Zinc-nickel electrolyte and method for depositing a zinc-nickel alloy therefrom

Abstract

A method for depositing a zinc-nickel alloy from a zinc-nickel electrolyte to which an additive has been added in order to broaden the usable current density range. An electrolyte suitable for this method is also presented. The additive is an aromatic or aliphatic carboxylic acid, salt, or derivative. The additive provides for the use of ammonium-free electrolytes.

What is claimed is:  
     
         1 . A process for deposition of a zinc-nickel alloy onto a substrate comprising: 
 preparing an electrolyte comprising a source of Zn ions and a source of Ni ions, which electrolyte is characterized by a first current density range within which a deposited coating of said alloy is substantially continuous, glossy, and provides corrosion protection;    incorporating a current density broadening agent into the electrolyte to modify the electrolyte such that it is characterized by a second current density range within which a deposited coating of said alloy is substantially continuous, glossy, and provides corrosion protection; and    supplying an external source of electrons to the electrolyte to electrolytically deposit the zinc-nickel alloy onto the substrate;    wherein said second current density range is broader than said first current density range;    wherein the current density broadening agent is selected from the group consisting of an aromatic carboxylic acid, an aromatic carboxylic acid salt, an aromatic carboxylic acid derivative, an aliphatic carboxylic acid, an aliphatic carboxylic acid salt, an aliphatic carboxylic acid derivative, and combinations thereof.    
     
     
         2 . The process according to  claim 1  wherein the electrolyte is an ammonium-free electrolyte which is slightly acidic.  
     
     
         3 . The process according to  claim 1  wherein the additive is selected from the group consisting of nicotinic acid, nicotinic acid salts, and nicotinic acid derivatives.  
     
     
         4 . The process according to  claim 3  wherein the additive is present in the electrolyte at a concentration ranging from about 0.25 to about 1 g/L.  
     
     
         5 . The process according to  claim 4  wherein the additive is present in the electrolyte at a concentration of about 0.75 g/L.  
     
     
         6 . The process according to  claim 1  wherein the additive is selected from the group consisting of salicylic acid, salicylic acid salts, and salicylic acid derivatives.  
     
     
         7 . The process according to  claim 6  wherein the additive is present in the electrolyte at a concentration ranging from about 0.5 to about 1.5 g/L.  
     
     
         8 . The process according to  claim 7  wherein the additive is present in the electrolyte at a concentration of about 1 g/L.  
     
     
         9 . The process according to  claim 1  wherein the electrolyte comprises a first additive selected from the group consisting of nicotinic acid, nicotinic acid salts, and nicotinic acid derivatives and a second additive selected from the group consisting of salicylic acid, salicylic acid salts, and salicylic acid derivatives.  
     
     
         10 . The process according to  claim 1  wherein the additive is selected from the group consisting of aminocarboxylic acids, aminocarboxylic acid salts, and aminocarboxylic acid derivatives.  
     
     
         11 . The process according to  claim 10  wherein the additive is selected from the group consisting of aminoacetic acid, an aminoacetic acid salt, and an aminoacetic acid derivative.  
     
     
         12 . The process according to  claim 1  wherein the additive is selected from the group consisting of hydroxy(poly)carboxylic acids, hydroxy(poly)carboxylic acid salts, and hydroxy(poly)carboxylic acid derivatives.  
     
     
         13 . The process according to  claim 12  wherein the additive is selected from the group consisting of 2-hydroxypropanoic acid, a 2-hydroxypropanoic acid salt, and a 2-hydroxypropanoic acid derivative.  
     
     
         14 . The process according to  claim 1  wherein the zinc-nickel alloy is deposited on a workpiece while the electrolyte is at a temperature which is no greater than 35° C.  
     
     
         15 . A process for deposition of a zinc-nickel alloy onto a substrate comprising: 
 preparing an electrolyte comprising a source of Zn ions, a source of Ni ions, and an additive selected from the group consisting of an aromatic carboxylic acid, an aromatic carboxylic acid salt, an aromatic carboxylic acid derivative, an aminocarboxylic acid, an aminocarboxylic acid salt, an aminocarboxylic acid derivative, an hydroxy(poly)carboxylic acid, an hydroxy(poly)carboxylic acid salt, an hydroxy(poly)carboxylic acid derivative, and combinations thereof; and    supplying an external source of electrons to the electrolyte to electrolytically deposit the zinc-nickel alloy onto the substrate.    
     
     
         16 . The process according to  claim 15  wherein the electrolyte is an ammonium-free electrolyte which is slightly acidic.  
     
     
         17 . The process according to  claim 15  wherein the additive is selected from the group consisting of nicotinic acid, nicotinic acid salts, and nicotinic acid derivatives.  
     
     
         18 . The process according to  claim 17  wherein the additive is present in the electrolyte at a concentration ranging from about 0.25 to about 1 g/L.  
     
     
         19 . The process according to  claim 18  wherein the additive is present in the electrolyte at a concentration of about 0.75 g/L.  
     
     
         20 . The process according to  claim 15  wherein the additive is selected from the group consisting of salicylic acid, salicylic acid salts, and salicylic acid derivatives.  
     
     
         21 . The process according to  claim 20  wherein the additive is present in the electrolyte at a concentration ranging from about 0.5 to about 1.5 g/L.  
     
     
         22 . The process according to  claim 21  wherein the additive is present in the electrolyte at a concentration of about 1 g/L.  
     
     
         23 . The process according to  claim 15  wherein the electrolyte comprises a first additive selected from the group consisting of nicotinic acid, nicotinic acid salts, and nicotinic acid derivatives and a second additive selected from the group consisting of salicylic acid, salicylic acid salts, and salicylic acid derivatives.  
     
     
         24 . The process according to  claim 15  wherein the additive is selected from the group consisting of aminocarboxylic acids, aminocarboxylic acid salts, and aminocarboxylic acid derivatives.  
     
     
         25 . The process according to  claim 24  wherein the additive is selected from the group consisting of aminoacetic acid, an aminoacetic acid salt, and an aminoacetic acid derivative.  
     
     
         26 . The process according to  claim 15  wherein the additive is selected from the group consisting of hydroxy(poly)carboxylic acids, hydroxy(poly)carboxylic acid salts, and hydroxy(poly)carboxylic acid derivatives.  
     
     
         27 . The process according to  claim 26  wherein the additive is selected from the group consisting of 2-hydroxypropanoic acid, a 2-hydroxypropanoic acid salt, and a 2-hydroxypropanoic acid derivative.  
     
     
         28 . The process according to  claim 15  wherein the zinc-nickel alloy is deposited on a workpiece while the electrolyte is at a temperature which is no greater than 35° C.  
     
     
         29 . An electrolyte for electrolytic deposition of a Zn-Ni alloy, the electrolyte comprising: 
 a source of Zn ions;    a source of Ni ions;    a current density broadening agent selected from the group consisting of an aromatic carboxylic acid, an aromatic carboxylic acid salt, an aromatic carboxylic acid derivative, an aliphatic carboxylic acid, an aliphatic carboxylic acid salt, an aliphatic carboxylic acid derivative, and combinations thereof.    
     
     
         30 . The electrolyte according to  claim 29  wherein the electrolyte is an ammonium-free electrolyte which is slightly acidic.  
     
     
         31 . The electrolyte according to  claim 29  wherein the additive is selected from the group consisting of nicotinic acid, nicotinic acid salts, and nicotinic acid derivatives.  
     
     
         32 . The electrolyte according to  claim 31  wherein the additive is present in the electrolyte at a concentration ranging from about 0.25 to about 1 g/L.  
     
     
         33 . The electrolyte according to  claim 32  wherein the additive is present in the electrolyte at a concentration of about 0.75 g/L.  
     
     
         34 . The electrolyte according to  claim 29  wherein the additive is selected from the group consisting of salicylic acid, salicylic acid salts, and salicylic acid derivatives.  
     
     
         35 . The electrolyte according to  claim 34  wherein the additive is present in the electrolyte at a concentration ranging from about 0.5 to about 1.5 g/L.  
     
     
         36 . The electrolyte according to  claim 35  wherein the additive is present in the electrolyte at a concentration of about 1 g/L.  
     
     
         37 . The electrolyte according to  claim 29  wherein the electrolyte comprises a first additive selected from the group consisting of nicotinic acid, nicotinic acid salts, and nicotinic acid derivatives and a second additive selected from the group consisting of salicylic acid, salicylic acid salts, and salicylic acid derivatives.  
     
     
         38 . The electrolyte according to  claim 37  wherein the first additive is present in the electrolyte at a concentration ranging from about 0.25 to about 1 g/L and the second additive is present in the electrolyte at a concentration ranging from about 0.5 to about 1.5 g/L.  
     
     
         39 . The electrolyte according to  claim 38  wherein the first additive is present in the electrolyte at a concentration of about 0.75 g/L and the second additive is present in the electrolyte at a concentration of about 1 g/L.  
     
     
         40 . The electrolyte according to  claim 29  wherein the additive is selected from the group consisting of aminocarboxylic acids, aminocarboxylic acid salts, and aminocarboxylic acid derivatives.  
     
     
         41 . The electrolyte according to  claim 40  wherein the additive is selected from the group consisting of aminoacetic acid, an aminoacetic acid salt, and an aminoacetic acid derivative.  
     
     
         42 . The electrolyte according to  claim 29  wherein the additive is selected from the group consisting of hydroxy(poly)carboxylic acids, hydroxy(poly)carboxylic acid salts, and hydroxy(poly)carboxylic acid derivatives.  
     
     
         43 . The electrolyte according to  claim 42  wherein the additive is selected from the group consisting of 2-hydroxypropanoic acid, a 2-hydroxypropanoic acid salt, and a 2-hydroxypropanoic acid derivative.