CA1314512C - Polyhydroxy compounds as additives in zinc alloy electrolytes - Google Patents
Polyhydroxy compounds as additives in zinc alloy electrolytesInfo
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- CA1314512C CA1314512C CA000530934A CA530934A CA1314512C CA 1314512 C CA1314512 C CA 1314512C CA 000530934 A CA000530934 A CA 000530934A CA 530934 A CA530934 A CA 530934A CA 1314512 C CA1314512 C CA 1314512C
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D3/00—Electroplating: Baths therefor
- C25D3/02—Electroplating: Baths therefor from solutions
- C25D3/56—Electroplating: Baths therefor from solutions of alloys
- C25D3/565—Electroplating: Baths therefor from solutions of alloys containing more than 50% by weight of zinc
Abstract
ABSTRACT OF THE DISCLOSURE
An improved aqueous acidic electrolyte suitable for electrodepositing zinc alloys comprising a combination of zinc and at least one metal selected from the group consisting of nickel, cobalt, iron, and mixtures thereof incorporating an effective amount of an additive agent for providing improved grain-refinement, reduced dendrite formation, increased adhesion and ductility, and unexpected adjustment in the codeposition of the alloying metals in the zinc alloy deposit. The additive agent comprises a bath soluble polyhydroxy compound having three ox more hydroxyl groups at least one of which is substituted with a polyoxyalkylene group. The present invention further encompasses the process of employing the aforementioned electrolyte for the deposition of functional and decorative zinc alloy electrodeposits.
An improved aqueous acidic electrolyte suitable for electrodepositing zinc alloys comprising a combination of zinc and at least one metal selected from the group consisting of nickel, cobalt, iron, and mixtures thereof incorporating an effective amount of an additive agent for providing improved grain-refinement, reduced dendrite formation, increased adhesion and ductility, and unexpected adjustment in the codeposition of the alloying metals in the zinc alloy deposit. The additive agent comprises a bath soluble polyhydroxy compound having three ox more hydroxyl groups at least one of which is substituted with a polyoxyalkylene group. The present invention further encompasses the process of employing the aforementioned electrolyte for the deposition of functional and decorative zinc alloy electrodeposits.
Description
'J 11,167/11,198 ~31~12 POLYOXY~LNYLPIED POLXHYDRDXY
~INC ALLOY ELECTROLYTES
Background of the Invention The present invention broadly relates to an improved electr~lyte and process for electrodepositing zinc alloys, and re particularly, to an improved aqueous acid zinc alloy electrolyte containing novel additive agents for providing improved grain-refinement, reduced dendrite formation, increased adhesion and ductility and an unexpected adjus~ent in the oodeposition of one or m~re alloying metals in the zinc alloy deposit.
Electrolytes inoorporating zinc ions in ~urther combination with one or a co~bination of nickel, cbbalt, iron or mixtures thereof have heretofore been used or proposed for use for depositing zinc alloy deposits of a decorative or functional type on a variety of oonductive substrates such as iron and sbeel, for example, to prw ide for improved oorrosion resistanoe , enhan oe appearan oe and/or bD build up the surfa oe of a wDrn p~rt enabling refinishing thereDf bo restore its original ~perating dimensions. Such zinc allo~y electrDlybes and processes are in widbspread oommercial use for industrial or functional plating including strip plating, oonduit plating, wire plating, rod plating, tube plating, oDupling plating, and the like. A ODntinUing problem associated with such p~ivr art zinc alloy electrolytes has been the Lnability to achieve the desixed grain-refinement of the alloy electrDdeposit to pro~ide the requisite semi-bright appearanoe and associated physical properties including adhesion and ductility. A further prablem has been the inability to incre~se ~he percentage of the alloying metal oonstituent such as nickel, o~balt and/or iron in the zinc alloy electrodeposit in 13145~2 order to achieve a desired physical and chemucal properties. me formation of dendrites on the substrate being plated at high current density areas has also been objectionable.
The present invention provides for an Lmproved electrolyte for electrodepositing zinc alloys incorporating an additive agent or mixture of additive agents which provides for improved grain-refinement, a reduction in dendrite formation, increase in adhesion and ductility while further adjusting the ~odeposition of the alloying metal ions achieving a zinc alloy electrodeposit of improved properties.
Summary of the Invention The benefits and advantages of the present invention in accordan oe with the ccmposition aspects thereof are achieved by an aqueous acidic zinc alloy electrolyte containing zinc ions in conventional amDunts in further cc~bination with controlled amounts of at least one additional alloying metal ion selec~ed from a group oonsisting of nickel, cobalt, iron and mixtures thereof. me electrolyte further contains as an essential constituent, an additive agent present in an amount effective to achi~ve improved physical characteristics of the zinc alloy deposit oomprising a bath soluble polyhydroxy oompound having three or mDre hy~roxyl groups of which at least one is substituted with a polyoxyalkylene group as well as mQxtures thereof. The ooncentration of the poly~xyalkylene-substituted polyhydr3xy additive agent is present in an amount effective to impart L~proved grain-refinement to the electrodeposit and the specific aoncentration will vary depending upon whether ~he electnvlyte is of the chloride, sulfate, fluoborate, sulfamate or mixed-chloride type.
In addition to the foregoing constituents, the zinc alloy electrolyte may additionally contain various other additive agents of the types conventionally employed including buffering agents, supplemental brightening agents, bath soluble and ccmpatible conductivity salts to increase the electrical oDnductivity of the electrolyte and the like.
In accordanoe with the pro oe ss aspects of the present inventian, a zinc alloy ooating is electrodeposited on a conductive substrate employing the aforementioned aqueous acidic zinc alloy electrolyte which is controlled at a temperature typically ranging from about room temperature (60F) up to about 180F and is qperated at an average cathode current density ranging from as low as about 1 up to as high as albout 2000 a~peres per square foot ~ASY) or higher which will vary depending upon the specific type and conposition of the electrolyte as well as the geometry and processing parameters e~ployed in the plating operation.
Furthex benefits and advantages of the present invention will beccme apparent upon a rea~ing of the Description of the Preferred Embodiments taken in conjunction with the specific examples pro~ided.
Description of the r f rr d e bcdiments The aqueou~ acidic zinc alloy electrolyte in acoordanoe with the composition aspects of the present invention oontains zinc ions present in an a~Dunt effective to electrodeposit zinc from the electrolyte and generally can range from as low as about 10 gJl up to saturation, Wlth oonoentrations of from about 15 bo about 225 g/l being mDre usual. Preferably, for mDst applications, the zinc ion con oe ntration is o~ntrolled within a range of about 20 to a~out 200 g/l.
~3~4512 1~e maximum conoentration of zinc ions will vary depend mg upon the temperature of the electrolyte with higher temperatures enabling use of higher oonoe ntrations. ~e zinc ion oOnoentratiQn will also vary depending upon the type of electrolyte employed which nay be of the chloride, sulfate, nuxed chloride-sulfate, sulfamate, as well as the fluoroborate types. In acid chloride-type electrolytes, the zinc ion concentration is generally controlled at 3 level within the lawer end of the permissible range whereas in acid sulfate-type electrolytes, the zinc ion conoe ntration is generally contrDlled at a level within the upper range of the permiss~ble conoe ntrations.
The zinc ions are intrcdu~ed into the electrolyte in the form of zinc anodes or soluble zinc salts such as a chloride, sulfate, sulfamate and/or fluoroborate salt in further oombination with an acid such as sulfuric acid, hydrochloric acid, fluorbboric acid, sulfamic acid, or the like oDrresponding to the type of zinc salt emplcyed.
Gbnerally the pH of the zinc alloy electrolyte is controlled within a range of about O up to about 7 with a pH of fram about 2 to about 6 ~eing preferred.
In addition to the zinc ions, the electrolyte further oontains oontrolled amounts of at least one of the all~ying metal ions including nickel, ccbalt, and/or iron which similarly are introduced in the fonm of soluble anodes or bath soluble salts of the alloying metal including the chloride, sulfate, fluoraborate, acetate, or sulfamate as well as mixtures thereof. When nickel and/or ccbalt are emplçyed as the alloying metal, each can be employed in the bath in amounts of fram about 0.5 g/l up to about 120 g/l to provid~ alloy deposits contaLning fro~ abcut 0.1 up to about 30 percent by weight of nickel and/or cobalt.
Preferably, the alloy deposit cDntains rom about 0.25 percent tv a ~3~ 2 total of about 15 percent of both nickel and/or cobalt, and the bath under such conditions contains nickel and/or obbalt ions in an amLunt usually ranging from about 3 g/l to about 65 g/l, respectively.
When iron oomprises an alloying metal in the electrolyte, the operating iron ion ooncentration can range of frcm about 5 g/l up to about 140 g/l wqth concentrations of from about 40 g/l up to about lO0 g/l being preferred.
When iron ions are present in the electr~lyte which is only weakly acidic or either neutral, such as at a pH of from about 4 to about 6.5, it is generally preferred to incorporate conventional oomplexing or chelating agents to maintain an effective a~ount of the iron metal ions in solution. Chelating or oomplexing agents which are particularly satisfactory for this purpose include citric acid, gluoonic acid, glucoheptanoic acid, tartaric acid, ascorbic acid, issasoorbic acid, malic acid, glutaric acid, muconic acid, glutamic acid, glycollic acid, aspartic acid, and the like as well as t~eir alkaline ~etal, ammDnium, zinc or ferrous salts.
While the iron ions are introduced into the electrolyte in the ferrous state, ferric ions are formed during the plating cperation and it has been ~ow ~ th3t ex oe ssive amounts of ferric ions are objeckionable resulting in the form~tion of striations on the zinc alloy plated surfa oe . AccordLngly, it has been fo~nd desirable to oontrDl the ferric ion ooncentration at a level usually less than abcut 2 g/l. This can be accomplished by employing a soluble zinc or iron anode in the electroplating bath or, alternatively, by immersing metallic zinc or iron Ln the holdLng tank through which the electroplating solution is circulated. When no soluble ano~es are empl~yed or no zLnc or iron metal is provided Ln the holding tank, proper oDntrol of the f rric ion 131~512 o~ncentration can ke achieved by employing suitable bath soluble and compatible organic and~or inorganic reducing agents such as, for example, bisulfite, isoascorbic acid, nDnosaccharides and disaccharides such as glucose or lactose.
It will be appreciated from the foregoing, that electrolytes can be for~ulated to provide for appropriate binary, ternary or quaternary alloys containing predomlnately zinc and at least one of the other three alloying metal o~nstituents.
When ternary alloy deposits are desired çontaining zinc-nickel-ir~n or zinc-cbbalt-iron, the ooncentration of the metal ions in the electrolyte are usually contrDlled so as to provide an alloy oontaining from about 1 percent to about 25 peroent ir~n in co~bination with either about 0.1 to about 20 percent by weight nickel or about 0.1 to about 12 percent cobalt and the balanoe essentially zinc.
In addition to the metal ions present in the electrolyte, the electrolyte further contains as an essential ingredient an additive agent comprising a bath soluble polyhydroxy oompound having three or more hydroxyl groups at least one of which is substituted with a~poly-oxyalkylene group. Typically, polyhydroxy compcunds such as sorbitol and methyl glucose having one or mDre of their hydraxyl groups substituted with oxyethylene or oxypropylene chains and nuxtures thereof have been found particulary satisfactory for use in such zinc-alloy electrolytes.
The molecular weight of the additive agent or mixtu}es thereof is oontr~lled to render the additive agent soluble in the el0ctrol~te at the oan3entration desired. It will be appreciated that the additi~
agent may oontain one polyoxyalkylene substitute group on ~he mDlecule or nay contain tWG, three or more substitute groups depending upon the 131~12 degree of substitution and the number of reactive hydroxyl groups on the mDlecule.
The conoe ntration of the additive agent in the electrolyte will vary depending upon the conoentration and types of other bath constituents present, the desired alloy deposit ccmposition, and whether the electrodeposit is to be empJoyed for functional or decorative purposes. Generally speakin~, the additive agent is employed in an amDunt effective to produ oe a refLnement of the grain of the electrodeposit, to reduce the tendency to form dendrites during the electrodeposition process, to enhance the adhesion and &ctility of the deposit to the substrate, and to adjust the codeposition of the alloying metal ions in the zinc alloy deposit and to regulate the alloy content at a more uniform, desired level. For this purpose, concentrations as low as about 0.005 up to about 20 ~/1 have been found usable while con oentrations of from about 0.02 up to akout 10 g/l are more typical and p~eferred for most uses.
In accordan oe with a preferred practi oe of the present invention, the additive agent is e~ployed in sulfate-based zinc-iron electrolytes in a ooncentration range of abcut 0.005 to about 0.1 g/l providing both an increase Ln the oodeposition of iron in the zinc-iron deposit and a gra~l refinement thereof. In sulfate-based zinc-nickel allo~ electrolytes, a oonoentration range of abDut O.005 to about 0.1 g/l is also ~referred providing improved ductility and adhesion of the deposit accompanied by a slight improvement in grain refinement. In sulfate-b2sed zinc-obbalt allcy electroly~es, the preferred ooncentration range of the additive agent ranges fram about 0.05 to about 5 g/l providing a grain refined, ductile and adherent electrodeposit. An all chloride system for alloy plating, on the otherhand, would require a preferred concentration of O.l-lOg/l for all alloy versions to be produoed.
~314~12 The additive agent can be employed by itself in co~bination with the metal ions in the electrolyte to produ oe a semi-bright electrDdeposit typical of a functional plating. When a deoorative electrodeposit is desired having enhanced brightness, supplemental brightening agents of the types known in the art can be LnoDrporated in the electrolyte in the usual amounts. Typical of supplemental brighteners that can be employed to further enhanoe the cxystal structure and brightness of the zinc alloy electrodeposit are those disclosed in United States Patents Nb. 4,170,526; 4,207,150; 4,176,017;
4,070,256 and 4,252,619. hhen ~mployed, such supplemental brightening agents can be used at concentrations up to about 10 g/l with concentrations as low as about 0.001 g/l beLng effective. Typically, the oon oe ntration of the supplemental brightening agents range from about 0.01 up to about 5 g/l.
In addition to the ~oregoing essential and optional constituents, the electrolyte Q n further include supplemental ad~itives such as buffers and bath nLdifiers such as boric acid, aoe tic acid, citric acid, ken~oic acid, salicylic acid, as well as their bath soluble and compatible salts, ammDnium chloride and the like. Cther bath soluble and conpatible salts such as ammDnium sulfate, ammonium chloride or bramide, sodium chloride, potassium chloride, ammonium fluoroborate, magnesium sulfate, s~dium sulfate, and combinations ~hereof and the lihe can also ~e employed in amcunts usually rangir,g frcm about 20 up to about 450 g/l t~ increase the electrical con & ctivity of the electrolyte. Typically, such cDnductivity salts comprise alkali metal salts such as chlorides, sulfates, sulfamates and fluoroborates~ Aaso, bath ~cdifiers such as bath soluble and compatible polyhydroxy compounds oDntainLng at least th~ee hydroxyl gro~ps and at least four carbon atoms of the class described in United States Patent No. 4,515,663, can be used in amounts of about 3 up to about 30 g/l to inhibit insoluble polyborate compound formation during operation of the bath.
In accordance wit~ the process aspects of the present invention, the zinc alloy electrolyte is e~ployed to electrodeposit a desired zinc alloy on a conductive substrate employing electrolyte temperatures ranging from about room te~perature (60F) up to about 180F and more typically, from ab~ut 70 to about 140F. me electrodeposition of the zinc allcy can be carried out at current densities ranging from as low as about 1 up to about 2000 ASF or higher.
For decorative chloride-type electrolytes, current densities of from about 1 to about 80 ASF are generally preferred, whereas for functional sulfate-type or chloride-type electrolytes, current densities of from about 20 to about 2000 ASF can be employed. During the elec~rodeposition process, the bath or electrolyte is preferably agitated mechanically or by solution circulation or part ncvewent.
~hile air agitation can be employed, the use of air agitation wqth electrolytes containing iron ions is less desirable due to the tendency to increase the fornE~tion of ferric ions in the bath.
In order to further illustrate the electrolyte composition and process of the present invention, the following examples are provided.
It will be understood that the examples are provided for illustrative purposes and are not intended to be limiting of the scope of the present invention as herein described and as set forth in the subjoined claims.
For oomparative purposes, an aqueous acidic sulfate-type zinc ir~n allcy electrolyte was prepared for functional electrodeposits 13~4~12 containing 110 g/l zinc sulfate nohydrate and 370 g/l ferrous sulfate heptahydrate. me pH of the electrolyte was about 2.
The electrolyte was employed for electrDdepositing a zinc-iron deposit on a steel rod cathode rotating at a speed of 3,055 rpm to provide a surface velocity of about 200 feet per mLnute. me electrolyte was controlled at a temperature of 50C (122 F) and soluble zinc a~odes were e~ployed. me electrodeposition was carried out at an average cathode current density of about 500 ASF. The resultant zinc-ir~n alloy deposit was abserved to be of a gray and grainy appearan oe which upon analysis oontained 13.8 % hy weight ir~n.
T~ the electrolyte as described in Example 1, 0.01 g/l of an additive agent comprising ethoxylated sorbitol of an average mDlecular weight of 1400 was added. A rotating steel cathcde was again plated under the same conditions as described in Exa~ple 1. me resultant zinc-iron alloy deposit was of a silvery-blue and semi-bright appearanoe which upon analysis was found to ODntain 13.2 % by weight iron.
EX~MELE 3 To the electrolyte as described in Example 1, 0.05 g/l of an additive agent was added comprising propoxylated sorbitol of an average molecular weight of 500. A rotating steel cathode was again electroplated under the same oonditions as described in Example 1. The resul~ant zinc-irDn alloy deposit was of a blue-gray and semi-bright appearan oe which up~n analysis was ~ound to oontain 18.6~ by weight iron.
EX~MPLE 4 Tb the electrolyte as described in Example 1, 0.01 g~l of an additive agent was added oomprisLng ethDxylated methyl gluoose 1~31~12 ~ethQxylated with 10 moles of ethylene oxide). A rotating steel cathode was electroplated under the same conditions as described in Ex~l~le 1.
The resultant zinc-iron alloy deposit was of a satiny-gray and semi-bright appearanoe which upon analysis was found to oontain 15.5% by weiqht iron.
EX~MPLE 5 To the electrolyte as described in Example 1, 0.01 g~l of an additive agent was added oomprising a propoxylated methyl glucose (propoxylated with 10 moles of propylene oxide). A rotating steel cathode was electrqplated under the same oonditions as described in Example 1. The resultant zinc-iron alloy deposit was of a satiny-qray appearan oe and up~n analysis oontained 17.1% by weight iron.
For ccmparative purposes, an agueous ~cid zinc-nickel all~y electrolyte of the sulfate-type was prepared for functional plating.
m e electrolyte oontained 310 g/l nickel sulfate hexahydrate, 205 g/l zinc-sulfate monohydrate and 36 g~l sulfuric acid. The electrolyte was adjusted to a temperature ranging from 60 to 65 C (140 to 150 F) and a rotating steel cathode was plated at an average cathode current density of 1,000 ASF employing insoluble lead anodes. Solution agitation was provided by rDtating the cathode. The cathDde was rotated at a speed of 4,600 rp~ providing a surfaoe velocity of 325 feet per minute. The nesultant deposit was of a light gray color, grainy appearan oe and evidenced poor adhesion in response to being bent through an angularity of greater than 90 as viewed under a 14X magnification.
ffle thickness of the zinc-nickel alloy deposit was approximately 0.25 to about 0.3 mil. Upon analysis, the alloy contained 13.5~ by weight nickel.
1314~1~
Tb the electrolyte as described in Example 6, 0.04 g/l of an additive agent was added oomprising an ethoxylated sorbitol of an a~erage molecular weight of 475. ~ rotating steel cathode W3S
electroplated under the same oonditions as described in Example 6. The resultant zinc-nickel alloy was of a fine-grained, semi-bright appearan oe and was adherent as evidenced by being substantially crack-free when bent through an angularity ~raater than 90 and viewed under 14X magnification. Upon analysis, the alloy contained 7% by weight nickel. ~pon atmospheric corrosion testing, this type of electrodeposit exhibits a 15%-20% improvement in oorrosion protection 3S
cc~par~d to the electrodeposit of Example 6, even though the nickel content is lower.
EX~MPLE 8 Tb the electrolyte as described in Example 6, 0.015 gtl of an additive agent was added co~prising ethoxylated and propoxylated so~bitol of an average m~lecular weight of 7,200. A rotating steel cathode was electr~plated under the same oonditions as described in Example 6. T~e zinc-nickel alloy deposit was of a fine-graLned, semi-bright appearan oe and was adherent as evi~enoed by a substantially -~` crack-free deposit when bent through an angularity greater than 90 and vie~ed under 14X nagnification. Upon analysis, the zinc-nichel alloy contained 9.6% by weight nickel.
` EX~T~ g Tb the electrolyte as described in Example 6, 0.02 q/l of an ~.
;~ additive agent was added comprising an ethoxylated m~ethyl gluoose -~b~ (ethDxylated with 10 mDles of ethylene oxide). A rotating steel cathode ~ was electroplated under the same osnditions as described in Exanple 6.
;: The result~nt zinc-nickel alloy deposit was of a fine-grained apQearanoe :
~f~ 2 and was adherent as evidenced by being suhstantially crack-free when bent through an angularity of grea~r than 90 and viewed under 14X
magnification. Upon analysis, the alloy contained 6.7% by weight nickel.
EX~MPLE 10 For oomparative purposes, an alternative aqueous acidic zinc-nickel electrolyte of the sulfate-type was prepared for functional plating. The electrolyte aontained 110 g/l nickel sulfate hexahydrate, 260 g/l zinc sulfate monohydrate and 36 g/l sulfuric acid.
A rotating steel rod cathndb was plated Ln the electrolyte at an average cathode current density of 1,000 ASF with an electrolyte temperature controlled within a range of 50 to 55 C (120-130 F).
Insoluble lead anodes were employed. Solution agitation was provided by rotating the steel rod cathode at a speed of 4,600 rpm to pm vide a Æ fa oe velocity of 325 feet per minute. The resultant zinc-nickel alloy deposit was of a light gray appearanoe r grainy and cracked when bent through an angularity of n~re than 90 as viewed under 14X
magnification. The electrodeposit was approximately 0.25 to 0.3 mils thick. Upon analysis, th~ nickel content was 6.7% by weight of the the alloy.
This example shcws that a reduction of the nickel oontent in the eJectrolyte and in the resultant deposit in comparison to that employed in prior E~ample 6 to a magnitude as obtained in supplemental E~amples 7 through 9, still did not produce a satisfactory zinc-nickel alloy electrodeposit in the absen oe of the additive agent.
EW~PIE 11 For ocmparative purposes, an aqueous acidic sulfate-type zinc-cobalt alloy electrolyte adapted for functional electrcplating 1~14~1~
was prepared ODntaining 60 g/l cc~alt sulfate heptahydrate, 450 g/l zinc sulfate mDnohydrate and 36 g/l sulfuric acid.
A rotating steel rod cathode was electroplated in the electr~lyte at an average cathode current density of 1,000 ASF with the el~ctrolyte controlled at a temperature ranging from 40 to 45 C
(104-112 F) and employing insoluble lead anodes. Agitation of the electrolyte was provided by rotating the cathode. Ihe rotation of the cathode was at 4,600 rpm providing a surfaoe velocity of 325 feet per minute. Upon inspection, the resultant zinc-cbbalt alloy electrodeposit was of a light-gray, coarse-grained, dull appearan oe. Upon analysis, the ocbalt oontent in the alloy deposit was 0.17% by weight.
EX~MPLE 12 Tb the electrolyte as described in EXample 11, 4 g/l of an additive agent was added co~prising ethoxylabed, propoxylated so~bitol of an average molecular weight of 6475. A rotating steel cathode was electrcplated under the same conditions as described in Ex~lyle 11 and the resultant zinc-cDbalt alloy deposit was of a semi-brigh~, ~beel-gray appearan oe . Upon analysis, the alloy deposit oontained 0.26 ~ by weight cobalt.
EX~MPLE 13 Ib ~he electroly~e as describ~d in E~ample 11, an additive agent was added at al con oentration of 0.5 g/l oo~prising a propoxylated methyl oe llulose (propoxylated with 10 mDles propylene oxide). A
r~tating s~eel cathode was electrcplated under the same conditions as described in Example 11 and the resultant zinc-cobal~ alloy depDsit was of a s3mi-bright and gray ool~r appearance. Upon analysis, the oobalt content was 0.29% by weight.
1314~12 T~ the electrolyte as described in Example 11, 0.2 g/l of an ethoxylated methyl glucose additive agent was added (ethyoxyla~ed with 20 moles of ethylene oxide). A rotating steel cathode was electroplated under the same oonditions as descriked in Example 11 and the resultant zinc-oobalt alloy deposit was of a semi-bright gray appearance. Upon analysis, the alloy deposit contained 0.22% by weight cbbalt.
For comparative purposes, an aqueous acidic electrolyte of the sulfate-type suitable for electrodepositing a zinc-iron-nickel-oobalt alloy was prepared containing 100 g/l zLnc sulfate monohydrate, 100 g/l ferrous sulfate heptahydrate, 50 g/l nickel sulfate hexahydrate and 50 g/l cbbalt sulfate heptahydrate. me pH of the electrolyte was about 4.5.
A rotating steel cathode was electroplated empl~ying the foreg~ing electrolyte at an average current density of 1,000 ASF with the electrol~te controlled at a tRmperature between about 50 to about 55 C (122-130 F) employing insoluble le3d ancdesO The cathode was rotated at a speed to provide a surfaoe velocity of 300 feet per minute.
The electrodeposition cDntinued until the deposit averaged about 6 micrometers (0.24 milsJ in thickness. Upon inspection, the electnodeposit was of a satiny-gray appearanoe with dentrites. Upon analysis, the alloy composition oontained 74~3% zincl 14.3~ iron, 6.4%
cobalt and 5% ~y weight nickel.
EX~MPLE 16 To the electrolyte as described Ln Example 15, OoOl g/l Of an additive agent was added oo~prising ethoxylated sorbitol of an average molecular weight of 1,400. A rotatiny steel cathodb was electroplated 131~12 e~>lo~ing tl~ same conditions as described in EscaTrple 15 and the resulting deposit evidenced an inpr~v~nt in grain refir~nt and slroot~ess of ~he deposit. Ilpon analysis, the alloy electrodeposit contained 72.1% zinc, 15.6% iron, 7.6~ ccbalt and 4.7~ by weight nickel.
EXAM~E 17 An aqueous acidic z~r~nickel alloy electrolyte of ~e chloride-type adapted for electrodepositing deoorative zinc-nickel electr~deposits was prepared containing 90 g/1 zinc chloride, 115 g/l nickel chloride hexa~drater 220 g/l amnonium chloride and 4 g~l of an additive agent c~nprising ethyoxylated gly~rine (et~cylated with 12 n~les ethylene oxide~. me electrolyte furt~x oontained as a secon~ary bxightening agent 0.050 g/l benzylidene acetone. qhe electrolyte was of a pH of about 5.6.
A steel test panel was plated at an average cath~e current density ranging frarn 10 to about 20 A ~ with the electrolyte controlled at a temperature of from about 30 to about 35 C (86-95 F). Ihe resultant zLnc-nickel allcy deposit was fully bright, deoorative and of unifonm appearanoe. Upon analysis, the alloy deposit contained 11.6% ky weight nickel.
EXWMæLE 18 An aqueous acidic zinc-obbalt-nickel electrolyte was prepared suitable for electrodepositing a deoorative alloy deposit of the chloride-type containing 90 g/l zinc chloride, 40 g/l oobalt chloride hexahydrate, 120 g/l nickel chloride hexahydrate, 200 g/l ammonium chloride, 3 g/l of an additive agent oomprising ethoxylabed glycerine (ethoxylated with 12 mDles ethylene oKide) and 2 g~l of sodium benzoate.
The electrolyte ~as contrDlled at a pH of about 5 and a temperature of about 20 to about 25 C (68-76F) was employed for electroplating a steel test panel at an average cathode current density ranging from 10 to about 20 ASF. The resultant electrodeposit was of a uniform, silvery semi-bright appearan oe which was commercially acoeptable. Upon analysis, the alloy deposit contaLned 12% by weight nickel, 6~ by weight cobalt and the balanoe zinc.
E~LE 1~
TD the electrolyte as described in Example 18, a supplemental brightener mixture was added oomprising 0.06 g/l of 4-phenyl-3-buten-2_one, 0.02 g/l of butyl nioot~nate dimethyl sulfate quaternary and 0.05 g/l of 4-phenyl-4-sulfobutan-2~one, scdium salt.
A steel test panel was electroplated employing zinc anodes Ln accordance with the prooedure as set forth in Example 18. The resultant alloy deposit was very decorative and fully bright in appearance. Upon analysis, the alloy deposit contained 11.9% by ~eight nickel, 6.5% ~y weight cobalt with the balance oomprising zinc.
EX~MELE 20 Fbr comparative purposes, an aqueous acidic zinc-cotalt electrolyte was prepared of the chloride-type suitable for electrodepositLng a decorative zLnc-obbalt deposit containiny 46 g/l zinc chloride, 10.5 g/l ocbalt chloride hexahydrate, 175 gJl sodium chloride, 20 g/l ~oric acid and 2 g/l sodium benzoate. me pH of the electrolyte was a~cut 5.2. Standard Hull oe ll panels were plated with the electrolyte at zbout 75 F at a current of 1 ampere for a period of 10 minutes in th2 absence of agitation. The resultant test panel was of a dull-black to gray-black grainy appearanoe. The average alloy content of the ,adherent electrodeposit in the current density range of 0-40 ASF
was 5.03% by weight oobalt and the balan oe zinc.
~31~12 EX~MæLE 21 T~ the electrolyte as ~escribed in Example 20, 3 g/l of an additive agent was added oo~prising ethoxylated gly oe rine (ethDxylated with 12 mDles of ethylene oxide). ~ Hull test panel was again plated u~der the same oonditions as described in Example 20 and the resultant electrodeposit was of a uniform, silver-white, semi-bright appearance in the current density range of from 2 to 60 ASF. m e average alloy content was 1.03% by weight cobalt and the balan oe zinc. fflis amount of alloy oontent in the electrodeposit has been shown to increase oorrosion resistan oe by 2 to 3 times over an ordinary zinc electrodeposit and is oommercially acoeptable.
EX~MPLE 22 .
T~ the electrolyte as described in Example 20, 4 g~l of an additive agent was added comprising ethoxylated gly oerine (ethoxylated with 26 moles of ethylene oxide). A Hull test panel was again plated un~er the sam,e oonditions as described in Example 20 and ~he resultant electrodbposit W3S of a uniform, silver-white, semi-bright appearan oe in the current deT~ity range between 2 to 60 ASF. me average 3110y oontent was 1.59% by weight oobalt and the ~alanoe zinc.
EX:MELE 23 For oomparative purpo æs, an aqueous acidic electrolyte of the chloride-type was prepared suitable for eleitrDdepositing a zinc-oobalt alloy oontaimng 46 g/l zinc chloride, 10.5 g/l oobalt chloride hexahydrate, 220 g~l potassium chloride, 20 g/l ~oric acid, and 3.5 g/l sDdium ~enzoate. m e pH of the electrolyte was oontrolled at about 5 and a temperature at 25 C ~77 F).
A test panel was plated in a standbrd Hhll oe ll at a current of 1 anFere for a period of 10 Tmnutes e~pl~ying a zinc anode in the absence of agitation. The resultant electrodeposit was dull-black to 131~2 gray-black and of a graLny appearan oe. The average alloy composition was l.~X by weight oobalt in the 0-20 ASF current density range and a~cut 5'7% by weight oobalt in the test panel area above 20 ASF current density.
Tb the electrolyte as described in Example 23, 4 g/l of an additive agent was ad~ed oomprising etho~ylated (15 moles) trimethylol propane. A Hull oe ll test panel was again plated under the same oonditions as described in Example 23 and the electrodeposit was uniform and of a silver-whi~e, semi-bright appearanoe across the entire surfaoe of the test panel. The average alloy composition was 1.15~ by weight cbbalt in the 0-20 ASF current density range and 6.82% by weight oobalt in the cathode current density range above 20 ASF.
EX~MPLE 25 T~ the electr~lyte as described in Example 24, 0.06 g/l was added of 4-phenyl-4-sulfobutan-2-one, sodium salt; 0.075 g/l ben2ylidene a oe tone and 0.003 g/l butyl niootinate diethyl sulfate quaternary. A
Hhll test panel was agaLn plated under the same oonditions as described in Exa~ple 23 and the electrodeposit was fully bright, unifon~ and of a decorative quality across the entire surfaoe of the test panel. me oobalt alloy distribution was l~ by weight cobalt in the 0-20 ASF
current density range and 2.1% by weight obbalt in the cathQde current density range above 20 ASF.
While it will be apparent that the preferred enicdments of the invention disclosed are well calculated to fulfill the objects abcve stated, it will be appreciated that the invention is susceptible to mDdification, variation and change without deFarting from the proFer scope or fair meaning of the subjoined claLms.
~INC ALLOY ELECTROLYTES
Background of the Invention The present invention broadly relates to an improved electr~lyte and process for electrodepositing zinc alloys, and re particularly, to an improved aqueous acid zinc alloy electrolyte containing novel additive agents for providing improved grain-refinement, reduced dendrite formation, increased adhesion and ductility and an unexpected adjus~ent in the oodeposition of one or m~re alloying metals in the zinc alloy deposit.
Electrolytes inoorporating zinc ions in ~urther combination with one or a co~bination of nickel, cbbalt, iron or mixtures thereof have heretofore been used or proposed for use for depositing zinc alloy deposits of a decorative or functional type on a variety of oonductive substrates such as iron and sbeel, for example, to prw ide for improved oorrosion resistanoe , enhan oe appearan oe and/or bD build up the surfa oe of a wDrn p~rt enabling refinishing thereDf bo restore its original ~perating dimensions. Such zinc allo~y electrDlybes and processes are in widbspread oommercial use for industrial or functional plating including strip plating, oonduit plating, wire plating, rod plating, tube plating, oDupling plating, and the like. A ODntinUing problem associated with such p~ivr art zinc alloy electrolytes has been the Lnability to achieve the desixed grain-refinement of the alloy electrDdeposit to pro~ide the requisite semi-bright appearanoe and associated physical properties including adhesion and ductility. A further prablem has been the inability to incre~se ~he percentage of the alloying metal oonstituent such as nickel, o~balt and/or iron in the zinc alloy electrodeposit in 13145~2 order to achieve a desired physical and chemucal properties. me formation of dendrites on the substrate being plated at high current density areas has also been objectionable.
The present invention provides for an Lmproved electrolyte for electrodepositing zinc alloys incorporating an additive agent or mixture of additive agents which provides for improved grain-refinement, a reduction in dendrite formation, increase in adhesion and ductility while further adjusting the ~odeposition of the alloying metal ions achieving a zinc alloy electrodeposit of improved properties.
Summary of the Invention The benefits and advantages of the present invention in accordan oe with the ccmposition aspects thereof are achieved by an aqueous acidic zinc alloy electrolyte containing zinc ions in conventional amDunts in further cc~bination with controlled amounts of at least one additional alloying metal ion selec~ed from a group oonsisting of nickel, cobalt, iron and mixtures thereof. me electrolyte further contains as an essential constituent, an additive agent present in an amount effective to achi~ve improved physical characteristics of the zinc alloy deposit oomprising a bath soluble polyhydroxy oompound having three or mDre hy~roxyl groups of which at least one is substituted with a polyoxyalkylene group as well as mQxtures thereof. The ooncentration of the poly~xyalkylene-substituted polyhydr3xy additive agent is present in an amount effective to impart L~proved grain-refinement to the electrodeposit and the specific aoncentration will vary depending upon whether ~he electnvlyte is of the chloride, sulfate, fluoborate, sulfamate or mixed-chloride type.
In addition to the foregoing constituents, the zinc alloy electrolyte may additionally contain various other additive agents of the types conventionally employed including buffering agents, supplemental brightening agents, bath soluble and ccmpatible conductivity salts to increase the electrical oDnductivity of the electrolyte and the like.
In accordanoe with the pro oe ss aspects of the present inventian, a zinc alloy ooating is electrodeposited on a conductive substrate employing the aforementioned aqueous acidic zinc alloy electrolyte which is controlled at a temperature typically ranging from about room temperature (60F) up to about 180F and is qperated at an average cathode current density ranging from as low as about 1 up to as high as albout 2000 a~peres per square foot ~ASY) or higher which will vary depending upon the specific type and conposition of the electrolyte as well as the geometry and processing parameters e~ployed in the plating operation.
Furthex benefits and advantages of the present invention will beccme apparent upon a rea~ing of the Description of the Preferred Embodiments taken in conjunction with the specific examples pro~ided.
Description of the r f rr d e bcdiments The aqueou~ acidic zinc alloy electrolyte in acoordanoe with the composition aspects of the present invention oontains zinc ions present in an a~Dunt effective to electrodeposit zinc from the electrolyte and generally can range from as low as about 10 gJl up to saturation, Wlth oonoentrations of from about 15 bo about 225 g/l being mDre usual. Preferably, for mDst applications, the zinc ion con oe ntration is o~ntrolled within a range of about 20 to a~out 200 g/l.
~3~4512 1~e maximum conoentration of zinc ions will vary depend mg upon the temperature of the electrolyte with higher temperatures enabling use of higher oonoe ntrations. ~e zinc ion oOnoentratiQn will also vary depending upon the type of electrolyte employed which nay be of the chloride, sulfate, nuxed chloride-sulfate, sulfamate, as well as the fluoroborate types. In acid chloride-type electrolytes, the zinc ion concentration is generally controlled at 3 level within the lawer end of the permissible range whereas in acid sulfate-type electrolytes, the zinc ion conoe ntration is generally contrDlled at a level within the upper range of the permiss~ble conoe ntrations.
The zinc ions are intrcdu~ed into the electrolyte in the form of zinc anodes or soluble zinc salts such as a chloride, sulfate, sulfamate and/or fluoroborate salt in further oombination with an acid such as sulfuric acid, hydrochloric acid, fluorbboric acid, sulfamic acid, or the like oDrresponding to the type of zinc salt emplcyed.
Gbnerally the pH of the zinc alloy electrolyte is controlled within a range of about O up to about 7 with a pH of fram about 2 to about 6 ~eing preferred.
In addition to the zinc ions, the electrolyte further oontains oontrolled amounts of at least one of the all~ying metal ions including nickel, ccbalt, and/or iron which similarly are introduced in the fonm of soluble anodes or bath soluble salts of the alloying metal including the chloride, sulfate, fluoraborate, acetate, or sulfamate as well as mixtures thereof. When nickel and/or ccbalt are emplçyed as the alloying metal, each can be employed in the bath in amounts of fram about 0.5 g/l up to about 120 g/l to provid~ alloy deposits contaLning fro~ abcut 0.1 up to about 30 percent by weight of nickel and/or cobalt.
Preferably, the alloy deposit cDntains rom about 0.25 percent tv a ~3~ 2 total of about 15 percent of both nickel and/or cobalt, and the bath under such conditions contains nickel and/or obbalt ions in an amLunt usually ranging from about 3 g/l to about 65 g/l, respectively.
When iron oomprises an alloying metal in the electrolyte, the operating iron ion ooncentration can range of frcm about 5 g/l up to about 140 g/l wqth concentrations of from about 40 g/l up to about lO0 g/l being preferred.
When iron ions are present in the electr~lyte which is only weakly acidic or either neutral, such as at a pH of from about 4 to about 6.5, it is generally preferred to incorporate conventional oomplexing or chelating agents to maintain an effective a~ount of the iron metal ions in solution. Chelating or oomplexing agents which are particularly satisfactory for this purpose include citric acid, gluoonic acid, glucoheptanoic acid, tartaric acid, ascorbic acid, issasoorbic acid, malic acid, glutaric acid, muconic acid, glutamic acid, glycollic acid, aspartic acid, and the like as well as t~eir alkaline ~etal, ammDnium, zinc or ferrous salts.
While the iron ions are introduced into the electrolyte in the ferrous state, ferric ions are formed during the plating cperation and it has been ~ow ~ th3t ex oe ssive amounts of ferric ions are objeckionable resulting in the form~tion of striations on the zinc alloy plated surfa oe . AccordLngly, it has been fo~nd desirable to oontrDl the ferric ion ooncentration at a level usually less than abcut 2 g/l. This can be accomplished by employing a soluble zinc or iron anode in the electroplating bath or, alternatively, by immersing metallic zinc or iron Ln the holdLng tank through which the electroplating solution is circulated. When no soluble ano~es are empl~yed or no zLnc or iron metal is provided Ln the holding tank, proper oDntrol of the f rric ion 131~512 o~ncentration can ke achieved by employing suitable bath soluble and compatible organic and~or inorganic reducing agents such as, for example, bisulfite, isoascorbic acid, nDnosaccharides and disaccharides such as glucose or lactose.
It will be appreciated from the foregoing, that electrolytes can be for~ulated to provide for appropriate binary, ternary or quaternary alloys containing predomlnately zinc and at least one of the other three alloying metal o~nstituents.
When ternary alloy deposits are desired çontaining zinc-nickel-ir~n or zinc-cbbalt-iron, the ooncentration of the metal ions in the electrolyte are usually contrDlled so as to provide an alloy oontaining from about 1 percent to about 25 peroent ir~n in co~bination with either about 0.1 to about 20 percent by weight nickel or about 0.1 to about 12 percent cobalt and the balanoe essentially zinc.
In addition to the metal ions present in the electrolyte, the electrolyte further contains as an essential ingredient an additive agent comprising a bath soluble polyhydroxy oompound having three or more hydroxyl groups at least one of which is substituted with a~poly-oxyalkylene group. Typically, polyhydroxy compcunds such as sorbitol and methyl glucose having one or mDre of their hydraxyl groups substituted with oxyethylene or oxypropylene chains and nuxtures thereof have been found particulary satisfactory for use in such zinc-alloy electrolytes.
The molecular weight of the additive agent or mixtu}es thereof is oontr~lled to render the additive agent soluble in the el0ctrol~te at the oan3entration desired. It will be appreciated that the additi~
agent may oontain one polyoxyalkylene substitute group on ~he mDlecule or nay contain tWG, three or more substitute groups depending upon the 131~12 degree of substitution and the number of reactive hydroxyl groups on the mDlecule.
The conoe ntration of the additive agent in the electrolyte will vary depending upon the conoentration and types of other bath constituents present, the desired alloy deposit ccmposition, and whether the electrodeposit is to be empJoyed for functional or decorative purposes. Generally speakin~, the additive agent is employed in an amDunt effective to produ oe a refLnement of the grain of the electrodeposit, to reduce the tendency to form dendrites during the electrodeposition process, to enhance the adhesion and &ctility of the deposit to the substrate, and to adjust the codeposition of the alloying metal ions in the zinc alloy deposit and to regulate the alloy content at a more uniform, desired level. For this purpose, concentrations as low as about 0.005 up to about 20 ~/1 have been found usable while con oentrations of from about 0.02 up to akout 10 g/l are more typical and p~eferred for most uses.
In accordan oe with a preferred practi oe of the present invention, the additive agent is e~ployed in sulfate-based zinc-iron electrolytes in a ooncentration range of abcut 0.005 to about 0.1 g/l providing both an increase Ln the oodeposition of iron in the zinc-iron deposit and a gra~l refinement thereof. In sulfate-based zinc-nickel allo~ electrolytes, a oonoentration range of abDut O.005 to about 0.1 g/l is also ~referred providing improved ductility and adhesion of the deposit accompanied by a slight improvement in grain refinement. In sulfate-b2sed zinc-obbalt allcy electroly~es, the preferred ooncentration range of the additive agent ranges fram about 0.05 to about 5 g/l providing a grain refined, ductile and adherent electrodeposit. An all chloride system for alloy plating, on the otherhand, would require a preferred concentration of O.l-lOg/l for all alloy versions to be produoed.
~314~12 The additive agent can be employed by itself in co~bination with the metal ions in the electrolyte to produ oe a semi-bright electrDdeposit typical of a functional plating. When a deoorative electrodeposit is desired having enhanced brightness, supplemental brightening agents of the types known in the art can be LnoDrporated in the electrolyte in the usual amounts. Typical of supplemental brighteners that can be employed to further enhanoe the cxystal structure and brightness of the zinc alloy electrodeposit are those disclosed in United States Patents Nb. 4,170,526; 4,207,150; 4,176,017;
4,070,256 and 4,252,619. hhen ~mployed, such supplemental brightening agents can be used at concentrations up to about 10 g/l with concentrations as low as about 0.001 g/l beLng effective. Typically, the oon oe ntration of the supplemental brightening agents range from about 0.01 up to about 5 g/l.
In addition to the ~oregoing essential and optional constituents, the electrolyte Q n further include supplemental ad~itives such as buffers and bath nLdifiers such as boric acid, aoe tic acid, citric acid, ken~oic acid, salicylic acid, as well as their bath soluble and compatible salts, ammDnium chloride and the like. Cther bath soluble and conpatible salts such as ammDnium sulfate, ammonium chloride or bramide, sodium chloride, potassium chloride, ammonium fluoroborate, magnesium sulfate, s~dium sulfate, and combinations ~hereof and the lihe can also ~e employed in amcunts usually rangir,g frcm about 20 up to about 450 g/l t~ increase the electrical con & ctivity of the electrolyte. Typically, such cDnductivity salts comprise alkali metal salts such as chlorides, sulfates, sulfamates and fluoroborates~ Aaso, bath ~cdifiers such as bath soluble and compatible polyhydroxy compounds oDntainLng at least th~ee hydroxyl gro~ps and at least four carbon atoms of the class described in United States Patent No. 4,515,663, can be used in amounts of about 3 up to about 30 g/l to inhibit insoluble polyborate compound formation during operation of the bath.
In accordance wit~ the process aspects of the present invention, the zinc alloy electrolyte is e~ployed to electrodeposit a desired zinc alloy on a conductive substrate employing electrolyte temperatures ranging from about room te~perature (60F) up to about 180F and more typically, from ab~ut 70 to about 140F. me electrodeposition of the zinc allcy can be carried out at current densities ranging from as low as about 1 up to about 2000 ASF or higher.
For decorative chloride-type electrolytes, current densities of from about 1 to about 80 ASF are generally preferred, whereas for functional sulfate-type or chloride-type electrolytes, current densities of from about 20 to about 2000 ASF can be employed. During the elec~rodeposition process, the bath or electrolyte is preferably agitated mechanically or by solution circulation or part ncvewent.
~hile air agitation can be employed, the use of air agitation wqth electrolytes containing iron ions is less desirable due to the tendency to increase the fornE~tion of ferric ions in the bath.
In order to further illustrate the electrolyte composition and process of the present invention, the following examples are provided.
It will be understood that the examples are provided for illustrative purposes and are not intended to be limiting of the scope of the present invention as herein described and as set forth in the subjoined claims.
For oomparative purposes, an aqueous acidic sulfate-type zinc ir~n allcy electrolyte was prepared for functional electrodeposits 13~4~12 containing 110 g/l zinc sulfate nohydrate and 370 g/l ferrous sulfate heptahydrate. me pH of the electrolyte was about 2.
The electrolyte was employed for electrDdepositing a zinc-iron deposit on a steel rod cathode rotating at a speed of 3,055 rpm to provide a surface velocity of about 200 feet per mLnute. me electrolyte was controlled at a temperature of 50C (122 F) and soluble zinc a~odes were e~ployed. me electrodeposition was carried out at an average cathode current density of about 500 ASF. The resultant zinc-ir~n alloy deposit was abserved to be of a gray and grainy appearan oe which upon analysis oontained 13.8 % hy weight ir~n.
T~ the electrolyte as described in Example 1, 0.01 g/l of an additive agent comprising ethoxylated sorbitol of an average mDlecular weight of 1400 was added. A rotating steel cathcde was again plated under the same conditions as described in Exa~ple 1. me resultant zinc-iron alloy deposit was of a silvery-blue and semi-bright appearanoe which upon analysis was found to ODntain 13.2 % by weight iron.
EX~MELE 3 To the electrolyte as described in Example 1, 0.05 g/l of an additive agent was added comprising propoxylated sorbitol of an average molecular weight of 500. A rotating steel cathode was again electroplated under the same oonditions as described in Example 1. The resul~ant zinc-irDn alloy deposit was of a blue-gray and semi-bright appearan oe which up~n analysis was ~ound to oontain 18.6~ by weight iron.
EX~MPLE 4 Tb the electrolyte as described in Example 1, 0.01 g~l of an additive agent was added oomprisLng ethDxylated methyl gluoose 1~31~12 ~ethQxylated with 10 moles of ethylene oxide). A rotating steel cathode was electroplated under the same conditions as described in Ex~l~le 1.
The resultant zinc-iron alloy deposit was of a satiny-gray and semi-bright appearanoe which upon analysis was found to oontain 15.5% by weiqht iron.
EX~MPLE 5 To the electrolyte as described in Example 1, 0.01 g~l of an additive agent was added oomprising a propoxylated methyl glucose (propoxylated with 10 moles of propylene oxide). A rotating steel cathode was electrqplated under the same oonditions as described in Example 1. The resultant zinc-iron alloy deposit was of a satiny-qray appearan oe and up~n analysis oontained 17.1% by weight iron.
For ccmparative purposes, an agueous ~cid zinc-nickel all~y electrolyte of the sulfate-type was prepared for functional plating.
m e electrolyte oontained 310 g/l nickel sulfate hexahydrate, 205 g/l zinc-sulfate monohydrate and 36 g~l sulfuric acid. The electrolyte was adjusted to a temperature ranging from 60 to 65 C (140 to 150 F) and a rotating steel cathode was plated at an average cathode current density of 1,000 ASF employing insoluble lead anodes. Solution agitation was provided by rDtating the cathode. The cathDde was rotated at a speed of 4,600 rp~ providing a surfaoe velocity of 325 feet per minute. The nesultant deposit was of a light gray color, grainy appearan oe and evidenced poor adhesion in response to being bent through an angularity of greater than 90 as viewed under a 14X magnification.
ffle thickness of the zinc-nickel alloy deposit was approximately 0.25 to about 0.3 mil. Upon analysis, the alloy contained 13.5~ by weight nickel.
1314~1~
Tb the electrolyte as described in Example 6, 0.04 g/l of an additive agent was added oomprising an ethoxylated sorbitol of an a~erage molecular weight of 475. ~ rotating steel cathode W3S
electroplated under the same oonditions as described in Example 6. The resultant zinc-nickel alloy was of a fine-grained, semi-bright appearan oe and was adherent as evidenced by being substantially crack-free when bent through an angularity ~raater than 90 and viewed under 14X magnification. Upon analysis, the alloy contained 7% by weight nickel. ~pon atmospheric corrosion testing, this type of electrodeposit exhibits a 15%-20% improvement in oorrosion protection 3S
cc~par~d to the electrodeposit of Example 6, even though the nickel content is lower.
EX~MPLE 8 Tb the electrolyte as described in Example 6, 0.015 gtl of an additive agent was added co~prising ethoxylated and propoxylated so~bitol of an average m~lecular weight of 7,200. A rotating steel cathode was electr~plated under the same oonditions as described in Example 6. T~e zinc-nickel alloy deposit was of a fine-graLned, semi-bright appearan oe and was adherent as evi~enoed by a substantially -~` crack-free deposit when bent through an angularity greater than 90 and vie~ed under 14X nagnification. Upon analysis, the zinc-nichel alloy contained 9.6% by weight nickel.
` EX~T~ g Tb the electrolyte as described in Example 6, 0.02 q/l of an ~.
;~ additive agent was added comprising an ethoxylated m~ethyl gluoose -~b~ (ethDxylated with 10 mDles of ethylene oxide). A rotating steel cathode ~ was electroplated under the same osnditions as described in Exanple 6.
;: The result~nt zinc-nickel alloy deposit was of a fine-grained apQearanoe :
~f~ 2 and was adherent as evidenced by being suhstantially crack-free when bent through an angularity of grea~r than 90 and viewed under 14X
magnification. Upon analysis, the alloy contained 6.7% by weight nickel.
EX~MPLE 10 For oomparative purposes, an alternative aqueous acidic zinc-nickel electrolyte of the sulfate-type was prepared for functional plating. The electrolyte aontained 110 g/l nickel sulfate hexahydrate, 260 g/l zinc sulfate monohydrate and 36 g/l sulfuric acid.
A rotating steel rod cathndb was plated Ln the electrolyte at an average cathode current density of 1,000 ASF with an electrolyte temperature controlled within a range of 50 to 55 C (120-130 F).
Insoluble lead anodes were employed. Solution agitation was provided by rotating the steel rod cathode at a speed of 4,600 rpm to pm vide a Æ fa oe velocity of 325 feet per minute. The resultant zinc-nickel alloy deposit was of a light gray appearanoe r grainy and cracked when bent through an angularity of n~re than 90 as viewed under 14X
magnification. The electrodeposit was approximately 0.25 to 0.3 mils thick. Upon analysis, th~ nickel content was 6.7% by weight of the the alloy.
This example shcws that a reduction of the nickel oontent in the eJectrolyte and in the resultant deposit in comparison to that employed in prior E~ample 6 to a magnitude as obtained in supplemental E~amples 7 through 9, still did not produce a satisfactory zinc-nickel alloy electrodeposit in the absen oe of the additive agent.
EW~PIE 11 For ocmparative purposes, an aqueous acidic sulfate-type zinc-cobalt alloy electrolyte adapted for functional electrcplating 1~14~1~
was prepared ODntaining 60 g/l cc~alt sulfate heptahydrate, 450 g/l zinc sulfate mDnohydrate and 36 g/l sulfuric acid.
A rotating steel rod cathode was electroplated in the electr~lyte at an average cathode current density of 1,000 ASF with the el~ctrolyte controlled at a temperature ranging from 40 to 45 C
(104-112 F) and employing insoluble lead anodes. Agitation of the electrolyte was provided by rotating the cathode. Ihe rotation of the cathode was at 4,600 rpm providing a surfaoe velocity of 325 feet per minute. Upon inspection, the resultant zinc-cbbalt alloy electrodeposit was of a light-gray, coarse-grained, dull appearan oe. Upon analysis, the ocbalt oontent in the alloy deposit was 0.17% by weight.
EX~MPLE 12 Tb the electrolyte as described in EXample 11, 4 g/l of an additive agent was added co~prising ethoxylabed, propoxylated so~bitol of an average molecular weight of 6475. A rotating steel cathode was electrcplated under the same conditions as described in Ex~lyle 11 and the resultant zinc-cDbalt alloy deposit was of a semi-brigh~, ~beel-gray appearan oe . Upon analysis, the alloy deposit oontained 0.26 ~ by weight cobalt.
EX~MPLE 13 Ib ~he electroly~e as describ~d in E~ample 11, an additive agent was added at al con oentration of 0.5 g/l oo~prising a propoxylated methyl oe llulose (propoxylated with 10 mDles propylene oxide). A
r~tating s~eel cathode was electrcplated under the same conditions as described in Example 11 and the resultant zinc-cobal~ alloy depDsit was of a s3mi-bright and gray ool~r appearance. Upon analysis, the oobalt content was 0.29% by weight.
1314~12 T~ the electrolyte as described in Example 11, 0.2 g/l of an ethoxylated methyl glucose additive agent was added (ethyoxyla~ed with 20 moles of ethylene oxide). A rotating steel cathode was electroplated under the same oonditions as descriked in Example 11 and the resultant zinc-oobalt alloy deposit was of a semi-bright gray appearance. Upon analysis, the alloy deposit contained 0.22% by weight cbbalt.
For comparative purposes, an aqueous acidic electrolyte of the sulfate-type suitable for electrodepositing a zinc-iron-nickel-oobalt alloy was prepared containing 100 g/l zLnc sulfate monohydrate, 100 g/l ferrous sulfate heptahydrate, 50 g/l nickel sulfate hexahydrate and 50 g/l cbbalt sulfate heptahydrate. me pH of the electrolyte was about 4.5.
A rotating steel cathode was electroplated empl~ying the foreg~ing electrolyte at an average current density of 1,000 ASF with the electrol~te controlled at a tRmperature between about 50 to about 55 C (122-130 F) employing insoluble le3d ancdesO The cathode was rotated at a speed to provide a surfaoe velocity of 300 feet per minute.
The electrodeposition cDntinued until the deposit averaged about 6 micrometers (0.24 milsJ in thickness. Upon inspection, the electnodeposit was of a satiny-gray appearanoe with dentrites. Upon analysis, the alloy composition oontained 74~3% zincl 14.3~ iron, 6.4%
cobalt and 5% ~y weight nickel.
EX~MPLE 16 To the electrolyte as described Ln Example 15, OoOl g/l Of an additive agent was added oo~prising ethoxylated sorbitol of an average molecular weight of 1,400. A rotatiny steel cathodb was electroplated 131~12 e~>lo~ing tl~ same conditions as described in EscaTrple 15 and the resulting deposit evidenced an inpr~v~nt in grain refir~nt and slroot~ess of ~he deposit. Ilpon analysis, the alloy electrodeposit contained 72.1% zinc, 15.6% iron, 7.6~ ccbalt and 4.7~ by weight nickel.
EXAM~E 17 An aqueous acidic z~r~nickel alloy electrolyte of ~e chloride-type adapted for electrodepositing deoorative zinc-nickel electr~deposits was prepared containing 90 g/1 zinc chloride, 115 g/l nickel chloride hexa~drater 220 g/l amnonium chloride and 4 g~l of an additive agent c~nprising ethyoxylated gly~rine (et~cylated with 12 n~les ethylene oxide~. me electrolyte furt~x oontained as a secon~ary bxightening agent 0.050 g/l benzylidene acetone. qhe electrolyte was of a pH of about 5.6.
A steel test panel was plated at an average cath~e current density ranging frarn 10 to about 20 A ~ with the electrolyte controlled at a temperature of from about 30 to about 35 C (86-95 F). Ihe resultant zLnc-nickel allcy deposit was fully bright, deoorative and of unifonm appearanoe. Upon analysis, the alloy deposit contained 11.6% ky weight nickel.
EXWMæLE 18 An aqueous acidic zinc-obbalt-nickel electrolyte was prepared suitable for electrodepositing a deoorative alloy deposit of the chloride-type containing 90 g/l zinc chloride, 40 g/l oobalt chloride hexahydrate, 120 g/l nickel chloride hexahydrate, 200 g/l ammonium chloride, 3 g/l of an additive agent oomprising ethoxylabed glycerine (ethoxylated with 12 mDles ethylene oKide) and 2 g~l of sodium benzoate.
The electrolyte ~as contrDlled at a pH of about 5 and a temperature of about 20 to about 25 C (68-76F) was employed for electroplating a steel test panel at an average cathode current density ranging from 10 to about 20 ASF. The resultant electrodeposit was of a uniform, silvery semi-bright appearan oe which was commercially acoeptable. Upon analysis, the alloy deposit contaLned 12% by weight nickel, 6~ by weight cobalt and the balanoe zinc.
E~LE 1~
TD the electrolyte as described in Example 18, a supplemental brightener mixture was added oomprising 0.06 g/l of 4-phenyl-3-buten-2_one, 0.02 g/l of butyl nioot~nate dimethyl sulfate quaternary and 0.05 g/l of 4-phenyl-4-sulfobutan-2~one, scdium salt.
A steel test panel was electroplated employing zinc anodes Ln accordance with the prooedure as set forth in Example 18. The resultant alloy deposit was very decorative and fully bright in appearance. Upon analysis, the alloy deposit contained 11.9% by ~eight nickel, 6.5% ~y weight cobalt with the balance oomprising zinc.
EX~MELE 20 Fbr comparative purposes, an aqueous acidic zinc-cotalt electrolyte was prepared of the chloride-type suitable for electrodepositLng a decorative zLnc-obbalt deposit containiny 46 g/l zinc chloride, 10.5 g/l ocbalt chloride hexahydrate, 175 gJl sodium chloride, 20 g/l ~oric acid and 2 g/l sodium benzoate. me pH of the electrolyte was a~cut 5.2. Standard Hull oe ll panels were plated with the electrolyte at zbout 75 F at a current of 1 ampere for a period of 10 minutes in th2 absence of agitation. The resultant test panel was of a dull-black to gray-black grainy appearanoe. The average alloy content of the ,adherent electrodeposit in the current density range of 0-40 ASF
was 5.03% by weight oobalt and the balan oe zinc.
~31~12 EX~MæLE 21 T~ the electrolyte as ~escribed in Example 20, 3 g/l of an additive agent was added oo~prising ethoxylated gly oe rine (ethDxylated with 12 mDles of ethylene oxide). ~ Hull test panel was again plated u~der the same oonditions as described in Example 20 and the resultant electrodeposit was of a uniform, silver-white, semi-bright appearance in the current density range of from 2 to 60 ASF. m e average alloy content was 1.03% by weight cobalt and the balan oe zinc. fflis amount of alloy oontent in the electrodeposit has been shown to increase oorrosion resistan oe by 2 to 3 times over an ordinary zinc electrodeposit and is oommercially acoeptable.
EX~MPLE 22 .
T~ the electrolyte as described in Example 20, 4 g~l of an additive agent was added comprising ethoxylated gly oerine (ethoxylated with 26 moles of ethylene oxide). A Hull test panel was again plated un~er the sam,e oonditions as described in Example 20 and ~he resultant electrodbposit W3S of a uniform, silver-white, semi-bright appearan oe in the current deT~ity range between 2 to 60 ASF. me average 3110y oontent was 1.59% by weight oobalt and the ~alanoe zinc.
EX:MELE 23 For oomparative purpo æs, an aqueous acidic electrolyte of the chloride-type was prepared suitable for eleitrDdepositing a zinc-oobalt alloy oontaimng 46 g/l zinc chloride, 10.5 g/l oobalt chloride hexahydrate, 220 g~l potassium chloride, 20 g/l ~oric acid, and 3.5 g/l sDdium ~enzoate. m e pH of the electrolyte was oontrolled at about 5 and a temperature at 25 C ~77 F).
A test panel was plated in a standbrd Hhll oe ll at a current of 1 anFere for a period of 10 Tmnutes e~pl~ying a zinc anode in the absence of agitation. The resultant electrodeposit was dull-black to 131~2 gray-black and of a graLny appearan oe. The average alloy composition was l.~X by weight oobalt in the 0-20 ASF current density range and a~cut 5'7% by weight oobalt in the test panel area above 20 ASF current density.
Tb the electrolyte as described in Example 23, 4 g/l of an additive agent was ad~ed oomprising etho~ylated (15 moles) trimethylol propane. A Hull oe ll test panel was again plated under the same oonditions as described in Example 23 and the electrodeposit was uniform and of a silver-whi~e, semi-bright appearanoe across the entire surfaoe of the test panel. The average alloy composition was 1.15~ by weight cbbalt in the 0-20 ASF current density range and 6.82% by weight oobalt in the cathode current density range above 20 ASF.
EX~MPLE 25 T~ the electr~lyte as described in Example 24, 0.06 g/l was added of 4-phenyl-4-sulfobutan-2-one, sodium salt; 0.075 g/l ben2ylidene a oe tone and 0.003 g/l butyl niootinate diethyl sulfate quaternary. A
Hhll test panel was agaLn plated under the same oonditions as described in Exa~ple 23 and the electrodeposit was fully bright, unifon~ and of a decorative quality across the entire surfaoe of the test panel. me oobalt alloy distribution was l~ by weight cobalt in the 0-20 ASF
current density range and 2.1% by weight obbalt in the cathQde current density range above 20 ASF.
While it will be apparent that the preferred enicdments of the invention disclosed are well calculated to fulfill the objects abcve stated, it will be appreciated that the invention is susceptible to mDdification, variation and change without deFarting from the proFer scope or fair meaning of the subjoined claLms.
Claims (19)
1. An aqueous acidic electrolyte suitable for electrodepositing zinc alloys on a conductive substrate comprising zinc ions and at least one additional metal ion selected from the group consisting of nickel, cobalt, iron and mixtures thereof present in an amount sufficient to electro-deposit a zinc alloy, the concentration of nickel and/or cobalt ions when present ranging from 0.5 to about 120 g/l and the concentration of iron ions when present ranging from about 5 to about 140 g/l, and about 0.005 to about 20 g/l of an additive agent comprising a bath soluble polyhydroxy compound having three or more hydroxyl groups at least one of which is substituted with an oxyalkylene group present in an amount effective to provide grain refinement of the zinc alloy electrodeposit.
2. The electrolyte as defined in claim 1 in which said zinc ions are present in an amount of about 10 g/l up to saturation.
3. The electrolyte as defined in claim 1 in which said additional metal ion comprises nickel, cobalt, and mixtures thereof present in an amount of about 3 to about 65 g/l.
4. The electrolyte as defined in claim 1 in which said additional metal ion comprises iron ions present in an amount of about 40 to about 100 g/l.
5. The electrolyte as defined in claim 1 in which said additional metal ion comprises iron ions and said electrolyte further including a complexing agent present in an amount sufficient to maintain an effective amount of iron ions in solution.
6. The electrolyte as defined in claim 1 in which said additional metal ion comprises iron ions and said electrolyte further including a reducing agent present in an amount effective to reduce at least a portion of the ferric ions to the ferrous state.
7. The electrolyte as defined in claim 1 in which said additional metal ion comprises iron ions and at least one of nickel ions and cobalt ions in combination with zinc ions to provide an alloy deposit containing about 1% to about 25% iron in combination with about 0.1% to about 20% by weight nickel and/or about 0.1% to about 12% cobalt and the balance essentially zinc.
8. The electrolyte as defined in claim 1 further containing conductivity salts present in an amount sufficient to increase the electrical conductivity of the electrolyte.
9. The electrolyte as defined in claim 1 further including hydrogen ions present in an amount to provide a pH of about 0 to about 7.
10. The electrolyte as defined in clai 1m further including hydrogen ions present in an amount to provide a pH of about 2 to about 6.
11. The electrolyte as defined in claim 1 in which said additive agent is present in an amount of about 0.02 to about 10 g/l.
12. The electrolyte as defined in claim 1 further including a supplemental brightening agent present in an amount up to about 10 g/l.
13. A process for electrodepositing a zinc alloy on a substrate comprising the steps of contacting a cathodically electrified substrate with an aqueous acidic electrolyte comprising zinc ions and at least one additional metal ion selected from the group consisting of nickel, cobalt, iron and mixtures thereof present in an amount sufficient to electrodeposit a zinc alloy, the concentration of nickel and/or cobalt ions when present ranging from 0.5 to about 120 g/l and the concentration of iron ions when present ranging from about 5 to about 140 g/l, and about 0.0005 to about 20 g/l of an additive agent comprising a bath soluble polyhydroxy compound having three or more hydroxyl groups at least one of which is substituted with an oxyalkylene group to impart grain refinement to the zinc alloy electrodeposit and continuing the electrodeposition of the zinc alloy until the desired thickness is obtained.
14. The process as defined in claim 13 including the further step of controlling the temperature of the electrolyte within a range of about 60° to about 180°F.
15. The process as defined in claim 13 including the further step of controlling the temperature of the electrolyte within a range of about 70 to about 140°F.
16. The process as defined in claim 13 in which the step of electrodepositing the zinc alloy is performed at an average cathode current density of about 1 to about 2000 ASF.
17. The process as defined in claim 13 including the further step of controlling the concentration of the zinc ions and either one of the nickel and/or cobalt ions to provide a zinc alloy containing about 0.1 to about 30% by weight nickel and/or cobalt.
18. The process as defined in claim 13 including the further step of controlling the concentration of the zinc ions, iron ions, and either one of the cobalt ions and/or nickel ions to electrodeposit a zinc alloy containing from about 1 to about 25% by weight iron, about 0.1 to about 20%
nickel and/or about 0.1 to about 12% cobalt.
nickel and/or about 0.1 to about 12% cobalt.
19. The process as defined in claim 14 including the further step of controlling the concentration of additive agent within a range of about 0.02 to about 10 g/l.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US83548986A | 1986-03-03 | 1986-03-03 | |
| US835489 | 1986-03-03 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1314512C true CA1314512C (en) | 1993-03-16 |
Family
ID=25269627
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000530934A Expired - Fee Related CA1314512C (en) | 1986-03-03 | 1987-03-02 | Polyhydroxy compounds as additives in zinc alloy electrolytes |
Country Status (7)
| Country | Link |
|---|---|
| CA (1) | CA1314512C (en) |
| DE (1) | DE3705949A1 (en) |
| ES (1) | ES2002580A6 (en) |
| FR (1) | FR2595102B1 (en) |
| GB (1) | GB2188334B (en) |
| IT (1) | IT1206252B (en) |
| SE (1) | SE8700716L (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3819892A1 (en) * | 1988-06-09 | 1989-12-14 | Schering Ag | ALKALINE AQUEOUS BATH FOR GALVANIC DEPOSITION OF ZINC-IRON ALLOYS |
| JPH0637711B2 (en) * | 1989-06-22 | 1994-05-18 | 新日本製鐵株式会社 | Method for producing black surface-treated steel sheet |
| JP3223829B2 (en) * | 1997-01-29 | 2001-10-29 | 新光電気工業株式会社 | Electric nickel plating bath or electric nickel alloy plating bath and plating method using the same |
| DE10033433A1 (en) * | 2000-07-10 | 2002-01-24 | Basf Ag | Process for electrolytic galvanizing from electrolytes containing alkanesulfonic acid |
Family Cites Families (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2542994A (en) * | 1945-07-09 | 1951-02-27 | Armco Steel Corp | Electrolytic surface treatment of steel |
| US4070256A (en) * | 1975-06-16 | 1978-01-24 | Minnesota Mining And Manufacturing Company | Acid zinc electroplating bath and process |
| US4170526A (en) * | 1978-01-16 | 1979-10-09 | Oxy Metal Industries Corporation | Electroplating bath and process |
| US4207150A (en) * | 1978-01-25 | 1980-06-10 | Oxy Metal Industries Corporation | Electroplating bath and process |
| US4176017A (en) * | 1979-01-31 | 1979-11-27 | Oxy Metal Industries Corporation | Brightening composition for acid zinc electroplating bath and process |
| US4252619A (en) * | 1979-10-24 | 1981-02-24 | Oxy Metal Industries Corporation | Brightener for zinc electroplating solutions and process |
| GB2064585B (en) * | 1979-11-19 | 1983-11-09 | Enthone | Acid zinc electro plating solutions and methods utilizing ethoxylated/propoxylated polyhydric alcohols |
| US4488942A (en) * | 1983-08-05 | 1984-12-18 | Omi International Corporation | Zinc and zinc alloy electroplating bath and process |
| US4515663A (en) * | 1984-01-09 | 1985-05-07 | Omi International Corporation | Acid zinc and zinc alloy electroplating solution and process |
| US4541906A (en) * | 1984-05-21 | 1985-09-17 | Omi International Corporation | Zinc electroplating and baths therefore containing carrier brighteners |
-
1987
- 1987-02-19 IT IT8747660A patent/IT1206252B/en active
- 1987-02-20 SE SE8700716A patent/SE8700716L/en unknown
- 1987-02-25 DE DE19873705949 patent/DE3705949A1/en active Granted
- 1987-03-02 CA CA000530934A patent/CA1314512C/en not_active Expired - Fee Related
- 1987-03-02 ES ES8700561A patent/ES2002580A6/en not_active Expired
- 1987-03-03 FR FR878702853A patent/FR2595102B1/en not_active Expired - Lifetime
- 1987-03-03 GB GB8704939A patent/GB2188334B/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| IT8747660A0 (en) | 1987-02-19 |
| FR2595102B1 (en) | 1991-07-26 |
| SE8700716D0 (en) | 1987-02-20 |
| GB8704939D0 (en) | 1987-04-08 |
| IT1206252B (en) | 1989-04-14 |
| DE3705949C2 (en) | 1990-10-25 |
| GB2188334A (en) | 1987-09-30 |
| SE8700716L (en) | 1987-09-04 |
| DE3705949A1 (en) | 1987-09-10 |
| FR2595102A1 (en) | 1987-09-04 |
| GB2188334B (en) | 1990-08-22 |
| ES2002580A6 (en) | 1988-08-16 |
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