The Pilling-Bedworth ratio of oxides preferentially formed from the precipitated phases in magnesium alloys were calculated. The results showed that the PBR value of Nd₂O₃ preferentially formed from Mg₁₂Nd was 1.0584, and the PBR value of Y₂O₃ preferentially formed from Mg₂₄Y₅ was 1.1923. Both the Nd₂O₃ and Y₂O₃ would provide a good protection to the Mg matrix. The Gd₂O₃ preferentially formed from Mg₃Gd, whereas the MgO preferentially formed from MgNi₂. The PBR value of these two oxides were both larger than 2. The corresponding oxides formed from the common precipitated phases Mg₁₇Al₁₂, MgZn₂, MgCu₂, Mg₂Ca, Mg₁₂Ce, and MgAg were all less than 1. The oxide films formed on surfaces of pure Mg and Mg-xY (x = 3, 5, 7 wt.%) alloys at high temperatures were analyzed. The results showed that the oxide films were composed of a Y₂O₃/MgO outer layer and an inner layer rich with Y₂O₃. The formation of Y₂O₃ was mainly caused by the oxidation of Mg₂₄Y₅. The more Y₂O₃ existed in the composite oxidation film, the better corrosion resistance of the Mg-Y samples.

The Mg-6%Al-3%Zn and Mg-6%Al-3%Zn-(1%, 1.5%, 2%)In alloys were prepared by melting and casting. Their microstructures were investigated via metallographic and energy-dispersive X-ray spectroscopy (EDS) analysis. Moreover, hydrogen evolution and electrochemical tests were carried out in 3.5 wt% NaCl solution aiming at identifying their corrosion mechanisms and discharge behaviors. The results suggested that indium exerts an improvement on both the corrosion rate and the discharge activity of Mg-Al-Zn alloy via the effects of grain refining, β-Mg₁₇Al₁₂ precipitation, dissolving-reprecipitation, and self-peeling. The Mg-6%Al-3%Zn-1.5%In alloy with the highest corrosion rate at free corrosion potential did not perform desirable discharge activity indicating that the barrier effect caused by the β-Mg₁₇Al₁₂ phase would have been enhanced under the conditions of anodic polarization. The Mg-6%Al-3%Zn-1.0%In alloy with a relative low corrosion rate and a high discharge activity is a promising anode material for both cathodic protection and chemical power source applications.