INFLUENCE OF ANODIZING TREATMENTS ON THE CORROSION-FATIGUE BEHAVIOR OF AZ31 MAGNESIUM ALLOY IN PHYSIOLOGICAL ENVIRONMENT

Abstract

The low corrosion resistance of magnesium alloys is unsuitable for a wide variety of industrial applications. In the biomedical field, though, this characteristic can be advantageous for developing temporary fixture devices. The main challenge is to control the velocity of dissolution inside the body, since the device must sustain its structural integrity for a period that is sufficient to allow the fractured bone to heal. In this scenario, control of the corrosion rate should be carried out by surface treatments, preventing excessive deterioration of the metallic alloy in the physiological fluid. Electrolytic processes such as anodizing can be applied to magnesium alloys in order to increase the corrosion resistance without introducing foreign elements to the alloy which could lead to biocompatibility concerns. As surface treatments are necessary to increase the chemical stability of magnesium alloys, the response of these materials to cyclic stresses typical of orthopedic applications is also of prime interest. Corrosion fatigue is responsible for most part of mechanical failures of implantable metallic devices. In this regard, the aim of this project is to investigate the effect of anodizing on the corrosion fatigue behavior of the AZ31 magnesium alloy. Scanning electrochemical microscopy (SECM) will be employed to identify localized corrosion spots on the surface of the AZ31 alloy, studying the correlation between these spots and the mechanism of corrosion fatigue. (AU)