Quantum Chemistry Calculation of Corrosion Inhibition Performance of Oleic-acid Imidazoline Corrosion Inhibitors

According to the characteristics of CO2 corrosion, using oleic-acid as raw material, three imidazoline intermediates were synthesized by reaction with diethylenetriamine, triethylenetetramine and etraethylenepentamine, respectively. And then three kinds of corrosion inhibitors A, B and C were prepared by quaterisation with benzyl chloride. The performance of these three kinds of corrosion inhibitiors on N80 carbon steel was evaluated in saturated CO2 and 6% NaCl solution by weight loss method, polarization curve, and scanning electron microscopy (SEM). Their adsorption behaviors on N80 carbon steel surface were also explored. The results showed that the optimal corrosion inhibition performance was exhibited by inhibitor C. The inhibition rate reached 86.74% when its concentration was 2×10-3 mol/L. The adsorption behaviors of these three kinds of inhibitors all obey the Langmuir adsorption isotherm, and belong to the chemical adsorption of mixed adsorption. The structures of three kinds of imidazoline inhibitors were optimized using Gaussian 03W program and the B3LYP/6-31G* method of density functional theory (DFT), and their stable structures and quantitative parameters were obtained. The quantum chemical calculations showed that the three kinds of molecules had relatively strong reaction activity, their active regions were concentrated in the imidazole ring and hydrophilic chain, the strongest reaction activity molecule was C, followed by B and A. The results were consistent with the theoretical calculation.