Influence of Pressure and Chromium Content on Corrosion Reactions at 600°C in a CO 2-H2O Atmosphere

Abstract Power plant components in Integrated Gasification Combined Cycles (IGCC) and gas turbines work under conditions of high pressure, high temperature and flowing gas with high levels of CO2. The corrosion process occurring under such service conditions of modern power plants is different from that under current conditions with air combustion. The effect of pressure and chromium content on the corrosion reaction of steels at a constant temperature of 600°C (873K) is discussed in the present paper. The flowing gas is simulated as a mixture of 30% H2O und 70% CO2. The influence of chromium contents of 1, 2, 9 and 11% were experimentally observed. Higher pressures cause thicker oxide scales and different phase compositions. The stable oxide for a low alloyed chromium steel is wustite. Under pressure a thick two-phase region close to the base material was observed, including iron oxides and iron carbides. For 9-12% chromium steels, oxides with the sequence Fe3O4, Fe-Cr-spinel and Cr2O3 in FeO from the gas/oxide interface to the oxide/alloy interface was characteristic. Carbides are only found in the case of Co- and W-free alloys. The influence of chromium content and corrosion time on phase compositions and scale thicknesses is presented.