Revealing physical interpretation of time constants in electrochemical impedance spectra of Mg via Tribo-EIS measurements

Highlights: • Tribo-EIS measurements were performed on Mg to clarify the origin of time constants. • Abrasion of tribometer influences two time constants of Mg EIS spectra differently. • Quantitative analyses of scratch introduced by tribometer on EIS spectra were done. • High frequency time constant originates from the barrier properties of surface film. • Middle frequency time constant reflects the charge transfer process of Mg corrosion. -- Abstract: Tribo-electrochemical impedance spectroscopy (Tribo-EIS) measurements of pure Mg were performed to identify the origin of two time constants during standard EIS measurements in NaCl solution. The influence of abrasion introduced by tribometer on EIS spectra was investigated under different rotation speeds. Further quantitative analyses of abrasion on Mg with different surface areas were performed. The resistances associated to the two time constants on the abraded surface were deduced from the fitted results, verifying that the high frequency time constant originates from the barrier properties of the MgO-based surface film and the middle frequency time constant stems from the charge transfer process.