Enhanced corrosion resistance of mild steel in normal sulfuric acid medium by 2,5-bis(n-thienyl)-1,3,4-thiadiazoles: Electrochemical, X-ray photoelectron spectroscopy and theoretical studies |
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Authors: | M Lebrini M Traisnel H Vezin |
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Institution: | a Laboratoire des Procédés d’Elaboration des Revêtements Fonctionnels, PERF-LSPES UMR-CNRS 8008, ENSCL, BP 90108, F-59652 Villeneuve d’Ascq Cedex, France b Unité de Catalyse et de Chimie du Solide, UMR-CNRS 8181, ENSCL, BP 90108, F-59652 Villeneuve d’Ascq Cedex, France c Laboratoire de Chimie Organique et Macromoléculaire, UMR-CNRS 8009, USTL Bât C4, F-59655 Villeneuve d’Ascq Cedex, France d Laboratoire de Chimie de Coordination et d’Analytique, Faculté des Sciences, Université Chouaib Doukkali, BP 20, M-24000 El Jadida, Morocco |
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Abstract: | The inhibitive action of some thiadiazole derivatives, namely 2,5-bis(2-thienyl)-1,3,4-thiadiazole (2-TTH) and 2,5-bis(3-thienyl)-1,3,4-thiadiazole (3-TTH) against the corrosion of mild steel in 0.5 M H2SO4 solution has been investigated using weight loss measurements, Tafel polarisation and electrochemical impedance spectroscopy (EIS) techniques. The experimental results obtained revealed that these compounds inhibited the steel corrosion in acid solution. The protection efficiency increased with increasing inhibitors concentration and the ability of the molecule to adsorb on the steel surface was dependent on the position of the sulphur atom on the thienyl substituent. Inhibition efficiency values obtained from various methods employed were in reasonable agreement. Potentiodynamic polarisation studies clearly showed that 2-TTH and 3-TTH acted as mixed inhibitors. Adsorption of these inhibitors on steel surface obeyed to Langmuir adsorption isotherm. X-ray photoelectron spectroscopy and the thermodynamic data of adsorption showed that inhibition of steel corrosion in normal sulphuric solution by n-TTH is due to the formation of a chemisorbed film on the steel surface. Molecular modelling was used to gain some insight, about structural and electronic effects in relation to the inhibiting efficiencies. |
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Keywords: | Acid corrosion inhibitors Thiadiazoles Mild steel Adsorption XPS Quantum chemical approach |
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