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

Abstract

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.