Surface Modification of AZ31 Magnesium Alloy and Its Effect on Hydroxyapatite Coatings Adhesion

Magnesium and its alloys are promising biomaterials for orthopedic applications due to their appropriate mechanical properties, bone‐like density, and biocompatibility. However, their rapid corrosion in physiological environments limits their clinical use. Hydroxyapatite (HA) coatings offer a viable solution to enhance the prosthesis/bone interface, improve biocompatibility, and reduce corrosion. A critical role for the success of these coatings is their adhesion to the substrate. This study investigates the adhesion mechanisms of HA coatings electrodeposited on AZ31 alloy subjected to three different surface treatments: untreated, acid, and basic. We employed scanning electron microscopy (SEM), atomic force microscopy (AFM), grazing incidence x‐ray diffraction (GIXRD), Fourier‐transform infrared spectroscopy (FTIR), x‐ray photoelectron spectroscopy (XPS), and scratch tests to characterize the coatings and assess their adhesion. Additionally, density functional theory (DFT) was utilized to explore the atomic interactions and support the experimental findings. The optimal HA adhesion was observed when AZ31 was treated with NaOH, leading to the formation of an Mg (OH) 2 surface. The enhanced adhesion can be attributed to mechanical interlocking and commensurable crystalline structure, which reduces strain in the coating, thereby improving its quality and lifetime for bone repair and prosthetic applications.