Quantum Chemical and Molecular Dynamic Simulations in Understanding the Inhibition Mechanism of Green Compounds on Brass Corrosion

While empirical studies confirm the efficacy of green corrosion inhibitors, the atomic-level interactions governing their adsorption onto brass surfaces remain inadequately characterized. This gap impedes the rational design of high-performance inhibitors. This study employs a combined computational and experimental approach to elucidate the inhibition mechanism of three green compounds—Rosmarinic acid (from Rosmarinus officinalis), Quercetagetin (from Tagetes erecta), and Punicalagin (from Punica granatum)—on Cu-Zn brass in acidic chloride environments. Density Functional Theory (DFT) calculations quantified global reactivity descriptors (ΔE= -2.81 eV for Punicalagin), while Molecular Dynamics (MD) simulations revealed adsorption energies in the order: Punicalagin (-423 kJ/mol) > Rosmarinic acid (-378 kJ/mol) > Quercetagetin (-345 kJ/mol). These computational predictions showed a strong correlation (R² = 0.96) with experimental inhibition efficiencies determined by electrochemical impedance spectroscopy. The findings provide a robust atomic-scale framework, moving beyond trial-and-error discovery to predictive inhibitor design, as advocated by leading corrosion engineering principles.