Influence of negative voltage on micro-arc oxidation of magnesium alloy under two steps voltage-increasing mode

摘要

The effects of different negative voltages on micro-arc oxidation coating fabricated on ZK60 Mg alloy were investigated under two steps increasing mode of 280-360V. The microstructure, coating thickness and corrosion resistance of coatings were evaluated by scanning electron microscopy (SEM), energy disperse spectroscopy (EDS), microscope with super-depth of field and electrochemical impedance spectroscopy (EIS). Current-time responses during MAO process were also analyzed combined with coating characteristic. The results reveal that higher negative voltage helped to develop a compact, smooth, thicker and better corrosion-resistant coating. The coating with maximum thickness of about 20.2um formed under negative voltage of 20V exhibits higher impedance value and the best corrosion resistance.