A Tracer Study on sCO₂ Corrosion with Multiple Oxygen-Bearing Impurities

Several modern power production systems utilize supercritical CO₂ (sCO₂), which can contain O₂ and H₂O as impurities. These impurities may degrade the compatibility of structural alloys through accelerated oxidation. However, it remains unclear which of these impurities plays a bigger role in high-temperature reactions taking place in sCO₂. In this study, various model and commercial Fe‐ and Ni‐based alloys were exposed in 300 bar sCO₂ at 750 °C to low levels (50 ppm) of O₂ and H₂O for 1,000 h. ¹⁸O-enriched water was used to enable the identification of the oxygen source in the post-exposure characterization of the samples. However, oxygen from the water did not accumulate in the scale, which consisted of Cr₂O₃ in the cases where a protective oxide formed. A 2wt.% Ti addition to a Ni-22%Cr model alloy resulted in the formation of thicker oxides in sCO₂, while a 1wt.% Al addition reduced the scale thickness. A synergistic effect of both Al and Ti additions resulted in an even thicker oxide than what was formed solely by Ti, similar to observations for Ni-based alloy 282.