Study on micro-arc oxidation technology and corrosion resistance of ceramic film on magnesium alloy
ZHANG Zhi-you, ZHAO Qing, LIU Yue-e Foxconn Science and Technique Group, Shenzhen 518109, China
The function of electrolyte components of microarc oxidation for magnesium alloy was discussed using single factor method. The optimal formula was obtained as follows: 10 g/L (NaPO3)6, 5 g/L NH4F, 6 g/L KOH, 6 mL/L C3H8O3. The surface and cross section morphology of the coating was observed by SEM. The phase structure and element distribution were analyzed by XRD and EDS. The corrosion resistance of the coating was determined by dropping test, ac impedance spectroscopy and salt-spray test. The results showed that a great deal of comparatively uniform discharge micropores with 1-3 μm diameter was distributed on the coating surface. The compact inner layer adheres well to the substrate. The coating is composed of amorphous and a small amount of MgO and has good corrosion resistance. The existence of P and F elements indicates that the electrolyte components participate in the micro-arc oxidation process.