Abstract <p>Magnesium and its alloys have gained significant prominence as promising biomaterials for healthcare applications due to their advantageous mechanical properties, notably their compatibility with bone tissue. Despite these advantages, their rapid rate of corrosion in physiological environments remains a substantial barrier, leading to the formation of hydrogen gas and elevation of pH levels that impede the process of tissue healing. Plasma electrolytic oxidation (PEO) has emerged as an effective surface treatment to improve the corrosion resistance of magnesium as it creates a protective oxide layer. Recent studies have revealed that the incorporation of hydroxyapatite (HA) and alumina (Al₂O₃) nanoparticles into PEO coatings significantly enhances the mechanical and electrochemical properties of magnesium alloys, improving biocompatibility, corrosion resistance, and surface hardness. This research aims to investigate and optimize the corrosion resistance and mechanical performance of a HA-Al₂O₃ composite coating on AZ31 magnesium alloy, with a focus on composition, morphology, adhesion, and corrosion resistance via advanced characterization techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical testing. Preliminary results demonstrate significant improvements in surface hardness and corrosion resistance, highlighting the potential for this composite coating to enhance the longevity and performance of magnesium-based biomedical implants.</p>