Microstructure and Corrosion Properties of Plasma Electrolytic Oxide Coatings on AZ31 Magnesium Matrix Composite

Plasma electrolytic oxidation (PEO) treatment was performed on squeeze cast AZ31 alloy and Al(18)B(4)O(33)w/AZ31 composite. Scanning electron microscope (SEM) was employed to characterize the surface morphology and cross-section microstructure of the coating. The phase structures of the PEO coating were analyzed by X-ray diffraction (XRD). The corrosion resistance of the PEO coating was evaluated by electrochemical method. The results showed that the Al(18)B(4)O(33) whisker on the surface of the composite was decomposed and MgAl(2)O(4) was formed in the PEO coating layer of Al(18)B(4)O(33)w/AZ31 composite during PEO treatment. As a result, the electrochemical corrosion potential of the PEO coated Al(18)B(4)O(33)w/AZ31 composite was increased compared with that of AZ31 alloy.