.] C). Stripping time will vary depending upon the configuration of the substrate, thickness of the brazing or coating alloy, concentrntion of the solution constituents, temperature and the type of agltation, if any, which is used. Generally, stripping will be completed within 2 to 24 hours, when using ultrasonic flgitation. Without use of ultrflsonics~ stripping times range betwcen about 10 to 120 hours. .
It should be understood that whilc the solution and method of the invention nre fully operable without use of ultrasonics, the time required to effect removal of the braze alloy is reduced by a factor of about 5 when ultrasonics are applied.
Furthermore, whell ultrasonics are used, while the conversion of electrical to mcchanical energy by the ultr~sonic trnnsducer tends to heat the operating solution, this does not adversely effect or degrade the substrate alloy being treated in accordance with the invention.
In accordflnee witll the invcntion, it is possible to selectively strip gold/nickel bra7ing or coating nlloys u~sing convcntional wnxes or other inexpensive mnsks, to cont arell~s of the substrntc wllicll 3O not rcquire stripping. For cxnlnple, u sul~strntc hnving portiolls brn7ed with gokl/niekcl nlloy may be first dippcd in n wnx ~hicll, following solidificntioll, can thcn b~! selectively removed from arcns hnV;I1g thC brn~.;ng nllt)Y. 'I`lle .~;nl)Strnte ;S thcn treated with R
solution ol` the inV(!lltiOn to cffe(!t relnovnl Or tllc brn~.c. Use of such masking mntcrials, while not ncccs~snry in nll h~stnn(!e~s, is nevcrthclccs preferred in many applicntiolls, bccnusc of the nddcd dcgrcc Or protection flffor-1ed to non-bra7.ed substrflte purt~ from the strong oxidiYirlg mfltcriflls contnined in the stripping solution.
Examples In order to illustrate more fu]ly thc improved solutions and method of the invention, the following examples nre set forth, but do not limit the scope of the invelltion. Exnmples I to 3 wcrc conducted to demonstrate the operability I' !;
~5~i~3 !
of the preferrccl organic corrosion inhibitors of the invention under laboratory conditions and did not include an organic surface active agent, due to the low temperaturcs used and li mited operflting parnmeters used for this evaluation.
E~ample I
A working solution was prepared by ndmixture of the following:
~' concentrated nitric acid (70%, 42 Be) I liter potassium chloride 19 grams .
ferric chloride 19 grams 1 2-butyne 1, 4 diol 1.65 grams This solution contained 21 grams per liter of chloride ion. A specimen, 1 comprising two strips of 410 Stainless Steel, ench I inch by I inch by 0.0625 I inches, joined to form a "T" Witll a bra7e of gold/nickel alloy, containing 80%
golcl nnd 20~i nickel, WJIS irnmcrscd in the solution for 30 minutes. An ultrasonic transducer wns used to administer ultrflsonic ngitation. ï'he sollltioll temp~rature ranged from betwecn 70 to 78 F (21.1 to 25.fi ~), with nn nveragc temperature of 7~ 1 (23.3 (~).
Inspection of the ~sr)ecill)cll nfter 30 minutes reveflle(3 1009~, removal of the goki/ni(!kel brn~c, without atlnck or dc!(rrn(lntion Or thc ~pecimen sllbstrntc.
x~mple 2 workillg solulion wns prcp~lre(l b~y ndlllixtllre of thc following:
collcclltrnted nitric ncid (709~, 42 E3e) 1 litcr potn~sil~ c hloride 19 grurns ferric chloridc! 19 grams ethoxylated butylle 1,4 diol 3.1fi grflms The ethoxylllte(l butyllc 1,4 diol wus uscd conlprised of butyne 1,4 diol ethoxylated with ethylelle o.xide in a ratio of ethylerle oxide to butyne diol of 1.8:1Ø
Tllis working solution contained 21 gram~s per liter of chloride ion. A
! spccimen, comprising two strips of 410 Stflirlless Steel, eflch I inch by 1 inch by 0.0625 inches, joined to form a "T" nnd brazed with a gold/nickel alloy containing !
11~5653 ao~6 gold m l 20~ nickel w~ immersed in the solution for 30 minutes. An ultrasonic transducer was used to administer ultrasonic ngitation. The tempera-ture ranged from between 66 to 76 F (18~9 to 24.4 C), with an average ~ temperature of 71 F (21.7 C).
¦ Inspection of the specimen after 30 minutes revealed 100% removal of the gold/nickel braze, without attacli or degradation of the specimen substrate.
F~xample 3 A working solution WflS prepnred by admixture of the following:
concentrQted nitric ncid (7096, 42 Be) I liter potassium chloride 19 grams ferric chloride 19 grams propnrgyl alcohol 1.07 grams I his WOI king solution also contnine(l 21 grnms per liter of chloride ion.
A specimen, similflr to those usecl in r:xnmples I and 2 was immersed in the solution for 30 rninutes. Ultrasonic ngitntion was agnin ndministered and the temperature r~mged from bctween 70 to 741~ (21.1 to 23.3C), with an average tempernture of 74l (23.3().
Inspecti()n of th(! ~spccimcll nftcr :~0 mim~tes revcnlc(l 989f removal of the gold/nickel l)rQ~c, without nttnck or dcgrn(lntion of tlle specimen substrate.
Fxame~
A working solution, in nccordnnce with tlle invention, was prepared comprising thc following:
nitric acid (70%, 42 Be) I liter potassium chloricle 18 grams ferric chloride, anhydrous 18 grams -
CON ï'AININC NICK~L WITII GOI,I), I'IIOSPIIOROUS OR CHROMIUM
PROM STI~INLESS ST~:EL ANI) REI A ï ED Nl(~Kl~L BASE ALLOYS
ackground The invention relates to chemical removal of alloys eontnining nickel with gold, phosphorous or chromium from stflinless steel or nickel base alloy substrates.
i More particu]rlrly, tl)e invention relates to selective stripping of A gold/nickel, niekeVphosphorous or nickel/chromillm alloy from substr~tes whiell are formed from 300 or 400 series Stninlc~s Stcels or niekel rieh, ehromiurn bcaring alloys, such as llastelloy, Ineonel or equivalent alloys.
Alloys of golc3 and niekel, which typically rnnge from between 70% to 80% gold nnci 18% to 30% niekel nre conventionnlly utilized as a brnze to join substrates, such ns ferrous nnd niekcl alloys in applications requiring struetural strength, yet resistnnce to cxtrctnc hent. (::old/nickel brn7.ing alloys hflve a melting point in exce.;s of 1000 F (537.8 C), nnd ar~ npplied in vnrying thieknesses by melting n paste or pre-formc(3 scglncllt with flux. In some applications, alloys of niel:cl ((~7% to 85~f) nnd ~ ospllorous (3~. to 15%) are used, eithcr as brnzing alloyt; or coatings. Nickel/cllrolllium nlloys may bc nE-plicd as a flame sprny, or plnslnn srlny, coatingr. I~clll~vnl, or "stripping", wllich is required to ¦ diSaSSell~blC ol' illSpC(!t pRl'tS nltlle'~ or colltc(l with such nlloys is prefernbly accomplislled t)y chcmicnl tecl~ lllcs, ratllor tllall l)y rehenting.
I WllilC tllC pre.qellt illVClltiOI~ i.S tlOt limitc(l to nny pnrticulnr application ¦ employin~r l~rll%il)g or corltillg nlloy~c:, citl~cr Or gol(l/nickcl, niekcl/pi~osphorous or nickel/ellrolllilln~, it Ls, however, Illo!;t prerclnl-ly nn(l n(lvflllta~cously utilizcd to seleetivcly strip sucll bra:zing nlloys whcll uscd to join segments of internal compolle-lts Or jct cngilles. For exnrnp]e, gold/nickel bra7ing alloys are used to secure nirfoil vnnes in stators uscd in thc turt ine section of a jet engine. These are stntionmy parts, downstream of the colnbustion chamber, which are exposed 1.
~r~lfle mc~ks , .
~' 11'~5~i53 I .
to extrenlely higll temperatures and stress. Ilowever, mandatory maintenMnce and inspection procedures require that such components are routinely removed, either for inspection or replacement. While it is necessary to selectively strip the gold/nickel nlloy from these components, it must be done in A manner which will not adversely effect, or degrnde, the substrflte alloys from which the stators or other components flre formed. I ypic~lly, fllloys of iron with chromium and in some instflnccs nickel, nnd nickel rich, chromium bearing alloys, some of wllich fllso cont~ iron, nrc use(l to m(lke such compollellts; for exarrlple, Stainless Steel, I-lastelloy, Incmlel or cquivnlerlt nlloys.
Fllrtllermore, the time requiled to complete stripping of the brazing alloy fronl jet engitlc cornponerlîs, in purlicul)lr, is of grent importance, in view of the fact th~t the nil craft mny l)e out of service durillg such procedures.
rrior m t techlli(llles for chclllicnlly stripping gold/nickel brHzing al~oys, for exarnple, involve rncthods cmployillg n .scries of step.s un~l vurious chclmic~l solutions. In ordcr to remove sllfficicnt l-ra7illg alloy, n substnlltial arnount of time was re(~uired, typicully ns m~lcll ns ~ to 18 days. Ilowever, with use of ultrasonic ~gitatioll, this timc co~lkl bc red~lced to 3 to 5 dnys.
l~lntherltlore, prior nrt techni(llles pre~ t disn(lvnlltnges due to employing citller sul~slantinl ~mo~ t~q of el(!ctl ic cllll~ent, or use of aq~leous solutions containing cynnides, nnd/or nitro-s~li)stitutc(l nromntic coml)ounds and chelàting a¢~nts, will~ tlle resulling toxicity ~Ind ellvironmentnl problcrns. Finally, prior art methods usllnlly re(lllire(l operlllioll nt clevllted tempernturcs, typic~lly rnn~ing flol~ 100 to 18S~ ~37.8 to 85~
l~xelnplnry of prior nrt tccllni(l~lcs for rcmoval of brnzirlg ulloys containing goki are those set forth in U. S. rnterlts No. 3,819,494 and No. 3,958,984.
llowcvel, the methods provided in nccordflllce with these pfltents involve the aforementiolled disadvantages, p~rticularly with regard to use of cyanides, ~nd are extremely slow in comparisoll to thc preserlt invention.
Anotller conventionully avflilnble gold/nickel braze stripping solution con-tnins concentruted nitric acid~ with copper, iron mld sodium chlorides. Not 1145~53 orlly is its actiorl very slow, in compurison witll the present invention, but pitting and degradation of the sub.strate nlloy is a problem, pQrticularly with longer exposure times. 1 he substantially longer exposure required for removal of the braze by prior art solutions renders the substrate much more susceptible to nttack on the St~inless Steel alloys, with resultant pitting, "smutting" or degrada-tion caused by intergranular nttack.
In accordunce with the prescnt invenlion, an improved solution is provided, which, used hy itself in preferred embodiments, is ~ully operable to strip gold/nickel, ni( kel/phosphorous or nicl<cl/chrolnium alloys from substrntes formed from 30U ~nd 40(~ series Stninlcss Steels, ~lustelloys, Inconels and eguivRlent alloys. Thc novel solution of tlle invclllion, nnd melllod provided for utilizing the snme to strip tllese bruzin~ or couting alloys, is opernble to remove the alloy in substlllltilllly less timc lh~n is possihle witll prior flrt techlliques or solutions, und witllout adversely effcctillg or dcgradirlg thc undcrlying substrate.
I`he novel SOIUt;OI1 nnd mcthod Or tlle invcntion haVe pnrticulflr utility for selectively stri~pill~ gold/nickel hrn7.inF nlk)ys uscd in jct engines~ wherc minimnl time and avc)icl~lncc of degrn(lll tion of tlle underlying substrnte is of utmo~st importnn~e nnd ctitic~llity.
'rhe hnproved solutions of thc invenlion provide n wide rnnge of operational utility, particulllrly witll respect to telllperlllurc Or trclltmcnt h~lths, or sprays, which while prefclnbly operal-lc nt nmt)icnt tempcrlJtllres~ mu<,t also be cnpQble of opcrntion nt higller tclnpelatures. I`his is purticulnrly udvnntu~eous t~ecnuse it pcrmits use of ultlnsonic ugitntion which tends to rnisc tlle tcmperature, ùs a result of the convcrsion of electricnl to n~cchullicnl ene Summ~ry of the Invention In ùccordance witll tlle present invention, an improved solution is provided for selectively ~stripping alloys containing nickel with gold, phosphorous or chromium from substrates formed from alloys~ containing iron with chromium and in some in~stunces nickel, or nickel rich, chromium bearing alloys such as 1~ ' r~ 3 l~astelloys, Inconel or qu:ivalent alloys. The improved solu-tion contains concentLated nitric acid, chloride ions sup-plied Erom one or more chloride salts, an organic corrosion inhibitor effective to inhibit degradation of the substrate and, preferably, an organic surface ac-tive agent, cGmpatible with and effective to reduce the surface tension of the solu-tion and, preferably contributing additional corrosion in-hibition.
The organic corrosion inhibitor may be an acetylenic al-]0 cohol, preferably 2-butyne 1,4 diol, ethoxylated butyne 1,4 diol or propargyl alcohol, and the organic surface active agent may be a polye-thoxylated arnine or diamine, preferably polyoxyethylene cocamine, po1.yoxyethylene soyaamine, polyoxy-ethylene oleylamine, polyoxycthylene octadecylamine or N,N',N'-polyoxyethylene ~15)-N-tallow 1,3 diaminopropane.
In accordance with the invention, a method is provided for stripping nickel contai.ning alloys with gold, phosphorous or chromium comprising application of an improved solution of the invention to a coated substrate formed of an alloy con-taining iron with chromium and in some instances nickel, or nickel rich, chLomium bearing alloy, such as llastell.oy, Inconel or equivalent all.oys. Appl.ication is, ~refcl-ably, by immersion or spray.in~, w:ith r~moval. oE ~I-e brli%in(3 or coati.llg all.oy completc!d withi.n tll)OUt 2 ~O 24 hours, at ~I t.(~ perclture of 70 to .l30F (21.1 to 24.4C). 'rhe me~hod may further includc exposure of Ille ';UbS~L~ allcl/or solu~ion to agi-tation, ei-ther mechallical or, pl-efcrably~ ultl-ason:ic, in orde~r to fu:rther increase the s~r.ipping speed.
In accordance with the present invention, gold/nickel, nickel/phosphorous or nickel/chromium alloys may be selec-tively strlpped from substrates utilized in structural com-ponents of jet engines more efficiently than possible using prior art materials or techniques, but without degradation of the substrate alloy.
Accordingly, it is an object of the invention to provide an improved solution for selectively stripping gold/nickel, nickel/phosphorous or nickel/chromium alloys, in particular, from substrates preferably formed from 300 to 400 series r ,.
31 l'~S~S3 - ~a -Stainless Steels or l~astelloy, Inconel or equivalent alloys over .....................................................
11~5~3 n wide range of opcralillg pfllnllletcrs, pnrticulArly tempcra~ure uncl eoneentration of chloride ions, witllout adverse effect upon or degr~d~ltion of the substrate, in subst~ntihlly le~s time than is preselltly possible utilizing prior art solutions or techniques.
It is an object of the illVClltiOIl to provide an improved method for seleetively stripping such alloys, which is particularly adaptable to removal thereoî from interllal components of jet engines and the like, and is capable of ~eeornplishing stripping witllout degrn-Jntiorl of the substrute nlloys and in su~
stantially less timc thnn eonventionally possil)le.
It is n furtller objeet of lhe illVCIlliOII to provide an improved solution I alld method for seleetively stripping suell alloys which, either with or witllout meehanieul or ultrasonie agi~ation, are enpnble of effeeting stripping in sub-stalltially less time thnn eonvelltion~llly possible.
~ t is yel nnotllcr objeet of tlle illVC!lltiOII to provide n sol(ltioll and method for seleetivcly strippirlg sueh nlloys, wlliell fn( ilitnte subse(ltlcnt reeovery of the gold, phosphorotls, ehrl)lllilllll ulld/or ni( I;el colllpollellts~ usinF corlventionnl re-eovery leelllliqlle ;.
It is vcl n fulther ohjeet Of tlle invelllioll to provide nn ilnproved solution nnd Inell~ocl r~"~ scle( tivcly stl il-pillg sllell nllovs wlliell po~:e~ n eommereinlly ndvnlltngeo~ls wi(lc rallge ,r Opel'ntiOnnl (!npal)ilitieS, pllrti('lllfll'ly ns to time nnd telllperalure, Ull(l wl~ich nvokl il~ oxcity~ ellvirolllllelltlll disposnl"lnd pollution disa~lvalltllgcs involvccl in usc Of cyalli(lcs, ~In(l whicll dt) llOt require use of IllUItipl(? soluliolls or trentlncllls"ls in lllc pl ior IlI't.
I)e~cription of Preferred l~mbodiments Ulld thc l~est Mod~ for CerryinF Out the Irlvention In a(colciallee witll preferred elllbo(3illlents of tllc present invention, a novel solution is providcd whicll hns utilily for stripping alloys eontaining niekel with gold, ph()sphorous or chromium, prcfcrn~)ly gold/nickel or niekel/phosphorous ~lloys, from suhstriltes formcd from alloys corrtnining iron with ehromium and in some instanccs nickel, or nickel ricll, chlolnium bcAring allays, some of whieh fllso conklill iroll. 1 his novel strippinE~ sollltio n has heen foulld to cause little, if any, degradatioll of the substr~lte, particularly with regal-i to intergrnnular ,,_ I
11~5~i53 attack of 410 Stainless Steel. l`hcrcfore, it is particularly useful to remove gold/nickel or nickel/phosphorous braze or eoating from eritical struetural eom-ponents which are subjected to high levels of tempernture and/or stress.
It is, however, fully within the purview of the invention that the substrate from whieh the alloy is stripped, or removed, is not a limiting faetor. Likewise, the eonfigurfltion, shape or size of a component from which these alloys can be removed in aceordance witll the invention is not limited. ~lowever, the configura-tion, shape or size of the substr~te may effcet the time or partieular manner of applieation of the improved solutions of the invention, QS will be readily apparent to one skilled in the nrt.
It has been found that the irnproved solutions and method of the invention can be uscd Witll pclrticular advantnge to remove gold/nickel alloys from substrates formed of Stninle~ Steel, prcfernbly 3no or 400 series Stainless ~teels, Hastelloy, Ineonel or equivl31(?nt flllOyS~ llowever, it is fully within the purview of the invention thnt other rclnted higl)-temperture nickel-contuining alloys, such as niekel/phos~horolls or nickel/chromium nlloys, wllich rrlny be used either as a coating or n brn7.c in higll-tempcr~lturc npr)lications, enn nlso be effeetively stripped fronl sllcll substratcs. I`helerorc, it is to be undcrstood that referenee herein to "golcJ/nickcl nlloys" nlso includcs ~sucll otller niekcl-eontflining alloys, pHrtieularly nickel/pllosphololls or nicl~el/(!luomium nlloys.
In one prefcrred crnbodirn(!nt, nn improved solution of the invention is eomprised of eoncelltrrltcd nitrie ncid, chloride ions froln nt least one salt, an orgnnic COl'l'O~;iOIl illhibi~ol which iS effectivc to inhibit degrsdation of the substl ate from whil h thc gold/nickel rllloy is removed, and an organic surface active agellt whicll is compfltiblc with ulld cffcctive to reduce the surfaee tension of the solution and, prefelat)ly contributcs additional corrosion inhibition.
Preferably, nitric aeid having eoncentr~tion ranging from between about 40% to 72~-, by weiglit, in ~queous solution is` utilized. Nitric acid having a eoncentration less tllfln nbout 40~, while functional, gcnerally produces a rate 11 .
llqS653 I!
~!
of brfl7c remoYFIl wllich is unacceptably slow. Use of nitric acid in a concentration of less than nhollt 40% in nqueous solution is also undesirable, because the increased water content tends to le~sen passivity, particularly of substrates made of Stainless Steel alloys, and increases the likelihood Or adverse effects on the substrate or degradation of the substrate alloy. Nitric acid above about 72%, by weight, can be used, but it is normally unavailable in quantity or commercial grades.
In accordance with the invention, a working solution is preferably prepared by ndrnixture of the other components to the concentrated nitric acid, on the basis of grarns pcr liter of nitric ncid.
lloride iOllS are provided in the improved solution of the invention from at least one chloride salt and, preferably, an inorganic chloride salt such as alkali metal chloridcs, particularly pota~ssium chloride, ferric chloride, calcium chloride, nic-kel chloride, magnesium chloride, aluminum chloride, or combinations thereof. The totnl chloride ion concerltratioll shoukl be at least 3.75 grams per liter of concenttute(i nitric ncid nn(l prcrcrnbly rnnges l etween about 3.75 to 90 grams E)el liter nlld, morc prefernl)ly bctween 15 to 27.5 grnms per liter.
In one embodimcnt Or thc inventioll, chloridc ions nre provlded from pota~qium clllol idc nn(l rcrri cllloride"lsc(l in comt)irlntion. 'I`he potassium fell ic iOn collcentrntioll cn(~h sllolll(l l~c nt Icll~;t ~.75 frrnms pcr liter of con-celltrntc(l nilric nci(l nn(l prcfcrnl)ly mny rnr)~c l)ctwcen nbollt 3.75 to fi0 grQms per liter nn(l~ most pl(~rerllt)ly, be~ween nl)nut 7.5 to hr~ ~rnms per liter. It is fully withirl thc purvicw of the invcntioll thllt potassiunl nll(l/or ferric ion can also be supplied froln potnssiurrl nn(l/or fcrric snlts other thall chloride salts;
for e~ample, from potn~ium nitrute, potn.ssiulll iodnte, potassium sulfate, potas-sium metaphospllate, potassium periodlltc, potassium selenate, potassium citrate, potassium tartrate or ferric nitrate, ferric sulfate or ferric phosphate, respec-tively.
Potas~siu~rl chloride is most preferably used in accordance with the inven-tion, because of its greater solubility characteristics, which allow it to provide higher levels of chloride ion in solution than other chloride salts, for example, sodium chloride. Furthermore, it is believed that the presence of potassium ions in the solutions of the invention enhance the solubility of gold, as the braze is stripped from the substrate.
It is also preferled to use ferric chloride as a source of chloride ions, most preferably in conjunction with potas-sium chloride. It is believed that ferric ion may benefic-ially function as a secondary oxidizer, in addition to nitric acid, the primary oxidizing agent. Furthermore, it is be-lieved that the presence of ferric ions in the working solu-tions of the invention may further accelerate stripping of the brazing al]oy, by acting as an electrical coupling acJent to establish an electromotive force which contributes to removal of the brazing alloy.
It has been found that the use of hydrochloric acid, particularly as a sole source of chloride ions, is undesir-able and results in a stripping solution which is inoperable in accordance with the present invention. Although a go]d/
nickel brazing alloy can be stripped using hydrochloric acid as the source of chloride ion, the substrate alloy is sub-jected to severe attack and degt-aclation. Accordingly, sub-stantial amounts of lly(ll-ochlo3ic ~cid should bc avoidcd in the improved stripping solu~ions of the invention, although it may be pe3rnlssible to in~orE~orate mlnor amoun~s to Lhe extent that its presence docs not adversely effcct or de-grade the substrate alloy.
Copper chloride has been found to cause problems, par-ticularly with pitting of the substrate alloy, which is believed to result from the galvanic effect of the presence of copper ions and ferric metal. Accordingly, the presence of copper ions, particularly in the form of copper chloride, in the improved solutions of the invention should be avoided, although its presence may be tolerated if it does not ad-versely effect or degrade the substrate alloy.
The organic corrosion inhibitors used in the strippingsolutions of the invention may be acetylenic alcohols and, preferably, 2-butyne 1,4 diol, ethoxylated ........
`'t, 1.1~}5~53 butyne 1,~ diol or propargyl nlcohol. rl`he organic corrosion inhibitor must be effective to inllibit degrndation of the substrate by the stripping solutions of the inventiorl, in view of the fact that they contain strong oxidizing agents.
Preferably, the orgnnic corrosion inhibitor is provided in a concentration ranging from about 1 to 30 grams per liter, based on the amount of nitric acid, and, most preferably, between about I to 3 grams per liter. The corrosion inhibitors are believed to contribute not only to the operability of the stripping solution in substantially reduced times of exposllre, without degradation or adverse effect upon the substrnte, but they also allow for operation over a wider range of ternperature and concentration of chloride ion.
In nccordnnce with the invention, an organic surface active agent which is compatiblc with the working solution nnd effective to reduce surfflce tension and, prefernbly contribute additionnl corrosion inhibition, is provided in the working solution, prefernbly in a conccntrntioll rnnging from about 1 to 30 grams per liter, bused upon the nmolltlt of nitric ncid pre~sent, and, most pr~ferably, in a concentlntion rnnging flom nbollt 1.0 to 3.0 grnms per liter. Preferably, a polyethoxylntecl nmine or dinmillc, for example polyoxycthylene cocoamine, polyoxyethylelle soynnmille, polyoxyethylenc oleylaminc, polyoxyethy1cne octa-decylnllline or N,N',N'-polyoxyetllylelle (15)-N-tnllow 1,3 dinminopropane, mny be utilized flS the orgnnic sulfnce ~ICtiVC ngcnt. Not only do these surface active agents appenl ~o mnil-tnin thc solubility of thc corrosion inhibitor, but they also appenl to huve n syncrgistic cfre( t, in collll)inQtion with the organic corrosion inhibitor, to provide improved protcction ngQirlSt intergrnllulnr attack or degrada-tion of the substrate alloys.
accordance with the method of the present invention a working solution of nny of th(~ preferred embodiments is prepared and applicd to the substrate, in fl manller which fncilitates physicnl removal of the products of the gold/nickel alloy from tlle alea of tlle surface of the bra7ed ~or coated substrate. Preferably, thc substrnle is imlllerscd in9 or sprnyed with, a working solution of the ,. , I
1, _9_ invcntion at n te-npcrature ranging bctween about 50 to 130E (10 to 54.4C), and, prefer~bly, between about 70 to 115 F (21.1 to 46.] C). Stripping time will vary depending upon the configuration of the substrate, thickness of the brazing or coating alloy, concentrntion of the solution constituents, temperature and the type of agltation, if any, which is used. Generally, stripping will be completed within 2 to 24 hours, when using ultrasonic flgitation. Without use of ultrflsonics~ stripping times range betwcen about 10 to 120 hours. .
It should be understood that whilc the solution and method of the invention nre fully operable without use of ultrasonics, the time required to effect removal of the braze alloy is reduced by a factor of about 5 when ultrasonics are applied.
Furthermore, whell ultrasonics are used, while the conversion of electrical to mcchanical energy by the ultr~sonic trnnsducer tends to heat the operating solution, this does not adversely effect or degrade the substrate alloy being treated in accordance with the invention.
In accordflnee witll the invcntion, it is possible to selectively strip gold/nickel bra7ing or coating nlloys u~sing convcntional wnxes or other inexpensive mnsks, to cont arell~s of the substrntc wllicll 3O not rcquire stripping. For cxnlnple, u sul~strntc hnving portiolls brn7ed with gokl/niekcl nlloy may be first dippcd in n wnx ~hicll, following solidificntioll, can thcn b~! selectively removed from arcns hnV;I1g thC brn~.;ng nllt)Y. 'I`lle .~;nl)Strnte ;S thcn treated with R
solution ol` the inV(!lltiOn to cffe(!t relnovnl Or tllc brn~.c. Use of such masking mntcrials, while not ncccs~snry in nll h~stnn(!e~s, is nevcrthclccs preferred in many applicntiolls, bccnusc of the nddcd dcgrcc Or protection flffor-1ed to non-bra7.ed substrflte purt~ from the strong oxidiYirlg mfltcriflls contnined in the stripping solution.
Examples In order to illustrate more fu]ly thc improved solutions and method of the invention, the following examples nre set forth, but do not limit the scope of the invelltion. Exnmples I to 3 wcrc conducted to demonstrate the operability I' !;
~5~i~3 !
of the preferrccl organic corrosion inhibitors of the invention under laboratory conditions and did not include an organic surface active agent, due to the low temperaturcs used and li mited operflting parnmeters used for this evaluation.
E~ample I
A working solution was prepared by ndmixture of the following:
~' concentrated nitric acid (70%, 42 Be) I liter potassium chloride 19 grams .
ferric chloride 19 grams 1 2-butyne 1, 4 diol 1.65 grams This solution contained 21 grams per liter of chloride ion. A specimen, 1 comprising two strips of 410 Stainless Steel, ench I inch by I inch by 0.0625 I inches, joined to form a "T" Witll a bra7e of gold/nickel alloy, containing 80%
golcl nnd 20~i nickel, WJIS irnmcrscd in the solution for 30 minutes. An ultrasonic transducer wns used to administer ultrflsonic ngitation. ï'he sollltioll temp~rature ranged from betwecn 70 to 78 F (21.1 to 25.fi ~), with nn nveragc temperature of 7~ 1 (23.3 (~).
Inspection of the ~sr)ecill)cll nfter 30 minutes reveflle(3 1009~, removal of the goki/ni(!kel brn~c, without atlnck or dc!(rrn(lntion Or thc ~pecimen sllbstrntc.
x~mple 2 workillg solulion wns prcp~lre(l b~y ndlllixtllre of thc following:
collcclltrnted nitric ncid (709~, 42 E3e) 1 litcr potn~sil~ c hloride 19 grurns ferric chloridc! 19 grams ethoxylated butylle 1,4 diol 3.1fi grflms The ethoxylllte(l butyllc 1,4 diol wus uscd conlprised of butyne 1,4 diol ethoxylated with ethylelle o.xide in a ratio of ethylerle oxide to butyne diol of 1.8:1Ø
Tllis working solution contained 21 gram~s per liter of chloride ion. A
! spccimen, comprising two strips of 410 Stflirlless Steel, eflch I inch by 1 inch by 0.0625 inches, joined to form a "T" nnd brazed with a gold/nickel alloy containing !
11~5653 ao~6 gold m l 20~ nickel w~ immersed in the solution for 30 minutes. An ultrasonic transducer was used to administer ultrasonic ngitation. The tempera-ture ranged from between 66 to 76 F (18~9 to 24.4 C), with an average ~ temperature of 71 F (21.7 C).
¦ Inspection of the specimen after 30 minutes revealed 100% removal of the gold/nickel braze, without attacli or degradation of the specimen substrate.
F~xample 3 A working solution WflS prepnred by admixture of the following:
concentrQted nitric ncid (7096, 42 Be) I liter potassium chloride 19 grams ferric chloride 19 grams propnrgyl alcohol 1.07 grams I his WOI king solution also contnine(l 21 grnms per liter of chloride ion.
A specimen, similflr to those usecl in r:xnmples I and 2 was immersed in the solution for 30 rninutes. Ultrasonic ngitntion was agnin ndministered and the temperature r~mged from bctween 70 to 741~ (21.1 to 23.3C), with an average tempernture of 74l (23.3().
Inspecti()n of th(! ~spccimcll nftcr :~0 mim~tes revcnlc(l 989f removal of the gold/nickel l)rQ~c, without nttnck or dcgrn(lntion of tlle specimen substrate.
Fxame~
A working solution, in nccordnnce with tlle invention, was prepared comprising thc following:
nitric acid (70%, 42 Be) I liter potassium chloricle 18 grams ferric chloride, anhydrous 18 grams -
2-butyne 14 diol 1.6 grams i N,N N-polyoxyethylene (15)-~ N-tnllow 13 diaminoprop1llle 2`1 grams ¦ A specimcn similar to thosc u~sed in Æxnlnples I to 3 was immersed in the working solution at a tempernturc rnnging between 98 to 118 F (36.7 to I
1~45653 47.8C). Ilowever, ultrasonic agitation was not employcd slnd after 70 minutes ¦ only tlalf of the gold/nickel bra7.ing nlloy wns rcmoved, with no visual attHck of the specimen substrate.
After 7 hours and 50 minutes, 95~, of the brnæe was removed, again without visual evidencc of attack or degradation of the segrnent substrate. Using I the same working solution, however, with the slddition of ultrasonic agitation, i like specimens were completcly stripped in 45 minutes, with the temperature ranging between 80 to 100 I; (26.7 to 37.8 C). .
Example 5 .
For purposes of comparison, the following solution of nitric acid and hydrochloric acid wns prepared to dcrnonstrate the unsatisfnctory performance of such solutioms, due to their atts~ck upon and degladntion of the substrate alloy. 56 grnlrls of llydrochloric acid (37'~" I\R grad~) wns n~mixed with 1 liter of concentrs~ted nitric acid (70, 4213c), yiclcling a cllloride ion concentration of 20 grflms p~r litcr. A spccimcn cirnilnr to those uscd hl the other examples was immerscd, witll ultrnsonic ngilfltiol~, in tl~is solution flt n tcmperflture rslnging from bctwecn ~iG to 811~ (18.9 to 27.2(`). /~fter 1' mitllltes, ~severe attack WflS observc~d On thc spccimcn SUI).';tl'lltC. t~ftcr a totnl of 45 minutes~ while effectivcly slll Or ttlc ~old/nickcl brll~.ill~ nlloy wns rcmovc(l, the specimen ;
substrntc wns scvcrcly slttncked fln(l dCI~rrld(!~5. .
~ lthougll tllc preccdill~ 1~kYSII11I)ICS fll'C prC!SClltCd solcly for purpo.ses of illustrfltion, il is to l~c ulldcrstood tllnt SII(!I1 sollJtiolls nn(l mclho~ls for selectively stripping alloys COllTnillillg nickcl willl ~old, pllospllorous or cllromium in accor-llCe Witll tll(! inVentiOIl Illfly bc nlt('l'Cd, Vnl'iC(~ or mo~liricd without departingI frolll tl~e spirit or scopc Or thc illVClltiOI~ /U; dCfillC(I l.)y tl~e nppended claims.
Il
1~45653 47.8C). Ilowever, ultrasonic agitation was not employcd slnd after 70 minutes ¦ only tlalf of the gold/nickel bra7.ing nlloy wns rcmoved, with no visual attHck of the specimen substrate.
After 7 hours and 50 minutes, 95~, of the brnæe was removed, again without visual evidencc of attack or degradation of the segrnent substrate. Using I the same working solution, however, with the slddition of ultrasonic agitation, i like specimens were completcly stripped in 45 minutes, with the temperature ranging between 80 to 100 I; (26.7 to 37.8 C). .
Example 5 .
For purposes of comparison, the following solution of nitric acid and hydrochloric acid wns prepared to dcrnonstrate the unsatisfnctory performance of such solutioms, due to their atts~ck upon and degladntion of the substrate alloy. 56 grnlrls of llydrochloric acid (37'~" I\R grad~) wns n~mixed with 1 liter of concentrs~ted nitric acid (70, 4213c), yiclcling a cllloride ion concentration of 20 grflms p~r litcr. A spccimcn cirnilnr to those uscd hl the other examples was immerscd, witll ultrnsonic ngilfltiol~, in tl~is solution flt n tcmperflture rslnging from bctwecn ~iG to 811~ (18.9 to 27.2(`). /~fter 1' mitllltes, ~severe attack WflS observc~d On thc spccimcn SUI).';tl'lltC. t~ftcr a totnl of 45 minutes~ while effectivcly slll Or ttlc ~old/nickcl brll~.ill~ nlloy wns rcmovc(l, the specimen ;
substrntc wns scvcrcly slttncked fln(l dCI~rrld(!~5. .
~ lthougll tllc preccdill~ 1~kYSII11I)ICS fll'C prC!SClltCd solcly for purpo.ses of illustrfltion, il is to l~c ulldcrstood tllnt SII(!I1 sollJtiolls nn(l mclho~ls for selectively stripping alloys COllTnillillg nickcl willl ~old, pllospllorous or cllromium in accor-llCe Witll tll(! inVentiOIl Illfly bc nlt('l'Cd, Vnl'iC(~ or mo~liricd without departingI frolll tl~e spirit or scopc Or thc illVClltiOI~ /U; dCfillC(I l.)y tl~e nppended claims.
Il
Claims (22)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An improved solution for selectively stripping an alloy containing nickel with gold, phosphorous or chromium from substrates formed from alloys containing iron with chromium alone or with nickel, or nickel rich, chromium bearing alloys, said solution comprising:
(a) concentrated nitric acid;
(b) chloride ions from at least one chloride salt; and (c) an organic corrosion inhibitor effective to inhibit degradation of said substrate by said solution.
(a) concentrated nitric acid;
(b) chloride ions from at least one chloride salt; and (c) an organic corrosion inhibitor effective to inhibit degradation of said substrate by said solution.
2. The improved solution of claim 1 further including an organic surface active agent, said agent being compatible with and effective to reduce the surface tension of said solution.
3. The improved solution of claim 2 wherein said surface active agent further contributes to corrosion inhibition of said solution.
4. The improved solution of claim 1 wherein said concentrated nitric acid ranges from about 40% to 72% by weight aqueous solution.
5. The improved solution of claim 1 wherein said chloride salt is an inorganic chloride selected from the group consisting of alkali metal chlorides, ferric chloride, calcium chloride, nickel chloride, aluminum chloride or magnesium chloride.
6. The improved solution of claim 5 wherein said chloride salt is ferric chloride or potassium chloride.
7. The improved solution of claim 1 wherein said organic corrosion inhibitor is an acetylenic alcohol.
8. The improved solution of claim 7 wherein said organic corrosion inhibitor is selected from 2-butyne 1,4 diol, ethoxylated butyne 1,4 diol or propargyl alcohol.
9. The improved solution of claim 2 wherein said organic surface active agent is selected from polyethoxylated amines or diamines.
10. The improved solution of claim 9 wherein said organic surface active agent is either polyoxyethylene cocamine, polyoxyethylene soyaamine, polyoxy-ethylene oleylamine, polyoxyethylene octadecylamine or N,N',N' - polyoxyethylene (15)-N-tallow 1,3 diaminopropane .
11. The improved solution of claim 1 wherein said substrates are formed from alloys selected from 300 or 400 series Stainless Steels, Hastelloy, Inconel or equivalent alloys.
12. The improved solution of claim 7 wherein said substrate is formed from 410 Stainless Steel.
13. An improved solution for selectively stripping gold/nickel brazing alloys from a substrate formed from 300 or 400 series Stainless Steels, Hastelloy, Inconel or equivalent alloys, said solution compromising:
(a) nitric acid in a concentration ranging from about 40% to about 72%
by weight;
(b) potassium ion in a concentration ranging from about 3.75 to 60 grams per liter of nitric acid;
(c) chloride ion in a concentration ranging from about 3.75 to about 90 grams per liter of nitric acid;
(d) ferric ion in a concentration ranging from about 3.75 to 60 grams per liter of nitric acid;
(e) a polyethoxylated amine or diamine in a concentration ranging from about 1.0 to 30 grams per liter of nitric acid; and (f) an acetylenic alcohol in a concentration ranging from about 1.0 to 30 grams per liter of nitric acid.
(a) nitric acid in a concentration ranging from about 40% to about 72%
by weight;
(b) potassium ion in a concentration ranging from about 3.75 to 60 grams per liter of nitric acid;
(c) chloride ion in a concentration ranging from about 3.75 to about 90 grams per liter of nitric acid;
(d) ferric ion in a concentration ranging from about 3.75 to 60 grams per liter of nitric acid;
(e) a polyethoxylated amine or diamine in a concentration ranging from about 1.0 to 30 grams per liter of nitric acid; and (f) an acetylenic alcohol in a concentration ranging from about 1.0 to 30 grams per liter of nitric acid.
14. An improved solution for selectively stripping gold/nickel, nickel/phosphorous or nickel/chromium alloy from a substrate formed from 300 or 400 series Stainless Steels, Hastelloy, Inconel or equivalent alloys, said solution comprising nitric acid in n concentration ranging from about 40% to 72% by weight, potassium ion in a concentration ranging from 7.5 to 15 grams per liter of nitric acid, chloride ions ranging between about 15 to 27.5 grams per liter of nitric acid, ferric ion in a concentration ranging from about 3.75 to 15.0 grams per liter of nitric acid, an acetylenic alcohol ranging from about 1.0 to 3.0 grams per liter of nitric acid, and a polyethoxylated amine or diamine ranging from about 1.0 to 3.0 grams per liter of nitric acid.
15. The improved solution of claim 14 wherein said potassium ion is provided in solution from potassium compounds selected from the group consisting of potassium nitrate, potassium iodate, potassium sulfate, potassium meta-phosphate, potassium periodate, potassium selenate, potassium citrate or potas-sium tartrate, said chloride ion is provided from a chloride compound selected from the group consisting of sodium chloride, potassium chloride, lithium chloride, calcium chloride, nickel chloride, aluminum chloride, or magnesium chloride, and said ferric ion is provided by a ferric compound selected from a group comprising ferric nitrate, ferric sulfate or ferric phosphate.
16. An improved method for selectively stripping brazing or coating alloy containing nickel with gold, phosphorous or chromium from substrates formed from alloys containing iron with chromium alone or with nickel, or nickel rich, chromium bearing alloys, comprising application by immersion or spraying of the improved solution of claim 1 to said substrate, at a temperature ranging from about 70° to 130° F, for between 2 to 24 hours, until said brazing or coating alloy is removed from said substrate.
17. The method of claim 16 further including application of ultrasonic agitation to said substrate.
18. An improved method for selectively removing gold/nickel, nickel/phosphorous or nickel/chromium alloy from substrates formed from 300 or 400 series Stainless Steels, Hastelloy, Inconel or equivalent alloys, said method comprising the steps of:
(a) preparation of a working solution from concentrated nitric acid, one or more chloride salts selected from the group consisting of alkali metal chlorides, ferric chloride, aluminum chloride, calcium chloride, nickel chloride or magnesium chloride, an acetylenic alcohol and a polyethoxylated amine or diamine, and (b) application of said working solution to said substrate, at a temperature ranging between 70° to 130°F, for between 2 to 24 hours.
(a) preparation of a working solution from concentrated nitric acid, one or more chloride salts selected from the group consisting of alkali metal chlorides, ferric chloride, aluminum chloride, calcium chloride, nickel chloride or magnesium chloride, an acetylenic alcohol and a polyethoxylated amine or diamine, and (b) application of said working solution to said substrate, at a temperature ranging between 70° to 130°F, for between 2 to 24 hours.
(19) The method of claim 18 further including application of ultrasonic agitation to said substrate.
(20) The method of claim 18 wherein acetylenic alcohol is selected from 2-butyne, 1,4 diol, ethoxylated butyne 1,4 diol or propargyl alcohol.
(21) The method of claim 18 wherein said polyethoxylated amine or diamine is either polyoxyethylene cocamine, polyoxyethylene soyaamine, polyoxyethylene oleylamine, polyoxyethylene octadeclyamine or N,N',N'-polyoxyethylene (15)-N-tallow 1,3 diaminopropane.
(21) The method of claim 18 wherein said polyethoxylated amine or diamine is either polyoxyethylene cocamine, polyoxyethylene soyaamine, polyoxyethylene oleylamine, polyoxyethylene octadeclyamine or N,N',N'-polyoxyethylene (15)-N-tallow 1,3 diaminopropane.
17
22. The method of claim 18 wherein said nitric acid ranges from about 40% to 72% by weight aqueous solution and said chloride salt is added in an amount to provide chloride ions in an amount of at least 3.75 grams per liter of said nitric acid.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000373803A CA1145653A (en) | 1981-03-25 | 1981-03-25 | Solution and method for selectively stripping alloys containing nickel with gold, phosphorous or chromium from stainless steel and related nickel base alloys |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000373803A CA1145653A (en) | 1981-03-25 | 1981-03-25 | Solution and method for selectively stripping alloys containing nickel with gold, phosphorous or chromium from stainless steel and related nickel base alloys |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1145653A true CA1145653A (en) | 1983-05-03 |
Family
ID=4119532
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000373803A Expired CA1145653A (en) | 1981-03-25 | 1981-03-25 | Solution and method for selectively stripping alloys containing nickel with gold, phosphorous or chromium from stainless steel and related nickel base alloys |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1145653A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115448282A (en) * | 2022-09-15 | 2022-12-09 | 广东邦普循环科技有限公司 | Method for preparing lithium iron phosphate from nickel-iron alloy and application of lithium iron phosphate |
-
1981
- 1981-03-25 CA CA000373803A patent/CA1145653A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115448282A (en) * | 2022-09-15 | 2022-12-09 | 广东邦普循环科技有限公司 | Method for preparing lithium iron phosphate from nickel-iron alloy and application of lithium iron phosphate |
| CN115448282B (en) * | 2022-09-15 | 2024-01-05 | 广东邦普循环科技有限公司 | Method for preparing lithium iron phosphate from nickel-iron alloy and application |
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