Plasma Electrolytic Oxidation: A Versatile Tool to Modulate the Degradation of Biodegradable Metals in Medical Applications

Biodegradable metallic materials have attracted increasing interest for temporary implant applications due to their promising mechanical and corrosion properties. However, their degradation kinetics, release of corrosion products, and active interaction with the biological environment still present several criticalities that need to be addressed. Plasma electrolytic oxidation (PEO) is an interesting and versatile surface modification technique that can be exploited to both tune the degradation behavior and add surface functionalities to these materials, particularly magnesium and zinc alloys. This study provides an overview of the main problems of magnesium- and zinc-based biomaterials which can be addressed by PEO, how the technique can be tuned for this purpose, and the current emerging developments of the technique to further improve its effectiveness. In addition, a case study is reported on the tuning of PEO coatings on magnesium for orthopedic applications, demonstrating the ability to fine-tune surface properties by manipulating electrical process parameters alone.