Corrosion inhibition behavior of the synthesized pyrazoline-sulfonamide hybrid of mild steel in aqueous solutions: experimental and quantum investigations

This study deals with the preparation and corrosion inhibition investigations of pyrazoline-sulfonamide hybrid, namely 4-((3-methyl-5-oxo-4,5-dihydro-1H-pyrazol-4-yl)diazenyl) benzene sulfonamide 4 . Elemental analysis, Fourier transform infrared spectroscopy, 1 H nuclear magnetic resonance ( 1 H NMR), and 13 CNMR spectra investigated the pyrazoline-sulfonamide structure. The mild steel corrosion inhibition was investigated in 1 M HCl and 3.5% NaCl solutions using various techniques, including electrochemical, gravimetric, and microscopic techniques. The inhibition efficiency was 95.4 and 87.7% at 500 ppm inhibitor in 1 M HCl and 3.5% NaCl, respectively. The positive values of ∆ H ads (44.184 and 31.403 kJ/mol, in 1 M HCl and 3.5% NaCl, respectively) indicate that inhibitor adsorption is an endothermic process. Moreover, the high values of K ads (0.281 and 0.148 M -1 ) indicate more significant adsorption and thus stronger inhibitory efficiency. Langmuir adsorption isotherm was used to evaluate mild steel corrosion inhibition by pyrazoline-sulfonamide. Experimental data agree with data obtained from B3LYP density functional theory calculations. Therefore, based on the experimental and theoretical data, pyrazoline-sulfonamide is recommended as a corrosion inhibitor of mild steel in aqueous media. Graphical abstract Pyrazoline-sulfonamide (PS) has been prepared and used as novel corrosion inhibitors of mild steel. Langmuir adsorption isotherm was used to evaluate MS corrosion inhibition by PS. Experimental data are in good agreement with B3LYP DFT calculations. Therefore, PS is recommended as a corrosion inhibitor of mild steel in aqueous media.