Zinc alloy electroplating baths and processes

Abstract

The present invention relates to the electrodeposition of zinc nickel alloy on a variety of electrically conducting substrates in a medium which seeks to provide improved deposit distribution and operable current density range. This is achieved through a bath comprising zinc ions, nickel metal ions, and a suitable combination of one or more urea based polymers and non-polymeric complexing agents capable of holding nickel metal ions in alkaline solution and an electrolytic process whereby the bath is used to electrodeposit zinc nickel alloy on electrically conducting substrates.

1 . An alkaline aqueous electrolytic bath capable of electrodeposition of a zinc-nickel alloy comprising:
 (i) 5-25 g/l zinc ions;   (ii) 0.25-10 g/l nickel ions;   (iii) 50-500 g/l of sodium or potassium hydroxide;   (iv) at least one non-polymeric complexing agent capable of complexing the nickel ions selected from the group consisting of monoethanolamine, diethanolamine, trimethanolamine, triethanolamine, tripropanolamine and N, N, N′, N′ tetrakishydroxyisopropylethylene diamine; and   (v) at least one urea based polymer selected from the group consisting of (a) urea, N,N′-bis[3-(dialkylamino)alkyl]-, polymer with 1,4-[2-haloalkane], (b) urea, N,N′-bis[3-(dialkylamino)alkyl]-, polymer with 1,1′-oxybis[2-haloalkane], wherein for (a) or (b) the alkyl functional groups are selected from the group consisting of methyl, ethyl, propyl, butyl, pentyl, and hexyl and the halogen functional group is selected from the group consisting of chloro, bromo, fluoro, and iodo, and (c) random co-polymers comprising the reaction product of (1) one or more di-tertiary amines, including an amide or thioamide functional group, and (2) one or more second di-tertiary amines, including an unsaturated moiety, with (3) one or more first linking agents capable of reaction with said amines (1) and (2);   
     wherein the pH of the bath is above 13 and the bath contains no polymeric complexants. 
   
   
       2 . The alkaline aqueous electrolytic bath according to  claim 1  wherein the non-polymeric complexing agent is selected from the group consisting of monoethanolamine, triethanolamine, and N,N,N′,N′ tetrakis-hydroxyisopropylethylenediamine. 
   
   
       3 . The alkaline aqueous electrolytic bath according to  claim 1  further comprising more than one non-polymeric complexing agent. 
   
   
       4 . The alkaline aqueous electrolytic bath according to  claim 3  wherein the more than one non-polymeric complexing agent comprises triethanolamine and N,N,N′,N′ tetrekis-hydroxyisopropylethylenediamine. 
   
   
       5 . The alkaline aqueous electrolytic bath according to  claim 1  wherein the urea based polymer comprises urea N,N′-bis[3-(dimethylamino)propyl]-, polymer with 1,1′-oxybis[2-chloroethane]. 
   
   
       6 . The alkaline aqueous electrolytic bath according to  claim 1  wherein the urea based polymer comprises is urea, N,N′-bis[3-(dimethylamino)propyl]-, polymer with 1,4-dichlorobutane. 
   
   
       7 . The alkaline aqueous electrolytic bath according to  claim 1  wherein the bath further comprises sodium hydroxide in an amount of about 50 g/L to about 500 g/L. 
   
   
       8 . The alkaline aqueous electrolytic bath according to  claim 1  wherein the zinc ions are present in a concentration of about 2 g/L to about 30 g/L. 
   
   
       9 . The alkaline aqueous electrolytic bath according to  claim 1  wherein the nickel ions are present in a concentration of about 0.251 g/L to about 106 g/L. 
   
   
       10 . The alkaline aqueous electrolytic bath according to  claim 1  wherein the at least one non-polymeric complexing agent is present in a concentration of about 5 g/L to about 150 g/L. 
   
   
       11 . The alkaline aqueous electrolytic bath according to  claim 1  wherein the urea based polymer is present in a concentration of about 0.02 g/L to about 20 g/L. 
   
   
       12 . A method for electrodeposition of a zinc-nickel alloy on a conductive substrate comprising the steps of:
 (a) contacting the conductive substrate with an alkaline aqueous electrolytic bath comprising:
 (i) 5-25 g/l or zinc ions; 
 (ii) 0.25-10 g/l of nickel ions; 
 (iii) 50-500 g/l of sodium or potassium hydroxide, 
 (iv) at least one non-polymeric complexing agent capable of complexing the nickel ions selected from the group consisting of monoethanolamine, diethanolamine, trimethanolamine, triethanolamine, tripropanolamine, and N, N, N′, N′ tetrakishydroxyisopropylethylene diamine; and 
 (v) at least one urea based polymer selected from the group consisting of (a) urea, N,N′-bis[3-(dialkylamino)alkyl]-, polymer with 1,4-[2-haloalkane] and (b) urea, N,N′-bis[3-(dialkylamino)alkyl]-, polymer with 1,1′-oxybis[2-haloalkane], wherein for (a) or (b) the alkyl functional groups are selected from the group consisting of methyl, ethyl, propyl, butyl, pentyl, and hexyl and the halogen functional group is selected from the group consisting of chloro, bromo, fluoro, and iodo, and (c) random co-polymers comprising the reaction product of (1) one or more di-tertiary amines including an amide or thioamide functional group, and (2) one or more second di-tertiary amines, including an unsaturated moiety with (3) one or more first linking agents capable or reacting with said amines (1) and (2); and 
   (b) electrolytically depositing zinc-nickel alloy onto the surface of the conductive substrate; wherein the pH of the bath is above 13 and wherein the deposited zinc-nickel alloy comprises 12-15 percent nickel and wherein the bath comprises no polymeric complexants.   
   
   
       13 . The method according to  claim 12  wherein the step of electrolytcally depositing occurs with a cathode current density in the range of about 0.1 ampere per square decimeter to about 25 ampere per square decimeter. 
   
   
       14 . The method according to  claim 12  wherein the non-polymeric complexing agent is selected from the group consisting of monoethanolamine, triethanolamine, and N,N,N′,N′ tetrakis-hydroxyisopropylethylenediamine. 
   
   
       15 . The method according to  claim 12  wherein the at least one complexing agents comprises triethanolamine and N,N,N′,N′ tetrekis-hydroxyisopropylethylenediamine. 
   
   
       16 . The method according to  claim 12  wherein the urea based polymer comprises urea, N,N′-bis[3-(dimethylamino)propyl]-, polymer with 1,1′-oxybis [2-chloroethane]. 
   
   
       17 . The method according to  claim 12  wherein the urea based polymer comprises urea, N,N′-bis[3-(dimethylamino)propyl]-, polymer with 1,4-dichlorobutane. 
   
   
       18 . The method according to  claim 12  wherein the non-polymeric complexing agent is present in a concentration of about 5 g/L to about 150 g/L. 
   
   
       19 . The method according to  claim 12  wherein the urea based polymer is present in a concentration of about 0.02 g/L to about 20 g/L.