Influence of pH values on electroless Ni-P-SiC plating on AZ91D magnesium alloy

A novel Ni-P-SiC composite coating was prepared by electroless plating in order to improve the corrosion capacity and wear resistance of AZ91D magnesium alloy. The influence of pH values on deposition rates and properties of the coatings was studied. The microstructure and phase structure of the Ni-P-SiC coatings were analyzed by scanning electron microscopy (SEM) and X-ray diffractometry (XRD). The corrosion and wear resistance performances of the coatings were also investigated through electrochemical technique and pin-on-disk tribometer, respectively. The results indicate that the composite coating is composed of Ni, P and SiC. It exhibits an amorphous structure and good adhesion to the substrate. The coatings have higher open circuit potential than that of the substrate. The composite coating obtained at pH value of 5.2 possesses optimal integrated properties, which shows similar corrosion resistance and ascendant wear resistance properties to the substrate.