Computational Investigation of Anticorrosion Properties in Ethyl 4-[(E)-(2-Hydroxy-4-Methoxyphenyl) Methyleneamino] Benzoate and Its Pyrrole Substituted Variant on mild steel

Corrosion of mild steel in acidic environments, particularly hydrochloric acid, presents major challenges in industrial applications, resulting in significant economic losses. This study investigates the corrosion inhibition potential of ethyl 4-[(E)-(2-hydroxy-4-methoxyphenyl)methyleneamino]benzoate (EMAB), a Schiff base, and its pyrrole derivative in HCl solutions. Using Density Functional Theory (DFT), Monte Carlo (MC), and Molecular Dynamics (MD) simulations, we assess their adsorption behavior, inhibition efficiency, and mechanistic pathways. Quantum chemical calculations at the B3LYP/6-311 + + G** and CAM-B3LYP-D3/Def2TZVP levels reveal that both inhibitors adopt planar geometries favorable for adsorption on metal surfaces. Proton affinity analysis indicates their ability to bind protons in acidic media, potentially mitigating corrosion. MD simulations employing the COMPASS forcefield show stronger adsorption of EMAB onto the Fe(110) surface, characterized by a shorter adsorption distance (~ 1.1 Å) compared to the pyrrole derivative (~ 1.4 Å). Radial distribution function (g(r)) analysis further supports this, with EMAB exhibiting a higher interaction peak (g(r) = 489.56). MC simulations confirm EMAB’s stronger adsorption through a highly negative adsorption energy (-312.78 kcal/mol), suggestive of a chemisorption mechanism. Global reactivity descriptors and Fukui function analyses identify key nucleophilic centers in both molecules that contribute to their inhibition efficiency. Overall, EMAB demonstrates superior anticorrosion performance and eco-friendly characteristics, making it a promising candidate for sustainable corrosion protection of mild steel in industrial settings.