Micro-arc Oxidation and Sol-Gel Composite Coatings on Magnesium Alloy
镁合金微弧氧化—溶胶凝胶复合膜层的耐蚀性

Protective composite coatings were obtained on a magnesium alloy by micro–arc oxidation (MAO) and sol–gel technique. The cross–section morphologies and composition of the MAO coating and composite coatings were analyzed by scanning electron microscopy (SEM) and energy dispersive X–rays (EDX). The phase structure of the composite coatings was analyzed by X–ray diffractometer (XRD). The corrosion resistance of MAO coating and composite coatings in a 3.5% (mass fraction) NaCl solution was evaluated by potentiodynamic polarisation measures. The results show that SiO2–ZrO2 sol can effectively seal the micropores in the MAO coating, and the composite coatings are more compact and have good adhesion. The composite coatings are composed of MgO, MgAl2O4, SiO2 and ZrO2. The corrosion resistance of the sample with composite coatings is enhanced significantly.