Theoretical evaluation of corrosion inhibition performance of imidazoline compounds with different hydrophilic groups

Corrosion inhibition performance of four 1-R-2-undecyl-imidazoline compounds (RCH2COOH (A), CH2CH2OH (B), CH2CH2NH2 (C) and H (D)) for carbon steel was evaluated by quantum chemistry and molecular mechanics methods. Results indicated that the hydrophilic groups (R) have remarkable influence on molecular reactivity, binding strength between self-assembled monolayer (SAM) and Fe surface, and compactness of the inhibitor SAM. The inhibition efficiency evaluated via theoretical methods was well accorded with reported experimental ones, following the same order as A > B > C > D. This research might provide a theoretical inhibition performance evaluation approach for homologous inhibitors.

Research highlights
► The trend in inhibition efficiency of imidazoline derivatives was assessed by combination of quantum chemistry calculation and molecular mechanics simulation. Results from the theoretical investigation were in good accordance with previously published experimental ones, indicating a new theoretical solution for prediction of inhibition efficiency of corrosion inhibitors.
► Effect of hydrophilic side chain on corrosion inhibition performance was revealed from quantum chemistry calculation and molecular mechanics methods, which facilitates deeper understanding of microscopic inhibition mechanism of imidazoline derivatives.
► This theoretical work may provide a feasible idea in molecular design of new corrosion inhibitors.