Inhibition effect of some benzylidenes on mild steel in 1 M HCl: An experimental and theoretical correlation

The inhibition performance of four benzylidine malononitriles (BMNs) on mild steel (MS) in 1 M HCl was studied by weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The associated activation energy (Ea) and free energy of adsorption (ΔGads°) have been determined. The adsorption of inhibitors on MS surface obeyed the Langmuir’s adsorption isotherm. Potentiodynamic polarization measurements showed that all inhibitors are mixed type. The energy dispersive X-ray (EDX) and scanning electron microscope (SEM) observations confirmed the existence of a protective film of inhibitor on MS surface. The results of the quantum chemical calculations were correlated with experimental inhibition efficiencies.

► Inhibition of mild steel corrosion in 1 M HCl by some benzylidine malononitriles.
► EIS plots showed that the inhibitive performance depended on the adsorption of the molecule on the metal surface.
► Polarization measurements indicate that all the studied compounds are of mixed-type inhibitors.
► The SEM and EDX analyses were support the weight loss, EIS and polarization data.
► The results of quantum chemical calculations and experimental efficiencies were subjected to correlation analysis.