Innovative characterization of original green vanillin-derived Schiff bases as corrosion inhibitors by a synergic approach based on electrochemistry, microstructure, and computational analyses

Three vanillin derivatives (VTRIS, VTOS, and VCNG) were synthesized using the principles of Green Chemistry and evaluated as corrosion inhibitors for mild steel in acid media. Their anticorrosive efficiencies were obtained via gravimetric and electrochemical experiments, reaching an average maximum of 82.2%, 83.1%, and 93.1% efficiency for VTRIS, VTOS, and VCNG, respectively. Microstructure analysis alongside Atomic Force Microscopy images was used to rationalize the behavior of the polarization curves and verify the preferred adsorption sites of the organic molecules on the metallic surface. AFM and SEM confirmed the formation of a protective layer. Crossing data between gravimetric and electrochemical measurements showed the difference amid mono- and multi-layer adsorption inhibitors. Ab initio calculations were in excellent agreement with experimental results, unveiling the importance of the choice of the correct Electron Work Function for the calculation of the transferred electrons (ΔN). Such results are of fundamental importance to open the corrosion field for advanced analysis about reliable computed electrochemical parameters and crosslinked measurements able to understand the adsorption process of the inhibitors. Only the synergy among experimental and computed data made this possible.