Acidic zinc or zinc-nickel alloy electroplating bath for depositing a zinc or zinc-nickel alloy layer

1. An acidic zinc or zinc-nickel alloy electroplating bath for depositing a zinc or zinc-nickel alloy layer characterized in that the electroplating bath comprises:

(i) at least a zinc ion source;

(ii) at least one triazole derivative having the general formula (I):

wherein

R 1 is selected from the group consisting of hydrogen, thiol, carboxylic acid, amino, methyl, methylsulfonyl, and methyl carboxylate;

R 2 is hydrogen or phenyl; and

R 3 is selected from the group consisting of hydrogen, amino, thiol, and phenyl, and wherein concentration of the at least one triazole derivative ranges from 0.5 to 7.5 mg/l;

(iii) at least one first poly(ethylene glycol) derivative having the general formula (II):

R 4 —[O—CH 2 —CH 2 ] n —O—R 5   (II)

wherein

n is ranging from 2 to 200;

R 4 is selected from the group consisting of a linear or branched C 1 -C 18 alkyl, 4-nonylphenyl, and a linear or branched C 1 -C 18 alkyl having a carboxylic group;

R 5 is selected from the group consisting of —CH 2 —CH 2 —CH 2 —SO 3 Z, —CH 2 —CH 2 —SH, and tosyl;

wherein Z is a monovalent cation, and wherein concentration of the at least one first poly(ethylene glycol) derivative ranges from 0.5 to 7.5 g/l; and

(iv) in case of a zinc-nickel alloy electroplating bath at least a nickel ion source.

2. The acidic zinc or zinc-nickel alloy electroplating bath according to claim 1 characterized in that the bath is substantially free, preferably completely free, of other alloying metals than zinc and nickel ions.

3. The acidic zinc or zinc-nickel alloy electroplating bath according to claim 1 characterized in that the at least one triazole derivative is selected from the group consisting of 3-mercapto-1,2,4-triazole;

1,2,4-triazole; 1,2,4-triazole-3-carboxylic acid; 3-amino-1,2,4-triazole; 3-methyl-1H-1,2,4-triazole; 3,5-diamino-1,2,4-triazole; 3-amino-5-mercapto-1,2,4-triazole; 3-(methylsulfonyl)-1H-1,2,4-triazole; 5-phenyl-1H-1,2,4-triazole-3-thiol; 1-phenyl-1H-(1,2,4)-triazole-3-thiol; and methyl-1H-1,2,4-triazole-3-carboxylate.

4. The acidic zinc or zinc-nickel alloy electroplating bath according to claim 1 characterized in that the at least one first poly(ethylene glycol) derivative is selected from the group consisting of poly(ethylene glycol) 4-nonylphenyl 3-sulfopropyl ether potassium salt (CAS 119438-10-7); poly(ethylene glycol)alkyl(3-sulfopropyl)diether potassium salt (CAS 119481-71-9); poly(ethylene glycol)methyl ether thiol; poly(ethylene glycol)methyl ether tosylate (CAS 58320-73-3); and poly(ethylene glycol) 2-mercaptoethyl ether acetic acid (CAS 165729-81-7).

5. The acidic zinc or zinc-nickel alloy electroplating bath according to claim 1 characterized in that the at least one triazole derivative is 3-mercapto-1,2,4-triazole and that the at least one first poly(ethylene glycol) derivative is poly(ethylene glycol)alkyl(3-sulfopropyl)diether potassium salt (CAS 119481-71-9).

6. The acidic zinc or zinc-nickel alloy electroplating bath according to claim 1 characterized in that the bath is further comprising

(v) at least one second poly(ethylene glycol) derivative having the general formula (III):

R 6 —[O—CH 2 —CH 2 ] n —O—R 7   (III)

wherein

n is ranging from 2 to 200;

R 6 is selected from the group consisting of a linear or branched C 1 -C 18 alkyl, —CH 2 —COOH, glycidyl, and —CH 2 —CH 2 —NH 2 ; and

R 7 is selected from the group consisting of hydrogen, —CH 2 —COOH, glycidyl, and —O—CH 3 .

7. The acidic zinc or zinc-nickel alloy electroplating bath according to claim 6 characterized in that the at least one second poly(ethylene glycol) derivative is selected from the group consisting of octa(ethylene glycol) octyl ether (CAS 26468-86-0), poly(ethylene glycol) bis(carboxymethyl) ether (CAS 39927-08-7), poly(ethylene glycol) diglycidyl ether (CAS 72207-80-8), poly(ethylene glycol) dimethyl ether (CAS 24991-55-7), and poly(ethylene glycol) methyl ether amine (CAS 80506-64-5).

8. The acidic zinc or zinc-nickel alloy electroplating bath according to claim 6 characterized in that the concentration of the at least one second poly(ethylene glycol) derivative ranges from 0.5 to 7.5 g/l, preferably from 0.75 to 4.5 g/l, and more preferably from 1 to 5 g/l.

9. An acidic zinc or zinc-nickel alloy electroplating bath according to claim 6 characterized in that the at least one triazole derivative is 3-mercapto-1,2,4-triazole, the at least one first poly(ethylene glycol) derivative is poly(ethylene glycol)alkyl (3-sulfopropyl)diether potassium salt (CAS 119481-71-9), and the at least one second poly(ethylene glycol) derivative is octa(ethylene glycol)octyl ether (CAS 26468-86-0).

10. The acidic zinc or zinc-nickel alloy electroplating bath according to claim 6 characterized in that the bath is substantially free of boric acid.

11. The acidic zinc or zinc-nickel alloy electroplating bath according to claim 6 characterized in that the concentration of zinc ions ranges from 5 to 100 g/l.

12. The acidic zinc or zinc-nickel alloy electroplating bath according to claim 6 characterized in that in case of a zinc-nickel alloy electroplating bath the concentration of nickel ions ranges from 5 to 100 g/l.

13. The acidic zinc or zinc-nickel alloy electroplating bath according to claim 1 characterized in that the bath is substantially free, preferably completely free, of boric acid.

14. The acidic zinc or zinc-nickel alloy electroplating bath according to claim 1 characterized in that the concentration of zinc ions ranges from 5 to 100 g/l.

15. The acidic zinc or zinc-nickel alloy electroplating bath according to claim 1 characterized in that in case of a zinc-nickel alloy electroplating bath the concentration of nickel ions ranges from 5 to 100 g/l.

16. The acidic zinc or zinc-nickel alloy electroplating bath according to claim 1 characterized in that the at least one first poly(ethylene glycol) derivative is poly(ethylene glycol) 4-nonylphenyl 3-sulfopropyl ether potassium salt (CAS 119438-10-7).

17. A method for zinc or zinc-nickel alloy electroplating comprising, in this order, the steps of

(i) providing a substrate having a metallic surface as a cathode,

(ii) contacting said substrate with an acidic zinc or zinc-nickel alloy electroplating bath according to claim 1 , and

(iii) applying an electrical current between said substrate and at least one anode and thereby depositing a zinc or zinc-nickel alloy layer with an improved thickness onto said substrate.

18. A method for zinc or zinc-nickel alloy electroplating comprising, in this order, the steps of

(i) providing a substrate having a metallic surface as a cathode,

(ii) contacting said substrate with an acidic zinc or zinc-nickel alloy electroplating bath according to claim 6 , and

(iii) applying an electrical current between said substrate and at least one anode and thereby depositing a zinc or zinc-nickel alloy layer with an improved thickness onto said substrate.

19. A method for zinc or zinc-nickel alloy electroplating comprising, in this order, the steps of:

(i)providing a substrate having a metallic surface as a cathode,

(ii) contacting said substrate with an acidic zinc or zinc-nickel alloy electroplating bath comprising:

at least a zinc ion source;

at least one triazole derivative having the general formula (I):

wherein

R 1 is selected from the group consisting of hydrogen, thiol, carboxylic acid, amino, methyl, methylsulfonyl, and methyl carboxylate;

R 2 is hydrogen or phenyl; and

R 3 is selected from the group consisting of hydrogen, amino, thiol, and phenyl, and

wherein concentration of the at least one triazole derivative having the general formula (I) is in a range of 0.5 to 7.5 mg/I;

at least one first poly(ethylene glycol) derivative having the general formula (II):

R4-[O-CH2-CH2]n-O-R5 (II)

wherein

n is ranging from 2 to 200;

R4 is selected from the group consisting of a linear or branched C 1 -C 18 alkyl, 4-nonylphenyl, and a linear or branched C 1 -C 18 alkyl having a carboxylic group;

R5 is selected from the group consisting of —CH 2 —CH 2 —CH 2 —SO 3 Z, —CH 2 —CH 2 —SH, and tosyl;

wherein Z is a monovalent cation; and

in case of a zinc-nickel alloy electroplating bath at least a nickel ion source, and

(iii) applying an electrical current between said substrate and at least one anode and thereby depositing a zinc or zinc-nickel alloy layer with an improved thickness onto said substrate, wherein the electroplating bath is held at a temperature in the range of 20 to 50° C.

20. The method of claim 19 , wherein the electrical current has a current density in the range of 0.3 to 5 A/dm 2 .

21. The method of claim 19 applied for rack electroplating or for barrel electroplating.