Superior tribocorrosion resistance of Mg metal matrix composite by self-sealing PEO coating

SiC-reinforced Mg metal matrix composites (SiC/Mg MMCs) show mechanical advantages but suffer from severe corrosion. Protective self-sealing plasma electrolytic oxidation (PEO) coatings were developed using a phosphate-zirconium-fluoride (P-Zr-F) electrolyte, where additives (F − and ZrF 6 2− ) were strategically introduced to form low-melting MgF 2 and stable ZrO 2 phases. The findings revealed two orders of magnitude increase in corrosion resistance and achieved 5.3 GPa hardness after PEO treatment. The coating on MMC exhibited exceptional tribocorrosion resistance, attributed to partial reactive SiC incorporation into coating and MgF 2 -stabilized friction at sliding interfaces. Accelerated Mg dissolution in MMC promoted MgF 2 formation during PEO process, while SiC restricted inward coating growth, enabling outward fluoride-rich layer development. This work advances surface-tailoring strategies for MMCs in extreme environments. • SiC particles reduce 40 % wear of Mg alloy but raises 32 times for corrosion rate. • Self-sealing PEO coating boosts corrosion resistance and decreases 86 % wear. • SiC phases undergo oxidation, partially dissolving near matrix/coating interface. • MMC’s high activity causes Mg to dissolve and bond with F − instead of oxidation. • MgF 2 -stabilized friction and SiC incorporation enhance tribocorrosion resistance.