Abstract
The inhibition effect of 7-methyl-2-phenylimidazo[1,2-α]pyridine (PIP) on the corrosion of carbon steel in phosphoric acid solution was investigated for the first time by weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and quantum chemicals calculations. It was observed that inhibition efficiency increased with increasing inhibitor concentration. Potentiodynamic polarization studies show that PIP acts as a mixed type inhibitor. AC impedance results were interpreted using an equivalent circuit in which a constant phase element (CPE) was used in place of a double layer capacitance (Cdl) in order to give more accurate fit to the experimental results. The kinetic data such as apparent activation energies and pre-exponential factors at optimum concentration of the inhibitor were calculated and discussed. Adsorption of PIP molecules on carbon steel surface was found to obey the Langmuir adsorption isotherm. The relations between quantum chemical parameters and corrosion inhibition efficiency have been discussed to see if there is any correlation between the two of them.