Time-dependent mechanical integrity evolution and degradation behavior of optimized ZrO₂-coated biodegradable ZX11 alloy in physiological medium

This is the authors' abstract. We don't add key points for this paper.

Biodegradable magnesium alloys hold significant clinical potential for orthopedics, yet their application is hindered by rapid early-stage degradation products and subsequent mechanical failure. This study investigates the efficacy of an optimized thin ZrO₂ film deposited via magnetron sputtering on a ZX11 magnesium alloy to control the rate of the early-stage corrosion process, preserving the necessary mechanical integrity. Corrosion and degradation kinetics were evaluated using electrochemical testing, gas chromatography for H₂ evolution, and mass loss measurements at 12, 24, and 36 h in supplemented DMEM/F-12 + 10% v /v fetal bovine serum (FBS). From the electrochemical evaluation, the thin ZrO₂ coating increased corrosion resistance in the early stage by a factor of 3. More information about the degradation kinetics could be obtained by fitting the H₂ evolution plot with an empirical non-passivating exponential expression. The degradation rate of the coated alloy decreased by 50% after 12 h, then converged to that of the bare alloy due to localized film delamination. Tensile testing revealed that the ZrO₂ coating preserved mechanical integrity, maintaining a stable ultimate tensile strength (UTS) and yield strength (YS), 230 MPa and 142 MPa, respectively, throughout the immersion test up to 36 h, the maximum time tested in the present work; whereas the bare alloy's YS dropped by 14%. Although the coating's defect-controlled degradation slightly reduced elongation and toughness, the retained mechanical performance remained suitable for biodegradable temporary orthopedic applications. This work highlights the necessity of evaluating coating-driven degradation kinetics alongside the mechanical evolution of biodegradable temporary load-bearing orthopedic devices.