Protective effect of imidazobenzimidazoline dihydrochlorides against the acid corrosion of steel

• A.G. Berezhnaya, I.I. Krotky and V.V. Chernyavina

South Federal University, Bol’shaya Sadovaya str. 105/42, 344006 Rostov-on-Don, Russian Federation

Abstract: (2-Methyl-9-(2-(piperidin-1-yl)ethyl)-9H-benzo[d]imidazo[1,2-a]imidazol-3-yl)(thiophen-2-yl)¬methanone hydrochloride (I), 4-(2-(2-(3-methoxyphenyl)-9H-benzo[d]imidazo[1,2-a]imidazol-9-yl)ethyl)morpholine hydrochloride (II), and 2-(4-methoxyphenyl)-9-(2-(piperidin-1-yl)¬ethyl)-9H-benzo[d]imidazo[1,2-a]imidazole hydrochloride (III) were studied as steel corrosion inhibitors in 1 M hydrochloric acid at 20–80°C. The efficiency of the compounds was assessed by the gravimetric method, by recording polarization curves, and by electrochemical impedance spectroscopy. Quantum chemical calculations were carried out in two ways using the Hartree-Fock method and the density functional theory (DFT). The best inhibitor, compound III, was found to provide 91 and 71% protection for steel at temperatures of 25 and 60°C, respectively. The inhibitors primarily slow down the corrosion process by changing the structure of the electrical double layer, blocking a fraction of the surface, and increasing the effective activation energy. The additives are anodic type inhibitors. The structures of the inhibitors were calculated and optimized using the Hartree-Fock method and the density functional theory. The best correlation between the efficiency of the additives and the majority of the calculated characteristics was obtained using the density functional theory.

Keywords: inhibitor, acid corrosion, imidazobenzimidazoline dihydrochloride, quantum chemical calculations

Int. J. Corros. Scale Inhib., 2023, 12, no. 4, 2418-2430
doi: 10.17675/2305-6894-2023-12-4-51

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