Electrochemical and quantum chemical study of 4-[(E)-[(2,4-dihydroxy phenyl) methylidine] amino]-6-methyl-3-sulphanylidine-2,3,4,5-tetra hydro-1,2,4-triazin-5-one [DMSTT]

The inhibition of mild steel in aerated 1 M hydrochloric acid solution was studied using conventional weight loss method, potentiodynamic polarization studies (Tafel), linear polarization studies (LPR), electrochemical impedance spectroscopy (EIS) and quantum chemical calculation in the presence and absence of different concentrations of DMSTT. The inhibition efficiency increased markedly with increase in the additive concentrations, but slightly decreased with increasing temperature. The presence of DMSTT decreases the double layer capacitance and increases the charge-transfer resistance. The value of activation energy (Ea) for mild steel corrosion and thermodynamic parameters such as adsorption equilibrium constant (Kads), free energy of adsorption (ΔGads) values were calculated and discussed. The inhibitor molecule first adsorbed on mild steel surface according to Langmuir adsorption isotherm.