Performance of micro arc oxidation coating of ZM6 cast magnesium alloy

Micro-arc oxidation (MAO) process on ZM6 Mg alloy was carried out in a dual electrolyte system of sodium silicate and sodium hydroxide alkalescent solution. The microstructure characteristics of coatings were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The performance of adhesion, corrosion resistance and fatigue was evaluated by dynamic stretch training, neutral salt spray test and axial loading fatigue test. The results show that MAO coating consists of three layers, outer layer, medial layer and inner layer. The outer layer is porous and loose, however the inner layer has good bond strength with substrate, which is above 50 MPa. The MAO coating can improve corrosion resistance of substrate significantly. The neutral salt spray test is above 336 h. Compared with the sample without MAO coating, the reduction of fatigue is about 18%. ©, 2015, Beijing Institute of Aeronautical Materials (BIAM). All right reserved.