Four 2

5-diaryl-1

3

4-thiadiazole compounds

namely

2

5-diphenly-1

3

4-thiadiazole (DPTD)

2

5-di(2-hydroxyphenly)-1

3

4-thia-diazole (2-DHPTD)

2

5-di(3-hydroxyphenly)-1

3

4-thiadiazole (3-DHPTD)

and 2

5-di(4-hydroxyphenly)-1

3

4-thiadiazole (4-DHPTD) were synthesized. Their corrosion-inhibiting performance in S-ethanol system was evaluated by Tafel polarization and electrochemical impedance spectroscopy (EIS). Electrochemical experimental results showed that all the thiadiazole derivatives were excellent inhibitors. The corrosion current decreased and the inhibition efficiency increased with increasing concentrations of the inhibitors. The optimum concentration was 90 mg·L-1

while the inhibition efficiency of DPTD

2-DHPTD

3-DHPTD and 4-DHPTD was 85.8%

94.6%

96.4% and 97.1%

respectively. Scanning electronic microscope (SEM) and atom force microscope (AFM) were also carried out

and confirmed the existence of the adsorbed film which was prevailed in addition of thiadiazole derivatives. The adsorption of these compounds onto silver surface from 50 mg·L-1 S-ethanol was followed the Langmuir adsorption isotherm and attributed to mixed-type adsorption mainly dominated by chemisorption. Quantum chemical calculations and molecular dynamic simulations also demonstrated that thiadiazole derivatives were good inhibitors. The experimental results showed that the order of inhibition efficiency was [4-DHPDT]> [3-DHPDT]> [2-DHPDT]> [DPDT]

which was agreed with the theoretic method.