Novel neutral electrolytes were designed to substantially decrease porosity and increase barrier property of plasma electrolytic oxidation (PEO) coating on AM50 Mg surface. Presence of additives was effective in tuning coating microstructure and composition, leading to significantly enhanced corrosion and wear properties. 50% improvement in fatigue limit was detected for the optimized coating compared to conventional PEO coating. The low-porosity coating remained uncorroded after performing salt spray test for 1 month, and exposure 1 year in harsh South China Sea environment. This can be new strategy to evaluate coating lifespan and promote wide range of applications for Mg alloy.

The microstructure and precipitated phases of as-cast Mg-5Y-1.5Nd-xZn-0.5Zr (x = 0, 2, 4, 6 wt.%) alloys were investigated by optical microscopy, scanning electron microscopy, energy-dispersive spectrometry and X-ray Diffraction. The exposure corrosion experiment of these magnesium alloys was tested in South China Sea and KEXUE vessel atmospheric environment. The corrosion characteristic and mechanism of magnesium alloys of Mg-5Y-1.5Nd-xZn-0.5Zr (x = 0, 2, 4, 6 wt.%) alloys were analyzed by weight loss rate, corrosion depth, corrosion products and corrosion morphologies. The electrochemical corrosion tests were also measured in the natural seawater. The comprehensive results showed that Mg-5Y-1.5Nd-4Zn-0.5Zr magnesium alloy existed the best corrosion resistance whether in the marine atmospheric environment and natural seawater environment. That depended on the microstructure, type and distribution of precipitated phases in Mg-5Y-1.5Nd-4Zn-0.5Zr magnesium alloy. Sufficient quantity anodic precipitated phases in the microstructure of Mg-5Y-1.5Nd-4Zn-0.5Zr alloy played the key role in the corrosion resistance.