EP2032742A2

EP2032742A2 - Aqueous, alkaline bath, devoid of cyanide, for depositing electroplated zinc alloy coatings

Info

Publication number: EP2032742A2
Application number: EP07726121A
Authority: EP
Inventors: Heiko Brunner; Lars Kohlmann; Roland Vogel; Konstantin Thom
Original assignee: Atotech Deutschland GmbH and Co KG
Current assignee: Atotech Deutschland GmbH and Co KG
Priority date: 2006-06-21
Filing date: 2007-06-21
Publication date: 2009-03-11
Also published as: EP2038453A2; EP1870495A1; US20100236936A1; WO2007147605A3; JP2009541581A; US20100155257A1; WO2007147605A2; BRPI0713489A2; WO2007147604A3; BRPI0713500A2; WO2007147603A2; WO2007147603A3; WO2007147604A2; JP2009541580A

Abstract

The invention relates to an aqueous, alkaline electrolyte bath, devoid of cyanide, for depositing zinc alloy layers on substrate surfaces, said bath containing cationic pyridinium compounds as brighteners and polyamines as complexing reagents. The electrolyte bath is suitable for the deposition of glossy, uniform zinc alloy coatings.

Description

Aqueous alkaline, cyanide-free bath for the galvanic deposition of

Zinc alloy coatings

Field of the invention

The present invention relates to an aqueous alkaline galvanic bath without addition of cyanide ions as complexing reagents for the deposition of zinc alloy coatings, in particular zinc-nickel, zinc-iron and zinc-cobalt coatings containing as additives cationic heteroaromatic nitrogen compounds, and a method for depositing bright and even zinc alloy coatings using the bath.

Background of the invention

Zinc deposits of cyanide, alkaline solution have dominated the industrial market for many years. The ever-increasing legal requirements regarding the disposal of old zinc and zinc alloy electrolyte baths and the associated strict control of the wastewater have led to an increased interest in non-cyanide zinc and zinc alloy baths. Zinc alloying electrolytes are particularly important here.

Such metal coatings are used to improve the corrosion properties and to achieve certain optical properties.

For example, galvanized zinc has been used by the automotive industry for decades to provide an economical, highly corrosion resistant coating. With the ongoing demands for higher quality and comprehensive warranty, however, both the automotive manufacturers and the corresponding supplier industry had to develop new coating systems. Zinc-nickel alloy coatings show the best overall performance in terms of extended corrosion resistance.

It has been found that in these alloy coatings, the amount of nickel in the galvanic zinc-nickel coatings, which is useful for improved corrosion protection, is 4 to 18% nickel, with a proportion of 12 to 15% being particularly optimal. Both acidic and alkaline zinc-nickel baths are known in the art. The work "Modern Electroplating" (Ed. M. Schlesinger and M. Paunovic) 4 ^th edition (2000), John Wiley & Sons, p. 423 ^ * 60 gives an overview of technically relevant galvanic baths.

Acidic zinc-nickel alloy baths are typically based on inorganic zinc and nickel salts, such as zinc sulfate, zinc chloride, nickel sulfate or nickel chloride, which contain various additives that improve both gloss and grain structure and provide control over the zinc / nickel ratio ,

Acidic baths for zinc-nickel alloy deposits generally contain an acid, e.g. Boric acid or sulfuric acid and other additives, e.g. Brighteners, wetting agents etc.

A disadvantage of such acidic baths is the strong corrosion effect of the electrolyte on the galvanic plant. The alkaline baths have gained acceptance in practice because they have a better metal distribution and thus better protect the workpiece against corrosion. In addition, their nickel installation over a wide current density range is much more uniform, which is accompanied by better corrosion protection. However, they have a lower cathodic current efficiency, which is between 20 and 50%. Such a bath is described as a zinc-nickel bath in U.S. Patent 3,681,211 which teaches the use of polyethyleneimine to achieve a black coating. Here, an aqueous zinc-nickel solution is adjusted to a pH between 10 and 13 with sodium hydroxide solution. By the use of polyethyleneimine complexation of the zinc and in particular the nickel ions is achieved, which are present for example as a zinc hydroxide and nickel hydroxide precipitate in the solution.

The use of polyethyleneimines has been widely used since the early seventies of the last century in conjunction with alkaline zinc and zinc alloy baths. Polyethyleneimines which can be used for this purpose are described in US Pat. No. 3,881,211 where they have an average molecular weight of 600 to 100,000 and an often complex and branched structure. US Pat. No. 3,993,548 also describes the use of a high molecular weight polyethyleneimine and quaternary ammonium silicates for the electrodeposition of bright, homogeneous zinc layers. In this case, the bath may contain additional brighteners, such as benzyl betaine nicotinate.

In addition to polyethylenes, other complexing agents are also known as complexing reagents. Thus, US Pat. No. 4,861,442 describes aqueous alkaline baths comprising zinc and nickel ions, alkali metal hydroxide, an aminoalcohol polymer, a nickel complexing agent and an amino acid and / or a salt of an amino acid. The pH of the bath is 11 and higher.

U.S. Patent 4,877,496 describes aqueous alkaline baths comprising zinc and nickel ions, an alkali metal hydroxide, a metal complexing agent, a primary brightener, and a gloss enhancer. The primary brightener here is a condensation product of an amine, such as ethylenediamine with epihalodrin. The gloss enhancer is at least one aromatic aldehyde. Tertiary brighteners such as tellurium oxide, telluric acid or telluric acid or their salts may also be included in the baths.

No. 4,889,602 describes aqueous electrolyte baths which have a pH of more than 11 and comprise zinc and nickel ions and at least one compound from the series aliphatic amines, polymeric aliphatic amines and hydroxyaliphatic carboxylic acids and their salts.

US Pat. No. 5,417,840 describes the use of a bath system which mainly contains polyalkyleneimines as complexing reagents and pyridinium betaines, in particular sulfobetaines. DE 198 48 467 C2 describes the use of triethylenetetramine, tetraethylenepentamine or pentaethylene tetramine as a complexing system in combination with N-benzyl nicotinate betaine as primary brightener.

Benzylpyridinium compounds have long been known as brighteners for the deposition of zinc layers. For example, Kinzoku Hyomen Gijutsu (1980), 31, pp. 244-248, describes the effect of 3-substituted pyridinium compounds on the texture of the electrodeposited zinc layers U.S. Patent No. 6,652,728 describes the use of N-benzyl pyridinium-3-carboxylate and N, N'-p-xylylene bis (pyridinium-3-carboxylate) as a brightener in combination with cationic polymeric urea derivatives for alkaline zinc and zinc alloy baths, especially zinc-iron baths.

In all known in the literature for metal deposition baths there is the problem that often not over the entire current density range, a uniform layer or a uniform gloss is achieved. Often, zinc-nickel layers containing a nickel content greater than 15% are also obtained. Furthermore, the galvanic baths available on the market for the deposition of zinc-nickel alloy layers often only show a moderate cathodic current yield accompanied by a strong evolution of hydrogen.

Description of the invention

The invention is therefore based on the object to develop a galvanic bath for Zinklegie- tion deposits, which allows visually appealing zinc alloy layers. In addition, a more homogeneous zinc alloy metal distribution and an optimum zinc / alloy metal ratio should be set. In addition, a uniform layer thickness with high gloss and the uniformity of the alloy components in the coating should be maintained over a wide current density range.

The invention relates to an aqueous alkaline, cyanide-free electrolyte bath for the deposition of zinc alloy layers on substrate surfaces, comprising the following components:

a) a zinc ion source and a source of further metal ions;

b) hydroxide ions;

c) at least one pyridinium compound of the general formula I or II:

wherein Ri is a substituted or unsubstituted, saturated or unsaturated, aliphatic or araliphatic hydrocarbon radical having 1 to 12 carbon atoms,

R ₁ 'is a divalent substituted or unsubstituted, saturated or unsaturated, aliphatic or araliphatic hydrocarbon radical having 1 to 12 carbon atoms,

X _{1 is} NR _x Ry and X _{2 is} hydroxyl, OR _x or NR _x R _y , wherein R _x and R _{y may be the} same or different and are hydrogen or linear and / or branched alkyl groups having 1 to 12 carbon atoms, and

Y ^"is a counterion; and

d) at least one complexing reagent of the general formula III or IV:

III

IV

wherein Xi, X ₂ and X _{3 may be the} same or different and represent an alkoxy, or a primary, secondary or tertiary amino group, R1, R2 and R3 may be the same or different and represent hydrogen, a C ₁ -C ₂ - alkyl, C ₁ -C ₂ -AIkOXyI-, allyl, propargyl or benzyl group and

n and m can be the same or different and stand for an integer from 0 to 5.

According to a preferred embodiment, R 1 in formula I is substituted aryl of the following formulas R 1a to RI I:

wherein FG is a radical selected from the group consisting of carboxy, ester, sulfonic, carbamoyl, amino, cyano, alkyl, alkoxy, hydroxy, trifluoromethyl, allyl, propargyl, 4 Sulfobutyl, 3-sulfopropyl, 4-carboxybutyl, 3-carboxypropyl, hydrogen and halogens selected from fluoro, chloro and bromo,

and Ri 'is but-2-enyl, but-2-ynyl or aryl of the following formulas R1'a to R1'r:

R1'a R1'b R1'c

RVd R1'e R1'f

wherein FG is a radical selected from the group consisting of carboxy, ester, sulfonic acid, carbamoyl, amino, cyano, alkyl, alkoxy, trifluoromethyl radicals, hydrogen and halogens selected from fluoro, chloro and bromo , wherein all rings or individual fused rings may be substituted. Preferably, the radicals Ri and RT in the formulas I and II are bonded via a methylene group to the pyridinium radical.

Preferred araliphatic hydrocarbon radicals are e.g. Benzyl (R1a) and naphthylmethyl (R1b).

For the purposes of the present invention, fluorides, chlorides and bromides can be used as halides. Furthermore, in the bath according to the invention, it is possible to use those compounds which are similar to the halides in terms of their physical and chemical properties, ie. so-called pseudohalides. Such pseudohalides are known per se to those skilled in the art and are described, for example, in the Römpp Lexikon, Chemie, 10th Edition, page 3609. In the context of the present invention, the pseudohalides also include radicals such as e.g. Mesitylate and triflate.

Preferred counterions (Y ^" ) are halides (eg, fluoride, chloride, bromide) and pseudohalides.

Preferably, further components are included in the plating bath to improve the properties of the deposited alloy. These may be, for example, polymers of aliphatic amines and metal complexing agents.

The electroplating baths according to the invention contain an inorganic alkaline component, preferably a hydroxide of the alkali metals, and more preferably sodium hydroxide and / or potassium hydroxide, to adjust a pH of at least 10 and preferably at least 11 in the bath. In this case, amounts of 50 to about 250 g / l and particularly preferably from 90 to about 130 g / l of the alkaline component can be used.

The electrolyte baths of the invention usually contain zinc ions in concentrations ranging from about 1 to about 100 g / L, with concentrations of 4 to 30 g / L being preferred. The zinc ions may be present in the bath of the invention in the form of a soluble salt, such as zinc oxide, zinc sulfate, zinc carbonate, zinc acetate, zinc sulfamate, zinc hydroxide, zinc tartrate, etc. As alloying metal, the baths according to the invention contain about 0.1 to 50 g / l metal ions. Suitable metal salts are hydroxides, sulfates, carbonates, ammonium sulfates, sulfamates, acetates, formates and halides, preferably chloride and bromide.

The baths according to the invention preferably contain about 0.1 to 50 g / l of nickel ions as the alloying metal. Suitable nickel salts are nickel hydroxide, nickel sulfate, nickel carbonate, ammonium nickel sulfate, nickel sulfamate, nickel acetate, nickel formate and nickel halides.

The zinc and alloy metal sources that may be used in the electrolyte baths of the invention may include one or more of the nickel and zinc sources described above.

The electrolyte baths according to the invention contain the abovementioned aromatic heterocyclic nitrogen-containing compounds of the general formula I or II for the purpose of sustainably improving the leveling and luster formation of the deposited layers over a wide current density range. Accordingly, the compounds of the formulas I and II are also referred to below as brighteners according to the invention.

Preferred compounds of the formula I or II are 1-benzyl-3-carbamoylpyridinium chloride, 1,4-chlorobenzyl-S-carbamoylpyridinium chloride, 1- (2'-fluorobenzyl) -3- carbamoylpyridinium chloride, 1- (2'-methoxybenzyl) -3-carbamoylpyridinium chloride, 1- (2'-carboxybenzyl) -3-carbamoylpyridinium chloride, 1- (2'-carbamoyl) pyridinium chloride; Carbamoyl-benzyl) -3-carbamoyl-pyridinium chloride, i - ^ '- chloro-benzo-O-S-carbamoyl-pyridinium chloride, 1- (3'-fluoro-benzyl) -3-carbamoyl-pyridinium chloride, 1 - (3'-methoxy-benzyl) -3-carbamoyl-pyridinium chloride, i-β'-carboxy-benzo-O-S-carbamoyl-pyridinium chloride, 1- (3'-carbamoyl-benzo-O-S-carbamoyl-pyridinium chloride, 1- (4'-chlorobenzyl) -3-carbamoylpyridinium chloride, 1- (4'-fluorobenzyl) -3-carbamoylpyridinium chloride, 1- (4'-methoxybenzyl ) -3-carbamoyl-pyridinium chloride, 1- (4'-carboxy-benzyl) -3-carbamoyl-pyridinium chloride, 1- (4'-carbamoyl-benzyl) -3-carbamoyl-pyridinium chloride, (1 '-Methyl-naphthyl) -3-carbamoyl-pyridinium chloride, 1- (1'-methyl-naphthyl) -3-carbamoyl-pyridine ium bromide, 1- (1'-methyl-naphthyl) -3-carbamoyl-pyridinium-fluoride, i.i'-fBut ^ -enyO-S.S'-bis-carbamoyl-bispyridinium-dichloride, 1, 1 ' (But-2-enyl) -3,3'-bis-carboxy-bis-pyridinium dichloride, i-allyl-S-carbamoyl-pyridinium chloride, i-allyl-S-carboxy-pyridinium chloride, 1-propargyl 3-carbamoyl-pyridinium chloride, 1,1 '- (but-2-ynyl) -3,3'-bis-carbamoyl- bispyridinium dichloride, 1,1 '- (but-2-ynyl) -3,3'-bis-carboxy-bispyridinium dichloride, 1,1' - (xylenyl) -3,3'-bis-carbamoyl-bis- pyridinium dibromide, 1- (3'-sulfopropyl) -3-carbamoylpyridinium betaine and the corresponding bromides, fluorides, iodides and pseudo-halides (eg triflates, tosylates) of the compounds listed above.

The brighteners can be readily prepared by reacting the corresponding nicotinic acid amides or nicotinic acid derivatives with the corresponding benzyl halides in a suitable solvent, e.g. Ethanol, propanol, iso-propanol, butanol, isobutanol, methanol or mixtures thereof, DMF, DMAc, NMP, NEP, in bulk or in an aqueous medium in the heat under normal or elevated pressure. The reaction times required for this are between one and 48 hours, depending on the starting material used. For this purpose, in addition to the classic heat sources and a microwave oven can be used. The resulting pyridinium compounds can either be used directly as an aqueous or alcoholic reaction solution or, after cooling, isolated by filtration or removal of the appropriate solvent. Purification of the compounds may be carried out by recrystallization in a suitable solvent, e.g. Ethanol take place.

The bispyridinium compounds of general formula II can be prepared according to US Pat. No. 6,652,728.

The compounds of the formula I or II can be used alone or as a mixture in a concentration of 0.001 to 20 g / l and more preferably of 0.01 to 10 g / l. The baths may contain a combination of the pyridinium compounds of formula I or II.

The baths according to the invention for zinc-nickel deposits contain, as complexing reagents, compounds of the general formula III or IV. The baths may contain a combination of the complexing reagents of the formula III or IV.

The amounts of polyamine compounds of the formula III or IV used in the baths according to the invention are between 5 and 100 g / l, depending on the zinc and nickel ion concentration.

Examples of suitable complexing reagents for the baths according to the invention are, for example, diethylenetriamine, tetraethylenepentamine, pentaethylenehexamine. Furthermore, can Complexing reagents are used, as described in US Patent 5,417,840.

The baths according to the invention can be prepared by conventional methods, for example by adding the specific amounts of the above-described components to water. The amount of base component, e.g. Sodium hydroxide should be sufficient to achieve in the bath the desired pH of at least 10 and preferably above 11.

In a preferred embodiment, the electrolytic bath according to the invention comprises 1 to 100 g / l of zinc ions, 0.1 to 50 g / l of alloying metal ions, 5 to 100 g / l of at least one compound of general formula III or IV and 0.001 to 20 g / l of at least one Compound of general formula I or II or a combination thereof.

In a further preferred embodiment, the electrolytic bath according to the invention comprises 4 to 30 g / l of zinc ions, alloying metal ions selected from nickel, iron, cobalt, manganese and 0.01 to 10 g / l of at least one compound of general formula I or II or a combination of them.

In a further preferred embodiment, the electrolytic bath according to the invention contains as alloying metal nickel in an amount of 0.1 to 50 g / l, iron in an amount of 10 to 120 mg / l, manganese in an amount of 10 to 100 g / l and / or cobalt in an amount of 10 to 120 mg / l.

The baths according to the invention deposit a bright, level and ductile zinc alloy layer at any conventional temperature of about 15 ° C to 50 ⁰ C, preferably 20 ⁰ C to 30 ⁰ C, more preferably about 25 ° C, from. At these temperatures, the baths according to the invention are stable and effective over a wide current density range of 0.01 to 10 A / dm ² , more preferably from 0.5 to 4 A / dm ² .

The baths of the invention may be operated in a continuous or intermittent manner, and from time to time the components of the bath will have to be supplemented. The components of the bath may be added singly or in combination. Further, they can be varied over a wide range depending on the kind and properties of the zinc alloy baths to which the substances are added. Table 1 shows according to a preferred embodiment, with nickel as an alloying metal to influence the layer thickness and nickel incorporation in the inventive electrolyte for the deposition of a zinc-nickel alloy (using 4.03 ^• KT ⁴ ITIOI /! Indicated pyridinium respect and tetraethylenepentamine as compound of the formula III):

Table 1

Influence of pyridinium compounds on zinc-nickel alloy deposits

(Amount 4.03 ^• 10 ^ mol / l):

As can be seen from Table 1, when using the carbamoyl compounds (Examples 1 and 4 to 10) or compounds of the formula II (Example 3) in terms of the layer thickness, which is directly proportional to the current efficiency, as well as in terms of nickel incorporation rates more favorable Values received. Thus, with the brighteners according to the invention, current yields are obtained which are up to 38% higher than conventional brighteners, such as, for example, 1-benzyl-3-carboxy-pyridinium chloride (Example 2 - Comparative Example), which is described, for example, in DE 102 23 622 B4 mentioned, can lie. Table 2 shows the influence of the brighteners of the invention when using a uniform mass use:

Table 2

Influence of pyridinium compounds on zinc-nickel alloy deposits

(Amount used 100 mg / l):

By varying the groups present on the nitrogen, different nickel incorporation rates can be obtained, depending on the aryl or alkyl radical used and the groups attached thereto. Likewise, as shown in Tables 1 and 2, depending on the brightener used and its amount, different effects in terms of gloss, layer thickness and nickel incorporation rates over a large mass and mass range can be obtained and the baths of the invention depending on the desired Layer performance can be adjusted by selecting the additive or an additive mixture targeted.

Crucial for this is the interaction between the pyridinium compounds used as brighteners and the complexing agents of the baths according to the invention. Thus, as can be seen from Table 3, it has surprisingly been found that the additive combination as described for alkaline zinc deposits in US Patent 4,071,418, despite the use of the same pyridinium compounds for zinc alloy deposits, especially for zinc-nickel deposits , is completely unsuitable. In spite of the existence of a homogeneous zinc-nickel complex solution, when using these electrolytes, as described in the abovementioned patent, only zinc layers are deposited in significantly poorer current yields.

Table 3

Comparison of the zinc-nickel electrolytes of the invention with a zinc-nickel electrolyte containing the additive combination described in U.S. Patent 4,071,418:

A further advantage of the zinc-nickel alloy baths according to the invention is that, as a rule, the use of aromatic aldehydes and tellurite as brightener can be completely dispensed with.

An advantage of the electrolytes according to the invention in comparison with the electrolyte of DE 19848467 C2 is the surprisingly low consumption of the quaternized nicotinamide derivatives according to the invention in comparison to N-benzyl nicotinate. As Application Example 19 shows, the consumption of the pyridinium compounds acting as brighteners is compounds of the electrolytes according to the invention significantly lower and thus more economical than the market-standard pyridinium derivatives based on nicotinic acid.

The baths according to the invention may contain, in addition to the abovementioned additives, known planarizers such as 3-mercapto-1, 2,4-triazole and / or thiourea, with thiourea often being preferred.

Surprisingly, it has been found that in the case of the electrolytes according to the invention the usual use of aromatic aldehydes or their bisulphite adducts as additional brighteners, such as, for example, 4-hydroxybenzaldehyde, 4-hydroxy-3-methoxybenzaldehyde, 3,4-dimethoxybenzaldehyde, 3,4-methylenedioxybenzaldehyde, 2-hydroxybenzaldehyde or mixtures thereof can be dispensed with.

In a preferred embodiment, the electrolyte bath according to the invention thus contains no aromatic aldehydes or their bisulfite adducts as additional brighteners, in particular no 4-hydroxybenzaldehyde, 4-hydroxy-3-methoxybenzaldehyde, 3,4-dimethoxybenzaldehyde, 3,4-methylenedioxybenzaldehyde or 2-hydroxybenzaldehyde or bisulfite adduct thereof.

The aqueous alkaline baths according to the invention can generally be used for all types of substrates on which soft zinc alloys can be deposited. Examples of useful substrates include mild steel, spring steel, chrome steel, chromium-molybdenum steel, copper, copper-zinc alloys.

Another object of the invention is therefore a process for the electrodeposition of zinc alloy coatings on conventional substrates, wherein the electrolyte according to the invention is used. In this case, the substrate to be coated is introduced into the electrolyte bath.

Preferably, in the inventive method, the deposition of the coatings at a current density of 0.01 A / dm ² to 10 A / dm ² and at a temperature in the range of 15 to 50 ⁰ C, preferably 20 to 30 ⁰ C, more preferably about 25 ° C. The method according to the invention can be carried out in the application for mass parts, for example as a drum electroplating method and for depositing on larger workpieces as a rack electroplating method. Anodes are used which can be soluble, such as zinc anodes, which also serve as the zinc ion source, to replace the zinc deposited on the cathode by dissolving zinc at the anode.

On the other hand, insoluble anodes (e.g., platinized titanium mixed oxide anodes) may also be employed, and the zinc ions and / or other metal ions withdrawn from the electrolyte must be otherwise re-added in alloy depositions, e.g. using a zinc dissolving container.

As in the case of galvanic deposition, the method according to the invention can be operated with air injection, with goods movement or without movement, without resulting in any disadvantages for the coatings obtained. To avoid or reduce oxidations of the added additives, it is possible to work with the separation of the electrode spaces or with the use of membrane anodes.

The current source used are commercial DC converters or pulse rectifiers.

Examples

The following examples illustrate the invention without, however, limiting the invention to these.

Production Example 1: Synthesis of 1- (4'-methoxy-benzvπ-3-carbamoylpyridinium chloride

In a 100 ml round bottom flask with reflux condenser, 60 ml of water, 9.2 g of nicotinamide (98%) (0.0738 mol), 11.68 g of 4-methoxybenzyl chloride (99%) (0.07378 mol ) and refluxed for 24 hours. After completion of the reaction, the water is removed in vacuo and the residue taken up in 200 ml of ethanol and heated for a further hour under reflux. Subsequently, the reaction cooled to 4 ° C and the resulting white solid was filtered off and dried in vacuo. 16.92 g of a white solid were obtained (82.26% of theory).

Production Example 2: Synthesis of 1- (4'-chloro-benzyl) -3-carbamoyl-pyridinium-chloroth

In a 100 ml round bottom flask with reflux condenser, 60 ml of ethanol, 10 g of nicotinamide (98%) (0.0802 mol), 13.05 g of 4-chloro-benzyl chloride (99%) (0.0802 mol ) and refluxed for 24 hours. After completion of the reaction, the solid residue is boiled for an additional 15 minutes in 200 ml of an ethanol / methanol mixture and then cooled to 4 ° C. The resulting solid is filtered off and dried in vacuo. 18.82 g of a white solid were obtained (82.87% of theory).

Preparation Example 3: Synthesis of 1- (4'-carboxybenzyl) -3-carbamoylpyridinium chloride

60 ml of ethanol, 7.09 g of nicotinamide (98% strength) (0.0569 mol), 10.22 g of 4-chloro-benzoic acid (95% strength) (0, 100 g) are added to a 100 ml round-bottomed flask with reflux condenser. 0569 mol) and heated under reflux for 24 hours. After completion of the reaction, the reaction mixture is cooled to 4 ° C, the resulting solid was filtered off and dried in vacuo. There was obtained 13.21 g of a white solid (79.21% of theory).

Preparation 4: Synthesis of 1- (1'-methyl-naphthyl) -3-carbarnoyl-pyridinium chloride

60 ml of ethanol, 10 g of nicotinamide (98% strength) (0.0802 mol), 15.75 g of 1-chloro-methyl-naphthalene (90% strength) (0, 100 g) are added to a 100 ml round-bottom flask with reflux condenser. 0802 mol) and heated under reflux for 24 hours. After completion of the reaction, the solid residue is boiled for a further 15 minutes in 200 ml of an ethanol / methanol mixture (75:25) and then cooled to 4 ° C. The resulting solid is filtered off and dried in vacuo. 19.37 g of a white solid were obtained (80.84% of theory). Production Example 5: Synthesis of 1- (4'-fluorobenzyl) -3-carbamoylpyridinium chloride

In a 100 ml round bottom flask with reflux condenser, 60 ml of ethanol, 10 g of nicotinamide (98%) (0.0802 mol), 11, 72 g of 4-fluoro-benzyl chloride (99%) (0.0802 mol ) and refluxed for 24 hours. After completion of the reaction, the solid residue is boiled for an additional 15 minutes in 200 ml of an ethanol / methanol mixture and then cooled to 4 ° C. The resulting solid is filtered off and dried in vacuo. 18.13 g of a white solid were obtained (84.76% of theory).

Preparation 6: Synthesis of 1,1 '- (xylenyl) -3,3'-bis-carbamoyl-bis-pyridinium dichloride

In a 100 ml round-bottomed flask with reflux condenser, 60 ml of ethanol, 10 g of nicotinamide (98% strength) (0.0802 mol), 7.16 g of α, α'-dichloro-p-xylene (98% strength) (0.0401 mol) and heated under reflux for 24 hours. After completion of the reaction, the solid residue is boiled for an additional 15 minutes in 200 ml of an ethanol / methanol mixture and then cooled to 4 ° C. The resulting solid is filtered off and dried in vacuo. 12.29 g of a white solid were obtained (73.13% of theory).

Preparation Example 7: Synthesis of i-allyl-S-carbamoyl-pyridinium chloride

In a 100 ml round bottom flask with reflux condenser, 60 ml of ethanol, 10 g of nicotinamide (98%) (0.0802 mol), 6.26 g of allyl chloride (98%) (0.0802 mol) are added and 24 Heated under reflux for hours. After completion of the reaction, the reaction mixture is cooled to 4 ° C and the resulting solid is filtered off and dried in vacuo. 9.25 g of a white solid were obtained (58.07% of theory).

Preparation 8: Synthesis of benzyl 3-carbamoylpyridinium chloride

In a 100 ml round bottom flask with reflux condenser, 60 ml of ethanol, 10 g of quinoline (98%) (0.0802 mol), 10.252 g of benzyl chloride (99%) (0.0802 mol) and 24 hours under Reflux heated. After completion of the reaction, the reaction mixture Cooled 4 ° C, the resulting solid was filtered off and recrystallized from one liter of ethanol. There was obtained 19.00 g of a white crystalline solid (95.33% of theory).

Preparation 9: Synthesis of 1,1 '- (but-2-enyl) -3,3'-bis-carbamoyl-bis-pyridinium dichloride

60 ml of ethanol, 10 g of nicotinamide (98% strength) (0.0802 mol), 5.90 g (0.0401 mol) of trans-1, 4-dichloro-2-one in a 100 ml round-bottomed flask with reflux condenser. butene (85% - ig) and heated to reflux for 24 hours After completion of the reaction, the reaction mixture is cooled to 4 ⁰ C and the resulting solid was filtered off and dried in vacuo. 13.64 g of a white solid were obtained (92.19% of theory).

Application Example 1

An electrolyte with the following composition is used:

12 g / l Zn (OH) ₂

9.55 g / l NiSO ₄ ^■ 6 H ₂ O

120 g / l NaOH

36 g / l tetraethylene pentamine

100 mg / l 1-benzyl-3-carbamoyl-pyridinium chloride

250 ml of the electrolyte are filled into a Hull cell. The anode used is a nickel anode. The cathode sheet is coated at 1A for 15 minutes. After completion of the coating, the sheet is rinsed and dried under compressed air. The layer thickness measurement is made at two points (3 cm from the lower edge and 2.5 cm from the right and left edges) at high (3 A / dm ² ) and low current density (0.5 A / dm ² ). At these same places, the Ni content measurement is carried out. Measurements are taken with XRF at four different positions in the respective position in order to keep measurement errors as low as possible. A very shiny deposit was obtained.

The following layer thicknesses and nickel contents were obtained:

Application Example 2 (Comparative Example According to DE 102 23 622 AD:

Application Example 1 is repeated except that an electrolyte having the following composition is used:

12 g / l Zn (OH) ₂

9.55 g / l NiSO ₄ ^• 6H ₂ O

120 g / l NaOH

36 g / l tetraethylene pentamine

100 mg / l 1-benzyl-3-carboxy-pyridinium chloride

A bright deposit was obtained with the following layer thicknesses and nickel contents:

Application Example 3

12 g / l Zn (OH) ₂

9.55 g / l NiSO ₄ ^• 6H ₂ O

120 g / l NaOH

36 g / l tetraethylene pentamine

166 mg / l 1,1 '- (xylenyl) -3,3'-bis-carboxy-bis-pyndinium-dibromide

A very bright deposit was obtained with the following layer thicknesses and nickel contents:

Application Example 4:

12 g / l Zn (OH) ₂

9.55 g / l NiSO ₄ ^• 6H ₂ O

120 g / l NaOH

36 g / l tetraethylene pentamine

163.4 mg / l of 1,1 '- (xylenyl) -3,3'-bis-carbamoyl-bis-pyridinium dichloride

Application Example 5

12 g / l Zn (OH) ₂

9.55 g / l NiSO ₄ ^• 6H ₂ O

120 g / l NaOH

36 g / l tetraethylene pentamine

108 mg / l 1- (4'-fluorobenzyl) -3-carbamoyl-pyridinium chloride

Application Example 6:

12 g / l Zn (OH) ₂

9.55 g / l NiSO ₄ ^• 6H ₂ O

120 g / l NaOH

36 g / l tetraethylene pentamine

88 mg / l 1- (4'-methoxy-benzyl) -3-carbamoyl-pyridinium-chloroth

Application Example 7:

12 g / l Zn (OH) ₂

9.55 g / l NiSO ₄ ^■ 6 H ₂ O

120 g / l NaOH

36 g / l tetraethylene pentamine

123.5 mg / l 1- (1'-methyl-naphthyl) -3-carbamoyl-pyridinium chloride

Application Example 8:

12 g / l Zn (OH) ₂

9.55 g / l NiSO ₄ ^• 6H ₂ O

120 g / l NaOH

36 g / l tetraethylene pentamine

120.6 mg / l of 1- (4'-carboxybenzyl) -3-carbamoylpyridinium chloride

Application Example 9:

12 g / l Zn (OH) ₂

9.55 g / l NiSO ₄ ^• 6H ₂ O

120 g / l NaOH

36 g / l tetraethylene pentamine

139.9 mg / l 1,1 '- (but-2-enyl) -3,3'-bis-carbamoylpyridinium dichloride

Application Example 10

12 g / l Zn (OH) ₂

9.55 g / l NiSO ₄ ^• 6H ₂ O

120 g / l NaOH

36 g / l tetraethylene pentamine

76.85 mg / l of i-allyl-S-carbamoyl-pyridinium chloride

Application Example 11:

12 g / l Zn (OH) ₂

9.55 g / l NiSO ₄ ^• 6H ₂ O

120 g / l NaOH

36 g / l tetraethylene pentamine

100 mg / l 1,1 '- (xylenyl) -3,3'-bis-carboxy-bis-pyridinium-dibromide

Application Example 12:

12 g / l Zn (OH) ₂

9.55 g / l NiSO ₄ ^• 6H ₂ O

120 g / l NaOH

36 g / l tetraethylene pentamine

163.4 mg / l of 1,1 '- (xylenyl) -3,3'-bis-carbamoyl-bis-pyridinium dichloride

Application Example 13:

12 g / l Zn (OH) ₂

9.55 g / l NiSO ₄ ^• 6H ₂ O

120 g / l NaOH

36 g / l tetraethylene pentamine

88 mg / l 1- (4'-methoxybenzyl) -3-carbamoylpyridinium chloride

Application Example 14:

12 g / l Zn (OH) ₂

9.55 g / l NiSO ₄ ^• 6H ₂ O

120 g / l NaOH

36 g / l tetraethylene pentamine

100 mg / l 1- (1'-methyl-naphthyl) -3-carbamoyl-pyridinium chloride

Application Example 15

12 g / l Zn (OH) ₂

9.55 g / l NiSO ₄ ^■ 6 H ₂ O

120 g / l NaOH

36 g / l tetraethylene pentamine

100 mg / l 1- (4'-carboxybenzyl) -3-carbamoyl-pyridinium chloride

Application Example 16:

12 g / l Zn (OH) ₂

9.55 g / l NiSO ₄ ^• 6H ₂ O

120 g / l NaOH

36 g / l tetraethylene pentamine

300 mg / l of 1- (3'-sulfopropyl) -3-carbamoylpyridinium betaine

Application Example 17

12 g / l Zn (OH) ₂

9.55 g / l NiSO ₄ ^• 6H ₂ O

120 g / l NaOH

36 g / l tetraethylene pentamine

20 mg / l 1-benzyl-3-carbamoyl-pyridinium chloride

80 mg / l 1- (4'-fluorobenzyl) -3-carbamoylpyridinium chloride

Application Example 18 - Comparative Example according to US Pat. Nos. 4,071,418:

12 g / l Zn (OH) ₂

9.55 g / l NiSO ₄ ^■ 6 H ₂ O

120 g / l NaOH

76 ml of a 10% solution of the condensation product of dimethylaminopropylamine and 1, 3-dichloropropanol prepared according to Example 1 of US Patent 4,071, 418 100 mg / l of i-benzyl-3-carbamoyl-pyridinium chloride

A shiny, brownish shimmering deposit was obtained with the following layer thicknesses and nickel contents:

Application Example 19: Endurance test in a 5 l bath to determine the additive consumption

In a comparative experiment, electrolytes of the following composition are used ::

12 g / l Zn (OH) ₂

9.55 g / l NiSO ₄ ^• 6H ₂ O

120 g / l NaOH

36 g / l tetraethylene pentamine

100 mg / l of a pyridinium compound (N-benzyl nicotinate or 1-benzyl-3-carbamoyl-pyridinium chloride)

The use of N-benzyl nicotinate corresponds to the teaching of DE 19848467 C2.

In order to compare the Additiwerbrauch of the electrolyte of the invention and the electrolyte according to DE 198 48 467 C2, both electrolytes in a 5 I bath used analogously to the application examples described above for coating Nortonblechen. In this case, a Nortonblech is coated for 30 minutes at 6 A and then layer thickness and appearance are evaluated. With sufficient zinc and nickel content and good gloss appearance of the Norton sheets, the coating continues to be carried out. After each 50 Ah (10 Ah / l), a complete bath test consisting of a Hull cell test (as described above) and determination of the zinc and NaOH contents are carried out. If there is too little zinc or nickel (nominal value: 10 g / l zinc oxide, 2 g / l nickel) or NaOH, the corresponding lower quantity will be added. When the gloss decreases, the pyridinium compound is correspondingly replenished. Table 4 shows the additive consumption of pyridinium compounds as brighteners based on 10,000 Ah.

Table 4

Application example 19

Claims

claims

An aqueous alkaline, cyanide-free electrolyte bath for depositing zinc alloy layers on substrate surfaces, comprising the following components:

a) a zinc ion source and a source of further metal ions;

b) hydroxide ions;

c) at least one pyridinium compound of the general formula I or II:

wherein R-i is a substituted or unsubstituted, saturated or unsaturated, aliphatic or araliphatic hydrocarbon radical having 1 to 12 carbon atoms,

R-i 'is a divalent substituted or unsubstituted, saturated or unsaturated, aliphatic or araliphatic hydrocarbon radical having 1 to 12 carbon atoms,

X _{1 is} NR _x R _y and X _{2 is} hydroxyl, OR _x or NR _x R _y , wherein R _x and R _{y may be the} same or different and are hydrogen or linear and / or branched alkyl groups having 1 to 12 carbon atoms and

Y ^"is a counterion; and

d) at least one complexing reagent of the general formula III or IV:

IV

in which Xi, X ₂ and X _{3 may be} identical or different and represent an alkoxy, or a primary, secondary or tertiary amino group,

R1, R2 and R3 can and are hydrogen, a Ci-C ₁₂ alkyl, C ₁ -C ₁₂ -AIkOXyI- be identical or different, allyl, propargyl or benzyl group and

n and m can be the same or different and stand for an integer from 0 to 5.

2. Electrolyte bath according to claim 1, wherein R _{1 is} substituted aryl of the following formulas R1a to R1I:

wherein FG is a radical selected from the group consisting of carboxy, ester, sulfonic, carbamoyl, amino, cyano, alkyl, alkoxy, hydroxy, trifluoromethyl, allyl, propargyl, 4 Sulfobutyl, 3-sulfopropyl, 4-carboxybutyl, 3-carboxypropyl, hydrogen and halogens selected from fluoro, chloro and bromo, and

R 1 'is but-2-enyl, but-2-ynyl or aryl of the following formulas R 1'a to R 1'r:

RVa RVb RVc

RVd R1'e RVf

wherein FG is a radical selected from the group consisting of carboxy, ester, sulfonic acid, carbamoyl, amino, cyano, alkyl, alkoxy, trifluoromethyl radicals, hydrogen and halogens selected from fluoro, chloro and bromine, where all rings or individual fused rings may be substituted.

3. Electrolyte bath according to one of claims 1 or 2, comprising a combination of the pyridinium compounds of the formula I or II.

4. Electrolyte bath according to one of claims 1 to 3, containing a combination of complexing reagents of the formula III or IV.

5. electrolyte bath according to claim 1, comprising

1 to 100 g / l zinc ions,

0.1 to 50 g / l alloy metal ions,

5 to 100 g / l of at least one compound of the general formula III or IV and

0.001 to 20 g / l of at least one compound of general formula I or II or a combination thereof.

6. electrolyte bath according to claim 5, comprising

4 to 30 g / l zinc ions,

Alloy metal ions selected from nickel, iron, cobalt, manganese ions and

0.01 to 10 g / l of at least one compound of general formula I or II or a combination thereof.

7. An electrolyte bath according to claim 1, containing as alloying metal nickel in an amount of 0.1 to 50 g / l, iron in an amount of 10 to 120 mg / l, manganese in an amount of 10 to 100 g / l and / or Cobalt in an amount of 10 to 120 mg / l.

8. Electrolyte bath according to claim 1, containing as base an alkali metal hydroxide.

An electrolyte bath according to claim 8, wherein the alkali metal hydroxide is sodium hydroxide and / or potassium hydroxide and is present in an amount of 50 to 250 g / l.

10. electrolyte bath according to claims 1 to 10 having a pH of at least 10th

A method of electrodepositing bright and even zinc alloy coatings, comprising the step of introducing a substrate to be coated into a bath according to claims 1 to 10.

12. The method of claim 11, wherein the bath is operated at a current density of 0.01 to 10 A / dm ² .

13. The method of claim 11, wherein the bath is operated at a temperature of 15 to 50 ⁰ C.

14. The method of claim 11, wherein the bath is operated at a temperature of about 25 ° C.

The method of any of claims 11 to 14, wherein the coatings are deposited on a conductive substrate using a barrel plating process.

The method of any one of claims 11 to 14, wherein the coatings are deposited on a conductive substrate using a rack plating process.

17. The method of claim 11, wherein a coating of a zinc alloy with one or more metals selected from the group consisting of cobalt, nickel, manganese and iron is deposited on the substrate.