The role of surface oxidation on the degradation behavior of biodegradable Mg–RE (Gd, Y, Sc) alloys for resorbable implants

• Stainless Mg-based alloys driven by thermodynamics
• Oxidation kinetics of Mg–3X (X = Gd, Y, Sc) alloys
• Effect of passivation on in-vitro biodegradation

Biodegradable magnesium (Mg) alloys have the potential to replace currently used implants for fixation, thereby eliminating the need for removal surgeries. To achieve a controllable degradation rate, surface oxidation has been proposed as an avenue to reduce the initial degradation. This study aims to investigate the oxidation behavior of binary Mg-rare earth alloys and the effect on biodegradation. Cast Mg–3X alloys (X = Gd, Y, Sc) were prepared and then oxidized in pure oxygen. The oxidation rate was evaluated using TGA and the oxides were further investigated and characterized using SEM, AES and XPS. The effect of oxidation on the degradation rate was investigated by immersion testing in Hanks' solution. The thermodynamics and oxidation kinetics of the alloys are discussed in regard to the obtained results, and it was concluded that the experimental results are in agreement with thermodynamic predictions.