Commercial process for electroplating nickel-phosphorus coatings

Abstract

An aqueous bath for electroplating NiP coatings is provided comprising, generally, a solution containing nickel salts, either a mixture of nickel sulfate and nickel chloride or an all nickel chloride source, sodium hypophosphite and boric acid. Thiourea is added to an all chloride bath solution for decorative applications or other applications requiring enhanced brightness. Upon dissolution of the bath constituents, the bath pH is adjusted up to a value of 3.5 to 4.5 with sodium hydroxide and maintained for at least 15 minutes at or above room temperature, preferably in the range of 40° to 50° C., then the bath pH is reduced to the bath operating range of 2.0 to 3.0, preferably 2.2 to 2.6. Maintaining the elevated solution pH prior to electroplating a substrate prevents the oxidation of the hypophosphite anions and ensures long-term utilization of the bath.

What is claimed is:  
     
         1 . A composition of matter for producing electrodeposited nickel-phosphorus coatings, the composition being an aqueous electroplating bath comprising: a source of nickel selected from the group consisting of nickel sulfate and nickel chloride; sodium hypophosphite; boric acid; and thiourea.