A study of differential polarization curves and thermodynamic properties for mild steel in acidic solution with nitrophenyltriazole derivative

The nitrophenyltriazole derivative, namely 2-[1,2,4]-triazole-methyl-4-acetyl-5-nitrophenyl-[1,3,4]-oxadiazole (TMANO) was synthesized and its inhibiting action on the corrosion of mild steel in 0.5 M H2SO4 solution was investigated by weight loss test, electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and scanning electron microscopy (SEM). The selective desorption of TMANO from mild steel surface was also studied by the differential polarization curves. Both thermodynamic and kinetic parameters were calculated and discussed. The results showed that the adsorption of TMANO on steel surface obeys the Langmuir adsorption isotherm. The calculated values of ΔHads0 and ΔSads0 indicated that the adsorption process of TMANO on steel surface was exothermic and accompanied by a decrease in entropy.

► TMANO is a new effective corrosion inhibitor for mild steel in 0.5 M H2SO4 solution. ► Differential polarization curves were applied to determine the desorption peak potential. ► TMANO shows high inhibition efficiency in the temperatures range studied.