Anti-CO₂ Corrosion Performance of Thiourea Modified Imidazoline Inhibitor on Steels with Different Microstructures

A thiourea modified imidazoline inhibitor was synthesized. The inhibition effect of different concentrations of corrosion inhibitor on carbon steels L245、Q235 and low alloyed steel X70 in 3% NaCl solution were studied by potentiodynamic polarization curves and chemical immersion tests. SEM、XRD and surface profiler were employed to analyze the experimental results. The results showed that the adsorption of the corrosion inhibitor molecules on the steel surfaces related to the microstructure,corrosion inhibitor molecules preferentially adsorbed on Fe3C. In the corrosive medium with 2 mg/L corrosion inhibitor,the inhibition efficiency on Q235 was about 90%,while on X70 and L245 were 35% and 56%. respectively. Immersion results showed that Q235 steel was slightly corroded,but there was severe localized corrosion on the surfaces of X70 and L245 steels;Increasing the concentration of corrosion inhibitor to 50 mg/L,it had good inhibition efficiency on all the three steels.