Experimental, Density Functional Theory, and Dynamic Molecular Studies of Imidazopyridine Derivatives as Corrosion Inhibitors for Mild Steel in Hydrochloric Acid

Two imidazopyridine derivatives 6-chloro-2-(4-chlorophenyl) imidazo [1,2-a]pyridine (IPCl1) and 6-chloro-2-(4-chlorophenyl)imidazo[1,2-a]pyridine-3-carbal-dehyde (IPCl2) were investigated as corrosion inhibitors of mild steel in 1.0M HCl medium using potentiodynamic polarization curves and electrochemical impedance spectroscopy. The concentrations used in this work ranged between 1.0 x 10(-6) and 1.0 x 10(-3) M. Those compounds were found to be good inhibitors. In addition, their adsorption on the mild steel surface obeyed the Langmuir adsorption isotherm. A quantum chemical calculation was computed using Gaussian 09 based on the density-functional theory method at B3LYP/6-31G (d, p) in order to relate some electronic properties of the studied compounds to the inhibition efficiencies achieved experimentally. The Fukui functions were calculated to estimate the most reactive sites of nucleophilic and electrophilic attacks. Finally, the molecular dynamics simulation was implemented to search for the equilibrium configurations of IPCl1 and IPCl2/Fe(110) adsorption systems in a hydrochloric acid solution at various temperatures. The theoretical and experimental results obtained were in good correlation.