Silver-plated product and method for producing same

Abstract

There is provided a silver-plated product having a more excellent wear resistance than that of conventional silver-plated products while maintaining the high hardness thereof, and a method for producing the same. In a method for producing a silver-plated product by forming a surface layer of silver on a base material by electroplating in a silver-plating solution which is an aqueous solution containing silver potassium cyanide, potassium cyanide and a mercaptothiazole, the concentration of the mercaptothiazole in the silver-plating solution is not lower than 5 g/L, and the electroplating is carried out at a liquid temperature of not lower than 30° C. and at a current density of 1 to 15 A/cm2.

1 . A method for producing a silver-plated product, the method comprising the steps of:
 preparing a silver-plating solution which is an aqueous solution containing silver potassium cyanide, potassium cyanide and a mercaptothiazole; and   forming a surface layer of silver on a base material by electroplating at a liquid temperature of not lower than 30° C. and at a current density of 1 to 15 A/cm 2  in the silver-plating solution,   wherein the concentration of the mercaptothiazole in the silver-plating solution is not lower than 5 g/L.   
     
     
         2 . A method for producing a silver-plated product as set forth in  claim 1 , wherein the concentration of the mercaptothiazole in the silver-plating solution is not lower than 10 g/L. 
     
     
         3 . A method for producing a silver-plated product as set forth in  claim 1 , wherein the concentration of the mercaptothiazole in the silver-plating solution is not higher than 30 g/L. 
     
     
         4 . A method for producing a silver-plated product as set forth in  claim 1 , wherein the concentration of the mercaptothiazole in the silver-plating solution is not higher than 25 g/L. 
     
     
         5 . A method for producing a silver-plated product as set forth in  claim 1 , wherein the current density in said electroplating is in the range of from 2 A/cm 2  to 10 A/cm 2 . 
     
     
         6 . A method for producing a silver-plated product as set forth in  claim 1 , wherein the concentration of the silver potassium cyanide in the silver-plating solution is in the range of from 50 g/L to 200 g/L. 
     
     
         7 . A method for producing a silver-plated product as set forth in  claim 1 , wherein the concentration of the potassium cyanide in the silver-plating solution is in the range of from 20 g/L to 120 g/L. 
     
     
         8 . A method for producing a silver-plated product as set forth in  claim 1 , wherein the concentration of silver in the silver-plating solution is in the range of from 20 g/L to 120 g/L. 
     
     
         9 . A method for producing a silver-plated product as set forth in  claim 1 , wherein the concentration of free cyanide in the silver-plating solution is in the range of from 5 g/L to 50 g/L 
     
     
         10 . A method for producing a silver-plated product as set forth in  claim 1 , wherein said electroplating is carried out at a liquid temperature of not higher than 50° C. 
     
     
         11 . A method for producing a silver-plated product as set forth in  claim 1 , wherein said base material is made of copper or a copper alloy. 
     
     
         12 . A method for producing a silver-plated product as set forth in  claim 1 , wherein an underlying layer of nickel is formed between said base material and said surface layer. 
     
     
         13 . A silver-plated product comprising:
 a base material; and   a surface layer of silver which is formed on the base material, the surface layer having an average crystallite size of not greater than 23 nm and having a Vickers hardness HV of 100 to 160, the surface layer containing not less than 0.3% by weight of carbon, not less than 0.4% by weight of sulfur and not less than 0.1% by weight of nitrogen.   
     
     
         14 . A silver-plated product as set forth in  claim 13 , wherein said surface layer contains 90 to 99% by weight of silver. 
     
     
         15 . A silver-plated product as set forth in  claim 13 , wherein said surface layer contains not higher than 2% by weight of carbon. 
     
     
         16 . A silver-plated product as set forth in  claim 13 , wherein said surface layer contains not higher than 2% by weight of sulfur. 
     
     
         17 . A silver-plated product as set forth in  claim 13 , wherein said base material is made of copper or a copper alloy. 
     
     
         18 . A silver-plated product as set forth in  claim 13 , wherein an underlying layer of nickel is formed between said base material and said surface layer.