Protective Coatings for Ferritic Stainless Steel Interconnect Materials in High Temperature Solid Oxide Electrolyser Atmospheres

Abstract

Stainless steel interconnect materials used in solid oxide fuel cells and electrolysers need to be coated to improve oxidation resistance and to mitigate Cr-vaporization. This work aimed to explore the optimal steel/coating combinations suitable for use in reversible solid oxide stacks and evaluated (Co,Mn)3O4 spinel, LaFeO3 perovskite, Ce/Co and Y-based coatings, on AISI441 and Crofer 22 APU steels. The coatings were evaluated based on measurements of mass gain and oxide scale thickness after exposure at 700 and 800 °C to fuel side (90 vol.% H2O/10 vol.% H2) and air/oxygen side (pure O2) atmospheres. In pure O2, the most efficient coatings for limiting oxide scale formation and Cr evaporation, compared to the bare steel, were (Co,Mn)3O4 and CeCo on Crofer 22 APU. In 90 vol.% H2O/10 vol.% H2, the Y-based coating showed the largest improvement in oxidation resistance.

An Alternative Method of Measuring Area Specific Resistance of Chromia Scales Using Electrochemical Impedance Spectroscopy

“…The formation of the spinel seems to hinder the Cr 2 O 3 by consuming most of the oxygen in the initial stages. A similar behavior with two time constants has been described by Mikkola et al 52 Beneath the metalscale interface, an internal oxidation zone (IOZ) of titanium is present with a depth that increases with the exposure time as oxygen penetration into the alloy increases. The thin bright layer on top of the scale is gold sputtered after the exposure for sample preparation purposes.…”

Perovskites: Versatile Weaponry in the Arsenal of Energy Storage and Conversion

“…In a related topic, Mikkola et al [12] reported on another use of perovskite oxides in solid oxide electrolyzer cells. To overcome material wear in solid oxide fuel and electrolyzer cells, LaFeO 3 along with Co and Mn spinels were used as coatings on stainless steel connectors.…”