Oxidation of Ferritic Steels Subjected to Simulated SOFC Interconnect Environments

Abstract

Ferritic stainless steel (FSS) 441 with CoMnO coatings were subjected to solid oxide fuel cell interconnect exposures (800{degree sign}C air and dual atmospheres (air/H2)). Oxidation behavior was observed using complimentary analytical techniques. Significant differences in oxidation behavior were observed in samples exposed to dual atmosphere conditions compared with air-only exposures, indicating rapid transport of hydrogen through FSS 441 and its influence on air side corrosion. Observations and interpretations are presented and discussed in context of developing inexpensive and durable SOFC interconnects.

An Alternative Method of Measuring Area Specific Resistance of Chromia Scales Using Electrochemical Impedance Spectroscopy

“…A difficulty here is that the oxide scale of Crofer 22 APU is usually composed of chromium oxide and an outermost layer of Cr, Mn-spinel. 25,54,55 As presented in Table I, the ratio between the Cr 2 O 3 scale thickness and the (Cr, Mn) 3 O 4 changes with time. A trend for the variation of this ratio is reported in Table I using the values obtained from Fig.…”

Corrosion of Chromia-Forming and Alumina-Forming Ferritic Stainless Steels under Dual Atmosphere Exposure Conditions

“…This concept has been discussed in SOFC and electrochemistry literature with an emphasis on surface oxide chemistry and morphology. 13,15,20,[24][25][26][27][28][29] However, literature remains largely unpopulated on experimental evidence as to the exact role of hydrogen on influencing rapid iron oxidation and nodular growth. Despite this, there are a number of hypotheses that have been made which suggest how hydrogen leads to this corrosion phenomenon.…”

“…This effective positive defect would increase the metal vacancy concentration, which could enable more pathways for outward metal ion diffusion. 20,29,30 A hypothesis from Essuman et al 31,32 discussed by Alnegren et al 15 claimed that hydrogen from dissociated water vapor may diffuse into the metal as an interstitial, which could expand the metal lattice to induce a higher oxygen flux. 32 Water vapor also led to greater internal oxidation of chromium.…”