The results of the spectra fitting are summarized in Table . It can be seen that both R1 and R2 parameters increased significantly compared to the uninhibited solution as the concentration of the inhibitor in the solution was 50 mM or more. Table . Fitting data extracted from EIS measurements with a standard deviation of three measurements and calculated inhibition efficiency Concentration of inhibitor, mM The quantitative assessment of IE based on the EIS data can be performed using Eq. and Rct or Rp values and the difference between them is marked in Fig. and in Table . From EIS spectra, Rct can be assigned as the impedance value when Z" → 0, while Rp can be estimated as the low-frequency intersection of the total impedance with the abscissa when the frequency f → 0.