Kinetics corrosion process of carbon steel in hydrochloric acid in absence and presence of 2-(cyclohexylaminomercapto) benzothiazole

Abstract

The corrosion and inhibition behavior of carbon steel in 1 M HCl in the presence of 2-(cyclohexylaminomercapto) benzothiazole (CMB) was investigated using weight-loss measurements, galvanostatic polarization studies and UV-VIS spectrophotometry. The morphology of a surface was analyzed by using Mössbauer spectroscopy. Some samples were examined by scanning electron microscopy. The inhibition efficiency increased with increasing CM8 concentration and decreased with increasing temperature of the corrosion medium. The activation energy (Ea) was determined from Arrhenius equation. The activation enthalpy (ΔH°) and the activation entropy (ΔS°) were calculated from the diagram of the transition state. The experimental results suggest that the presence of CMB in the solution increases the surface coverage (θ) and therefore, indicates the adsorption of CMB. The adsorption of this compound on the metal surface is found to obey Langmuir's adsorption isotherm. The UV-VIS spectrophotometry shows a decrease of the concentration of CMB in HCl solution after corrosion, indicating that an adsorption process occurs between an organic compound from aqueous phase and the electrode surface. From the Mössbauerspectroscopy studied at this stage, it is expected that the main product of corrosion is a nonstoichiometric amorphous Fe3+ oxyhydroxide, consisting of a mixture of α, β and γ-FeOOH, where γ-FeOOH is the main phase. Copyright © 2008 John Wiley & Sons, Ltd.