Medical magnesium alloys are promising implant materials owing to favorable biodegradability and mechanical compatibility, but their rapid, uncontrolled corrosion impedes clinical application. In this work, femtosecond laser processing combined with low-temperature annealing was adopted to regulate the degradation behavior of AZ31 Mg alloy. Three surface textures (grid, porous and striped) were fabricated under different laser energy doses, and they all exhibited evidently enhanced anti-corrosion performance, which is closely related to their wettability transition. The laser-textured surfaces were superhydrophilic but converted to stable superhydrophobic after low-temperature annealing and ambient-air exposure. The annealing activates active sites for adsorption of airborne organics bearing hydrophobic groups in the following air exposure. The trapped air in the textures forms an air film that further mitigates contact between the substrate and corrosive medium, thereby greatly improving hydrophobicity and corrosion resistance. In vitro 12-week immersion tests show that the corrosion rates of all three superhydrophobic surfaces stay below the medical-implant safety threshold of 0.5 mm/a. The textured surfaces exhibit a gradient degradation characteristic that can be attributed to the complexity of the texture structure and the degree of oxidation. This study proves that femtosecond-laser-modified surfaces provide an effective strategy for regulating the degradation of magnesium-based medical implants.
