Enhancement of Corrosion Resistance of AZ31 Magnesium Alloy by a Protective System for Biomedical Applications

The removal of prosthetic implants, although normally necessary following the recovery of patients, inevitably has disadvantages in terms of costs, further pains and possible post-operative infections. A promising alternative is represented using bioresorbable implant structures. The magnesium alloy-based devices could be ideal candidate due to their poor corrosion resistance and high biocompatibility, but their degradation rate is dissimilar to that of hosting tissues healing. Therefore, a growing interest is addressed to design new magnesium alloys with a slow degradation process or to modify the surface of known magnesium alloys. This paper aims to investigate the enhancement of corrosion resistance of a protective system applied on the AZ31 magnesium alloy composed of three different superimposed layers: a) magnesium-based oxide, b) polydopamine and c) polylactic acid. Morphological and chemical analysis were performed. Roughness and microhardness measurements were carried out. Electrochemical behavior was studied in the Hanks’ solution at 37 °C. As expected, the findings showed that the magnesium oxide layer is able to reduce the degradation rate, in contrast to the polydopamine layer, that negatively affected the barrier protection of the only anodization. However, the presence of polydopamine together with the polylactic acid film improved the corrosion resistance of the alloy. Thus, the multilayers should represent a protective system to control the degradation process.