In this research novel synthesized Schiff bases components (Sb1, Sb2 and Sb3) were investigated as corrosion inhibitors for mild steel corrosion in 1M HCl solution. These new components contain S-S bonds, S and N heteroatoms, simultaneously. For evaluating of used Schiff bases, electrochemical tests (tafel polarization and electrochemical impedance) were used, also, weight loss measurements in presence of different concentrations of Schiff bases (10, 20, 30, 40 and 50 ppm) were used. Corrosion rate of mild steel in weight loss test in uninhibited solution was 1.177 mg/cm 2 .h that in the presence of maximum concentration of Sb1, Sb2 and Sb3 decreased to 0.0976, 0.137 and 0.0255 mg/cm 2 .h, respectively and inhibition efficiencies for three Schiff bases were91.7, 88.3 and 97.8%, respectively. These results show the significant impression of inhibitors on the corrosion inhibition of mild steel. Tafel polarization measurement results show that inhibitors with the adsorption performance, impress both cathodic and anodic branches.Corrosion current density in uninhibited solution was 640.1 A/cm 2 that in the presence of maximum concentration ofSb1, Sb2 and Sb3 decreased to the 63.5, 86.4 and 41.7 A/cm 2 values, respectively, and inhibition efficiencies in the presence of these inhibitors were 90.07, 86.50 and 93.48%, respectively. The results of EIS experiment showed that in the presence of the inhibitors in the corrosive solution, charge transfer resistance values increase and capacitance of the double layer decreases . Charge transfer resistance in the absence of the inhibitors was 26 ?.cm 2 which in presence of the maximum concentration of the Sb1, Sb2 and Sb3, increased to the 348, 233 and 515 ?.cm 2 values, respectively and the inhibition efficiencies for Sb1, Sb2 and Sb3 were 92.52, 88.84 and 94.95%, respectively. Adsorption of the three Schiff bases obeyed the Langmuir adsorption isotherm and high values of the standard free energy and adsorption equilibrium constant were indications of the strong adsorption of the Schiff bases onto the mild steel surface. Tafel polarization experiment was employed in the temperature range of 25 - 55 in absence and presence of the maximum concentration of the Schiff bases and the obtained results showed that increase in the corrosion current density in the presence of the inhibitors was extremely lower than that blank solution which confirms appropriate performance of the inhibitors even at the high temperatures. Quantum chemical calculations were used to be compared with the experimental results and some parameters like E HOMO , E LUMO , ?E and ?? were calculated and reported. Also, electron density distribution of the HOMO and LUMO were evaluated. Calculated values obtained from quantum chemical calculations did not show a direct relation with the data obtained from experimental results that is an indication of the complicated process of the corrosion inhibition. SEM images from metal surface showed that mild steel surface in the absence of the inhibitors is extremely damaged and corroded while in the presence of inhibitors metal surface was smooth and without severe damage K eywords Mild steel, Corrosion, Schiff base, Adsorption, Electrochemical test, Quantum chemical calculation. <