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 degrees 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 O-2 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, O-2 addition resulted in lower weight gains for all alloys, suggesting that 02 may be primarily affecting corrosion behavior.