Novel coatings for protecting solid oxide fuel cell interconnects against the dual-atmosphere effect

Journal article, 2023

A key component of a Solid Oxide Fuel Cell (SOFC) is the interconnect, which connects individual fuel cells in series to form a fuel cell stack to reach a desired electrical potential. The interconnect is exposed to air and fuel in parallel, these so-called dual-atmosphere conditions give rise to especially severe corrosion on the air-side. This work investigates coatings to mitigate this effect. Physical Vapour Deposition (PVD) CeCo-coated AISI 441 samples on the air-side and PVD metallic Al- and Al2O3-coated AISI 441 samples on the fuel-side were exposed under dual-atmosphere conditions for up to 7000 h. The evolution of the corrosion products was followed every 1000 h with an optical microscope. Scanning electron microscopy and energy-dispersive x-ray spectroscopy were performed on cross-sections of the samples after 3000 h of exposure. The SEM analysis showed that coating on the air-side improved the sample's life-time by reducing the level of Cr evaporation even in a dual-atmosphere. The use of fuel-side coatings suppressed the dual-atmosphere effect since the coatings formed a barrier to hydrogen permeation. The best results were observed with metallic Al and Al2O3 coating on the fuel-side, which drastically reduced the dual-atmosphere effect. However, the poor conductivity of Al2O3 makes its use as a coating challenging.