Reduced long term electrical resistance in Ce/Co-coated ferritic stainless steel for solid oxide fuel cell metallic interconnects

• Co and combined Ce/Co coatings have been tested on Sanergy HT (TM) stainless steel.
• Long term oxidation and ASR tests of the various interconnect coatings.
• Ce/Co coatings reduce oxide growth and ASR by more than a factor of two.

The present study is focused on the influence of selected coatings on a ferritic stainless steel (Sanergy HT™, Sandvik) on the evolution of the area specific resistance (ASR) as a function of time at high temperature. The samples are exposed in humidified air at 850 °C for up to 4200 h. It combines long-term ASR measurements with the thermogravimetric behavior and microstructural analysis of the cross sections by scanning electron microscopy. The results show that uncoated and Co-coated Sanergy HT™ exhibit similar oxidation kinetics and comparable ASRs, while a combined Ce/Co coating improves oxidation resistance and, consequently, reduces the ASR significantly. Other reports have earlier shown that Co- (and Ce/Co)-coated Sanergy HT™ reduces the evaporation of volatile chromium species. Overall, the study indicates that Ce/Co-coatings will render substantially improved performance for ferritic steel interconnects for solid oxide fuel cells.