Effect of micro-arc oxidation time on coating formation of AZ91 magnesium alloy in silicate electrolyte

Abstract

The micro-arc oxidation behavior of AZ91 magnesium alloy in silicate alkaline electrolyte was studied. The effects of micro-arc oxidation time on film formation and microstructure were investigated and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), emission spectrometry (ICP) and salt spray test. The results show that oxidation time has an important effect on the surface morphology, thickness, phase structure and corrosion resistance of micro-arc oxidation film. With the increase of treatment time, the surface roughness and pore size increased. The acid ion (SiO32-) in electrolyte plays an important role in the formation of phase in the early stage of micro-arc oxidation, and the formation rate of MgO is dominant in the later stage. The corrosion rate decreases first and then increases with the increase of treatment time, and the corrosion rate of the sample processing 30min is lower under our technological conditions.