Insight into physical interpretation of high frequency time constant in electrochemical impedance spectra of Mg

Electrochemical impedance spectroscopy measurements were performed to study the evolution of surface condition, which related to the high frequency time constant of Mg, in 0.05 M NaCl solution at three different pH. Based on the assumption that the high frequency time constant originates solely from the surface film, the thickness of MgO film was calculated via fitting EIS results. The deduced results were compared with the actual surface condition, characterized by transmission electron microscopy and local measurements. The results verified that the time constant at the high frequency range originates from the barrier properties of the surface film.

Automated summary

Electrochemical impedance spectroscopy measurements were used to study the surface evolution of magnesium in 0.05 M NaCl solution at three different pH levels. The thickness of the MgO film was calculated based on the assumption that the high frequency time constant originates from the surface film. Comparisons with actual surface conditions confirmed that the high frequency time constant is related to the barrier properties of the surface film.