Wear and Corrosion Performance of PEO-synthesized SiC Nanocomposite Coatings: Effect of Processing Time and Current Density

In the present study, a systematic investigation of the effect of the process parameters on the final properties of the PEO coatings was done. Protective oxide coatings were prepared on AZ31 magnesium alloy by plasma electrolytic oxidation (PEO) process using aluminate-silicate based electrolyte containing SiC nanoparticles in different current densities and time intervals. Microstructural characterization of the PEO treated samples was evaluated by scanning electron microscopy (SEM) followed by image analysis and energy dispersive spectroscopy (EDS). Wear resistance of the coatings was analyzed by ball-on disc tribometer. The corrosion resistance of the coatings was also investigated with potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests in 3.5 wt.% NaCl solution. It was found that the processing time and current density have a significant influence on the resulting coatings properties, such as microstructure, thickness, composition, hardness, wear and corrosion behavior. The thick coatings produced at higher current density and treatment time possess a high hardness and provide a low friction coefficient and wear rate against stainless steel balls. They also improved the corrosion resistance compared with the uncoated magnesium alloy, which can be mainly due to their compactness, thickness and microstructure.