Fabrication of reactive element oxide coatings on porous ferritic stainless steel for use in metal-supported solid oxide fuel cells

Abstract In this study, lanthanum, yttrium, and cerium oxide coatings were fabricated on porous 430 stainless steel substrates by sol-gel dip coating and subsequent heat treatment at 650 °C in air. The effects of viscosity of the sol-gel solution, the withdrawal speed of the substrate from the solution, and the number of dipping and drying steps on coating thickness and coating morphologies were characterized by scanning electron microscopy (SEM). During subsequent heating at 800 °C, the La 2 O 3 layer reacted with Cr from the substrate to form a LaCrO 3 layer on the substrate. The envelope of sol-gel dip coating parameters with which oxidation resistant coatings can be fabricated on porous stainless steel supports was determined from oxidation weight gain experiments of supports with various protective coatings. High temperature oxidation of the coated substrates showed that La 2 O 3 and Y 2 O 3 coatings were highly effective in decreasing the oxidation rates of the porous supports, while CeO 2 coatings were not found to be as effective for the protection of metallic substrates for metal-supported SOFCs. Rough estimation of oxide layer thicknesses after 40,000 h based on calculated oxidation rates of the Y 2 O 3 -coated and La 2 O 3 -coated substrates in air at 800 °C showed that oxide growth filling the pore structure would not be the factor limiting the lifetime of Y 2 O 3 -coated and La 2 O 3 -coated supports for SOFCs.