EP2431500A1 - Regeneration of zinc nickel alkali electrolytes by removing cyanide ions by using soluble quarternary ammonium compounds - Google Patents

Abstract

Use of a soluble quaternary ammonium compound for regeneration of a zinc nickel electrolyte by removal of cyanide, is claimed. An independent claim is also included for regenerating the zinc nickel electrolyte by removal of cyanide ions, comprising adding a soluble quaternary ammonium compound to the zinc nickel electrolyte, and removing the cyanide-containing precipitate.

Description

The invention relates to the use of soluble quaternary ammonium compounds for the regeneration of a zinc nickel electrolyte by removal of cyanide ions. In addition, the present invention relates to a process for the regeneration of a zinc nickel electrolyte, in which soluble quaternary ammonium compounds are added to the zinc nickel electrolyte, whereby the cyanide ions, which are present as Tetracyanonickelkomplex can be removed.

The deposition of zinc nickel alloy coatings with a proportion of 10-16 wt.% Nickel causes a very good corrosion protection on components made of ferrous materials and is therefore of great importance for technical corrosion protection. The deposition can be carried out from weakly acidic or strongly alkaline electrolytes. For the coating of components, in particular accessories for automotive production, the strongly alkaline electrolytes are preferred. These are distinguished from the weakly acidic processes by a much more uniform layer thickness distribution. This property is particularly noticeable in complex three-dimensional geometries of the components to be coated. To achieve a predetermined corrosion resistance, a minimum layer thickness must be adhered to the component. This is usually 5 microns. If an electrolyte has a poor metal distribution, this means that relatively high layer thicknesses are already deposited in regions of high current densities, before the required minimum layer thickness is reached in regions of low current densities. This leads to an increase in cost of the coating due to excessive metal deposition. In addition, too high layer thicknesses can also lead to technical problems, if, for example, the dimensional accuracy of functional areas of the component can no longer be complied with.

For the reasons mentioned above, in practice predominantly the strongly alkaline electrolytes are used for the deposition of zinc nickel alloy coatings. Zinc is an amphoteric metal and is present therein as zincation, Zn [(OH) ₄ ] ^2- . In contrast, nickel is not amphoteric and therefore can not be complexed by hydroxide ions. Alkaline zinc nickel electrolytes therefore contain special complexing agents for nickel. Preference is given to using amine compounds such as triethanolamine, ethylenediamine or homologous compounds of ethylenediamine, for example diethylenetriamine, tetraethylenepentamine and the like.

Zinc nickel alloy electrolytes are operated with insoluble anodes. The use of soluble zinc anodes is not possible because zinc is amphoteric and therefore chemically dissolves in a strongly alkaline solution. The use of soluble zinc anodes would therefore lead to a strong zinc increase in the electrolyte. In practice, this amphoteric behavior is used to supplement the zinc content in the electrolyte. For this purpose, zinc pieces are dissolved in the electrolyte in a separate zinc solution container. This zinc-enriched electrolyte is then replenished to the deposition electrolyte to the extent that the zinc is consumed in the deposition. The supplementation is usually carried out by continuous, automatic analyzes and dosing pumps controlled on the basis thereof.

Since nickel is not amphoteric and does not dissolve in the strongly alkaline electrolyte, it is suitable as an anode material for insoluble anodes. At the nickel anode, the main reaction is the formation of oxygen. Apart from nickel, other metals such as iron, stainless steel, cobalt or alloys of the metals mentioned are also suitable. One way to appreciate the favorable properties of nickel as an anode material On the other hand, however, to save costs, there is the use of galvanically nickel-plated steel anodes with nickel deposits of about 30 microns. The deposited nickel is supplemented in the form of suitable supplementary solutions containing nickel salts with high water solubility. Nickel sulfate solutions are preferably used for this purpose.

Unfortunately, in practice, it is unavoidable that oxygen is not only selectively generated on the surface of the insoluble anodes. Partly it also occurs an anodic oxidation of Badinhaltsstoffe, in particular the amines used as complexing agents. Thereby arise as reaction products cyanide ions. In practice electrolytes, values of up to 1000 mg / l of cyanide can be adjusted until a balance of regeneration and removal is achieved. The formation of cyanides is disadvantageous for several reasons. The electrolytes dragged out with the coated goods cause the cyanides to enter the wastewater and have to be extensively detoxified there. This is done in practice by oxidation, e.g. with sodium hypochlorite, hydrogen peroxide, sodium peroxodisulfate, potassium peroxomonosulfate or similar compounds. Since the removed electrolyte contains, in addition to the cyanide, further oxidizable substances, substantially more oxidizing agent is consumed for complete oxidation than could theoretically be determined from the cyanide content.

From a technical point of view, the cyanide content in the zinc nickel electrolyte is very disadvantageous. Thus, the accumulation of cyanide in a zinc nickel alloy electrolyte can adversely affect the composition and visual appearance of the deposit. In the high current density range, a milky-fogged deposit may occur. This can be partially corrected by higher dosage of brighteners again. This measure is but with an increased Consumption of brighteners and thus additional costs associated with the deposition.

When the cyanide concentration in a zinc nickel alloy electrolyte reaches values of about 1000 mg / L, it is recommended to partially renew the electrolyte. This in turn increases the cost of the separation. In addition, fall in such partial bath renovations large amounts of waste electrolytes, which must be disposed of consuming.

Due to the above-mentioned disadvantages, there is thus a need for measures to prevent the formation of cyanide ions in the electrolyte or their removal.

For example, in the EP 1 344 850 B1 claims a method in which the cathode space and the anode space are separated by an ion exchange membrane. This prevents the complexing agents from getting out of the cathode compartment to the anode. Cyanide formation is thereby prevented. The anode used is a platinized titanium anode. The anolyte is acidic and contains sulfuric acid, phosphoric acid, methanesulfonic acid, amidosulfonic acid and / or phosphonic acid.

A similar procedure is in EP 1 292 724 B1 claimed. Here also cathode and anode compartment are separated by an ion exchange membrane. As anolyte, a sodium or potassium hydroxide solution is used. As the anode, a metal or metal coating is selected from the group consisting of nickel, cobalt, iron, chromium or alloys thereof.

In both processes, the formation of cyanides is to be prevented. The disadvantage of both processes is that the incorporation of the ion exchange membranes results in very high investment costs. In addition, there must be a device for a separate circulation of the anolyte be installed. The incorporation of ion exchange membranes is also not generally feasible in zinc nickel deposition processes. To increase productivity and thus reduce coating costs, auxiliary anodes are often used to optimize the layer thickness distribution when the frames are tightly hung. For technical reasons, it is not possible here to separate these auxiliary anodes by ion exchange membranes. Cyanide formation can therefore not be completely avoided in this application.

EP 1 702 090 B1 claims a method which provides for the separation of the cathode and anode compartments through an open cell material. The separator is made of polytetrafluoroethylene or polyolefin, such as polypropylene or polyethylene. The pore diameters have a dimension between 10 nm and 50 μm. In contrast to the use of ion exchange membranes, where the charge transport through the membrane is carried out by the exchange of cations or anions, it can be carried out with the use of open-cell separators only by the electrolyte transport through the separator. Complete separation of the catholyte from the anolyte is not possible. It can therefore not be completely prevented that amines reach the anode and are oxidized there. Cyanide formation is therefore not completely ruled out in this process. A disadvantage of this method also that when using separators with a very small pore diameter (eg 10 nm) of the electrolyte exchange and thus the current transport is very much hindered. It is claimed that the increase in the bath voltage when using the separators should be less than 5 volts. The resulting bath voltage would be almost doubled compared to a process which operates without separation of cathode and anode compartment. This results in a much higher energy consumption during the deposition of the zinc nickel layers. The 5 Volt bath voltage also causes a strong warming of the Electrolyte. Since a prerequisite for the deposition of a constant alloy composition is the constant maintenance of the electrolyte temperature in the range of ± 2 ° C, so when applying such a high bath voltage, a considerable effort for the cooling of the electrolyte must be applied. The use of separators with a pore diameter of 50 microns causes a virtually unhindered exchange of electrolyte between the cathode and anode compartment and thus can not prevent the formation of cyanides.

A similar concept will be used in the EP 1 717 353 B1 claimed. The anode and cathode compartments are separated there by a filtration membrane. The size of the pores of the filtration membrane is in the range of 0.1 to 300 nm. A certain transfer of electrolyte from the cathode to the anode space is deliberately accepted. When using certain organic brighteners, zinc nickel electrolytes do not work satisfactorily when membrane processes accordingly EP 1 344 850 or EP 1 292 724 be used. These brighteners obviously require anodic activation to produce their full effect. This reaction is ensured when using filtration membranes. However, this also means that the formation of cyanides can not be completely avoided. Table 4 of the EP 1 717 353 it can be seen that when the filtration membranes are used at a bath load of 50 Ah / l, a new formation of 63 mg / l of cyanide takes place. Without the use of filtration membranes, a new formation of 647 mg / l cyanide occurs under otherwise identical conditions. The use of filtration membranes can thus reduce the formation of cyanide by about 90%, but not completely prevent it.

All of the abovementioned membrane processes also have the disadvantage that they have a considerable space requirement in a bath container of a zinc-nickel electrolyte. One Subsequent installation in an existing system is therefore usually not possible due to space limitations.

DE 10 2008 058 086 A1 claims a method for depositing functional layers from acidic or alkaline zinc or zinc alloy baths. The method includes a step of providing separation of cyanide ions by means of ion exchangers. According to the DE 10 2008 058 086 A1 For the separation of cyanide ions, any ion exchange resin capable of binding cyanide ions is suitable. As an example of such an ion exchange resin, which can attach cyanide ions to the anchor groups, inter alia, strongly basic anion exchangers are mentioned which have quaternary ammonium ions as functional groups. It is described that the subsequent regeneration of such anion exchangers is difficult and for a not even complete regeneration concentrated sodium chloride solutions have to be used.

In the light of the above-cited prior art, there remains a need for an agent that can be used to regenerate zinc alloy baths, and more particularly to an agent that can be easily and inexpensively disposed of after use for regeneration.

The object underlying the present invention is therefore to provide a means and a simplified method for the regeneration of a zinc nickel electrolyte by removing the cyanide ions.

Surprisingly, it has now been found that cyanide ions that have formed in a zinc nickel electrolyte can precipitate selectively in the form of a cyanide-containing precipitate when one or more soluble quaternary ammonium compounds are added to the zinc nickel electrolyte be added. Further studies have shown that the soluble quaternary ammonium compounds, in the sense of ion pair formation, react selectively with the tetracyanoxide anions present in the electrolyte and precipitate as a sparingly soluble product. The cyanide-containing reaction product can be easily removed by, for example, filtration from the electrolyte.

The present invention is particularly against the background of the teaching of the above-mentioned DE 10 2008 058 086 A1 Surprisingly, because it describes that only the cyanide ions bind to the ion exchanger used. This is confirmed by the embodiments describing the regeneration of a zinc-nickel alloy bath with a strongly basic ion exchanger. Here, as in the present invention, a tetracyanonickel anion complex does not react with the strongly basic ion exchanger, but only the cyanide ions. It is explicitly described that the nickel concentration in the electrolyte remains constant. On the other hand, for the present invention, it is critical that a tetracyanonickel complex react with the quaternary ammonium compound, because only in this case can a sparingly soluble product which is easily separable be obtained.

Regeneration literally means "restoration". For the purposes of this invention, the term "regeneration" refers to the recovery of a zinc nickel electrolyte in its trouble-free state by the removal of cyanide ions which have formed during the operation of the electrolyte.

For the regeneration of the zinc nickel electrolyte, any soluble quaternary ammonium compound can be used according to this invention. A quaternary ammonium compound is "soluble" in the sense of this invention if it has a solubility in the zinc nickel electrolyte of at least twice the molar amount in which the cyanide concentration calculated as tetracyanone nickel complex is present. In order to lower the cyanide concentration as much as possible, it is possible to use the soluble quaternary ammonium compound in excess of the cyanide concentration. It is therefore preferred if the solubility of the quaternary ammonium compound in the zinc nickel electrolyte is 10 times the molar amount of the molar amount of Tetracyanonickelkomp calculated based on the cyanide concentration.

The soluble quaternary ammonium compound preferably corresponds to the general formula [R ¹ R ² R ³ R ⁴ N] ⁺ X ^- , where R ¹ to R ^{4 are} identical or different and are C _1-24 -alkyl or -alkenyl, which may be may be mono- or polysubstituted by oxygen or may be substituted by hydroxyl or by an aryl radical optionally substituted by one or more halogen atoms or C _1-8 -alkyl radicals, or R ¹ to R ⁴ by ring closure of three radicals 5- or 6 -membered heterocyclic rings, such as pyridine or thiazoline, form, which in turn are optionally mono- or polysubstituted by C _1-4 alkyl or C _1-4 alkenyl, which optionally carry an aryl radical, which in turn with halogen, Amino or dimethylamino may be substituted, and X ^- for hydroxide, sulfate, halide, such as chloride, bromide or iodide, in particular chloride. Particular preference is given to those compounds having higher organic radicals, for example quaternary ammonium compounds of the general formula [R ¹ R ² R ³ R ⁴ N] ⁺ X ^- , where R ¹ = C _6-18 and R ² , R ⁸ , R ⁴ = C _1-4 . Particularly suitable quaternary ammonium compounds are listed below. The listing is only an example.
Dodecyl trimethyl ammonium chloride
Tetradecyltrimethylammonium chloride
Hexadecyltrimethylammonium chloride
Octadecyltrimethylammonium chloride
Bisoctyl-dimethyl
Bis-decyl-dimethyl-ammonium chloride
To tetradecyl dimethyl
Bis-hexadecyl dimethyl
Bis-octadecyl-dimethyl
Methyltrioctylammonium chloride
Methyl-tripropylammoniumchlorid
Trinonyl-methyl ammonium chloride
Tridecyl methyl ammonium chloride
Tridodecyl-methyl ammonium chloride
Tritetradecyl-methyl ammonium chloride
Trihexadecyl-methyl ammonium chloride
tetrabutylammonium
tetraoctylammonium
Benzyltriethylammonium chloride
Benzyl-tripropylammoniumchlorid
Benzyl-tributylammonium

Many of the above quaternary ammonium compounds are commercial products. For example, trialkylamines and alkyl halides, e.g. Alkyl chloride, alkyl bromide or alkyl iodide. The quaternary ammonium compounds thus formed have chloride, bromide or iodide as counterion. Furthermore, as alkylating agents and dialkylsulfates such. Dimethyl sulfate or diethyl sulfate used. The quaternary ammonium compounds are then obtained as alkyl sulfates, e.g. Methylsulfate or ethylsulfate.

The quaternary ammonium compounds can be used in the form obtained in the alkylation of tertiary amines for the precipitation of tetracyanonickel complexes according to the invention. However, it is preferred to use the ammonium compounds as hydroxide or sulfate salts. In order to prevent accumulation of, for example, halogen ions in the zinc nickel electrolyte, it is preferred to use quaternary ammonium halides before their use in quaternary Convert ammonium hydroxides. The conversion can be carried out by reactions known to the person skilled in the art. For example, the conversion of halide salts to hydroxide salts may be by anion exchange using basic ion exchangers or by double reaction with an alcoholic solution of sodium or potassium hydroxide. Quaternary ammonium compounds are also commercially available in the form of their hydroxide compounds. These may be neutralized with any acid, if necessary, to form quaternary ammonium compounds with any anion X ^- .

The zinc-nickel electrolyte regenerated according to the present invention is an aqueous electrolyte and typically has a zinc ion concentration in the new batch in the range of 5 to 15 g / l, preferably 6 to 10 g / l calculated as zinc, and a nickel ion concentration in the range of 0 , 6 to 3 g / l, preferably 0.6 to 1 g / l, calculated as nickel. For electrolytes that have been in production for a long time, due to the cyanide content, it is necessary to increase the nickel concentration equivalent to the cyanide contamination in the electrolyte. The zinc and nickel compounds used for the production of the zinc nickel electrolyte are not particularly limited. Usable are, for example, nickel sulfate, nickel chloride, nickel sulfamate or nickel methanesulfonate. Particularly preferred is the use of nickel sulfate. Further, the zinc nickel electrolytes contain an amine compound as a complexing agent for nickel. This amine compound is, for example, triethanolamine or ethylenediamine or homologous compounds of ethylenediamine, such as diethylenetriamine and tetraethylenepentamine. The complexing agent or mixtures of these complexing agents is / are usually employed in a concentration ranging from 5 g / l to 100 g / l, preferably 10 to 50 g / l, more preferably 20 g / l.

The zinc nickel electrolyte is strongly basic. To adjust the pH, for example, NaOH or KOH can be used, particularly preferably NaOH. Usually, a zinc nickel bath contains 80 to 160 g / l of sodium hydroxide. This corresponds to an approximately 2-4 molar solution.

The zinc nickel electrolyte may also contain various additives commonly used to deposit zinc nickel alloys. These are, for example, aromatic or heteroaromatic compounds as brighteners, such as benzylpyridinium carboxylate or pyridinium-N-propane-3-sulfonic acid.

In the method for regenerating a zinc nickel electrolyte according to this invention, the quaternary ammonium compound is preferably added to the zinc nickel electrolyte as an aqueous solution. Depending on the technical availability but also the use of a methanolic solution is possible. The addition of the quaternary ammonium compound in solid form is also possible. Preferably, a partial volume of the electrolyte to be treated is removed and treated in a treatment vessel with the previously calculated amount of quaternary ammonium compound as a precipitant. The required amount of quaternary ammonium compound results from the cyanide concentration in the zinc nickel electrolyte. Per 1 g / l of cyanide, an addition of at least 0.02 mol / l of quaternary ammonium compound is required. After a reaction time of about 0.5 to 24 hours, the precipitated reaction product can be separated, preferably by filtration, and the purified electrolyte can be returned to the production bath. The volume of the withdrawn partial electrolyte is calculated so that the production with the zinc nickel bath does not have to be interrupted.

In an alkaline zinc nickel bath usually a regular carbonate removal by strong cooling and Crystallization of the sodium carbonate performed. Preferably, cyanide removal by ion pairing is associated with this carbonate freezing. The precipitated ion pair can thus be separated together with the Natriumcarbonatschlamm and fed to a disposal.

The advantage of regenerating a zinc nickel electrolyte by ion pair formation between quaternary ammonium compounds and the Tetracyanonickelanion compared to the purification by use of strongly basic ion exchangers is above all that no complex and expensive ion exchange system is needed.

When quaternary ammonium compounds are used which do not lead to precipitation of ionic pairs in crystalline form, but oily phases are formed, separation by conventional phase separation techniques as known in the electroplating art (e.g., oil separators) is possible. Furthermore, it is also possible to remove ion pairs, which do not form directly in a depositable form, by treatment of the electrolyte with activated carbon.

EXAMPLES Inventive Example 1

• Zn: 7,8 g/l
• Ni: 1,45 g/l
• NaOH: 98,5 g/l
• Cyanid: 775 mg/l

The removal of cyanide was studied on a practice electrolyte with the following analytical values:

• Zn: 7.8 g / l
• Ni: 1.45 g / l
• NaOH: 98.5 g / l
• Cyanide: 775 mg / l

to 600 ml of the zinc nickel electrolyte was added at 20 ° C 6.2 g of tetrabutylammonium hydroxide (as 40 wt.% Aqueous solution) added and stirred for 2 hours. After a further 20 hours, it was filtered off. In the filtrate, a residual content of 42 mg / l cyanide was found. The cyanide concentration was thus reduced by 95%.

The determination of the cyanide was carried out with the cuvette test LCK 319 for slightly releasable cyanides of Fa. Long.

In the filtrate, 7.8 g / l zinc and 1.1 g / l nickel were measured. The decrease of the nickel value thus corresponds almost to the theoretical value (calculated as 0.24 g Ni, found 0.21 g) of the tetracyanone anion, when calculated on the absolute amount of cyanide removed. This shows that the separation of the cyanide is carried out in the form of Tetracyanonickelanions.

Inventive Example 2

In a second experiment, the quaternary ammonium compound used was benzyltriethylammonium chloride. 4.5 g of benzyltriethylammonium chloride were added to 600 ml of the zinc nickel electrolyte at 20 ° C. and stirred for 2 hours. After a further 20 hours, it was filtered off. In the filtrate a residual content of 82 mg / l cyanide was found. The cyanide concentration was thus reduced by 90%.

As in Example 1, 7.8 g / l zinc and 1.1 g / l nickel were measured in the filtrate. The decrease of the nickel value corresponds to the decrease in the accuracy of analysis as Tetracyanonickelanion.

Inventive Example 3

In a third experiment, the quaternary ammonium compound used was benzyltributylammonium chloride. To 600 ml of the zinc nickel electrolyte were added 20 ° C 2.9 g of benzyltributylammonium chloride and stirred for 2 hours. After a further 20 hours, it was filtered off. In the filtrate, a residual content of 31 mg / l cyanide was found. The cyanide concentration was thus reduced by 96%. In the filtrate, as in Examples 1 and 2, 7.8 g / l of zinc and 1.1 g / l of nickel were measured. The decrease of the nickel value corresponds to the decrease in the accuracy of analysis as Tetracyanonickelanion.

settling tests

• Testblech: Stahlblech
• Zellstrom: 2 A
• Versuchsdauer: 15 Minuten
• Elektrolyttemperatur: 35 °C

The deposition of the practice electrolyte with 775 mg / l cyanide was tested in a Hull cell test according to DIN 50957. The experimental conditions were:

• Test sheet: sheet steel
• Cell current: 2 A
• Duration of the experiment: 15 minutes
• Electrolyte temperature: 35 ° C

Result: Starting from the edge of the low current density range up to about 80% of the test sheet, the test sheet showed a semigloss, stainless steel-like appearance. The remaining 20% of the test sheet was dull gray.

The experiment was repeated with the sample after the precipitation of Tetracyanonickelanions by ion pair formation according to Example 1 of the invention. The deposition showed in the highest current density range again a uniform semi-glossy stainless steel look.

The examination of the treated electrolyte samples according to Examples 2 and 3 according to the invention gave an identical result to Example 1 according to the invention.

Claims (12)

Use of a soluble quaternary ammonium compound to regenerate a zinc nickel electrolyte by removing cyanide ions. Use according to claim 1, wherein the soluble quaternary ammonium compound has the general formula [R ¹ R ² R ³ R ⁴ N] ⁺ X ^- wherein R ¹ to R ^{4 are the} same or different and are C _1-24 alkyl or alkenyl which may optionally be interrupted once or several times by oxygen or may be substituted by hydroxyl or by an aryl radical optionally substituted by one or more halogen atoms or C _1-8 -alkyl radicals, or R ¹ to R ⁴ by ring closure of three Radicals form 5- or 6-membered heterocyclic rings, such as, for example, pyridine or thiazoline, which in turn are optionally mono- or polysubstituted by C _1-4 -alkyl or C _1-4 -alkenyl which may carry an aryl radical, which in turn may be substituted with halogen, amino or dimethylamino, and X- represents chloride, bromide, iodide, methanesulfonate, methylsulfate, ethylsulfate, hydrogensulfate, sulfate or hydroxide. Use according to claim 2, wherein R ^{1 is} a C _6-18 alkyl group and R ² , R ³ , R ^{4 are} each independently a C _1-4 alkyl group. Use according to any one of claims 1 to 3, wherein X is ^- chloride, bromide, iodide, methanesulfonate, methylsulfate, ethylsulfate, bisulfate, sulfate or hydroxide. Use according to any one of claims 1 to 4, wherein the zinc-nickel electrolyte is an aqueous electrolyte comprising the following composition: one or more soluble Zn (II) salts in an amount of 5-15 g / l calculated as zinc, one or more soluble Ni (II) salts in an amount of 0.6-3 g / l calculated as nickel, and one or more amine compounds in an amount of 5-100 g / l, and wherein the zinc nickel electrolyte has a hydroxide ion concentration of about 2-4 mol / l. Process for the regeneration of a zinc nickel electrolyte by removing cyanide ions, characterized by the steps: Adding a soluble quaternary ammonium compound to the zinc nickel electrolyte and - Removal of the cyanide-containing precipitate. The method of claim 6, wherein the cyanide-containing precipitate is removed by filtration. A process according to claim 6 or 7, wherein the soluble quaternary ammonium compound has the general formula [R ¹ R ² R ³ R ⁴ N] ⁺ X ^- wherein R ¹ to R ^{4 are the} same or different and are C _1-24 alkyl or Alkenyl which may optionally be interrupted once or several times by oxygen or may be substituted by hydroxyl or by an optionally substituted by one or more halogen atoms or C _1-8 alkyl radicals substituted aryl, or R ¹ to R ⁴ by ring closure of three radicals form 5- or 6-membered heterocyclic rings, such as pyridine or thiazoline, which in turn are optionally mono- or polysubstituted by C _1-4 -alkyl or C _1-4 -alkenyl, which may be an aryl radical which in turn may be substituted with halogen, amino or dimethylamino, and X ^{- is} chloride, bromide, iodide, methanesulfonate, methylsulfate, ethylsulfate, hydrogensulfate, sulfate or hydroxide. The method of claim 8, wherein R ^{1 is} a C _6-18 alkyl group and R ² , R ³ , R ^{4 are} each independently a C _1-4 alkyl group. A process according to any one of claims 6 to 9, wherein X is ^- chloride, bromide, iodide, methanesulfonate, methylsulfate, ethylsulfate, bisulfate, sulfate or hydroxide. Preference is given to X ^- hydrogen sulfate, sulfate or hydroxide. A method according to any one of claims 6 to 10, wherein the zinc nickel alloying electrolyte is an aqueous electrolyte comprising the following composition: one or more soluble Zn (II) salts in an amount of 5-15 g / l calculated as zinc,
one or more soluble Ni (II) salts in an amount of 0.6-3 g / l calculated as nickel, and
one or more amine compounds in an amount of 5-100 g / l,
and wherein the zinc nickel electrolyte has a hydroxide ion concentration of about 2-4 mol / l. A method according to any one of claims 6 to 11, wherein the thus-regenerated zinc nickel electrolyte is used for the deposition of Zinknickellegierungen.