Comparison of Mechanical, Corrosion, and Hydrogen Permeation Properties of Electroless Ni-Zn-P Alloys with Electrolytic Zn-Ni and Cd Coatings

Abstract

Abstract Novel Ni-Zn-P alloys containing 74 wt% Ni was prepared from a sulfate electrolyte using an electroless process. The mechanical, corrosion, and hydrogen permeation resistance characteristics of the developed Ni-Zn-P alloys were studied and compared with those of electrodeposited Cd and Zn-Ni coatings. Comparison of the mechanical properties shows that the developed alloy possesses engineering attributes comparable to those of Cd coatings. Corrosion studies in a 0.5-M sodium sulfate (Na2SO4) + 0.5-M boric acid (H3BO3) solution at pH 7.0 reveals that the dissolution rate of Ni-Zn-P alloys is five times lower than that of Zn-Ni and Cd coatings. In addition to the corrosion and engineering properties, comparison of the hydrogen permeation characteristics of the developed coating was made with that of Cd and Zn-Ni coatings. The exchange current density, i0; thickness dependent adsorption-absorption rate constant, k″; recombination rate constant, k3; and the surface hydrogen coverage, θs, that character...