The comparison of imidazolium Gemini surfactant [C14-4-C14im]Br2 and its corresponding monomer as corrosion inhibitors for A3 carbon steel in hydrochloric acid solutions: Experimental and quantum chemical studies

The inhibitory behaviors of imidazolium Gemini surfactant ([C-14-4-C(14)im]Br-2) on A3 carbon steel in HCl solutions, which is compared with its corresponding monomer ([C(14)mim]Br), have been investigated using electrochemical impedance spectroscopy (EIS), polarization curves, weight loss measurement and the quantum chemical study. Results reveal that the corrosion inhibition efficiency (IE) of [C-14-4-C(14)im]Br(2 )reaches 96% at 1.0 x 10(-5)mol.L-1, and its IE value is higher than that of [C(14)mim]Br at the same concentration. Based on weight loss results, the adsorption of inhibitors on the carbon steel surface follows Langmuir isotherm, and thermodynamic parameters of adsorption such as the standard free energy of adsorption (Delta G(ads)(0)) and the en-thalpy of adsorption (Delta H-ads(0)) are calculated and discussed. The adsorption of [C-14-4-C(14)im]Br(2 )is an endothermic processes, which is suitable to use in the relatively high temperature, while the opposite for [C(14)mim]Br is the case with an exothermic processes. The quantum chemical calculation is employed to interpret the possible inhibition mechanism of [C-14-4-C(14)im]Br-2 and [C(14)mim]Br. This work would supply basis data of the inhibitive ability of Gemini surfactants and have certain theoretical guidance on designing and developing new imidazolium derivatives used as corrosion inhibitors.