Improvement of corrosion properties of microarc oxidation coating on magnesium alloy by optimizing current density parameters

The microstructure, composition and corrosion performance of oxide coatings formed on AM60B alloy using microarc oxidation techniques at different waveforms of applied current densities were investigated within this study. It is found that the use of optimizing current density waveforms, i.e. decaying freely current density in the later stage and stepped decreasing current density, significantly improved the microstructure of oxide coatings compared with the constant current density mode, which are connected with changes in behaviors of spark discharges on the surface in oxidation process. The optimal waveform of current density is showed to be decaying freely current density in the later stage, which results in sealing the originally formed large micropores. The optimisation of the microstructure results in a significant improvement of the corrosion resistance of oxide coating.