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

Abstract

The electrodeposition f a family of NiZnP coatings was studied at a rotating cylinder electrode by varying the tem-perature (45~176 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 composi-tion 59Ni-39Zn-2P was obtained at all temperatures in the high speed electrodeposition current density range 0.6-1.0 A/cm 2. The supersaturated alloy could be deposited at current efficiencies higher than 80 % at all temperatures. The corro-sion rate of this coating, estimated from polarization resistance measurements in 5 % NaC1 at pH 5.0, was the lowest among the various NiZnP coatings. The electrodeposition process can be effectively em= ployed to create new alloy materials that possess novel structures and properties that are distinctly different from those obtained by metallurgical techniques (1). One of the convenient features of electrodeposition is that nonmetal-lic inclusions uch as boron, phosphorus, carbon, oxygen,