Droplet Corrosion of CO₂ Transport Pipeline Steels Available to Purchase

In this work, the focus was set on the corrosion process of condensate as drops on the surface of carbon steels (X52, X70), martensitic steel UNS S41500, and superaustenite UNS N08031 in CO₂ atmosphere with impurities at 278 K (to simulate the transportation condition in a buried pipeline). Exposure tests were performed at both normal pressure and high pressure where CO₂ is supercritical or in dense phase. The drop, 1 ‑ 10 μL in volume, was prepared by dropping CO₂ saturated ultra-pure water onto the surface of steel coupons in a one-liter-autoclave. The CO₂ gas stream, simulating the oxyfuel flue gas with varying concentration of impurities (SO₂ and O₂), was then pumped into the autoclave to observe the condensation and corrosion impacts of impurities. Comparable exposure tests were carried out with the same gas mixture and the same volume of water as vapor to observe the drop formation and the corrosion process that follows. The wettability and stability of drops on the surface of steel coupons in CO₂ supercritical/dense phase environment was evaluated additionally by contact angle measurement.