The proposed work will continue to address the materials issues associated with scaling-up supercritical carbon dioxide (sCO2) Brayton cycle systems to higher temperatures for increased efficiency and larger size for commercial power production. The effort is intended to understand the applicable corrosion mechanisms in sCO2 as a function of impurity (e.g., O2, H2O) levels in both closed and open systems. Once this experimental capability is established, the experimental plan will also continue to study environmental effects on alloy mechanical properties with complimentary efforts in characterization and lifetime modeling.