New imidazole-Schiff base compounds for environmentally friendly anticorrosion protection in industrial pickling of mild steel

Abstract

As part of the development of a new organic entity, we synthesized a new series of Schiff bases belonging to the imidazo[1,2-a]pyridine (IMP) family, named: (E)-2-methoxy-4-(((2-phenylimidazo[1,2-a]pyridin-3-yl)imino)methyl)phenol(IM1) and (E)-4-(((2-phenylimidazo[1,2-a]pyridine-3-yl)imino)methyl)phenol (IM2). Molecular structures were confirmed through chemical analyses, including nuclear magnetic resonance (NMR) and mass spectroscopy. In order to develop new organic ligands to inhibit mild steel corrosion in 1M HCl solution, various weight loss and electrochemical methods, such as electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP), along with surface visualization through scanning electron microscopy (SEM) and atomic force microscopy (AFM), were employed. EIS results revealed excellent inhibition by compounds IM1 and IM2 (98% and 92%, respectively) at a concentration of 1 mM. These findings were supported by the observation of a protective layer formation during prolonged immersion of mild steel in a corrosive solution, with or without inhibitors. Finally, theoretical studies such as density functional theory (DFT) and molecular dynamics simulations were conducted to explore the adsorption behaviour of inhibitors IM1 and IM2 on the iron surface, providing insight into the inhibitor-metal interaction during the adsorption process.