Corrosion behaviour of VTS, STS and DTS inhibitors in formic and acetic acids

Abstract

Three organic inhibitors namely,1-Vanillin thiosemicarbazone (VTS), 1-Salicy laldehyde thiosemicarbazone (STS).1-Dimethyl aminobenzaldehyde thiosemicarbazone (DTS) were synthesized to investigate their inhibiting actions on corrosion of mild steel (MS) in aqueous solutions containing 20% formic acid and 20% acetic acid by weight loss and potentiodynamic

polarization methods. All of these compounds have shown good inhibition efficiency (IE) in formic acid solutions. IE of these compounds has been found to vary with the concentration of the compounds, temperature and immersion time. The adsorption of these compounds on the steel surface from the acids has been found to obey Temkin's adsorption isotherm. The values of activation energy (<i>E</i>_a) and free energy of adsorption (Δ<i>G</i>_ads) indicated physical adsorption of these compounds on the steel surface. The potentiodynamic polarization experiments revealed that all the compounds are mixed type inhibitors.