Anticorrosive properties of green-synthetized benzylidene derivatives for mild steel in hydrochloric acid: An experimental study combined with DFTB and molecular dynamics simulations

Abstract

Two benzylidene derivatives anisaldehyde-cyanoguanidine imine (CMBG) and p–dimethylaminobenzaldehyde-TRIS imine (DBHP) were prepared according to the 12 Principles of Green Chemistry. They were evaluated as corrosion inhibitors for 1020 mild steel in acidic media (HCl 1 mol L–1) by gravimetric and electrochemical measurements and reached 82 and 92% anticorrosive efficiency, respectively, at 2.20 mmol L-1. A comprehensive theoretical study was carried out using Density-Functional Based Tight Binding (DFTB) and molecular dynamics (MD) simulations. Electrochemical results indicated that inhibitors had a robust inhibitive effect on the corrosion process, significantly increasing the polarization resistance of the working electrode while reducing both cathodic and anodic corrosion reactions. Physical-chemical calculations indicated the formation of a protective multilayer and that physical–chemical adsorption governed the inhibition process. AFM and SEM with EDX analyses depicted a smoother surface in the presence of the organic molecules, pointing to the formation of a protective barrier. DFTB calculations revealed that inhibitor molecules formed covalent bonds with iron atoms, which was confirmed by the Projected Density of States (PDOS) of adsorbed systems.