An electrochemical method to assess the chromium volatility of chromia-forming metallic interconnect for SOFCs

The polarization behavior of (La0.8 Sr0.2) 0.9 Mn O3 (LSM) electrodes in contact with different chromia-forming alloys including a Ni-Cr-based superalloy (R600), and ferritic stainless steels (RA446 and Crofer22 APU) was studied under solid oxide fuel cell (SOFC) operating conditions. The magnitude of the polarization potential increase, ΔE, depended on the composition and microstructure of the oxide scale formed on the alloy surface. Crofer22 APU alloy showed the lowest ΔE change as a function of the cathodic polarization time among the chromia-forming alloys studied. This is most likely due to the formation of the dense and void-free oxide scale and the (Cr,Mn)3 O4 spinel phase formed in the top layer of the oxide scale decreases the chromium volatility of the scale. The result demonstrates the feasibility of the electrochemical polarization method in the qualitative diagnosis of the Cr volatility of chromia-forming alloys as interconnect for SOFC applications.