The influence of imidazoline-based inhibitor on the formation, microstructure, and thickness of the corrosion product film that formed on X52 steel after exposure in an environment of high pressure CO2 containing formation water at high temperature was studied by using weight loss measurement, linear polarization resistance, scanning electron microscopy, energy dispersive x-ray, x-ray diffraction, and x-ray photoelectron spectroscopy. The results showed that the inhibitor significantly influenced the surface morphology and thickness of the corrosion product film. The severity of localized corrosion (pitting) increased with decreased inhibitor concentration. Inhibitor efficiency was observed to be strongly affected by the concentration of inhibitor and CO2 pressure. The corrosion product film was mainly composed of FeCO3. © 2012 ASM International.