In the measurement without the permanganate ions, all recorded impedance spectra (Fig. ) had comparable time-dependence profiles. The radii of the spectra decreased with time, with the lowest corrosion resistance observed for the AZ31-12Li alloy. All spectra have a single semiarch shape. At some conditions, spectra also contained low-frequency inductive tail, which in this case can be associated with the charged species generated in the near-electrode area in the course of corrosion . In the next series of experiments (Fig. ), the protective effect of potassium permanganate was studied by its progressive addition to the solution following the concentration profile shown in Fig. in Supplementary Information. The addition of even small amounts of the inhibitor resulted in a considerable increase in the radii of DEIS spectra of all examined alloys. It implies that the inhibitor is adsorbed onto the metal surface and forms a protective layer, decreasing the corrosion rate. Permanganate ions provided high effectiveness in retarding corrosion in 0.05 M NaCl solutions. With an increase in the amount of the added inhibitor, the radii of the Nyquist spectra were generally increasing (Fig. ), and Bode plots showed lower phase angles and wider frequency intervals corresponding to the capacitive response (Fig. ).