Correlation between electrochemical impedance measurements and corrosion rates of Mg-1Ca alloy in simulated body fluid

The corrosion behaviour of an Mg-1Ca alloy in simulated body fluid (SBF) for 14 days was investigated by electrochemical impedance spectroscopy (EIS), hydrogen evolution measurement, weight loss and observation of the corroded alloy surfaces, with the aim of establishing a clear correlation between the values of the parameter obtained from EIS fitting and corrosion rates. It was found that corrosion proceeds in three stages, characterized by differences in the values of resistances and by the weight of the relative contribution of the inductive behaviour to the overall EIS response. Among all the parameters obtained from EIS fitting, only the charge transfer resistance presented a good correlation with the corrosion rate over the whole duration of the measurement, and an apparent Stearn-Geary coefficient could be calculated. Based on the EIS results, a better understanding of the corrosion behaviour of the Mg-1Ca alloy in SBF solution was attained.