FR2595102A1 - POLYOXYALKYL POLYHYDROXYL COMPOUNDS AS ADDITIVES IN ZINC ALLOY ELECTROLYTES - Google Patents

Abstract

IMPROVED AQUEOUS ACID ELECTROLYTE SUITABLE FOR THE ELECTRODEPOSITION OF ZINC ALLOY INCLUDING A COMBINATION OF ZINC AND AT LEAST ONE METAL CHOSEN FROM NICKEL, COBALT, IRON AND MIXTURES OF THEIR, CONTAINING AN EFFECTIVE QUANTITY OF AN ADDITIVE TO ACHIEVE GRAIN REFINING AND IMPROVE THE ADJUSTMENT OF THE SIMULTANEOUS DEPOSIT OF ADDITIONAL METALS IN THE ZINC ALLOY DEPOSIT. THE ADDITIVE INCLUDES A BATH-SOLUBLE POLYHYDROXYL COMPOUND, HAVING THREE OR MORE HYDROXYL GROUPS, OF WHICH AT LEAST ONE IS SUBSTITUTED BY ONE POLYOXYALKYLENE GROUP. THE PRESENT INVENTION FURTHER COVERS THE PROCESS OF USING THE ABOVE ELECTROLYTE FOR THE ELECTROLYTIC DEPOSIT OF FUNCTIONAL AND DECORATIVE ZINC ALLOYS.

Description

The present invention relates generally to

  an improved electrolyte and process for depositing

  electrolytically zinc alloys, and more particularly

  an improved aqueous acid zinc alloy electrolyte containing novel additives to achieve improved performance.

  improvement of grain ripening, a reduction of the

  of dendrites, an increase in adhesion and

  ductility and an unexpected adjustment in the simul-

  tane of one or more addition metals in the

zinc binding.

  Electrolytes containing zinc ions

  In addition, one or a combination of nickel, cobalt, iron ions or mixtures thereof have been used or heretofore proposed for use in depositing zinc alloys of a decorative or functional type. on various conductive substrates such as iron and steel, for example, to obtain an improvement of the resistance

  corrosion, an improvement of the appearance and / or

  make up the surface of a worn part, allowing it to be

  to restore its original service dimensions.

  The use of these electrolytes of zinc alloys and

  these processes are widely used industrially for the

  industrial or functional metallization, for example the

  plate metallization, metallization of canalisa-

  wire metallization, metallization of rods, metallization of tubes, metallization of fittings, etc. A permanent problem posed by these electrolytes of alloys

  of the prior art has been the inability to

  to achieve the desired grain refinement of the alloy electrolytic deposit to achieve the desired semi-gloss appearance and associated physical properties, including adhesion

  and ductility. Another problem was the inability to increase

  the percentage of the constituent addition metal such as

  ckel, cobalt and / or iron in the zinc alloy electrolytic deposit to achieve the physical and chemical properties

  desired. The formation of dendrites on the metallic substrate

  in areas of high current density

also a disadvantage.

  The present invention provides an improved electrolyte

  for the electrolytic deposition of zinc alloys containing

  an additive or a mixture of additives which produces a

  improvement of grain ripening, a reduction of the

  the addition of additives, an increase in adhesion and ductility, while at the same time adjusting the simultaneous deposition of the addition metal ions, achieving electrolytic deposition

  zinc alloy having improved properties.

  The advantages of the present invention with respect to compositional aspects thereof are achieved by an aqueous acid zinc alloy electrolyte containing zinc ions in conventional amounts, furthermore associated with controlled amounts of at least one additional metal addition ion selected from nickel, cobalt, iron and mixtures thereof. The electrolyte also contains, as an essential constituent, an additive

  present in an effective amount to make a

  The physical characterization of the zinc alloy deposit comprising a bath-soluble polyhydroxy compound having three or more hydroxyl groups, at least one of which is substituted by a polyoxyalkylene group, and mixtures thereof. The concentration of the polyhydroxy substituted polyhydroxy-substituted additive is such that it gives the electrolytic deposition improved grain refining, and the specific concentration will vary depending on whether the electrolyte is chloride, sulfate,

  fluoroborate, sulfamate or mixed chloride.

  In addition to the preceding constituents, electricity

  zinc alloy trolyte may additionally contain various additives of the types conventionally used, among which

  buffer agents, additional brighteners

  res, conductibility salts soluble in the bath and compatible with it to increase the conductivity

  electric electrolyte, etc ...

  In accordance with the aspects of the present invention,

  process, a zinc alloy coating is deposited electrolytically on a conductive

  using the aqueous acid zinc alloy electrolyte pre-

  quoted, which is set to a temperature generally

  from ambient temperature (15 C) to

  is 82 C, and operates at cathodic current density

  average of 10 amps / m2 to about 21500 amperes / m2, or more, which will vary depending on the type and particular composition of the electrolyte, as well as geometry and treatment parameters

  used in the metallization operation.

  Other advantages of the present invention

  will appear on reading the description of the modes of

  the most preferred examples, as well as specific examples

  ned. The aqueous acidic zinc alloy electrolyte according to the aspects of the present invention relating to the composition contains zinc ions present in an amount effective to electrolytically deposit zinc from the electrolyte, and this may range from a My-.

  generally about 10 g / l only until saturation

  the concentration range from about 15 to about 225 g / l being more common. In most applications, it is preferred that the concentration of zinc ions be regulated in

  an interval of about 20 to about 200 g / l.

  The maximum concentration of zinc ions will vary

  depending on the temperature of the electrolyte, the temperatures

  higher levels allowing the use of concentrations

  higher. The concentration of zinc ions will also vary

  depending on the type of electrolyte used, which may be chloride, sulphate, chloride-sulfate mixed, sulphamate, as well as fluoroborate types. In acid chloride electrolytes, the concentration of zinc ions is generally set at a level in the lower end

  permissible range, while in electrolytic

  acid sulfate type, the concentration of zinc ions

  is usually set at a level in the upper part of the

  re of the allowable concentration range Zinc ions are introduced into the electrolyte in the form of zinc anodes or soluble zinc salts,

  such as chloride, sulphate, sulphamate and / or fluoborate,

  in addition to an acid such as sulfuric acid, hydrochloric acid, fluoboric acid, sulfamic acid, etc., corresponding to the type of zinc salt used. In general, the pH of the zinc alloy electrolyte is set in a range from about 0 to about 7, a fold of about 2

at about 6 being preferred.

  In addition to zinc ions, the electrolyte contains

  in addition to specific amounts of at least one of the

  addition rates, including nickel, cobalt and / or

  iron, which are introduced in the same way in the form of ano-

  soluble or soluble salts in the bath of the addi-

  including chloride, sulphate, fluoborate,

  acetate or sulfamate as well as mixtures thereof.

  When nickel and / or cobalt are used as the addition metal, each of them can be used in the bath in amounts ranging from about 0.5 g / l to about 120 g / l to achieve alloy deposits containing from about 0.1 to about 30% by weight nickel and / or cobalt. The

  alloy deposition preferably comprises about 0.25%

  than a total of about 15% of nickel and / or cobalt, and under these conditions, the bath contains nickel and / or cobalt ions in a proportion usually ranging from

  3 g / l to about 65 g / l, respectively.

  When iron is an additive metal in the electrolyte, the iron ion concentration may

  from about 5 g / l to about 140 g / l, concentrates

  from about 40 g / l to about 100 g / l being preferred.

Rees.

  When iron ions are present in the electro-

  lyte which is only weakly acidic or neutral, whose pHI is, for example, from about 4 to about 6.5, it is preferred in

  generally incorporate complexing or chelating agents

  to keep in the solution an effective amount of iron ions. Chelating or complexing agents which are

  particularly satisfactory for this purpose include the

  citric acid, gluconic acid, glucoheptanoic acid, tartaric acid, ascorbic acid, iso-ascorbic acid,

  malic acid, glutaric acid, muconic acid, acetic acid,

  glutamic acid, glicolic acid, aspartic acid, etc., as well as their salts of alkali metals, ammonium, zinc

or ferrous.

  Although iron ions are introduced into

  ferrous electrolyte, ferric ions are formed.

  during the metallization process, and we found

  However, excessive amounts of ferric ions are a disadvantage because they lead to the formation of streaks on the surface coated with zinc alloy. As a result, it has been found desirable to control the ferric ion concentration at a level usually below about 2 g / l. This can be accomplished by using an anode of

  zinc or iron soluble in the electroplating bath.

  lytic, or by dipping metallic zinc or iron

  in the holding tank through which one circulates

  ler the electrolytic metallization solution. When no soluble anodes are used or no zinc or metallic iron is added to the holding tank, appropriate adjustment of the ferric ion concentration can be achieved by using organic reducing agents. and / or minerals soluble in the bath and compatible with it, such as for example bisulfites, iso-ascorbic acid, monosaccharides and disaccharides such as glucose or

lactose.

  It will be appreciated from the foregoing that

  electrolytes can be formulated to give alliances

  appropriate binary, ternary or quaternary

  mainly zinc and at least three of the other

constitutive edition.

  When ternary alloy deposits are desired

  containing zinc-nickel-iron, or zinc-cobalt-iron, the concentration

  tion of the metal alloy ions in the electrolyte is usually

  to give an alloy containing about 1%

  about 25% iron associated with about 0.1 to about

  20% by weight of nickel, ie 0.1 to about 12% of

  balt, the rest being essentially zinc.

  In addition to metal ions present in the elec-

  trolyte, the electrolyte still contains, as an essential ingredient,

  or an additive comprising a bath-soluble polyhydroxy compound having three or more hydroxyl groups, at least one of which is substituted by a polyoxyalkylene group. In general, polyhydroxy compounds such as sorbitol and

  methylglucose having one or more of their

  droxyl substituted with oxyethylene or oxypropylene chains

  pylene and mixtures thereof have been shown to be particularly

  satisfactory for the use in its electro-

lytes of zinc alloy.

  The molecular weight of the additive or mixtures thereof is adjusted to render the additive soluble in the electrolyte at the desired concentration. Note that the additive may contain a polyoxyalkylene substituent group

  on its molecule or may contain two, three

  more or less depending on the degree of substitution and the

  of reactive hydroxyl groups on the molecule.

  The concentration of the additive in the electrolyte

  will vary according to the concentration and types of

  very present constituents of the bath, the composition of the

  desired alloy deposit, and the functional or decorative purpose of the electrolytic deposition. In a general way,

  the additive is used in an amount effective to

  to obtain refinement of the grain of the electrolytic deposit, to re-

  the tendency to form dendrites during the process

  electrolytic deposition, to improve adhesion and

  substrate deposition, and to adjust the simultaneous deposition

  metal ions in the zinc alloy deposit and to adjust the alloy content to a higher level.

  uniform, desired. For this purpose, concentrations as low as

  about 0.005 to about 20 g / l were found to be

  readable, while concentrations of about 0.02 to

  10 g / l are more typical and are preferred for the

most uses.

  In accordance with a preferred practice of

  In this invention, the additive is used in sulfate-based zinc-iron electrolytes in a range of concentrations.

  from about 0.005 to about 0.1 g / l, giving both an increase

  the simultaneous deposition of iron in zinc-iron

  a refining of the grains thereof. In the electrolytes of

  zinc-nickel binders based on sulphate, a concentration range

  tratiom from about 0.005 to about 0.1 g / l is also preferred.

  it brings an improvement in ductility and adhesion

  In the electrolytes of sulphate-based zinc-cobalt alloys, the concentration range of the preferred additive is approximately 0.05. at about 5 g / l, giving electrolytic deposition to the ductile and adherent refined grains. On the other hand, an all-chloride system for the electrolytic deposition of an alloy would require a preferred concentration of 0.110 g / l.

  for all versions of the alloy to be produced.

  The additive can be used by itself, in combination with

  with the metal ions of the electrolyte, to produce

  a semi-gloss electrolytic deposit typical of a metal

  functional situation. When electrolytic deposition is required

  with an improved gloss, gloss agents

  additional types known in the art may be

  incorporated into the electrolyte in the usual amounts.

  Typical compounds of the additional glossing agents which can

  can be used to further improve the crystal structure

  and the gloss of zinc alloy electroplating are those described in US-A-4,170,526; 4,207,150; 4,176,017; 4,070,256 and 4,252,619. When used, these

  additional brilliance can be used at

  up to approximately 10 g / l, concentrations also

  so low that about 0.001 g / l being effective. In general, the concentration of additional brighteners

is from about 0.01 to about 5 g / l.

  In addition to essential and optional constituents

  above, the electrolyte may further contain additives

  Additional agents such as buffers and bath modifiers such as boric acid, acetic acid, citric acid, benzoic acid, salicylic acid, and their bath-soluble salts compatible with it. , ammonium chloride, etc ... Other salts soluble in the bath and compatible with it such as ammonium sulfate, ammonium chloride or bromide, sodium chloride,

  potassium chloride, ammonium fluoroborate, sulphate

  magnesium fate, sodium sulphate and combinations thereof etc. may also be used in

  usually from about 20 to about

  450 g / l to increase the electrical conductivity of

  the electrolyte. In general, these conductivity salts comprise

  alkali metal salts such as chlorides, sulfates, sulfamates and fluoborates. Similarly, bath modifiers such as polyhydroxy compounds soluble in the bath and

  compatible with it, containing at least three hydro-

  xyl and at least four carbon atoms, of the class de-

  in US-A-4,515,663, the contents of which are hereby incorporated by reference, may be used in amounts of from about 3 to about 30 g / l to inhibit the formation of insoluble polyborate during the

bath functioning.

  In accordance with the aspects of the present invention

  related to the process, the zinc alloy electrolyte is

  electrolytically depositing a desired zinc alloy.

  on a conductive substrate using electrolyte temperatures ranging from about ambient temperature (15 C) to about 82 C, and more generally from about 21 C to about 60 C. Electrolytic deposition of the alloy of

  zinc can be carried out at current densities

  from about 10 amperes / m 2 only to about 21,500 amperes / m 2. For decorative chloride electrolytes, current densities of from about 10 to about 860 A / m 2 are

  generally preferred, whereas for electrolytes

  sulphate or chloride type, densities of

  from about 215 to about 21,500 A / m2 can be used.

  lisées. During the electroplating process, the bath or electrolyte is preferably agitated mechanically or by circulation of the solution or by movement of the parts. Although air agitation may be used, the use of air agitation with electrolytes containing

  iron ions is less desirable because of the tendency to increase

  lead to the formation of ferric ions in the bath. The following nonlimiting examples are given by way of illustration of the electrolyte composition and

  of the process of the present invention.

EXAMPLE 1

  By way of comparison, an electrolytic

  zinc-iron alloy of the aqueous acidic sulfate type for

  functional electrolytic deposits containing 110 g / l of sulphate

  zinc fats monohydrate and 370 g / l ferrous sulphate hepta-

  hydrate. The pH of the electrolyte was about 2.

  The electrolyte has been used to deposit electro-

  lytically a zinc-iron deposit on a cathode made of steel rod

  at a speed of 3.55 rpm, giving a top speed

  peril of about 61 m / min. The electrolyte has been set to

  temperature of 50 ° C., and soot zinc anodes were used.

  lubles. Electroplating was performed at an average cathodic current density of about 5400 A / m2. The zinc-iron alloy deposit obtained was gray in color and had a granular appearance, the analysis showed that it contained 13.8%

in weight of iron.

EXAMPLE 2

  With the electrolyte as described in Example 1,

  added 0.01 g / l of an additive comprising ethoxylated sorbitol

  having an average molecular weight of 1400. A cathode

  revolving steel has been coated here again in the same

  than in Example 1. The deposit of zinc-iron alloy ob-

  held a silver-blue color and a semi-

  brilliant, it turned out to contain 13.2% by weight

of iron.

  EXAMPLE 3 To the electrolyte as described in Example 1, 1

  0.05 g / l of an additive comprising sorbitol

  with an average molecular weight of 500. A catheter

  rotating steel was here again coated electrolytic-

  under the same conditions as in Example 1. The deposit of zinc-iron alloy obtained had a gray-blue color and a semi-glossy appearance, it was revealed to contain

18.6% by weight of iron.

EXAMPLE 4

  To the electrolyte as described in Example 1, 0.01 g / l of an additive comprising methylglucose was added.

  ethoxylated (ethoxylated with 10 moles of ethylene oxide). A

  steel rotating thode has been electrolytically coated

  under the same conditions as in example 1. The filing of

  zinc-iron bonding obtained was a gray-satin color and had a

  semi-gloss, it turned out to contain 15.5

% by weight of iron.

EXAMPLE 5

  To the electrolyte as described in Example 1 was added 0.01 g / l of an additive comprising propoxylated methylglucose (propoxylated with 10 moles of propylene oxide). A rotating steel cathode has been electrolytically coated

  under the same conditions as in example 1. The filing of

  binding obtained iron-gray had a satin gray appearance, and it was

  revealed in the analysis contain 17.1% by weight of iron.

EXAMPLE 6

  By way of comparison, we have prepared for a

  functional metallization a zinc-nialloy electrolyte

  aqueous acid of the sulphate type. The electrolyte contained 310 g / l of nickel sulphate hexahydrate, 205 g / l of sulphate

  zinc monohydrate and 36 g / l sulfuric acid. The electro-

  lyte has been adjusted to a temperature ranging from 60 to 65 C, and

  a rotating steel cathode has been metallized

  average cathodic current of 10 750 A / m2 using

  insoluble lead anodes. The agitation of the solu-

  This was done by rotating the cathode. The cathode was rotated at a speed of 4600 rpm, giving a

  superficial velocity of 99 m / min. The deposit obtained was

  their light gray, it had a grainy appearance and exhibited poor adhesion when bent at an angle greater than 90 and examined at a magnification of 14. The thickness of the zinc-nickel alloy deposit was about 6, 3 microns to about 7.6 microns. At the analysis,

  the alloy was found to contain 13.5% by weight of nickel.

EXAMPLE 7

* To the electrolyte as described in Example 6,

  0.04 g / l of an additive comprising an ethoxylated sorbitol was added.

  xylated having an average molecular weight of 475. A rotating steel cathode was electrolytically coated under the same conditions as in Example 6. The resulting zinc-nickel alloy had a finely granular, semi-glossy appearance and was adherent , as evidenced by the fact that he remained practically free from cracks when he was bent to a

  angle greater than 90 and examined under a magnification of 14.

  On analysis, the alloy was found to contain 7% by weight of nickel. In the atmospheric corrosion test, this type of electroplating exhibits a 15% to 20% improvement in corrosion protection compared to

  electrolytic deposition of Example 6, although its content in

this is lower.

EXAMPLE 8

  To the electrolyte as described in Example 6, 0.015 g / l of an additive consisting of ethoxylated sorbitol is added.

  and propoxylated having an average molecular weight of 7,200.

  A rotating steel cathode is electrolytically coated

  under the same conditions as in example 6. The filing of

  zinc-nickel bonding has a finely granular, semi-glossy

  lant, and it is adherent, as shown by a deposit practically free of cracks when the curve of an angle greater than

    and examine it under a magnification of 14. At the anal-

  the zinc-nickel alloy is found to contain 9.6% nickel.

EXAMPLE 9

  To the electrolyte as in Example 6, 0.02 g / l of an additive consisting of an ethoxylated methylglucose (ethoxylated with 10 ethylene oxide molecules) is added. A rotating steel cathode is electrolytically coated under the same conditions as in Example 6. The zinc-nickel alloy deposit obtained has a finely granular appearance, and is adherent, as shown by the fact that it is practically free cracks when bent at an angle greater than 90 and examined at a magnification of 14. On analysis, the alloy

  is found to contain 6.7% by weight of nickel.

EXEMPTION 10

  As a comparison, we prepare another election

  zinc-nickel aqueous acidic trichloride sulfate type for the

  functionalization. The electrolyte contains 110 g / l of

  nickel sulphate hexahydrate, 260 g / l of

  nohNdrate and 36 g / l of sulfuric acid.

  A rotating cathode of forged steel is metallized with

  of steel in the electrolyte under a current density of

o

  average of 10 750 A / m ', the temperature of the electro-

  lyte being adjusted in a range of 50 to 55 C. Insoluble lead anodes are used. A stirring of the solution

  is obtained by rotating the cathode of steel rod at a speed of

  from 4600 rpm, to obtain a superficial velocity of 99 m / min. The resultant zinc-nickel alloy coating has a light gray appearance, is granular and cracked when curved at an angle greater than 90, and is examined at a magnification of 14. The electrolytic deposition has a thickness of about 6.3 to 7.6 microns. By analysis, we find that the nickel content

is 6.7% of the weight of the alloy.

  This example shows that a reduction in the content

  nickel in the electrolyte and in the deposit obtained by

  parison to that used in Example 6 above at a

  as obtained in the additional examples 7 to 9, still does not produce an electrolytic deposit of alloy

  zinc-nickel satisfactory in the absence of the additive.

EXAMPLE 11

  By way of comparison, a zinc-cobalt alloy electrolyte of the aqueous acidic sulphate type, designed for functional electrolytic metallization, containing g / l of cobalt sulfate heptahydrate and 450 g / l of sulphate is prepared.

  zinc monohydrate and 36 g / l sulfuric acid.

  Electrolytically metallizing a steel rod

  rotating electrode serving as a cathode in the electrolyte,

  average cathodic current of 10 750 A / m2 the electro-

  lyte being adjusted to a temperature ranging from 40 to 45 C and using insoluble lead anodes. Stirring of the electrolyte is obtained by rotating the cathode. The rotational speed of the cathode is 4600 rpm, giving a surface velocity of 99 m / min. On examination, the electrolytic deposition of zinc-cobalt alloy obtained has a light gray, roughly granular, matte appearance. The analysis shows that the content encobalt in the alloy deposit is 0.17% by weight.

EXAMPLE 12

  To the electrolyte as described in Example 11, 4 g / l of an additive consisting of an ethoxylated sorbitol,

  propoxylated having an average molecular weight of 6,475.

  electrolytically tallizes a rotating cathode made of steel in

  the same conditions as in Example 11, and the filing of

  zinc-cobalt bonds obtained with a semi-glossy appearance, steel gray. The analysis shows that the alloy deposit contains 0.26

by weight of cobalt.

EXAMPLE 13

  With the electrolyte described in Example 11,

  an additive at a concentration of 0.5 g / l, consisting of a propoxylated methylcellulose (propoxylated with 10 moles of

  propylene). An electrolytic cathode is electrolytically metallized

  steel under the same conditions as in Example 11,

  and the resulting zinc-cobalt alloy deposit has a semi-shiny appearance

  lant and a gray coloring. The analysis shows that the content

cobalt is 0.29% by weight.

EXAMPLE 14

  With the electrolyte as described in Example 11, 0.2 g / l of an ethoxylated methylglucose additive (ethoxylated

  with 20 moles of ethylene oxide). Electrolytic metallization is

  a steel rotating cathode under the same conditions.

  than in Example 11, and the deposition of zinc-co-alloys

  balt obtained has a semi-glossy, gray appearance. The analysis shows

  that the alloy deposit contains 0.22% by weight of cobalt.

EXAMPLE 15

  For comparison, an electrolyte is prepared

  sulphate-type aqueous acid suitable for electro-

  lytic solution of a zinc-iron-nickel-cobalt alloy, containing 100 g / l

  of zinc sulphate monohydrate, 100 g / l of ferrous sulphate

  tahydrate, 50 g / l of nickel sulfate hexahydrate and 50 g / l of cobalt sulfate heptahydrate. The pH of the electrolyte is

about 4.5.

  An electrolytic cathode is electrolytically metallized

  Using the above electrolyte at a medium current density of 10 750 A / m 2, the electrolyte is adjusted to a temperature between about 50 and about C, using insoluble lead anodes. We do

  turn the cathode at such a speed that it gives a

  superficial velocity of 99 m / min. Electrodepositions are continued

  until the deposit has an average thickness of about

  6 microns. On examination, the electrolytic deposit has a satin gray appearance, with dendrites. By analysis, we find that the alloy contains 74.3% zinc, 14.3% iron, 6.4 cobalt

and 5% by weight of nickel.

EXAMPLE 16

  To the electrolyte as described in Example 15 is added 0.01 g / l of an additive comprising ethoxylated sorbitol having an average molecular weight of 1400. Electrolytically a rotating steel cathode is metallized under the same conditions than in Example 15, and the deposit obtained

  has improved grain refinement and smoothness.

  The analysis shows that the electrolytic deposition of alloy

  It contains 72.1% zinc, 15.6% iron, 7.6% cobalt and 4.7% nickel by weight.

EXAMPLE 17

  An aqueous zinc-nickel acidic acid electrolyte of the chloride type prepared for the electroplating of decorative zinc nickel electrolytic deposits, containing 90 g / l of zinc chloride, 115 g / l of nickel chloride hexahydrate, is prepared.

  220 g / l of ammonium chloride and 4 g / l of an additive

  of ethoxylated glycerol (ethoxylated with 12 moles of

  lene). The electrolyte also contains, as a brightening agent,

  secondary stage, 0.050 g / l of benzylidene acetone. The electrolytic

has a pH of about 5.6.

  A steel test plate is metallized at an average cathodic current density of from about 107 to about

  215 A / m2, the electrolyte being set at a temperature of about

  at around 35 ° C. The zinc-nickel alloy deposit obtained

  naked is perfectly bright, decorative and of a uniform

  me. The analysis shows that the alloy deposit contains 11.6%

by weight of nickel.

EXAMPLE 18

  A zinc-cobalt-nickel electrolyte con-

  coming for the electroplating of a decorative alloy deposit

  chloride type containing 90 g / l of zinc chloride, g / l of cobalt chloride hexahydrate, 120 g / l of nickel chloride hexahydrate, 200 g / l of ammonium chloride, 3 g / l of a additive consisting of ethoxylated glycerol (ethoxylated with

  12 moles of ethylene oxide) and 2 g / l of sodium benzoate.

  The electrolyte is adjusted to a pH of about 5 and

  uses a temperature of about 20 to about 25 C for

  electrolytically cladding a steel test plate at an average cathodic current density of from about 107 to about 215 A / min. The electrolytic deposition obtained has an appearance

  uniform, silvery, semi-gloss, which is commercially

  ceptable. The analysis shows that the alloy deposit contains 12% by weight of nickel, 6% by weight of cobalt and the rest

of zinc.

EXAMPLE 19

  To the electrolyte as described in Example 18 is added an additional brightening mixture comprising 0.06 g / l of 4-phenyl-3-buten-2-one, 0.02 g / l of butyl nicotinate quaternary dimethyl sulphate and 0.05 g / l of

  4-phenyl-4-sulfobutan-2-one, sodium salt.

  A steel test plate is electrolytically metallized using zinc anodes in accordance with the procedure set forth in Example 18. The resulting alloy deposit

  is very decorative, and of a perfectly brilliant appearance.

  The analysis shows that the alloy deposit contains 11.9% by weight of nickel, 6.5% by weight of cobalt, the rest being

made of zinc.

EXAMPLE 20

  By way of comparison, an aqueous zinc-cobalt acid electrolyte of the chloride type, suitable for the electrodeposition of a decorative zinc-cobalt deposit, containing 46 g / l of zinc chloride and 10.5 g / l of chloride, is prepared. cobalt

  hexahydrate, 175 g / l of sodium chloride, 20 g / l of boiling acid

  and 2 g / l of sodium benzoate. The pH of the electrolyte is about 5.2. Plates of standard Hull cells are metallized with the electrolyte at about 24 under a 1 ampere stream for a period of 10 minutes, in the absence of agitation. The resulting test plate has a matt black appearance to

  greyish black granular. The average alloy content of the

  In the current density range of 0 to 430 A / m 2, the electrolytic electrode is 5.03% by weight of cobalt and

the rest of zinc.

EXAMPLE 21

  To the electrolyte as described in Example 20 is added 3 g / l of an additive comprising ethoxylated glycerol (ethoxylated with 12 moles of ethylene oxide). A Hull test plate is again metallized under the same conditions as in Example 20, and the electrolytic deposition obtained has a uniform appearance, a silver white, semi-gloss, in the range of densities current from 21.5 to 645 A / m2. The average grade of

  the alloy is 1.03% by weight of cobalt and the remainder of zinc.

  This content of the alloy in the electrolytic deposition has

  2 to 3 times the corrosion resistance of ordinary zinc, and is

commercially acceptable.

EXAMPLE 22

  To the electrolyte described in Example 20 is added 4 g / l of an additive consisting of ethoxylated glycerol (ethoxylated with 26 moles of ethylene oxide). A Hull test plate is again metallized under the same conditions as in Example 20, and the electrolytic deposit obtained has an appearance

  uniform, a silver white, semi-gloss, in the interval-

  the current density between 21.5 and 645 A / m-. The average content of the alloy is 1.59% by weight of cobalt and the

remaining zinc.

EXAMPLE 23

  For comparison, an electrolyte is prepared

  chloride-type aqueous acid suitable for electrodeposition

  zinc-cobalt alloy containing 46 g / l of zinc chloride, 10.5 g / l of cobalt chloride hexahydrate, 220 g / l of potassium chloride, 20 g / l of boric acid and 3, 5 g / l of

  sodium benzoate. The pH of the electrolyte is set to approximately

5 and the temperature at 25 C.

  A test plate is metallized in a cell

  the standard Hull under a current of 1 ampere, for a duration of 10 minutes, using an anode of

  zinc in the absence of agitation. Electrolytic deposition

  nude is matte black to greyish black, and has a grainy appearance.

  The average composition of the alloy is 1.2% by weight of cobalt in the range of current densities from 0 to 215 A / m 2 19. and about 5.7% by weight of cobalt in the region of the

  test plate above a current density of 215 A / m2.

EXAMPLE 24

  To the electrolyte as described in Example 23 is added 4 g / l of an additive consisting of ethoxylated trimethylolpropane (15 moles). A Hull cell test plate is again metallized under the same conditions as in Example 23, and the electrolytic deposition is uniform, it has an appearance

  silver white, semi-gloss on the whole surface of the

  that test. The average composition of the alloy is 1.15% by weight of cobalt in the range of current densities

  from 0 to 215 A / m2 and 6.82% by weight of cobalt in the

  cathodic current density range greater than 215 A / m2.

EXAMPLE 25

  With the electrolyte as described in Example 24,

  adds 0.06 g / l of 4-phenyl-4-sulfobutar-2-one, sodium salt,

  dium; 0.075 g / l of benzylidene acetone and 0.003 g / l of nicotine

  butyl ester diethyl quaternary sulfate. A plate

  The Hull test is here again metallized in the same way.

  than in Example 23, and the electrolytic deposition is completely brilliant, uniform and of decorative quality on

  the entire surface of the test plate. The distribution of

  cobalt bonding is 1% by weight of cobalt in the range

  the current density of 0 to 215 A / m2, and 2.1% by weight of cobalt in the cathodic current density range greater than 215 A / m

Claims (21)

  1. Aqueous acidic electrolyte suitable for electri-   trowelposition of zinc alloys on a conductive substrate,   zinc ions and / or at least one additional metal ion   selected from nickel, cobalt, iron and mixtures thereof, present in an amount sufficient to deposit   electrolytically a zinc alloy, and an effective amount   an additive comprising a bath-soluble polyhydroxyl compound having three or more hydroxyl groups, at least one of which is substituted by an oxyalkylene group present in an amount effective to provide grain refinement;   electrolytic deposition of zinc alloy.   2. Electrolyte according to claim 1, in   which these zinc ions are present in an amount of about 10 g / l until saturation.   An electrolyte according to claim 1, wherein said additional metal ion comprises nickel,   cobalt and mixtures thereof, present in a quantity   from about 0.5 to about 120 g / l.   The electrolyte of claim 1, wherein said additional metal ion comprises ions   iron present in an amount of about 5 to about 140 g / l.   An electrolyte according to claim 1, wherein said additional metal ion comprises iron ions, and said electrolyte further contains a complexing agent   present in an amount sufficient to maintain a quantity   effective ionization of iron ions in solution.   The electrolyte of claim 1, wherein said additional metal ion comprises iron ions   and this electrolyte further contains a reducing agent   in an effective amount to reduce at least one   ferric ions in the ferrous state.   The electrolyte of claim 1, wherein said additional metal ion comprises iron ions and at least one of nickel and cobalt ions in combination with   zinc ions to give an alloy deposit containing   from 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, the remainder being essentially zinc.   8. An electrolyte according to claim 1, further containing conductivity salts present in a   sufficient to increase the electrical conductibility only electrolyte.   9. Electrolyte according to claim 1,   additionally hydrogen ions present in a quantity   giving a pH of about 0 to about 7. -   10. Electrolyte according to claim 1,   additionally hydrogen ions present in a quantity   giving a pH of about 2 to about 6.   An electrolyte according to claim 1, wherein said additive is present in an amount of about 0.005 to about 20 g / l.   The electrolyte of claim 1, wherein said additive is present in an amount of about 0.02 to about 10 g / l.   13. Electrolyte according to claim 1,   additionally an additional brightening agent   in an amount of up to about 10 g / l.   14. Process for electroplating an alloy of   zinc on a substrate, including the steps of   contacting a cathodically electrified substrate with an aqueous acid electrolyte containing zinc ions and at least one additional metal ion selected from nickel, cobalt, iron and mixtures thereof, present in a   sufficient to electrolytically deposit an alloy   zinc, and an effective amount of an additive comprising a bath-soluble polyhydroxy compound, having three   hydroxyl groups or more, at least one of which is   killed by an oxyalkylene group to confer refining   electrolytic deposits of zinc alloy and   follow the electrodeposition of the zinc alloy until the desired thickness.   The method of claim 14 including   the additional stage of adjusting the temperature of the electri-   trolyte in the range of about 15 C to about 80 C.   16. The process of claim 14 comprising   both the extra stage of setting the temperature of   the electrolyte in a range of about 21 to about 60 C.   17. The method of claim 14, wherein   what the electrodeposition stage of the zinc alloy is   performed under a mean cathodic current density of about 10 to about 21,500 A / m2.   18. The process of claim 14 comprising   both the additional stage of adjusting the concentration of the zinc ions, and either of the nickel and / or cobalt ions to give a zinc alloy containing about 0.1   about 30% by weight of nickel and / or cobalt.   19. The process of claim 14 comprising   both the additional stage of adjusting the concentration of zinc ions, iron ions and one or other of the ions   cobalt and / or nickel for electrolytically depositing an alloy   zinc containing from about 1 to about 25% by weight iron, about 0.1 to about 20% nickel and / or about 0.1 to about about 12% cobalt.   20. The process of claim 14 comprising   both the additional stage of concentration adjustment   the additive in a range of about 0.005 to about 20 g / l.   21. The method of claim 14 including   the additional stage of adjusting the concentration of the ad-   in a range of about 0.02 to about 10 g / l.