Abstract: Magnesium has attracted a lot of attention over the last few decades due to its light weight and potential use as biomaterial. However, the poor corrosion resistance of magnesium restricts its practical use for application where exposure to aggressive aqueous media is unavoidable. This paper describes the growth, characterization and corrosion analyses of Al₂O₃ and ZrO₂ thin film coatings aimed at slowing down the fast degradation of Mg in saline solution. In this study, different thicknesses of Al₂O₃ and ZrO₂ were deposited on pure magnesium (99.95%) disk using pulsed-DC reactive sputtering process. The microstructure and phase analyses were performed using scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The corrosion protection behavior of the Al₂O₃ and ZrO₂ coated magnesium samples immersed in 0.9 wt% NaCl solution were evaluated using electrochemical measurement techniques, such as open-circuit potential (OCP), potentiodynamic polarization (PD) and electrochemical impedance spectroscopy (EIS). The microstructural analyses showed that the Al₂O₃ thin film coatings have circular grains between 5 and 25?nm, while the ZrO₂ coatings have bigger ellipsoidal grains. The results from the electrochemical corrosion analyses showed that the Al₂O₃ coated Mg disk had corrosion resistance of approximately 3 times that of ZrO₂ coated Mg disk. It was also observed that increasing the thickness of the Al₂O₃ coating improved the corrosion resistance of the Mg disk. These results suggest that Al₂O₃ and ZrO₂ coating can be used to effectively control the fast degradation of magnesium for medical implant applications.

Key words: Magnetron sputtering, Magnesium, Aluminum oxide, Zirconium oxide, Porosity