Corrosion Resistance of Super Duplex Stainless Steel for CCS Usage under Supercritical CO₂ Conditions with Impurity Gas

In carbon capture and storage (CCS), the CO₂ emitted from various industries containing impurities is captured and injected to underground in dense or supercritical phase through a tubing. In order to evaluate corrosion resistance of the tubing materials in supercritical CO₂ environment with impurity, corrosion tests were performed in the conditions of CO₂, containing 5 wt% NaCl with O₂ or SO₂ at total pressure of 130 bar and temperature of 100 °C. The corrosion rates of UNS S41426 (13Cr super martensitic stainless steel) were higher than 1 mm/y in the solution saturated CO₂ with 2% O₂, as well as with 0.02% SO₂. On the other hand, UNS82551 (25Cr duplex stainless steel) and UNS S39274 (25Cr super duplex stainless steel) showed the corrosion rates of 0.1 mm/year or less and no pitting corrosion when the impurity gas concentration was 0.02% SO₂. UNS S39274 showed the same results even in the condition with 4% O₂ or 0.50% SO₂.The authors conducted the analysis by X-ray photoelectron spectroscopy and confirmed that Cr concentrated in the passivation film of S39274 after the corrosion test. Therefore, it is considered that UNS S39274 would be a suitable material even in the supercritical CO₂ environment contaminated with impurities (O₂ or SO₂).