Recent advances in surface modification of plasma electrolytic oxidation coatings treated by non-biodegradable polymers

The surface modification of Mg and its alloys is critical in improving their structural stability and wide usability. Plasma electrolytic oxidation (PEO) is a reforming technique can generate in-situ ceramic coatings on Mg alloy substrates by the rapid solidification of molten oxide through arc discharges. However, the inherent porosity of PEO coatings could limit the protection efficiency of PEO coatings made on high active metals and alloys like Mg. The sealing of PEO coatings by application of polymeric materials was found to be a practical approach to control the amount of damage and improve the long-term anti-corrosion properties. Therefore, this work reviewed the recent progress of PEO coatings sealed by a couple of thermoplastic and thermoset polymers, such as fluoropolymers, polypropylene, polyurethane, epoxy/silane, and polyetherimide. The main fabrication approaches, such as dip coating, spin coating, spray coating, and electrophoretic coating, were highlighted. Based on the type of each polymer, the application site, hydrophobicity, super-hydrophobicity, wear-resistant, antifriction, anti-corrosion properties, respectively, were discussed. Finally, the challenges and future prospects for the further development of PEO/polymer composite are discussed.