Investigation of Corrosion Inhibition of Two Thiazole Derivatives for AISI Steel Alloy in HCl Solution

In most industrial processes, acidic solution are commonly used for the pickling, industrial acid cleaning, acid descaling, oil well acidifying, etc. Corrosion prevention systems favor the use of corrosion inhibitors with low or zero environmental impacts. In this work, the inhibition ability of 2-Mercaptobenzothiazole (MBT) and 2-amino-5-nitrothiazole (Nitramine) (two thiazole derivatives) against the corrosion of AISI steel 4130 in 1 M HCl solution were evaluated by polarization and electrochemical impedance spectroscopy (EIS). Polarization studies indicated that MBT retards both the cathodic and anodic reaction and Nitramine retards anodic reaction through chemical adsorption and blocking the active corrosion sites. EIS data was analyzed to equivalent circuit model shows that as the inhibitor concentration increased the charge transfer resistance of steel increased whilst double layer capacitance decreased. Thermodynamic parameters such as activation energy, enthalpy, entropy and free energy of adsorption were calculated and Atomic force microscopy (AFM) was used to study the steel surface with and without inhibitors.