The results obtained in the 0.05 M NaCl solution (Fig. ) without the inhibitor showed similar behavior for all alloys. At each point of the measurement, the Nyquist spectra display dispersed capacitive loops. The content of Li in the examined Mg alloys to some extent affects the corrosion kinetics, represented by the shape of the impedance spectra, and has a crucial impact on the radii of the Nyquist spectra in time. A comparison of the g-DEIS spectra obtained at the same immersion time revealed higher corrosion resistance of the alloy with lower amounts of Li. For all alloys, the radii of the g-DEIS spectra decreased with immersion time, showing high corrosion rates and low corrosion resistance of the formed surface films of corrosion products. After 2000 s, the radii and shape of the spectra are comparable for all alloys (Fig. ), suggesting that the surface of the alloys is covered with a layer of corrosion products, which to some extinction decreases corrosion rate. To further examine the protective action of sodium molybdate, it was gradually added into the 0.05 M NaCl solution after initial pre-exposure for 10 min in the non-inhibited solution (Fig. ). The introduction of the molybdate inhibitor significantly increases the radii of the g-DEIS spectra of all studied alloys. It suggests rapid adsorption of the inhibitor on the surface with the formation of a protective layer, which suppresses the active corrosion of the alloys. The highest initial increase in the impedance values was observed for the AZ31-4Li alloy. The further increase in the inhibitor concentration results in a monotonous increase in the impedance values, with its rate decreasing in the row AZ31-4Li → AZ31-8Li → AZ31-12Li alloy. Nevertheless, for all alloys, the molybdate inhibitor showed high effectiveness. The inhibition mechanism is concentration-dependent with relatively large concentrations required in the solution. This coincides well with our previous data on the corrosion inhibition of the AZ31 and WE43 Mg alloys by aqueous molybdate in 0.05 M NaCl solutions .