claim: 1. The method of galvanizing a ferrous metal article v.,b-ich comprises wetting the article with an aqueous am65 moriacal zinc chloride solution, drying the article, introducing the dried article into a bath of molten zinc through a moltensalt blanket floatin.- thereon, said salt b-',anket being composed predominantly of 40% to 80% 70 by weight of zinc chloride and 15% to 45% by weight of potassium cbloride, said salt blanket having a melting point below 700' F. and being and remaining substantiahy free of ammonia, and withdrawing the article with a thin adherent coatin.- of zinc from the zinc bath. T'he ferrous metal is held immersed in the molten zinc 7,5 2. The method of galvanizing a ferrous metal article

@P2040,870 which co the article with an aqueous solumplises wettin,g zme @an am'mom'diii chloride tic of a flux nuxture pf -dcontaining f]Lom 10% by',5@eight of'animohium 16ride, @drying. - e led-@e a thin re, @h th -article tc ffi6reo@, 1,@airodu@ini the diied aiticle . int6 a bath of 5 iine thfough a inolt6ii salt @bl-a-nk6t -flodting ' sa@(1 sgt blanket consistiiii 6sseiitially 6f @0,171, to 75To by i@6ight 6f zinc chl6@ide, to 45% by ,Weight - of - poias@iu-ni chlor@de., ian-d up to 20"llo by weight of oth er hajides of ihe @ilk@li ind alkali cafih mei@ls,. io s a@@g a iii6ltihgp6int below aid salt b@l@nlret b aiid being aiid -reinaini-ng substantially fre6 of ammonia, with and withl-awing the arucle a thin adherent;coating of zinc from ihe zinc bath. 3. The method of galvanizmg a errous metal articla -15 @7.,hich comprii.-s weitini the -article v@ith an aqueous ammonlacal Z-'LUC chloride solution, -drying the article, introducing the &ie@d article iiito a bath 6f @,molten zinc ugn a m co thro olten salt blamlet floatinlg ther n said sgt Wei by wei-ht of potassium--chlo ride, 5% to 15% by weight of sodium chlon'de, and up to 10% by weight of an alkali earth metal chlokide, s-aid salt 'olanket hdvin-g -a melting point below 600' @F. and being and rem@aining substaiitially free cf amm6nia, and 25 withdrawing the article vn'th a thin @dherent coating of zinc froni the zinc bath. 4. Tiie m--thod of galvanizing -a ferrous metal article 9 v,,hich compriscs - wettin the article with an aqueous solu,iion of a fiux niixture of zinc -and =unonium chlo- 30 rides containing froin 10-% to 1-501. by weight of ammonium @bloT@id6, drying the iarticle to l@ave a thin r@sid,.l-e'of flux thereon, introducin.- thedried a-i-tieli,- @6tO a bath of rnolten zinc through a molten@ salt blanket. floatiAg '.thereon, -said salt blanket containing approxiniately .35 go 6o by-weight of zinc chloride approximately 25% by weight 'of totassium chloride, approxirnxtely 10% -by weight of sodium @,,hlolide, @and @ppioxiinately 501o @by Weig,ht <)f calcium chloride and having a melting p6int below 500' F., said salt blanket beiiig and re -ma-inin 40 substantially free of am--Donia, and withdiawing the article with a thin qdherent coating or zinc.irom the zinc bat-h. 5. The rrefnod of galvanizing a ferrous metal article -,vhich compnses inmersing +he- article in an aqueous so- 45 Iiition containing from 1/2 to 3 pounds per gallon of a mixturecomprising +from 10% to 75% by @N,eiiht of aminomum cl-loride and the balance essentially zinc 'blariket c6nsisting esse@-tiafl@ of -55% to 6501o by iht of 2o -.Salt @blaAet.havin,- -.a- melting -point zinc chloride,.15% to 35% .-being an '- @@@i@@ubst@@tially free a, -chloride, dr article, introdu ying.the cing the dried -article mto Aat-h o f m,oiten zin@; throu gh;a.mQ] [t@n';s@li-blank@t -flb'4tiiig sa'id.,sa"I't- b@laiiiket.-b 6,hi6rides '@r@ ll:&Vi @iRg a m6iting point bel@w 656' P., said safit' @--ei-n, g and--remajg@ ing substaittially 7 free @of @ammionial - and -vnthdr.,a,'-wip-g -Lhe -ai.-ticle -with-a tbin,@adh'e'rznt@co@ii@iof;z@pc..from t@he zinc '-b@Lth. The meihod,,of ,galvanizing a -,ferrGUS metal -article ,wlilch compn'ses th -rt; I g -thp g e -a ic e, inimer-sip cleaned arti@ie It: an aque as an@mo@i@cal zinc chloride P], solution, -heated 7.to a ttmperatpro abpve 120' -F.@-until the e- is -@@'juit@d',,s@bsta@ti@hy -@t-o the temperat =ticl ure of @t@p solut-'io@L, withdra@ving -the -article irom the @-solution and drying , it @u@stantially completely, introd eing,tile zfl(.d u ariicl-e into a l@ath of! @i@c ihrdu,-h @a;molten sai@c -@la,@kpt fl6,ti@,i @i,@,oi@,@id @salt blanketbeipg,composed predomi'Lnaiitly of 40% to 86@'o -by @@ig@t Qf zi,nc,chloride and 15% ; tp 45 % by weight of @pGtassium.-chlori. e, Aaid d B@@IGNV 700' @F. aiid d remaii -of ammoni @and wiili&@a@,iiig -the -AMple with -a :thin adlierent -coatin of zinc from -thezmc bath. 7.-' @h6@ jalvaniz. fC-pu@ @metal,Artir-le The,Met mg ?L ,which- c-omprises immersiiilgthe,@i qlp in s Sol rti au aqueou . iition of a -flw-,: nuxture of zinc ind allmonium clilorides cout@iiiing fr 0 of @ ammonium PM I' I 0/11 to @y w@@@9]@t chlo:ride@heated tp@.a,,teipperature a@ove j29" -F. until the arti6le i@ --h6ated- -substantiall y @o -,the --le mpeTature of the solutio@, @vfthdrawii- -th art@ql@,- from -ffi @solution and qg , e -1 . @, , e, aowing -i'@ -to -becc Yme substantiaRycomplpte@l@.@dri6d,@,inirodLici-n 'ed -ar'ticle into @a -@bath of molte c g the dn - . P ztn 'ilir6u@g@--h,@ a iii6lie@ :bi@il@@t -floatiiqg--thI@reQn, sqid.- ,satt blank . et -coin@isii@g @i@@sentially of -50% to 75,-Olo -.,by weight -of Zinc chloride@, @1501@ to 45-'Y@, -by wei-ght of @potas$lum chloride, -and,up,to 269o by weight of oihprhalides:of the -alkali and alkali e@ifthmetals, said '@salt l@ lanYet:'hoLying -,a -@aelting point' be'low 656- F. and being aipd rema@niggsilbstantially @.free of ammonia and -ivithdrawing the-;article w'ith -'dh c 'th :zincbath. a@thin:a erent--coating of @zin from e Wf@reAcos., fited -in @the, -Ale of -this patent 'UNITED.STATES PATENTS 1,330,399 S-hoemaker ------- -10@ 1920 1,75-51,5@59 Plets,ch ------------ 2,106,9@82 Kepfer ------- Felp..:I, t,938 -2 1;@2,933 ID@aown@.et S@Ppt. 1), 4939

Uni'ted States flatent Office p 2@9409870 2,940,870 MZIHOD OF HOT DILP GALVANIZING A FERROUS AWTAL ARen T. Baldwin, Montclair, NJ., awguor to Hanson. Van WhMe-Munning Company, a coxporation of New Jers ey Filed Feb. 19, 1959, Ser. No. 794;234 7 Chdm. (el. 117-52) This invention relates to galvanizing ferrous nietai articles by the hot dip method, and is particularly directed to the provision of an improved procedure for fluxing the ferrous metal to insure formation thereon of a continuous, tightly adfierent film of zinc. The process of the invention involves wetting the ferrous metal with an aqueous solution of a flux of amrnoniacal zinc chloride and drying the solution to form a thin deposit of the flux on the article, after which the article is dipped in a raolten bath of zinc covered by a fluid salt blanket which is at aR times essentiauy free of ammonia (including am.rnonium salts). Hot dip galvanizing of iron and steel to protect the ferrous metal from corrosion has been practiced on a large scale for more than a century. The procedure has always entailed fluxing the ferrous metal with a salt or salt ndxture to clean it of oxides and other surface contamina@ts, so that the zinc may wet it effectively, and then immersmg the fluxed article in a bath of molten zinc. The flux that has been most extensixely used, and probably for the longest time, is zinc ammonium c'nloride. Traditionally, in hot dip galvanizing operations, the zinc bath has been maintained molten in a heated steel pot and has been covered with a fused layer of a molten salt flux consisting solely, or composed in large part, of zinc and qmmom'um chlorides (or zinc ammonium chloride). The long continued use of this flux is owing to its extensively effective cleaning actio@ on the ferrous metal surface, which makes for easy formation of a continuous, adherent film of zinc, substantia@'ly free of pin holes and other imperfections. Despite this prime virtue, however, the use of an ammoniacal flux in hot dip galvanizing is not without "ts scriousdisadvantages. Theveryeffectivenessofthesaltas a flux is owing to its rapid attack on the ferrous metal surface. This attack unfortunately does not stop with preparation of the ractal surfaces for receiving the zinc coating-it promotes the formation of zinc-iron alloy inte,rfacial layers of undesirably great thickness ff the time of the galvanizing operation is not carefury controlled. Furthermore" a molten flux blanket composed to a substantial extent of ammonium chloride floating on the zinc bath under.-oes a significant change in composition withcontinueduse. Itlosesammonia,itipartbyvolatizat,ion of the ammonium chloride itseff and in part by volatilizallion of reaction products formed by its attack on the ferrous metal or on constituents (such as aiumin,im) of the zinc bath; and it accumulates iron. Such composition changes always lead to decreased fluidity of the flux and decreased effectiveness in its fluxing properties. It is periodicauy necessary to skim.off the old flux blank-et and replace it with a fresh melt of the flux salts. Chan@-ing the ffux blanket necessitates discontinuing for the time being the @alvanizing operation' Interruptions of this sort have become increasingly objectionable with increasing mechanization of the handling of the ferrous articles.through the galvanizing operation. t -Because of these disadvantages, considerable effort has been - devoted -to finding a fluxing pfocedure which v@ill assure close r-ontrol over the chemical attack of the flux kL atenl%.-ed June 14, 1960 2 oji the metal surface, and wW at the same time minimize the costly and time consuming skimming cv.4L old ffux and :@eplacement of it with new on the surface er.L' the zinc bath. 'E@e only subsiantial, advance heretofore -@nade toward achievi@g th-es6 objectives has been the development of the so-called tdi-y galvan'm'ng process., This process involves imr.p-ersi.ng the ferrous article i4 an aqueous solution of, ammomacal zinc chloride, and dryin the article to leave a thin deposit of the flux on the surface of the metal. 10 The article is immersed in the molten zinc after it has been dried (whence the name "dry galvanizin- " to dis.1 tinguish this process froni one in which the article is wetted with molten flux before being immersed in the molten zinc, a procedure cailed "wet galvanizing"). No 1.5 flux, in the conventional sense, is employed on the surface of the zinc bath in dry galvanizing, for the residue of the salt film on the surface of the article as it is immersed in the zinc is relied on to ae ate the s metal surface for reception of the zinc. There is, how20 ever, an accumulation of "ashes" or spent flux or both which accrues.on the, surface of the rnolten metal and which rnust be periodicaily skimmed off. Hence dry galvanizing, while it reduces substantially the adverse efferts of uncontrofied fluxing of the ferrous inetal sur2r) faces and excessive loss of aluminum from the zinc bath, does not avoid the need for periodic skimming, and it increases the difriculty of maintaining a good clean and fi@ld surface on the zinc bath. The present invention provides an imdroved galvaniz3o ing process which combines the best features of -dry and wet gaivaniz@;ng while elininating largely the disadvanta,@es of both. The Drocess of the invention entails fluxing the ferrous r@ietal article substantially by the prpcedure of dry galvanizing, using zinc ammonium chloride as the 3,5 acti've flux salt, and maintainin.- a ffuid protective blanket o'L an ammonia-free salt mixture --n the bath of molten zinc. The salt blan@ket provides a thinly fluid protective cover on the molten zinc; and in accordance with the invention it is sabstantiauy free of ammonia (or any am40 monium salt@ and has the property of remaining free of ammonia by favori@g volatilization of such ammonia as is introduced into it by the flux-coated ferrous metal aiticles. thus the salt blanket is of stable composition which retains its fluidity for prolonged,periods of time, 45 and need 6nly be replenished from time to time by fresh -- addilions o.'L the same co@nposition to make up for dragout or other losses. By ilse of the proc-ess of the invention, interruption of the galvanizing operation to skim the surface o'l tl-.e molten zipe is eliminated. ro The new galvanizing method comprises wetting the s met@Ll article with an aqueous ammoniacal zinc chlorides sol I ution, then drying the article (either at room temperature or by heating to a temperature which may range _up to 400' F. or mdre) and then introdi4cing the 55 dried @rticle into a bath of molt.en zinc through a molten salt blanket floating thereon. The salt blanket is composed predominantly of zinc chloride (constituting 40% to 80 %.by w.-i.-ht of the blanket) and potassium chlorid-- (cdnstituting 15 % to 45 % by weight of the blanket), and 60 it preferably in addition contains other halides (especiary chlorides) in arnounts up to 20% by weight; its melting point should be well below 700' F., and it should be thihly fluid at that temperature. The salt blanket as prepared is substantially free, of ammonia (and ammonium r substantially free thereof during use. ,5 salt@), and reniains Ammonia compounds introduced into the salt blanket by intrdduction of the flux-co@ted ferro-as metal articles rapidly are _dissipa:ted by volatilization, so that even after' apr6longed period of us6 the blanket contains only a ver@ 70 sn@ar quantity of ammonia -(generally not over a 117,; or .2%-@)i. - It is -therefore a -highly stable composition which retains its high degree of fluidity and prdtective

qiial Iity indefinitely. It is only necessary to add niake-u@ b6c@dnie heated @ubstantially td the t6mperdtiire of the alh&,ints the same salt co@@osition from tinie to time, solution. Then when the article is withdrawn from the W;,'hout having to s@im the bath at a-n'y firii6,- -S-'o@f'ut'i'on it dries rapidly by eyaporation of the water from 'ne new galvanizing metkod may be carried out either the adhering film of flux solution. Rapid drying is desiras an,intc!rmittent operation -iu which the articles to be r) able, but drying should be,conducted under conditions @,@Vanii6d@ @ie fiEiii4r@@ -:@hdr-e - iiian'uiff which do not cause injury-to the flux film Drying ordi@o-itiiilioii-sopera,ti@o,-n,ipnarily is effected by simp y--exposmg the articles, after g, q rd6t6@ tii@oidgh the -sev'f-,'r@al, . tfp5 js, arge y or eveneomp et@.e@iy-' withdrgw4l .@from the !flux -solution; -,t @ iti@- -,jitmosphere. It 19 'bhi@'bf th@ Dryi@'g- i@ay, howeve -,b d'id-@ a drying ov avdfit,@k6s of e mven --e @&zte en m Qwl-vei,'ti@iii ift@erm'@ts ineeh'@- "- d f M h the zlificles are Ixeated.to a ter4perature,,Vp to 400' ti,6n h anize . aqi . ing 9 10 w c th6 'af@616@ 'ilii6ugh the- --gaIV-ani-z-@ip-g""bai]@@w-- 'it'h--ou@t -nee F--..'- -'@M6 time re 'while @'sliort, _quge, td iiiterrupt overa ions at -int6fV@ls-.to @kiin speht.,, flux v a r i e s' W i t h t @ e i -e@m" p@ 'e t'a i 7u- -r- @e r y'i @n g@ I d - I @ e a I fo, @, e d ashb- 'fr6in t@6 @@th. - Atticles ",,,u@t @@s "@ir6ii '@he@et to continue long enough for the article to be quiie comiii&.al a're most- e-as@-y-pissed- tlii6i@Lh ap"i?xng pletely dritd -,biit@tli6f@ is -ng'iid@.aiifag6@fi)r -ii t-0 continue 9. v I I - 6@ @r@ti-' @b" @,dis@ 5 longer and it m4y even have the disadvantage of pro,@@6c@ration in an esset ltiaii 7,tilili6ij@ y,con - .'' @op;- vti as pal S, c d:'df@er@ itid-0 cr&te'Artiel6s -s-uch- -'I ans, ta- ni-s,, - a-ii h moting undesirable 'Ei,tf,acks 'f --t,hi, @ffiii on the ferrous ware @it6has are -tnd@t coiivdiii6iitly h@inat@d on al@@t6h metal. The dried article has dn its surface a thin film l@a@is, @sp,@,ci@lly @if their n@@i@er is not large and does- not mad6 pp pf, a Tp.@id@ie.,Of.t-he-zi moniu n c a n d a m ' n i c h l o j t i s t i f y i n s t a l l b l t i o h - , d ' - " a s i i i t d b l e c 6 h i e v 6 r s y @ t e m . r i d q s p l t i d p f ; i q ( 7 l i - ) r g a c t i o n p r o d v c t s : a s b a v e f o r m e d : i n Tjie a@corr.Danymg fiow h66t @cli'em6ticaRy sho*s tke 20 ppgspquq@4-ce p attac@. iDf the flux on -stirfaize of f the @the seque@r-.ce ibf- @telis -einplo@ed @i@n ca'rry',ng out ;i - ,preferr&d the -ffiet4i. @f ihe i @ii einbodiihetit on, *hich emb-o-di'm6ni id6- T-he drie @,atti sho be immersed @in the molten d r-le -,Wct stiibed bet6w iii 66nsidei@bld (idto. g4lv4igizi - bat - as p 2;iAr - .1aa -romptly 4s@@is practical after @me @irlticies to be 'g@l*@iiiii&'d ro ghly f the article are first iho u dr-yipg. it i@ Og@si able @iq minimize exposure o cleafied. ne i@ventioii cofitemsame sort0 2o plati-,s th6 f td',the a:tir,Aftpr -Aryijqg olnd before dipping in the molten clednii@g that-nciW--i pradtii@'ed'ixi'coiiveniioiiai i@Llvd4iz- z@qp @?ltli to cops@@r-vp the heat ()f the dried article and to i id]@oration . It-in@6iv6s usually a thoiou@h degr-e-as'- ng minimizp .f. e ppp m qTtL@ @y -for atmospheric oxidation or ih,6 tl -t or bdth @i liquid 6r v;ipor ddgieasij@g chaiub6r in ei ni. other attack . pA @ts @ atix-c@oati@d sufface. Immersion ina,lid' aii a-,Ikali,n.6 6lehning S61.iiti6h, and the'n-@?,--@i v@i@es @@;-@i-ng the article through the molten @salt blanket operdtioji-m acid. @d coy,en -lbe molti@ti zitic@ to beifte;at4. tho zinc surface, and A's- s -o-o'n - -as 'p-r -a@ctic al zifter cleaning, th6 arti6le is -v@ctied t6@. withdiawing the- article again: from the zinc bath. 2 with ifie---ammomacai ziiid@ @@l@ride Aiii -s-olution., , -T@hi g a r t i c l e i s c o a t e d w i t h a @ t h i n , O P @ @ r a t i o n c a n b e c a r r i e d o u t - i ' n ' 4 ' n ' y - ' i 6 i @ t - F @ i ' - o f z i n 6 . ponven qrL@ f The 4rticle is cooled.%to room qr ILM e the a-t@tic-l-e@s ma be dipped in a, b'ath'df the flux tpMpey4ture, in a y ny desired manner, advantageously by or the- -flux s-olution inay be'ap@lied by spraying 3@ qqenq@ingwith wqti5r. it on the @@ids. 'fte fliix @oliition itself is prime@i.ity, @Ig -accordarice the invjention the molten salt an aqUOdu @6l@iion-6f zinc,and airim6niiim chlorides. @lan@p@ floated on the molten @:ific ;s initiallyprepared Thes6 -s-@iis -are pr6ferably ii@i@d fn the @y6@orii6ns of 1 6 % free fr o@-n -arnmo4i and to 75% ilmiiioiiium chloride by,weight of the miitiife of h@s @tlic qf f-4yoring elimination of @ammonia by prq salts anii 90 % to 25% @-,ine chloride b@ weight of the mix'- 4 - - . PPrty alt blai*ot is composed predomi0 wigtilizgtticm TNS ture.. - Pi7@fdidbly. @bese @alts @afedi solved in *aiei to @@a nantly of -4Q% tp -$Ql@p by weight-bf ziiie chl@oride and Co. 3 pouhqs o r 1. IZ6 iiceiiir@tiofi -6f ftbffi 1/2 to f th,6- mixture "-ppof-.pot@Ls@ium chloride. Adto@45 % by Wei. V,44tpLg usl , it 41s@p pqnt 't 20% by weight of 6nium I@p_@ y - am$ - UP 0 'E@stedd b-f using a of zi c alid amm olhf@r. h4lides', parti-cularly -chlorides of the -alkali: and, chiot-id6 @ (@zlilci@+ NH,Cl) eqiially gati fact@r@ - r@,i@lis 45 alkqlj is adtory salt @blankpts are P4,rth mc @lL 4ts. 'Vpr y @sa t, f may'@@e'-obt-a-ined'.us;i'ng- -a 'zinc --animoiiiii @m clil6rid6 -(P.-g. @Qlro -t<) .750/o:-by weight:of zinc chloride, ZnCI2.2NI-1,C@l 6r '-iiiC!,.3NRCl) a the acti@@ potassium chloride WI-iglit Qf and -up s j@i filix 96fi@t'ion. 0-1@94 q aqueops to20%- by _wwgh -,4Dther:h@Llides, eg. 5%@ to,15%:by a'mrao niu@i 6@16ridet, --ID . _ t Q f 'In@ -@addieidn fh& zinc and -6r - i @ - s o di q ui ih lo ri d e. ai x d u p, ,t o 1 0 % b y. *. ei g ht o f 66 an @?A Ali .:met4 -chlorid@-such as calciiim chloride g agent suc a@ il3i@@rine, or --m4gn-@@iv-nj (zhlorid6. - -Wit iii this comrosition range, 0 amc'itoth'm h' sals - @o@iai@s otg h" a soluble -giucosicte or carbohYdrat6 t6ll6w emulsion, or e r"ults -have been a:ttained v@.ith s p e @ , i z Q ! y f s a t i s i ' a c t q r y the like. !he -frdthin agent facilitdtes the flu-xiinig @ictin - r " p o s i , ! . d - , o f ' 5 5 , Y c @ t o 6 5 % b y w e i g b t o f o f t h e z i n c a m i i i d n i u m c h l o r i d e . A i l y o f t h 6 f r 6 i h i j i g s / a b y w e i g h t o f p o t zinc to 3- 5 asium chloagi@,pts used in- gal,@a-nizing s ma@ be emplo-ye'd in 55 weight of sodi . chlori , and @1294z um d e carryiflg'outthepr6 entiTiVe.ntion. Th6a@iounioffr6th- 3 0/p to 7 'Ko -by weigjxt of-,@iat4@,ium chloride. ing a nt;l e@h]@loyed 6idi@arijy'is fr6m 0.10zl@- io i -Y,2 -by Z:Ipv chlo:ddp i$. tije main -ingredient ',Df the salt blanket, weight of thd @Oluiioil. Also a-w6ttin- agent 'i@iay with potalsiuin chloride in proporiions aA4 is @ro;m -bino with ,jre@ent iii th6,- flux soltition' to insil@e t@@t sq4zb@ - as - t@ Y:Io@ld @a - mixtwe w @advantage b,e p hich is completely molten it 'eff,-ctively wOt@ all pai7ts bf th6:article td be gal@anized - ily, flu@d -4at,a7 temperature well below 700' F. 60 and-thii. AiR@ -coiiventic,@,ill:;@@@tffhg ainay be employe for de -s emfijoyed @both because in com@ gent P,otassiixm thlqri purpose. su@h b@n -w at@IQn @ i - L z-m@@ qtiloride--it yields a low melting mixBy W;iy df exabiple, qn a4ueo s solutio:n 6oiitaining 2, and,.bm s -low -ause it,@5@@preence in-@the poiinds p-c@r @alion (2.Ao -grams per. liter) o@'@L ftiix wq r=.iure fA -n:z bt- such @ ammo-bia as becomes Y.Ors. ip@liminatio d@ed of -40 -Vc@ bY *6iiIii Of @hldride @ a@qd 65 illtrodug The addition - of o.ther c p halide is de 60;, by Weight 6f zini:i'chlorfde, ab6iit il,@,2 ouinces per -the and potassium e@oijonuze on gglo;n (Il ktain per. liter) O,f @lycerine, -@nd a-bO-Ut' V4 "'d- -d t -fluidity.- and'@tabilitY @of the chl pri, - P,_s @atl :@:0- lmprovq -@2 gr@ms -b6r'lii6r) of a i@@tti@g alge@'i ounpe,pe,r g@ii6id fus Sodiu m chlbride i@ advantageous becau@e suc as sorb"d@.n- m'on-- opalmitatp, is a very- satis,f,actpry, it@ n ivc., diliient-for ttie salt iiaxtiire aiid be fitl* sd;lution@ 70 ca4w. ;n,@-,proper.,@.qu e& itiniproves -stability of@ the antiti 'Most @ommoiily,the-flux solution is adpl.ied-hot to the,, aiikqiint @,Df. -calcium -chl<)ride @is desii@ @article to be plvanized. In general it is he . ated to'a temabLle_@f_Qt!Cithilar Ke-as-ons,'and gso t6 h(;Ip low.er th6 meltabove 120 @- F., -up to ;3qy It is desira in.- point and the-,@d@cosity,-vihen,inolten' cif- themi)Cture @9p' -F pp-r 't@e 'immersed in (qr pthe@"e -ii@ t, to-@,@vhich-- - added. - Other salts men -, en sq&um; oride lias b6 the 4 e@ uW! in @&,pn@ie.@ases@wWadvintago in the:' 7'5 t;@q@.wit4) h(@t c@n Vga ja rtic. e-s@ vf@ m s@Llts and in fact

imtxtur6, either " addition to or as substitutes for the m calcium chloride and for a part or all of the sodium chloride, include magnesium chloride, sodium aluminum fluoride, tin chloride, barium cbloride, and strontium chloride. T'he salt mixtare should be thinly fluid at the temperature of the zinc bath on which it floats as a covering blanket, and it should have a low, watery viscosity at such temperature so as to flow readily over the entire surface of the zinc bath and to drain quickly and quite completely from the ferrous metal articles Nvithdrawn from the molten zinc. To this end the flux blanket preferably is composed <)f salts in such proportions as to yield a mixture vihich is completely molten at 650' F., and preferably at 600' F. or lower. It is possible, with salt mixtures of the character contemplated, to attain melting points (temperature at which the mixture is completely molten) below 500' F. In addition to low melting point and low viscosity, the salt mixture should possess a high degree of StabilitY at the galvanizin.@ temperature. It should not exert a corrosive or other undesirable attack on either the ferrous metal articles being galvanized, or on the molteit zinc or any component of the zinc bath. It should not tend to change in composition during use to the extent that it increases substantially in melting point or viscosity. Hence it should neither tend to accumulate substantial amounts of foreign salts or other compounds from the zinc or ferrous metal, and should not tend to decompose or lose any of its ingredients preferentiauy. An example of a particularly satisfactory salt mixture, which melts at a temperature below 5GO' F. and possesses in a high degree the at>ove mentioned properties of low viscosity and high stability at -the galvanizing temperature, is one composcd nominally of 609'o by weight of zinc chloride, 25% by weight of potassium chloride, 10% by weight of sodium chloride, and 5% by weight of calcium chloride. The salt mixture may be deposited in solid form on the surface of the molten zinc, where it is melted by @the heat of the zinc. The zinc bath is heated to about 825' F. or 850' F. (a normal gaivani7ing temperature), during galvanizing and the salt mixture is fused and heated to such temperature by the heat of the molten metal. The fused salt, being of low viscosity, spreads uniformly over the entire surface of the molten metal. Preferably enough is employed to cover the surface of the zinc with a layer about onehalf inch, more or less, in thickness. When the dry fluxed ferrous metal is introduced through the fused salt blanket iiato the molten zinc, the residue of ammoniacal compound on the ferrous surface fuses and mixes with the salt blanket. However, it is quite rapidly expefled again, by volatijization, at the temperature at which the salt blanket is maintained during galvanizing. Consequently it does not cause any signfficant change -to occur in the composition of the salt bla@-iket. "n particular it does not accumulate therein in sufficient quantily to cause the blanket to react undesirably with the niolten zinc or any other compon ent (such as aluminum) of the galvanizing bath, or to cause it to attack the ferrous metal or pronaote an excessive thickness of iron-zinc alloy at the interface of the ferrous meW and the zinc coating. The particular salt blanket composition mentioned above by way of ex ample wiU not generally accumulate more than about 0.25% by weight of ammonia even after prolonged use in a galvanizing operation according to this invention. Some iron does enter the fused salt blanket, by reason of fusion therein of ferrous reaction products of the ammoniacal flux with the ferrous meW article. It is quickly reduced by reaction with the molten zinc, however, and collects in the dross which forms during operation of the process. only long eriougi2 to be wetted by it, @nd i's then'wit'hdrawn again from the zinc bath. It is prefer-able practice to withdraw the articles from the bath at a point when the bath is free of molten salt, in order to avoid @picking up salt on the emerging zinc-coated article. To this end a partition may extend across the surface of the zinc bath, to confine the molten salt blanket to that part of the bath when the articles bein.- coated are introduced, and to exclude it firom the surface of the bath in the 10 vicinity where the articles are withdrawn. In some cases such partition may be omitted, and the surface of the zinc bath may be kept free of molten salt in the region where the articles emerge by skimming. In other cases special forms of galvanizing pots may be provided to per 15 mit withdrawal of the articles without bringing them in contact with the mol' en salt blanket. In yet other cases, especiahy where the molten flux has a low melting temperature and a low viscosity, it may be satisfactory to withdraw the articles through the salt bracket, and to 20 wash off any thin film of salt adhering to them. It is desirable to cool the articles promptly after they emer.-e from the zinc bath, to prevent undue growth of the iron-zinc aroy at the interface of the zinc coating and the basic metal. Cooling advantageously is by a water 25 quench, either in a pool of water or by a water spray. It is undesirable to hold the articles in the quench water longer than is necessary to -cool it to a temperatures low enough to substantiauy stop -further development of the interfacial alloy. The quenched articles should still be 30 hot enough to dry rapidly by evaporation of the water adhering to its surface. Often for this reason, it is preferred to use hot water (at a temperature from 120' F. to 200' F.) for quenching. If the galvanized arecle has been withdrawn from the 3,5 molten zinc bath through the fused, salt blanket, salt adhering to it may be washed off by the quench water. Salt removed from the bath cover in this manner (socalled "drag-out") cannot conveniently be recovered. It is replaced from time to time by simply adding make-up 40 amounts of the original salt niixture to the surface of the zinc bath. The zinc coating on properly cleaned articles galvanized by the method of this invention is of excellent quality. It is of uniform thicl@,.ness, tightly adherent to 15 the underlying metal, substantiany free of pin holes, and with a desirably thin lwyer of iron-zinc afloy at the interface between the ferrdus metal and the zinc coating. Control of the attack of the ammoniacal flux on the ferrous motal is readily achieved by controlling the concen50 tration and relative proportions of zinc and ammonium chlorides in the flux solution, and by controlling the temperature and duration of the drying operation. The process is adn@drably adki)ted to being highly mechanized, for the step of coating with flux s6lution, drying, and 55 carrying through the galvanizing bath can aH be performed as the articles being galvanized are being conve@yed on @a mechanical conveyor system. The stability and low viscosity of the fused salt blanket which covers the molt.-n zinc bath eliminates the need for periodic -kimming of the bath. Owing to sor@ie or all of these 60 ' des@irable features, the new process may be used with advantage in almost all galvan:lzing operations.