Patent ID: 9228268
Filing Date: 2016-01-05
CPC Classification: C25D

Claim Text:
1. A method comprising: a) providing an aqueous solution consisting of one or more sources of silver ions, one or more imide derivatives chosen from hydantoin, 1-methylhydantoin, 1,3-dimethylhydantoin, 5,5-dimethylhydantoin, 1-methanol-5,5-dimethylhydantoin and 5,5-diphenylhydantoin, sulfamic acid or salts of sulfamic acid in amounts of 5 g/L to 100 g/L and one or more alkali metal nitrates in amounts of 3 g/L to 30 g/L, and one or more optional components chosen from surfactants, buffers, levelers, anti-tarnish agents and ductility agents, the solution is cyanide-free; b) contacting a substrate comprising nickel or nickel alloy with the solution; c) electroplating a silver strike layer 0.01 μm to 0.2 μm thick onto the nickel or nickel alloy of the substrate; and d) electroplating a second silver layer onto the silver strike layer, wherein the one or more alkali metal nitrates of the silver strike layer provide for the second silver layer to have a mirror bright appearance.