Abstract
The inhibition ability of 2-Mercaptobenzothiazole (MBT) against the corrosion of AISI steel 4130 in 1 M HCl solution was evaluated by polarization, electrochemical impedance spectroscopy (EIS) and chronoamperometry. Polarization studies indicated that MBT retarded both the cathodic and anodic reactions through chemical adsorption and blocking the active corrosion sites. The adsorption of this compound obeyed the Langmuir adsorption isotherm. The inhibition efficiency was increased with inhibitor concentration as well as temperature. EIS data was analyzed for an equivalent circuit model and showed that as the inhibitor concentration increased the charge transfer resistance of steel increased whilst double layer capacitance decreased. Kinetic and thermodynamic parameters such as activation energy, enthalpy, entropy and free energy of activation and adsorption were calculated. Atomic force microscopy (AFM) and optical microscope were used to study the steel surface with and without inhibitor.

Key words
steel 4130, corrosion, inhibitor, adsorption isotherm, Langmuir

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