Oxidation and Electrical Behavior of a Ferritic Stainless Steel with a Mn–Co-Based Coating for SOFC Interconnect Applications

Abstract

Protective coatings with high electrical conductivity that resist oxide scale growth are required for stainless steel interconnect materials in the long-term durable operation of solid oxide fuel cells. This work evaluates the oxidation and electrical behavior of Crofer 22 APU ferritic stainless steel coated with manganese and cobalt by electrodeposition. Isothermal and cyclic oxidation (800 °C in air) tests were done to evaluate the role of the coating layer during oxidation. Area-specific resistance (ASR) of the coated and uncoated substrates was also tested at 800 °C in air. Results show that the coating layer transforms into Mn1.5Co1.5O4 spinel during oxidation. The mass gain and spallation indicated that the formation of Mn–Co spinel improves the high temperature oxidation. These spinels also cause a reduction in ASR for electroplated substrates (12.42 mΩ cm2) as compared to uncoated ones (38.74 mΩ cm2) after 400 h of isothermal oxidation at 800 °C.