Advances in hydroxyapatite coatings on biodegradable magnesium and its alloys

Magnesium is a candidate metal for biodegradable implant applications for its biodegradation tendency and excellent biocompatibility. Unfortunately, the high degradation rate of magnesium and also its localized degradation in physiological conditions are the main issues for its successful implant applications. The degradation rate of magnesium has been reduced to some degree via alloying, but the localized degradation susceptibility is a great concern. For many years, hydroxyapatite (HAp), a biocompatible ceramic material, has been extensively used for bio-implant applications. Recently, a substantial amount of research has been carried out on coating HAp on magnesium-based materials for improved degradation resistance in particular and also to enhance the biocompatibility. This review article focuses on the different methods of HAp coating on magnesium-based materials and also the recent cutting-edge advancements made in the coating process for improved degradation resistance and biocompatibility. The mechanical stability of the HAp coated magnesium-based materials is also discussed.