Retardation of degradation of biomedical magnesium alloy by plasma-based deposition technique

Magnesium-based materials have been reconsidered as revolutionary metallic biomaterials due to their favorable biodegradation and Young´s modulus similar to that of human bone. However, most magnesium alloys suffer from a biodegradation rate that is too high, particularly in the early stage. Hydrogen bubbles and surface alkalization can also influence tissue growth during the degradation process. Therefore, it is necessary to modify the surface of Mg alloys in order to mitigate degradation in the early stage to ensure proper tissue healing and growth. In this work, ceramic coatings are deposited on biodegradable magnesium alloys by sputtering to reduce the electrochemical activity in the simulated physiological environment. AlO_xN_y ceramic coatings are successfully deposited on AZ31 magnesium alloys with Al or Ti interlayers. Polarization tests and electrochemical impedance spectroscopy (EIS) are conducted to evaluate the corrosion resistance in the cell culture medium. The AlO_xN_y ceramic coating can effectively reduce the electrochemical activity of AZ31 and significantly improve the surface mechanical properties. The Ti interlayer increases corrosion of Mg alloy due to the presence of defects. The Al interlayer compromises the surface mechanical properties, but does not produce negative effects on the degradation in the cell culture media.