Current advancements on magnesium alloy coatings for bioimplants: A closer look for biocompatibility and corrosion mitigation

The healthcare industry has closely considered magnesium (Mg) alloy because of its exceptional mechanical qualities, biological solid compatibility, and biodegradable properties. Since it has reactive chemistry of natural world, magnesium alloy typically exhibits excessive rate of deterioration in the physiological environment. Thus, surface modification research has become a hotspot for obtaining different potential abilities of magnesium alloy in medical applications. The coatings of magnesium alloy surfaces are discussed in this work based on their many types: metals (metal hydroxides and oxides), inorganic/nonmetallic, and natural/synthetic polymers. The metal oxide coating is loose and porous, and it is often used together with other types of coatings to form a composite coating. The metal hydroxide coating is easily damaged by Cl^- ions in corrosive medium and cannot provide long-term effective protection to substrate. Inorganic nonmetallic coatings have more space defects and greater brittleness, which used in few bone implantation procedures. Polymer materials generally have better biocompatibility and biodegradability. However, polymer coatings have a weak binding force to the substrate and limited mechanical properties. The development prospects of magnesium alloy surface coatings for biomedical applications are forecasted together with the manufacturing techniques, resistance to corrosion, and compatibility for biological systems has been discussed.