A review of effective strides in amelioration of the biocompatibility of PEO coatings on Mg alloys

Recently, developing bioactive and biocompatible materials based on Mg and Mg-alloys for implant applications has drawn attention among researchers owing to their suitable body degradability. Implementing Mg and its alloys reduces the risk of long-term incompatibility with tissues because of their close mechanical properties and no need for re-operation to remove the implant. Nevertheless, the degradation rate of the implant needs to be controlled because production of hydrogen gas and accumulation of its bubbles increases local pH around the implants. To confine the integrity of implants and the body, the corrosion concern in the body fluid requires to be addressed. Surface modification as one of the effective strategies can improve corrosion resistance. Besides, it creates a suitable surface for bone grafting and cell growth. The development of proper surface-coated implants needs appropriate techniques and approaches. Plasma electrolytic oxidation (PEO) coating can provide long-term protection by providing a ceramic layer and improving the implant's biocompatibility. Herein, a general review of in-vivo and in-vitro evaluation of PEO coatings on Mg and Mg-alloys has been carried out. Recent advances in surface modification on Mg and Mg-alloys have been discussed, however, the need for reliable laboratory models to predict in-vivo degradation is still valid.