Synergistic experimental and DFT insights into a tetradentate imine schiff base for mild steel corrosion protection in acidic media

A tetradentate organic imine-based Schiff base inhibitor, L10, was produced through the straightforward condensation reaction. The structural illustration of the synthesized inhibitor was characterized using FT-IR, UV-Vis, ¹H, and 13 C NMR spectroscopy. The corrosion inhibition property of L10 in 1 M HCl was examined under different temperature conditions using electrochemical methods, including Electrochemical Impedance Spectroscopy (EIS) and Tafel polarization analysis. The weight loss method was employed to analyze real-time inhibition monitoring, surface adsorption, and activation characteristics of L10. All results indicated that L10 exhibited a remarkable inhibition efficiency at a 400 ppm concentration, with an observed lower corrosion current density (I corr = 73.67 A cm −2 ), making it 91.75 % more effective relative to bare mild steel. Scanning electron microscopy investigations revealed that the compound adheres to the mild steel surface, creating a barrier that obstructs direct contact between the inhibitor and the unoccupied d -orbitals of iron from the mild steel surface. All measurements demonstrate that inhibition efficiencies increase with increasing inhibitor concentrations. This observation suggests that the principal inhibitory mechanism arises from the adsorption of the inhibitor onto the surface of mild steel, conforming to the Langmuir adsorption isotherm model. The effect of temperature on the corrosion behavior of Mild steel in the presence of an inhibitor was investigated across a temperature range of 30–60 °C. Corrosion inhibition was evaluated through activation energy and thermodynamic studies. Density Functional Theory (DFT) revealed frontier orbital interactions, confirming donor–acceptor relations between the metal and inhibitor. Fukui function analysis pinpointed the reactive sites governing adsorption, while Molecular Dynamics (MD) simulations verified stable binding and favorable orientation of the inhibitor on the metal surface. Collectively, these findings demonstrate the inhibitor’s strong protective efficiency against aggressive corrosive environment. • New novel tetraaza Schiff base inhibitor (L10) were successfully synthesized and structurally confirmed. • Achieved 91 % inhibition efficiency at 400 ppm in 1 M HCl. • Adsorption follows Langmuir isotherm; mixed-type inhibition confirmed. • DFT, Fukui, and MD simulations reveal strong binding on Fe(110). • Protective film formation validated by microscopy and electrochemical studies.