Abstract
The mechanism for codeposition of nickel and phosphorus in electrodeposited Ni‐P amorphous alloys has not been clearly established. This paper presents experimental observations supporting the "indirect mechanism" for Ni‐P alloy formation by electrodeposition from a phosphorous acid‐based bath. Specifically, the indirect mechanism proposes that phosphine, 
, is an intermediate in Ni‐P electrodeposition. The experiments described here are; (i) reaction of nickel in aqueous solution with gaseous phosphine, (ii) electrodeposition from a nickel phosphite bath, and (iii) titration studies.