As revolutionary bone implant materials, Mg alloys have gained extensive attention because of their biodegradability, good biocompatibility, and mechanical properties. [1][2][3][4][5][6] Mg is one of the most important divalent ions in the formation of bioapatite and a key factor in bone metabolism. [7] Moreover, it has a similar elastic modulus to the natural bone, which is beneficial for reducing the stress shielding effect. [8] As a highly electronegative metal, Mg can gradually degrade in the human physiological environment, thereby avoiding second surgical resection. [9,10] However, Mg alloys are also well known for their too fast degradation which may result in premature failure after implantation. [11][12][13] Consequently, it has long been a research hotspot to improve the biodegradation resistance of Mg alloys.Alloying has been recognized as a common method for slowing down the degradation of Mg alloys. Soo-Min et al. fabricated extruded MgâAlâCaâY alloy by alloying Y and the corrosion resistance of the alloy in NaCl solution was improved owing to the increased corrosion potential. [14] However, the improvement always compromises with the type and concentration of the alloying element due to the potential biosafety problem and/or galvanic corrosion. In addition, coating is one of the most effective ways to prevent corrosion. Gray et al. and Chen et al. successively summarized the advances in protective coatings and corrosion-resistant