Ceramic Coating Based on La, Sr and Co on Ferritic Stainless Steel for ITSOFC Interconnects

Abstract

Ferritic stainless steels have been used to produce interconnects for intermediate temperature solid oxide fuel cells (ITSOFC) due to their appropriate properties. Ferritic stainless steel presents mechanical stability, much higher thermal and electronic conductivities; significantly lower cost, and mechanical resistance than austenitic steels. Besides, it presents a thermal expansion coefficient compatible with the other materials of the cell components. However, in the range of this device operating temperature (600 °C 800 °C) it can occur the formation of poorly conducting oxide (Cr2O3) reducing the fuel cell performance. The aim of this work was to obtain oxide coatings starting with La, Sr and Co nitrates applied by spray-pyrolysis technique on a stainless steel AISI 430 substrate. The coatings obtained were characterized by X-ray diffraction and scanning electron microscopy/energy dispersive spectroscopy. The oxidation resistance of the ferritic stainless steel, coated with a perovskite (La0,6Sr0,4CoO3) film, was investigated by isothermal oxidation. The results showed that the coating obtained promoted the increase of the ferritic stainless steel oxidation resistance. However, after the oxidation test, it was observed a Cr enrichment and a very pronounced Sr enrichment, near to the alloy/coating interface, which can be associate to the decomposition of La0,6Sr0,4CoO3 film.