Corrosion Behavior of Fe- and Ni-Base Alloys in High Temperature Carbon Dioxide Environment with Impurity Additions

The effect of gas impurities on corrosion behavior of candidate Fe- and Ni-base alloys (SS 316LN, Alloy 800HT, Alloy 600) in high temperature CO₂ environment was investigated in consideration of actual S-CO₂ cycle applications. Preliminary testing in research and industrial grade S-CO₂ at 600 °C (20 MPa) for 1000 h showed that oxidation rates were significantly reduced in industrial-grade S-CO₂ environment. Meanwhile, controlled tests with individual impurity additions such as CH₄, CO, and O₂ in research-grade CO₂ were performed. The results indicated that CH₄ and CO additions did not seem to significantly affect oxidation rates. On the other hand, O₂ addition resulted in lower weight gains for all alloys, suggesting that O₂ may be primarily affecting corrosion behavior.