Inhibition Performance of an Imidazoline Derivative as a Gas-Liquid Two-Phase Inhibitor for Q235 Steel against CO2 Corrosion

We investigated the inhibition performance of a new imidazoline derivative inhibitor. TAI, which can be used as a gas-liquid two-phase inhibitor against CO2 corrosion by weight-loss method, electrochemical impedance spectroscopy (EIS), Fourier transform-infrared (FT-IR) spectroscopy, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). Results revealed that the thioureido imidazoline inhibitor was an effective inhibitor against CO2 corrosion in gas and liquid two phases. Surface analysis by AFM showed that damage to the metallic surface was considerably reduced in the presence of the TAI inhibitor. A bigger adhesive for between the AFM probe and the steel surface was detected owing to hydrophobic interaction from the inhibitors in the two phases. The long range repulsive force between the AFM probe and the steel surface increased in gas phase but decreased in liquid phase by the screening effect of surface charges. XPS and FT-IR spectra proved that the adsorption films on the metal surfaces with protective properties of TAI and acid hydrolysis products (amides) of the TAI were present in liquid phase and in gas phase, respectively. The above results further confirmed the hydrolysis mechanism of imidazoline derivatives in acid solution.