Design multifunctional Mg–Zr coatings regulating Mg alloy bioabsorption

Magnesium (Mg) alloys are widely used for temporary bone implants due to their favorable biodegradability, cytocompatibility, hemocompatibility, and close mechanical properties to bone. However, rapid degradation and inadequate strength limit their applicability. To overcome this, the direct current magnetron sputtering technique is employed for surface coating in Mg-based alloys using various zirconium (Zr) content. This approach presents a promising strategy for simultaneously improving corrosion resistance, maintaining biocompatibility, and enhancing strength without compromising osseointegration. By leveraging Mg's inherent biodegradability, it has the potential to minimize the need for secondary surgeries, thereby reducing costs and resources. This paper is a systematic study aimed at understanding the corrosion mechanisms of Mg–Zr coatings, denoted Mg-xZr (x = 0–5 at.%). Zr-doped coatings exhibited columnar growth leading to denser and refined structures with increasing Zr content. XRD analysis confirmed the presence of the Mg (00.2) basal plane, shifting towards higher angles (1.15°) with 5 at.% Zr doping due to lattice parameter changes (i.e., decrease and increase of ``c” and ``a” lattice parameters, respectively). Mg–Zr coatings exhibited ``liquidphilic” behavior, while Young's modulus retained a steady value around 80 GPa across all samples. However, the hardness has significantly improved across all samples’ coating, reaching the highest value of (2.2 ± 0.3) GPa for 5 at.% Zr. Electrochemical testing in simulated body fluid (SBF) at 37 °C revealed a significant enhancement in corrosion resistance for Mg–Zr coatings containing 1.0–3.4 at.% Zr. Compared with the 5 at.% Zr coating which exhibited a corrosion rate of 32 mm/year, these coatings displayed lower corrosion rates, ranging from 1 to 12 mm/year. This synergistic enhancement in mechanical properties and corrosion resistance, achieved with 2.0–3.4 at.% Zr, suggests potential ability for reducing stress shielding and controlled degradation performance, and consequently, promising functional biodegradable materials for temporary bone implants.