Development of Annealed Mn–Co and Mn–Co–Cu Coated AISI 430 Stainless Steels for SOFC Interconnect Application

The developed Mn–Co and Mn–Co–Cu electroplated AISI 430 stainless steels were annealed in argon and further treated in oxygen, at 800 °C for 4 h in each step. The XRD results after the heat treatment exhibited the formation of MnCo2O4 and Co3O4 for the Mn–Co sample, and CoCuMnOx and Co3O4 for the Mn–Co–Cu sample. A further oxidation test in O2–5%H2O at 600–800 °C showed that the oxidation kinetics of the coated samples followed the parabolic rate law and the Arrhenius relation. The oxidation rate of the steel was reduced by the coatings. The Cr-species volatilisation from the coated samples exposed to O2–5%H2O at 800 °C was measured and gave values in the order of 10–11 g cm–2 s–1. The additional annealing process could help form a dense coating, thus contributing to a reduced rate of oxidation.