Electrochemical and structural properties of electroless Ni-P-SiC nanocomposite coatings

Silicon carbide (SiC) nanoparticles were co-deposited with nickel-phosphorous (Ni-P) coatings through electroless deposition process. The effects of annealing temperature and SiC contents on properties of the coatings were investigated. Corrosion performance of the coatings was examined using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). X-ray diffraction and Scanning Electron Microscopy (SEM) were employed for structural and morphological studies, respectively. It was shown that the structure of the as-deposited Ni-P-SiC nanocomposite coating was amorphous, and changed to the nickel crystal, nickel phosphide (Ni3P) and silicide compounds (NixSiy) with heat treatment. Addition of the SiC concentration in the coating bath affected both composition and morphology of the coating. Presence of SiC nanoparticles in the Ni-P coating enhanced the corrosion resistance of the coating. Higher SiC contents, however, negatively affected the corrosion behavior of the coatings. Heat treatment also improved the corrosion resistance of the Ni-P-SiC coating. Annealing at 400 °C decreased the corrosion current density of the coating by approximately 60%.