Evaluation of Corrosion Inhibition of a Bis-imidazoline Corrosion Inhibitor

Bis-imidazoline (BIM) was synthesized with butanedioic acid and diethylenetriamine as raw materials. And bis-imidazoline quaternary ammonium salt (BIMI), a novel corrosion inhibitor, was obtained through the reaction of BIM with benzyl chloride. The corrosion inhibition of BIMI inhibitor to N80 steel in 15% (mass) HCl solution was investigated via static weight loss method and electrochemical method, respectively. And the adsorption behavior of BIMI on N80 steel surface was also studied. Synthesized single-imidazoline quaternary ammonium salt (SIMI) was also studied as a corrosion inhibitor in comparison of BIMI. Gaussian 03W program and density functional theory (DFT) B3LYP/6-311G* method were used to optimize the structure of two kinds of imidazoline, and the stable configuration and related quantum-chemical parameters were obtained respectively. And molecular dynamics (MD) simulation of the adsorption of two molecules on Fe (001) plane was also carried out. The results show that the inhibition efficiency of BIMI inhibitor was significantly better than that of SIMI. The inhibition efficiency of BIMI reached 93.30% when the concentration of inhibitor was 3.0 mmol/L, while that of SIMI was only 76.93% under the same condition. The adsorption of two inhibitors on the metal surface obeyed the Langmuir adsorption isotherm and was a mixed adsorption based on chemical adsorption. The differences between these two corrosion inhibitors were well explained from molecular level by quantum-chemistry calculation and MD simulation, which had corresponding results with testing.