Electrochemical and Quantum Chemical Studies of Azoles as Corrosion Inhibitors for Mild Steel in Hydrochloric Acid

The inhibition effect of three azole compounds, 2-aminobenzimidazole(ABM), 2-aminothiazole(AT) and 2-aminobenzothiazole(ABT), on the corrosion of mild steel in a 1 mol/L HCl solution was investigated by means of potentiodynamic polarization measurement, electrochemical impedance spectroscopy(EIS) and scanning electron microscopy(SEM). The correlation between inhibition efficiency and molecular structure of inhibitor was theoretically studied via quantum chemical calculations. The results show that the inhibition efficiency(eta) of the inhibitors follows the order of eta(ABT)>eta(AT)>eta(ABM). Moreover, ABM, AT and ABT belong to mixed-type inhibitors. The adsorption of the inhibitors on the steel surface follows the Langmuir adsorption isotherm, with both physisorption and chemisorption.