Characteristics and Corrosion Behavior of Bioresorbable Mg–1Ca Alloy

Abstract

In recent years, the field of magnesium-based biomaterials has regained popularity owing to advancements in technologies that allow for better control over corrosion. This work presents a comprehensive study on the influence of high pressure torsion (HPT) on the corrosion behavior of a biodegradable magnesium alloy in Ringer’s solution. The alloy was investigated in three states: as-homogenized, after HPT, and after HPT followed by heat treatment at 250°C. It was shown that HPT treatment leads to a significant grain refinement in the alloys, with an average grain size of about 210 nm; however, the corrosion resistance values of the samples after HPT treatment differ significantly from those in the homogenized state (by an order of magnitude). The surface of the samples after immersion in physiological Ringer’s solution was analyzed using scanning electron microscopy (SEM). The surface structure reveals that, in the homogenized state, a large corrosion pit forms at the site of the eutectic, resulting from micro-galvanic corrosion caused by the interaction of α-Mg and Mg₂Ca. On the surface of the sample subjected to high pressure torsion (HPT), which demonstrated the best corrosion resistance, specific channels and small pits were observed in areas where Mg₂Ca particles were located. Precision studies using TEM and XRD indicate that the difference in corrosion behavior is attributed to variations in the morphology and origin of the nanoscale second-phase particles, as well as the utilization of the electrochemical properties of the “particle–α-Mg” pair.