Pingping Jia, Lang Yu, Liuyuqing Yang, XiangYang Mu, Yingjie Wang, Yongxiao Wang, Yaokun Pan
Magnesium (Mg) alloys have emerged as a highly promising material for bone implants due to their biodegradability and biocompatibility. The clinical application of biodegradable Mg alloys remains constrained by rapid degradation kinetics in physiological environments. To enhance their corrosion resistance, a novel composite coating system through CO 2 -assisted micro-arc oxidation (MAO), subsequent hydrothermal treatment (HT), and poly(lactic-co-glycolic acid) (PLGA) sealing for Mg-Nd-Zn-Ca alloys were developed. The chemical composition and morphology of the coatings were analyzed using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), fourier transform attenuated total reflection infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). Results shows that the CO 2 introduction during initial MAO process achieves significant micropore refinement and promotes the formation of protective MgCO 3 layers. HT facilitates uniform Sr 2+ incorporation with the assistance of phytic acid, while PLGA-based physical sealing completes the multi-layered protection architecture. This hierarchical architecture achieved superior corrosion resistance. Electrochemical tests reveal that the composite coating exhibits 10 6 -times reduction in current density compared to untreated alloy. The coating system combines physical barrier protection with chemical passivation, and provides valuable insights into gas-assisted MAO and its post-treatment technologies, and their potential for clinical translation in orthopaedic applications.