Degradation of model biomedical Mg alloys in aqueous media

Sammanfattning: This project investigates the influence of alloying elements, heat treatment and corrosion medium on the corrosion rates of three magnesium alloys Mg-5Zn, Mg0.27Ca, and Mg-0.27Ca-5Zn for use in bio-medical applications. A new method combining isothermal calorimetry and pressure measurements was used as a prime experimental tool in this investigation. Material samples were tested in a physiological 0.9 wt.% NaCl solution and modified simulated body fluid (m-SBF) that mimic the concentrations of Cl– and other ions in human blood plasma. Corrosion resistance generally improves with the material heat treatment when supersaturated solid solution is formed, and corrosion medium promotes passivation of a protective film from degradation products. For instance, Mg-5Zn alloy in m-SBF exhibits the lowest corrosion rate. The level of the solution pH also affects the kinetics of corrosion reaction, but the effect depends on a specific material composition.