Behavior of Nickel Deposition from Electroless Ni-W-P Plating Bath

Abstract

The behavior of nickel deposition from electroless Ni-W-P plating bath was studied from the adsorption spectra of nickel complexes contained in the bath, the amount of phosphorous acid produced in the plating bath, and the effect of WO₄^2- concentration on anodic and cathodic polarization curves of Pd electrode. Nickel-ammonia-citrate complexes seemed to be formed in the plating bath solution. The relative amount of sodium hypophosphite used in the plating of nickel increased from 16 to 25% in the addition of Na₂WO₄. The partial anodic polarization curves for the oxidation of hypophosphite ion and the cathodic polarization curves for the nickel deposition showed that these reactions were accelerated with the addition of Na₂WO₄. These results were in good agreement with those obtained in electroless Ni-W-P plating tests.