Electrochemical anodizing treatment of WE43 magnesium alloy for biomedical applications

Magnesium and its alloys are promising candidates as biodegradable materials for biomedical applications due to their low corrosion resistance and biocompatibility. However, the degradation process is too rapid and results in the development of hydrogen and the alkalinisation of the surrounding environment. Therefore, ad-hoc surface treatments or alloys are required to improve corrosion resistance. The electrolytic plasma process is a simple and environmentally friendly electrochemical surface treatment, which allows the growth of an oxide-based coating that is very adherent to the substrate. The oxide morphology, and consequently its chemical-physical properties, can be influenced by various parameters adopted during the treatment. In this work, it is proposed to study the influence of the current density applied during electrolytic plasma oxidation on the microstructure and corrosion properties of the rare-earth magnesium alloy, WE43. The morphology of the coatings was analysed by means of scanning electron microscopy (SEM) and laser scanning confocal microscopy. Additional microhardness measurements were carried out. Electrochemical properties were investigated through potentiodynamic polarisation tests and electrochemical impedance spectroscopy in Hanks' solution at 37 °C. The results revealed a peculiar morphology of the oxide layer, as well as the possibility of decreasing and controlling the corrosion rate of the alloy under investigation.