Testing of Ni‐Plated Ferritic Steel Interconnect in SOFC Stacks

Abstract

AbstractStack tests were run at 850 °C for periods from 80 hours to 1,150 hours to develop contacting procedures and at the same time evaluate the performance of a 5 μm electroplated nickel coating on a ferritic Fe22Cr interconnect. The metallic nickel coating reacted relatively quickly during the initial heating to 1,030 °C. During this time, 20–70 μm thick surface layers of austenitic steel were formed, which were covered by a 1–4 μm chromia layer on the anode side and by a layer of mixed Cr‐Fe‐Ni‐spinels over a 1–4 μm chromia layer on the cathode side. The microstructure and composition of the protective scale on the cathode side was susceptible to pitting‐type corrosion patterns, which may limit the life expectancy to less than 2,000 hours for the 200 μm thick interconnect tested. The initial area‐specific resistances (ASR) at the interconnect/cathode current collector interface and the interconnect/anode current collector interface were very low (2 and 10 mΩ cm2, respectively). The cathode side interface resistance increased over the 1,150 hours by ∼7 mΩ cm2/103�h, but the anode side interface resistance decreased during the first 600 hours of the experiment before it started to show a slight increase, < 1 mΩ cm2/103�h, maintaining values below 1 mΩ cm2.