Design and development of thiadiazole derived Schiff base as efficient corrosion inhibitor for steel materials: Experimental and quantum analysis

This study investigates the corrosion inhibition performance of a novel organic compound, 2-amino-1,3,4-(4-hydroxybenzylidene)thiadiazole (AHBT), which is non-toxic and possesses antimicrobial properties, for protecting mild steel in 1 M hydrochloric acid (HCl) medium using both experimental techniques and computational methods. Inhibition effects of AHBT on mild steel corrosion in 1 M HCl were analyzed using gravimetric analysis and electrochemical techniques, including potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The corrosion inhibition efficiency increases with inhibitor concentration, reaching a maximum value of 95.60% at 80 μM in gravimetric analysis. Polarization tests confirmed that AHBT acts as a mixed-type inhibition nature. Studies conducted at temperatures from 303 to 333 K revealed that AHBT adsorption on the MS surface takes place as an exothermic reaction consistent with the Langmuir adsorption isotherm. The activation energy was 35.46 kJ mol⁻¹ for the uninhibited medium and increased markedly to 86.65 kJ mol⁻¹ with the addition of AHBT. Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX) and Atomic Force Microscopy (AFM) micrographs revealed the formation of a protective adsorption layer of AHBT on the mild steel surface. The DFT results reveal that the neutral and protonated species of AHBT exhibit significant interaction with the metallic surface via lone pair electrons present on heteroatoms (S, N, and O) and the π-electrons of the conjugated framework. The calculated Fukui indices indicate that sulfur and nitrogen atoms serve as the major reactive sites within the molecule.