Constructing correlations between ion concentration, temperature and pH: A novel strategy to improve the corrosion resistance of electroless NiP plating on AZ91D magnesium alloy

Abstract

Most of the optimization methods for electroless nickel plating solutions are based on practical experience in production. This work reports a novel indicator for guiding the optimization of electroless plating baths, NiPT/pH ($lg\left(\frac{\left(C_{{\mathrm{Ni}}^{2+}}+0.3\ast C_{H_2{\mathrm{PO}}_2^{-}}\right)\ast T}{\mathrm{pH}}\right)$). Compared to conventional models that solely regulate the deposition rate, the NiPT/pH system demonstrates significant advancements by elucidating the influences of various factors on the deposition process from both thermodynamic and kinetic perspectives, while simultaneously offering a more streamlined and efficient modeling approach. The SEM analysis indicated that the compactness of the Ni-P coatings increased with the increase of NiPT/pH. The electrochemical measurements confirm the enhanced corrosion resistance of the optimized coatings. The main contribution of this work is the proposition of a model that takes into account various parameters for the design and estimation of the performance of electroless nickel plating bath, which also facilitate the application of such a process to the industry.