The multisine dynamic electrochemical impedance spectroscopy (g-DEIS) monitoring was performed using a two-channel Biologic SP-300 potentiostat connected to a PXI-4464 AC measurement card and a PXI-6124 AC/DC signal module. Since the dynamic nature of the g-DEIS measurement, spectra were recorded in a narrower frequency range of 22 kHz-0.7 Hz with 10 points per frequency decade. To evaluate the protective ability of the molybdate inhibitor depending on its concentration, a Lead Fluid peristaltic micropump was used. In this case, during the first 600 s of the experiment, g-DEIS spectra were recorded in a 0.05 M NaCl solution without the inhibitor. After this, the concentrated solution of the molybdate inhibitor was gradually introduced into the measured system by the peristaltic pump for 3000 s to achieve the final concentration of the inhibitor in the examined solution of 150 mM. The measurement was then continued for 600 s in the solution containing 150 mM of the inhibitor (Fig. in Supplementary Information). These data were also used to plot the adsorption isotherms. Further details on the experimental setup and the measurement conditions are reported elsewhere . The fitting of the obtained impedance spectra was performed based on the Nelder-Mead algorithm .