Stability of Layer Forming for Corrosion Inhibitor on Mild Steel Surface under Hydrodynamic Conditions

Change of open circuit potential (OCP) with immersion time, Tafel polarization, and electrochemical impedance spectroscopy (EIS) were performed to investigate the corrosion inhibitor layer forming on mild steel surface. 4-Amino-5-phenyl-4H-1, 2, 4-trizole-3-thiol (APTT) was used through out the experiments as the corrosion inhibitor in this study. The investigation was conducted under hydrodynamic conditions with different pickling solutions of 0.5M HCl and 2.5M H2SO4 at 30 °C. The hydrodynamic conditions experiments were simulated using the rotating cylinder electrode (RCE). In both solutions, the values of OCP were shifted to more positive direction, the corrosion current densities were decreased, and charge transfer resistances were increased with flow velocity, respectively. The fitted data recoded from EIS were in line with those of polarization measurements. Experimental results obtained from change of OCP with immersion time, Tafel polarization, and EIS measurements showed indicated that the formation and the development of the inhibitor layer in both pickling solutions were flow velocity dependence