DFT Quantum Mechanical and Electrochemical Methods for Evaluation of Corrosion Inhibition of Aryl-triazino-benzimidazole-2-thiones in Acid Media

Corrosion inhibition of aryl-triazino-benzimidazole-2-thiones on carbon steel in 2 M HCl solution was investigated using quantum mechanical, polarization, and electrochemical impedance methods. Moreover, the polarization curves show that these compounds act as a mixed inhibitor. The results of electrochemical impedance indicated that Bode-phase curves have a time constant in the concentrations less than 50 mg.L-1 of inhibitor, but Bode plots show two time-constants in the concentrations which are more than 50 mg.L-1. Adsorption of these aryl-triazino-benzimidazole-2-thions on the carbon steel surface obeyed Langmuir’s adsorption isotherm. The values of indicate that adsorption of inhibitors on the metal surface is possibly chemisorption. In addition, the geometric structures of all the compounds were optimized, and their performances were structurally compared with the DFT quantum method. Finally, the results obtained from quantum mechanical, electrochemical impedance and polarization measurements were in good agreement with each other.