Study on inhibition behavior of dissymmetric bis-quaternary ammonium with imidazoline ring

Dissymmetric bis-quaternary ammonium with imidazoline ring was studied for inhibition behavior in 1.0 mol·L^-1 hydrochloric acid solution at room temperature by mass loss, potentio-dynamic polarization, electrochemical impedance spectrum (EIS) and scanning electron microscopy (SEM). The result of mass loss indicated that the inhibition efficiency increased with the increase in inhibitor concentration and was over 98 % with the addition of 50 mg·L^-1 inhibitor. Polarization data showed that the compound acted as a cathodic inhibitor for Q235 steel by changing the OCP to more negative value and changing the anodic reaction progress in 1.0 mol·L^-1 hydrochloric acid solution according to the double of b_a. EIS results showed that the associated values of the charge transfer resistance (R_ct) increased with increasing inhibitor concentrations and immersing time whereas the associated values of double layer capacitance (C_dl) decreased. These changes in the impedance parameters (R_ct and C_dl) were indicative of adsorption of the compound on Q235 steel surface leading to the formation of a protective film. The relationship between molecular structure of the compound and the inhibition efficiency was investigated by PM6 quantum chemistry calculation. The correlations and theoretical conclusions were in good harmony with the experimental results.