Preliminary Analysis of High-Temperature Corrosion of Metallic Alloys With CO2 and CO2-Based Working Mixtures for Power Plants Applications

CO2 has been proposed in the past decades as a suitable working fluid in power plants. One way to reduce costs is to use carbon dioxide blends instead. There is a lack of knowledge about the behavior of sCO2 blending in the interaction with commercial alloys at high temperatures, so this aspect must be strictly considered. A preliminary study has been performed considering the oxidation behavior of some Ni-based and Fe-based alloy (i.e., alloy 625, AISI 304, and AISI 316) in different conditions. In each case, the oxidation layer developed on the alloy surface was investigated by scanning electron microscope (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS). The analysis was also performed on the cross-section of the sample to evaluate the penetration depth of damage. The results show that the interaction with fluorine-containing compounds is more corrosive than pure CO2. This confirms that although the mixture improves the thermodynamic efficiency of the cycle, their compatibility with materials must be carefully investigated. However, in all the cases studied, in the test conditions, the preliminary analysis doesn’t recommend the use of the tested materials.