Electrochemical corrosion behavior of P110 tubing steel in CO2-saturated brine containing NO2

During CO 2 sequestration, injected gas contains various carbon source impurities. This work conducted in situ electrochemical testing on P110 tubing steel at 90°C under conditions where the carbon source impurity NO 2 content was 0, 100 ppm, and 900 ppm respectively. Impedance spectroscopy and dynamic potential scanning polarisation curve testing techniques were employed to characterise the microstructural information of different post-corrosion films, product film/substrate interfaces, and product film/corrosion medium interfaces. Results indicate that under pure CO 2 conditions, the capacitive arc radius is maximal, with a dense and highly protective corrosion product film. The charge transfer resistance (R t ) is 220.674 Ω·cm 2 , and the anodic active area is suppressed, resulting in a low and uniform corrosion rate. The introduction of NO 2 significantly compromises the integrity and stability of the corrosion product film, leading to intensified localised corrosion. As NO 2 concentration increased from 0 ppm to 900 ppm, the electrode surface potential distribution became more dispersed, the anodic current peak intensified, and the number of active sites increased. Consequently, I corr rose, E corr shifted negatively, the capacitive arc radius decreased, and R t dropped sharply. These changes significantly exacerbated both generalised and localised corrosion tendencies in the material.