FABRICATION AND CHARACTERIZATION OF A BIOCOMPATIBLE COATING FORMED ON A HEAT-TREATED MAGNESIUM ALLOY USING MICRO-ARC OXIDATION

The fast corrosion rate of magnesium (Mg) alloys is the main problem associated with the use of such biocompatible alloys for bone fixation applications. The corrosion resistance of Mg alloys can be improved by different post-fabrication processes such as heat treatment and coating. We have heat treated a biocompatible Mg-1.2Zn-0.5Ca (wt.%) alloy at optimized heat treatment parameters to achieve the highest mechanical strength and corrosion resistance. Afterwards, the heat-treated alloy was coated with a ceramic layer using micro arc oxidation (MAO) process to further enhance the corrosion resistance. The microstructure of the prepared samples was investigated using optical microscopy and scanning electron microscopy (SEM). The corrosion characteristics were determined by conducting in vitro electrochemical and immersion corrosion tests. The results showed that the heat treatment process successfully improved the mechanical and corrosion properties of the Mg-1.2Zn-0.5Mn (wt.%) alloy. Both the in vitro electrochemical and immersion corrosion tests showed that the MAO-coated samples have a \significantly higher corrosion resistance which results in a significantly lower corrosion rate. This study indicated that the biocompatible coating produced by MAO process may be suitable for providing heat-treated Mg-Zn-Ca-based alloys with protection from corrosion towards synthesizing bone fixation materials in clinical application.