Corrosion Behavior of Newly Designed Fe-Ni-Base Alloys in High-Temperature CO₂ at 700 °C

Several newly designed Fe-Ni-base alloys are prepared, and the effects of the elements Cr and Si on corrosion behavior of these alloys are investigated in high-temperature CO₂ at 700 °C. The mass gain of the investigated alloys decreases with the Cr content of Fe-Ni-base alloys, while the reverse is true with respect to Si. The kinetic curves of the three investigated alloys with different Cr contents followed a parabolic law. An oxide film containing Cr₂O₃/SiO₂/Al₂O₃ about 1 μm thick is formed on these alloys, providing excellent corrosion resistance against high-temperature CO₂. Some nodular oxides with an outer layer of Fe-rich oxide and an inner layer of Cr-rich oxide are found in the local areas of the 16Cr alloy, and the SiO₂ layer is difficult to form on the 0.1Si alloy. Moreover, the activities of Cr, Si and C in the alloy are affected by increasing the content of Cr and Si, which improves the corrosion and carburization resistance against high-temperature CO₂. The nucleation of Cr₂O₃ oxide was promoted via the Si element, and the increase in Cr content can improve the activity of Si, indicating that interaction between Si and Cr is more favorable to the corrosion resistance of the alloys. The alloys contain 20%Cr and 0.3%Si have the best corrosion resistance performance.