Potentiodynamic polarization, electrochemical impedance spectroscopy, and weight loss methods were used to study the inhibition of the corrosion of X70 and Q235 steels in CO2-saturated 3 wt% NaCI solution with various concentrations of imidazoline-based inhibitor. The inhibition efficiencies for X70 and Q235 reached 97.8% and 98.6%, respectively, with sufficient concentration of inhibitor. The results indicated that, the inhibition efficiencies for X70 and Q235 were dramatically different with low concentration of inhibitor. Compared with X70, Q235 exhibited higher inhibition efficiency and stronger adsorption ability because of the larger amount and more homogeneous distribution of carbides. The adsorption of the inhibitor on the metal surface consisted of a mix of physisorption and chemisorption and was observed to follow the Langmuir adsorption isotherm. (c) 2017 Elsevier B.V. All rights reserved.