Influence of cryogenic treatment on the corrosion of AZ91 and AM60 magnesium alloys in an isotonic solution

Abstract Biodegradable stents made of magnesium alloys have become revolutionary in the cardiovascular area. However, rapid corrosion in a body fluid environment is harmful to the mechanical properties and stability. In this study, untreated and cryogenically treated samples of AZ91 and AM60 alloy were employed at −196 °C for 48 h. Afterwards, the corrosion performance of the AZ91 and AM60 samples was tested in an isotonic solution containing 0.9 wt.-% NaCl. Electrochemical methods such as open-circuit potential measurement (OCP), potentiodynamic polarization, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) were used to evaluate the corrosion performance. In general, the results obtained for the electrochemical studies show that the cryogenically treated AZ91 and AM60 samples maintain superior corrosion resistance when compared to the former sample. The OCP results indicated that the cryogenically treated AZ91 and AM60 outperformed untreated samples after 1 h. The potentiodynamic studies confirmed that cryogenically treated AZ91 and AM60 had superior anodic pitting potential (E pit ) and that the passivation zone is higher than AZ91 and AM60 when untreated. The EIS confirmed the lower corrosion kinetics for AZ91 and AM60 treated in the former sample.