Strategies to improve the corrosion resistance of microarc oxidation coatings on magnesium and its alloys: Implications for biomedical applications

The development of magnesium-based biodegradable implants is indeed fascinating. However, the rapid corrosion, generation of a large volume of hydrogen gas, accumulation of hydrogen bubbles in gas pockets adjacent to the implant, and increase in the local pH of the body fluid are the major impediments in using Mg and its alloys as implant materials. Among the various surface modification processes explored to increase the corrosion resistance of Mg and its alloys, microarc oxidation (MAO) has received considerable attention. However, the higher pore density of MAO coatings increased the effective surface area and the tendency of the corrosive medium to adsorb and concentrate in these pores, thus causing a deleterious influence on the corrosion protective ability. Hence, it is not only essential but also mandatory to increase the corrosion resistance of MAO coatings. This chapter addresses the various strategies explored for improving the corrosion resistance of MAO coatings deposited on Mg and its Mg alloys.