Inhibiting properties and adsorption of some thioamides on mild steel in sulphuric acid solutions |
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| Authors: | E. Lazarova G. Petkova T. Iankova L. Ivan G. Neikov |
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| Affiliation: | (1) Department of Physical Chemistry, University of Chemical Technology and Metallurgy, 8 Kliment Ohridski str., 1756 Sofia, Bulgaria;(2) Institute of Electrochemistry and Energy Systems, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria;(3) Department of Chemistry, University of Rousse, Rousse, Bulgaria;(4) Department of Chem. Organic, University of Bucarest, Bucarest, Romania;(5) Department of Natural Science, University of Schumen, Schumen, Bulgaria |
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| Abstract: | The inhibiting properties and adsorption behaviour of thioacetamide (TAA), thiobenzamide (TBA) and thiocinnamamide (TCA) on mild steel in sulphuric acid solution were studied by gravimetric, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements. TBA and TCA were found to be mixed type inhibitors providing good corrosion inhibition. Different mechanisms of adsorption and corrosion inhibition were observed for the tested thioamides. In the cases of TBA and TCA, the adsorption of the compounds is chemical and the values of the activation energy (Ea) and the pre-exponential factor (A) are lower than the corresponding values observed in inhibitor free solution. The adsorption of TAA is physical and the values of Ea and А are higher than the corresponding values in sulphuric acid solution. The adsorption process of TBA and TCA on the mild steel/sulphuric acid solution interface is described by Langmuir’s isotherm. A correlation between the adsorption capability and the inhibiting efficiency of the molecules and their donor–acceptor properties (E HOMO and E LUMO) has been established. It is ascertained that the protection effect of TAA depends on the amount of hydrolysis products. |
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| Keywords: | Corrosion inhibition Adsorption Thioamides Mild steel Sulphuric acid |
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