An attempt was made to estimate the corrosion rate of AZ31 and AZ61 magnesium alloys immersed in 0.6 M NaCl during long‐term exposure using electrochemical impedance spectroscopy (EIS). The EIS results were compared with the corrosion rate independently assessed by the hydrogen evolution test. A correlation was established between the integration of the polarization resistance (Rp) and charge transfer resistance (Rt) over time, as evaluated by EIS and hydrogen gas measurements. Regardless of the immersion time, a strong link was found between the Rt and Rp values determined by EIS. This relation seems to depend on the composition of the alloy. The influence of immersion time on the estimated corrosion rate reliability was investigated. The typical deviations of the measurement methods are apparently decreasing upon prolonging the immersion time. No significant errors were obtained in the measurement of the corrosion rate when using Rt or Rp determined by EIS with their corresponding “apparent” Stern‐Geary coefficient values compared with the real values determined by gravimetric measurements.
Part of the book: Magnesium Alloys