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 Mn 1.5 Co 1.5 O 4 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 mX cm 2 ) as compared to uncoated ones (38.74 mX cm 2 ) after 400 h of isothermal oxidation at 800°C.

Impact of Different Atmospheres on Oxidation and Electrical Performance of a Solid Oxide Fuel Cell Interconnect with Co-Containing Protective Coating

“…Solid oxide fuel cells (SOFCs) are quite promising electrochemical energy conversion systems, thanks to their less contaminate discharge and high-energy transformation efficiency. , A unitary fundamental unit of the SOFC can solely offer about 1 V potential; accordingly, a range of fundamental units are linked to manufacture an SOFC stack that generates a higher operating potential for realistic application. As a plate-type SOFC stack, an interconnect is an intensely significant multifunctional part that associates units with the stack and supplies the fuel gas and oxidant for the anode and cathode, respectively. − Over the past few decades, the LaCrO 3 -based ceramic materials have been applied at high temperature (about 1000 °C), but the cost of preparation of the ceramic interconnect is higher than that of the metallic interconnect. , As the SOFC working temperature has been decreased from 1000 to 800 °C or even 600 °C, ceramic materials have been replaced by Cr-based metallic alloys. The Cr-based metallic interconnect has been extensively investigated as a potential candidate interconnect because of its inexpensive cost, excellent electronic conductivity, and exceptional thermal conductivity. , Unfortunately, there are still a considerable number of degradation problems in utilizing the Cr-based metal interconnect, including surface oxidation and Cr evaporation at high temperature, and the surface oxidation of the metallic interconnect obviously increases the contact resistance. , In addition, Cr species evaporating from the interconnect are electrochemically deposited to hinder the oxygen reduction reaction, hence shortening cathode behavior (i.e., chromium poisoning). , …”

Corrosion Behavior of Fe–Al Coatings Fabricated by Pack Aluminizing Method

“…The pack cementation process is an in situ chemical vapor deposition (CVD) process, which is usually used to deposit certain elements on a steel substrate [12][13][14][15][16]. Pack aluminizing is a common method used to form Fe-Al coatings.…”