Electrochemical Behavior Al[sub 2]O[sub 3]∕Al Coated Surgical AZ91 Magnesium Alloy in Simulated Body Fluids

Magnesium alloys are potential materials for use in biodegradable hard-tissue implants, but the fast degradation rate in a biological environment limits their applications. In order to improve the corrosion resistance, a dense, adhesive, and biocompatible bilayered coating is fabricated on AZ91 magnesium alloy by means of filtered cathodic arc deposition. The electrochemical behavior is systematically studied in simulated body fluids using a potentiodynamic polarization test, open-circuit potential evolution, as well as electrochemical impedance spectroscopy. Our results indicate that the corrosion resistance of the coated alloy is significantly enhanced. The deterioration mechanism and corrosion process of the coating during immersion are discussed.