Inhibition Behavior of Two Imidazoline-Based Inhibitors in Single Liquid Phase Flow

Abstract

With the increase of domestic oil demand and oil production intensification, CO2 corrosion problems were more and more prominent in oil production. Among many corrosion control methods, the injection of organic inhibitors is one of the most cost-effective methods, such as imidazoline and its derivatives. Two imidazoline inhibitors with different groups, i.e., 2-undecyl-1-ethylamino imidazoline (UEI) and 2-phenyl-1-ethylamino imidazoline (PEI), were used for resisting CO2 corrosion of Q235 steel in single liquid phase. The inhibitory behavior of UEI and PEI on CO2 corrosion of Q235 steel under static and flow conditions was investigated using electrochemical impedance spectroscopy (EIS). The results showed that flow velocity had strong effect on the inhibitor performance. When the rotate speed is under 200 rpm, the Rct increased along with increasing the rotate speed at each concentration of UEI and PEI, and Rct decreased and kept almost constant when its rotate speed was over 200 rpm. The adsorption of UEI and PEI on Q235 steel surface obeyed Langmuir isotherm not only under static condition but also under flow condition. The Gibbs adsorption energy was higher than −30 kJ/mol and illustrates there is chemical absorption at the Q235 steel surface. Quantum chemical calculation on the two imidazolines inhibition abilities was also carried out.