Accelerated High-Temperature Oxidation Behavior of Ferritic Stainless Steel under Air / H2+H2O Dual Atmosphere

Abstract

Abstract Improvement in durability is one of the important subjects for utilizing solid oxide electrolyzer cell (SOEC) systems widely. In SOEC stacks, separators are exposed to complexed dual atmosphere (i.e. hydrogen - steam mixed gases and oxygen rich air are on each side). In this study, the degradation phenomena of separator materials (SUS430, ZMG232G10, Crofer22APU) in SOEC dual atmosphere were investigated. The samples were exposed in SOEC dual and simple atmospheres at 700°C for 500 h. Then, their cross sections were analyzed by X-ray diffraction and scanning electron microscopy/energy-dispersive X-ray analysis. The degradation mechanisms of the separator materials in the SOEC stack operating conditions were discussed. ZMG232G10 and Crofer22APU with high Cr content showed thin oxide layer under both the dual or single atmosphere, while SUS430 with low Cr content showed significant oxidation in the H2-steam atmosphere and on the air side under the dual atmosphere condition. The significant oxidation on the air side of the dual atmosphere of SUS430 observed in this study is a unique phenomenon under the dual atmosphere condition and not observed in a single air atmosphere.