Microstructure and element distribution in thin MgO coatings on pure magnesium by microarc oxidation

A ceramic like coating was deposited on the substrate of pure magnesium by microarc oxidation. X-ray diffraction, scanning electron microscopy and energy dispersive spectrometry were used to analyse the structure and composition of the coating. X-ray diffraction showed that the phases present in the coating were mainly MgO with some Mg(OH)(2). Energy dispersive spectrometry indicated that silicon could be absorbed into the coating in the microarc oxidation process. Scanning electron microscopy showed that the coating surface possessed a porous microstructure, and the pore size was in the range of 1-3 mu m. The coating matrix was relatively dense and had a homogeneous thickness. The hardness of the MgO coating could reach 530 HV(0.025 g) and was similar to 10 times higher than that of the substrate.