Interfacial electrochemistry and corrosion inhibition of 2-amino-1,3,4-thiadiazole derived Schiff base: Experimental and quantum analysis

This investigation reports on the application of 5-amino-1,3,4-thiadiazole(4-nitro-benzylidine)-2-thiol (ATNBT) as a corrosion inhibitor for mild steel (MS) in 1 M hydrochloric acid. ATNBT exhibits significant protective action in acidic environments owing to its dissolution in water. The pursuit of highly efficient inhibitors remains a key objective in corrosion science to protect the metallic structures. The inhibition performance was assessed using electrochemical impedance spectroscopy and potentiodynamic polarization techniques. Experimental results revealed that inhibition efficiency increased with inhibitor dosage, with a maximum of 96.4% at 90 μM. Potentiodynamic polarization confirmed ATNBT as a mixed-type inhibitor, and the adsorption process was consistent with the Langmuir adsorption isotherm. The activation energy () in the absence of the inhibitor was found to be 42.06 kJ mol⁻¹ , whereas it increased to 103.01 kJ mol⁻¹ in the presence of ATNBT. The changes in the surface morphology of mild steel and the chemical interactions between the inhibitor molecules and the specimen surface were examined using scanning electron microscopy (SEM). The mechanism of ATNBT’s inhibition action was explored in greater detail through quantum chemical analysis. The Fukui index values indicated that the active sites are predominantly located on the heteroatoms (sulfur and nitrogen) of the molecule.