Electrochemical and Theoretical Evaluation of Some Quinoline Derivatives as Corrosion Inhibitors of Mild Steel in Acidic Medium

The corrosion inhibition performances of some quinoline derivatives corrosion inhibitors on mild steel in acidic medium, namely, 5-((4-chlorophenyl)-benzimidazol-1-yl)- methyl)-quinolin-8-ol (Q-Cl) and 5-((2-phenylbenzimidazol-1-yl)-methyl)-quinolin-8-ol (Q-H) on the corrosion of mild steel were investigated in this work by using electrochemical and quantum chemical calculations. The experimental results confirmed by Electrochemical impedance spectroscopy and potentiodynamic polarization measurements show that (Q-Cl) may exhibit the best inhibitive performance among (Q-H) for mild steel in hydrochloric acid solution. Furthermore, quantum chemical calculations of density function theory (DFT) and Actives sites (Fukui function) for quinoline derivatives were applied to theoretically determine the relationship between molecular structure and inhibition efficiency. 5-((4-chlorophenyl)- benzimidazol-1-yl)-methyl)-quinolin-8-ol (Q-Cl) shows the highest reaction activity among the 5-((2-phenylbenzimidazol-1-yl)-methyl)-quinolin-8-ol (Q-H) molecule. The binding energies of the corrosion inhibitor molecules and iron surface follow the order of Q-Cl > Q-H, which agrees well with the experimental findings.