Adsorption and corrosion inhibition effect of Schiff base molecules on the mild steel surface in 1 M HCl medium: a combined experimental and theoretical approach

Corrosion inhibition performance of 2-(2-hydroxybenzylideneamino)phenol (L-1), 2-(5-chloro-2-hydroxybenzylideneamino)phenol (L-2) and 2-(2-hydroxy-5-nitrobenzylideneamino)phenol (L-3) on the corrosion behaviour of mild steel surface in a 1 M hydrochloric acid (HCl) solution is investigated by sophisticated analytical methods like potentiodynamic polarization, electrochemical impedance spectroscopy and weight loss measurements. Polarization studies showed that all the compounds are mixed type (cathodic and anodic) inhibitors and the inhibition efficiency (eta%) increased with increasing inhibitor concentration. The inhibition actions of these Schiff base molecules are discussed in view of blocking the electrode surface by means of adsorption of the inhibitor molecule obeying the Langmuir adsorption isotherm. Scanning electron microscopy (SEM) studies of the metal surfaces confirmed the existence of an adsorbed film. Density functional theory (DFT) and molecular dynamics (MD) simulation have been used to determine the relationship between molecular configuration and their inhibition efficiencies. The order of inhibition performance obtained from experimental results is successfully verified by DFT and MD simulation.