A composite coating formed on AZ91D magnesium alloy by micro-arc oxidation and electrochemical deposition

Abstract

A composite coating was prepared by micro-arc oxidation and electrochemical deposition onto the polished magnesium alloy substrate. The effects of deposition voltage and deposition time on the surface morphologies, deposition mass and thickness of the biological composite coating were studied. The phase compositions, surface morphologies, element contents and thickness of the coatings were investigated by X-ray diffraction, scanning electron microscope with energy dispersive spectroscopy and thickness gauge, respectively. The corrosion resistance of the coatings in the simulated body fluid (SBF) was evaluated by potentiodynamic polarisation tests and immersion tests. Finally, the mechanical properties of the coatings after immersion were characterised by tensile fatigue testing machine (INSTRON8801). The results showed that the optimal deposition voltage and deposition time was 5 V and 120 min. The duplex treatment dramatically improved the corrosion resistance and the fatigue life of the magnesium alloys in SBF solution. Therefore, the composite coating with potential bioactivity can be a candidate for magnesium alloys as biomedical materials.