Surface Studies of T409 Stainless Steel at 700 °C in Wet or Dry Air or N2 With and Without Contacting Ceramic Fibers.

Ferritic stainless steel (FSS) is widely used in high-temperature (> 500 °C) applications, often in contact with various ceramic components, e.g. solid oxide fuel cell systems, combustion exhaust systems, and in various chemical process and balance-of-plant equipment. To expand current understanding of the corrosion behaviors of stainless steels in these applications, FSS T409 was investigated after 700 °C exposures (94 h) to dry or wet air or N2, and with or without contacting aluminosilicate fibers. Surface compositions and structures were characterized using FESEM, EDS, and XRD. The fibers were observed to have a substantial impact on corrosion behaviors, likely serving as a mass transport barrier for corrosive gas species. Observed corrosion behaviors under these different environments and their potential mechanisms are presented and discussed. Additionally, quantification of total chromium content on contacting fibers was performed using ICP-MS. Contacting fibers were only observed to collect chromium in dry/moist air consistent with the formation of volatile chromium species CrO3 and CrO2(OH)2, respectively. [ABSTRACT FROM AUTHOR]