The influence of temperature, H2O, and NO2 on corrosion in CO2 transportation pipelines

The expansion of Carbon Capture, Utilization, and Storage (CCUS) highlights the growing need for carbon dioxide (CO₂) pipeline transportation. While pure CO₂ is non-corrosive, impurities such as H₂O and NO₂ create a corrosive environment that risks pipeline integrity. This study investigates how H₂O and NO₂ concentrations, along with temperature, influence corrosion under CO₂ pipeline conditions. The investigation was performed in an autoclave setup emulating a linear velocity of 0.96 m/s at 100 bar and temperatures of 5 ^∘C and 25 ^∘C, testing X52 and GR70, and a more corrosion-resistant 9Cr alloy. The results indicated that the presence of NO₂ elevated the corrosion rate compared to scenarios without. Low H₂O concentration led to a corrosion rate of up to five times higher at 5 ^∘C, compared to at 25 ^∘C, in the presence of NO₂. Low to moderate corrosion was observed for the carbon steels without NO₂ and with 70 ppmv H₂O at both temperatures. Reducing the H₂O concentration below 70 ppmv and removing NO₂, while SO₂ and O₂ are present, will only result in low to moderate corrosion in the carbon steel CO₂ pipeline. The corrosion rate for X52 and GR70 was 0.065 mm/y and 0.016 mm/y higher or 5 and 3 times greater, respectively, at 5 ^∘C compared to 25 ^∘C. The study concludes that H₂O should be maintained below 70 ppmv and NO₂ should be eliminated to prevent severe corrosion. Emphasizing the importance of CO₂ specification compliance and the need for further research into CO₂ compositions that align with the specifications.