Experimental and Theoretical Investigation of Clemastine Drug for Corrosion Protection of Carbon Steel in Sulfuric Acid Solution

Polarization and electrochemical impedance spectroscopy (EIS) were employed for investigating the behavior of clemastine drug on the corrosion protection of carbon steel in 0.5 M H2SO4 solution which was enhanced by increasing the clemastine concentration in acid solution. As evidenced by polarization data, clemastine behaved as a mixed-type inhibitor and retards both anodic and cathodic processes. Adsorption of clemastine on carbon steel in acid solution obeyed the Langmuir adsorption isotherm. A reasonable correlation was observed between the ∆Goads values obtained from EIS and potentiodynamic polarization measurements. The calculated ∆Goads values of clemastine confirmed comprehensive adsorption that is a combination of physical and chemical adsorption. The electronic properties of clemastine were calculated via density functional theory (DFT) approach to establish the relationship between the inhibitive effect and molecular structure of the clemastine. According to the obtained quantum chemical parameters, clemastine showed higher EHOMO, lower EHOMO, lower energy gap, and higher dipole moment than some inhibitors earlier reported as good corrosion inhibitors.