Theoretical–experimental study of new synthesized hydrazine–hydrazone benzenesulfonamide inhibitors for carbon steel in a 1.0 M hcl: DFT, QSAR

Abstract In this study, quantitative structure-activity relationship (QSAR) modeling using genetic function approximation was applied to predict the corrosion inhibition efficiency of three synthesized hydrazone derivatives, IHE, BHE, and AHE, on N80 carbon steel in 1.0 M HCl solution at various concentrations (50–400 ppm) and temperatures (298–358 K). The inhibitors’ performance was evaluated via electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), weight loss (WL), and surface analysis techniques. Corrosion inhibition increased with concentration, reaching maximum efficiencies of 90.34% (IHE), 85.93% (BHE), and 67.97% (AHE) at 400 ppm. Adsorption followed the Langmuir isotherm, indicating monolayer formation. High adsorption equilibrium constants (K ads ) and negative free energy changes ( $$\:{{\Delta\:}\text{G}}_{\text{a}\text{d}\text{s}}^{\text{o}}$$ : − 36.00, − 32.78, − 30.05 kJ/mol) confirmed strong, spontaneous adsorption of the inhibitors onto the steel surface. Density functional theory (DFT) and molecular simulations further revealed favorable electronic properties and stable adsorption behavior, supporting the experimental results. The combined theoretical and experimental data highlight the efficiency of the hydrazone derivatives as promising corrosion inhibitors for carbon steel in acidic environments.