Imidazoline-based dissymmetric bis-quaternary ammonium salt (DBA), a type of environmentally friendly surfactant, was compounded with thiourea (TU). The inhibition properties of the compound inhibitor for Q235 steel in a simulated oil field that produced water saturated with CO 2 at high temperature were studied by weight loss measurement, polarization curves, cyclic voltammetry, electrochemical impedance spectroscopy, and observation of surface morphology. Weight loss measurements show that DBA alone has poor inhibition efficiency at high temperature, and TU has a narrow inhibition concentration range. However, DBA and TU together show a synergistic effect, which not only overcomes the short comings when used individually, but also significantly reduces the corrosion rate at reduced dosage. DBA-TU acts as a mixed prohibition inhibitor, and can rapidly form a protective film. The inhibition efficiency decreased slowly with soaking time, which shows it has good substantivity. In conclusion, DBA-TU can be used as high temperature corrosion inhibitor against CO 2 corrosion.Keywords Imidazoline-based dissymmetric bis-quaternary ammonium salts Á Thiourea Á High temperature Á Synergistic effect Á CO 2 corrosion & Jing Zhang

Polyacrylamide containing capsaicin‐derived monomer P(AM‐MAA‐AMPS‐HDDE‐SA) (PAMAHS) was investigated as a novel green polymer inhibitor for Q235 mild steel at 298 K in 1 M hydrochloric acid solution. Weight loss measurements, electrochemical techniques, and surface investigation methods were conducted to evaluate the inhibition performance and mechanism. The results indicated that the green inhibitor performed well in inhibiting the corrosion of mild steel and that the inhibition efficiency increased with the increase in the PAMAHS concentration. The polarization curves revealed that PAMAHS functions as a mixed‐type inhibitor. The outstanding anticorrosion effects could contribute to the PAMAHS molecule film adsorbed on the metal surface following a Langmuir adsorption isotherm, and the hydrophobic groups played an important role in protecting the metal surfaces from corrosion media.