Effective yttrium based coating for steel interconnects of solid oxide cells: Corrosion evaluation in steam-hydrogen atmosphere

This work describes manufacture, analysis and test of a new well conducting corrosion-protection coating that can be applied on steel types with high chromium content. Electrolytic deposition of yttrium salts is used to form thin (<100 nm) coatings on both flat steel sheets (material: Crofer 22 APU) and its properties are proven on woven wire-meshes (materials from two different sources: SUS316 and SUS316L). The oxide scale on the coated Crofer 22 APU sheet remains intact after 2000 h operation at 750 °C in H₂ with 90% H₂O. The corrosion rate at 750 °C of the coated Crofer 22 APU sheets is compared with that of uncoated samples and of samples with a commercial magneton sputtered CGO coating revealing that the coatings reduce the parabolic rate constant characteristic of the corrosion by a factor of 10 and 20 for the CGO and the Y, respectively.

The coated meshes also exhibit high corrosion resistance and long-term-stable low electrical resistance at 650 °C, both in 90% H₂O in H₂, and in air. In addition to the experimental work, Y–Cr–O₂ phase diagrams are constructed illustrating the high stability of the YCrO₃ phase (that forms during corrosion) over a wide temperature and pO₂ range.