Corrosion Inhibition Performance Of Imidazoline Derivatives Investigated By Theoretical Methods

Corrosion prevention is of great importance for industrial application of materials. Among numerous corrosion prevention measures, corrosion inhibitor, bearing advantages of economy, high-efficiency, and wide-applicability, has been applied in various fields, such as petroleum extraction and refining, iron and steel, electric power, and construction, etc. Traditional research and developing routes are based on large-scale trial-and-error experiments, and bring along high cost and long cycle. Therefore, theoretical guidance is critical in design and application of new corrosion inhibitors.Imidazoline and its derivatives was one kind of excellent inhibitor which could effectively inhibit the corrosion of carbon steel against CO2 and H2S. The chosen compounds have the same alkyl chain (R1, undecyl), while they have different hydrophilic groups (R2), where R2 = CH2COOH (A), CH2CH2OH (B), CH2CH2NH2 (C), and H (D). Corrosion inhibition performance of four imidazoline compounds was evaluated by combination of quantum chemical calculations, molecular mechanics and molecular dynamics simulation. The global reactivity indices, such as frontier orbital energy, hardness and electrophilicity index, were investigated via quantum chemical calculations to analyze the molecular reactivity. The self-assembled monolayer was studied through molecular mechanics method to determine the interaction between inhibitor molecule and Fe surface. The adsorption behavior of these molecules in liquid phase was studied by molecular dynamics simulation. These results indicated that the structure of hydrophilic group had remarkable influence on molecular reactivity, bonding strength of molecule and Fe surface, and compactness of the monolayer. The corrosion inhibition efficiency of four imidazoline compounds by theoretical methods followed the order of A>B>C>D, which was in good agreement with previous reported experimental results. These theoretical methods would provide a practice to asses the inhibition efficiency of corrosion inhibitor and to search for newly-inhibitor with desired properties.