Significantly enhanced corrosion resistance of Ni–Cu coating modified by minor cerium

Abstract

Ni–Cu coatings were obtained through direct current electrodeposition in electroplating bath with ceric sulfate in varying concentration (0–1.2 g/L), respectively. Effects of ceric sulfate on microstructure and corrosion resistance of the coatings were analyzed through high-resolution transmission electron microscopy, potentiodynamic polarization, and localized electrochemical impedance spectroscopy. Semiconductor performance of a passive film formed on the Ni–Cu coatings was characterized by the Mott–Schottky measurements. Results demonstrated that Ce was co-deposited in the Ni–Cu coating obtained in the ceric sulfate containing electroplating bath. The trace addition of Ce distinctly improved corrosion resistance of the Ni–Cu coatings, which is ascribed to that the interfacial reactions between Ni–Cu coating and the passive film were suppressed by the reduction of the point defect diffusivity after the formation of a dense cerium oxide film.