Synthesis and Characterization of New Benzimidazoles Derivatives of 8-hydroxyquinoline as a Corrosion Inhibitor for Mild Steel in 1.0 M Hydrochloric Acid Medium

A new benzimidazoles derivatives of 8-hydroxyquinoline, namely 5-((4chlorophenyl)-benzimidazol-1-yl)-methyl)-quinolin-8-ol (Q-Cl) and 5-((2phenylbenzimidazol-1-yl)-methyl)-quinolin-8-ol (Q-H) have been synthesized and their chemical structure has been elucidated and confirmed using 1H and 13C NMR spectroscopy s 1H and 13C NMR spectroscopy. Their inhibitive action against the corrosion of mild steel in 1.0 M hydrochloric acid solution were investigated at different temperatures in the range from 298 to 328±2 K by a series of known techniques such as weight loss, polarization and electrochemical impedance spectroscopy (EIS). It was found that the studied compounds exhibit a very good performance as inhibitors for mild steel corrosion in 1.0 M HCl. Results show that the inhibition efficiency increases with decreasing temperature and increasing concentration of inhibitor’s. It has been determined that the adsorption for the studied inhibitors on mild steel complies with the Langmuir adsorption isotherm at all studied temperatures. Results show that the order of inhibition efficiency is Q-Cl > Q-H due to the presence of electron donating -Cl group in Q-Cl thereby enhances its ability to donate charges to the metal during the adsorption process. The kinetic and thermodynamic parameters for mild steel corrosion and inhibitor’s adsorption were determined and discussed. Scanning electron microscopy (SEM) confirmed both of the inhibitors played a significant protective effect in mild steel corrosion in 1.0 M HCl.