Experimental and theoretical examinations of triazole linked saccharin derivatives as organic corrosion inhibitors for mild steel in hydrochloric acid

Abstract

The new triazole linked saccharin derivatives namely, 2-(3-methyl-1H-1,2,4-triazol-5-yl)benzo[d]isothiazol-3(2H)-one 1,1-dioxide (MTD) and 2-(3-isopropyl-1H-1,2,4-triazol-5-yl)benzo[d]isothiazol-3(2H)-one 1,1-dioxide (ITD) were synthesized under microwave irradiation method. The newly synthesized inhibitors were characterized by 1H NMR, 13C NMR, FT-IR and mass spectroscopic techniques. The ability for these two compounds to act as corrosion inhibitors for mild steel (MS) in 0.5 M HCl was confirmed by electrochemical impedance spectroscopy (EIS), weight loss and potentiodynamic polarization studies. Within the scope of concentrations and temperatures studied, the tested MTD and ITD demonstrated significant anticorrosion performances, with highs of 94 and 96% at 0.8 mM, respectively. Polarization studies revealed that the MTD and ITD behave as mixed-type inhibitors. The examined inhibitors strong adsorption mirrored the Langmuir model with excellent correlation values. The values obtained of the standard adsorption free energy indicated the typical physisorption and chemisorption behaviour of MTD and ITD on MS. Further, SEM, XPS and XRD were used to analyze the surface morphology of the MS surface. DFT calculations was employed as a supplementary tool to demonstrate the reported inhibition efficiencies.