Characterization of New Corrosion Resistant Nickel‐Zinc‐Phosphorus Alloys Obtained by Electrodeposition

Abstract

The electrodeposition of a family of coatings was studied at a rotating cylinder electrode by varying the temperature (45°–80°C) and the applied current density (0.03–0.95 A/cm2). Two of the coatings were nickel‐rich, two were zinc‐rich, and a fifth coating had approximately equal amounts of Ni and Zn. The coatings were characterized using SEM/EDX and Auger depth profile techniques. A Ni‐rich alloy with a supersaturated amount of zinc and the approximate composition 59Ni‐39Zn‐2P was obtained at all temperatures in the high speed electrodeposition current density range 0.6–1.0 A/cm2. The supersaturated alloy could be deposited at current efficiencies higher than 80% at all temperatures. The corrosion rate of this coating, estimated from polarization resistance measurements in 5% at pH 5.0, was the lowest among the various coatings.