Droplet Corrosion of CO₂ Transport Pipeline Steels in Simulated Oxyfuel Flue Gas

The research focus of this study was set on the corrosion process of condensate as droplets on the surface of carbon steels (X52, X70), martensitic steel UNS S41500, and super austenite UNS N08031 in CO₂ atmosphere with impurities at 278 K (to simulate the offshore transportation condition in a buried pipeline). The possibility of dew/droplet formation on the steel surface and wetting behavior of corresponding materials were evaluated by contact angle measurement in dense CO₂ at 278 K. To observe the effect of impurities (SO₂ and O₂) on droplet corrosion process, exposure tests were performed in the mixed atmosphere with a drop, 1 μL to 10 μL in volume, of CO₂-saturated ultrapure water on steel surface. Comparable exposure tests were performed with the same gas mixture and the same volume of water, as vapor, to observe the droplet formation and the corrosion process that follows. Effects of surface roughness on the droplet formation and its corrosion process were further studied and showed no significant role upon long time exposure. The results from droplet experiments were compared to those from the bulk electrolyte for the further recommendation on the quality control of gas stream along with the use of carbon steels as transport pipelines in carbon capture and storage system (CCS).