Corrosion resistance and wear resistance of plasma electrolytic oxidation coatings on metal matrix composites

Protective coating was successfully prepared on SiCp/A356 composites by plasma electrolytic oxidation(PEO) technique. XRD analysis showed that the PEO coating was mainly composed of α-Al2O3 γ-Al2O3 and mullite. The electrochemical corrosion behavior of coated and uncoated SiCp/A356 composites was tested in 3.5 wt.% NaCl solution by potentiodynamic polarization technique with low scanning rates. It was found that the corrosion potential was shifted significantly in the anodic direction and the corrosion current density was much lower due to the presence of the PEO coating. Additionally, the wear behavior of the PEO coating was also tested using a ring-on-ring wear tester. The PEO coating showed a low specific wear of 4.76 × 10− 6 mm3/(N·m) against bearing steel at a speed of 0.52 m/s and a contact pressure of 0.75 MPa.