Oxidation Behavior and Electrical Properties of De-siliconized AISI 430 Alloy with Mn1.5Co1.5O4 Coating for Solid Oxide Fuel Cell Interconnect

Abstract

The effect of de-siliconization on the oxidation behavior of AISI 430 stainless steel used for solid oxide fuel cell interconnect application was investigated. De-siliconization treatment was conducted via heating steel parts in an H2 environment. The de-siliconized substrates were then coated with a Mn1.5Co1.5O4 spinel coating, using wet spray method. For comparison, a similar coating process was applied on the as-received AISI 430 stainless steel specimens. Oxidation kinetics of coated interconnects were evaluated at 700, 800 and 900 °C in air. Results showed that the de-siliconization surface treatment decreased oxidation rates, with kinetic rates (g2 cm−4 s−1) of 4.39 × 10−14 at 700 °C, 1.71 × 10−13 at 800 °C and 1.62 × 10−12 at 900 °C, i.e., 55, 48 and 22% lower compared to the as-received coated substrates, respectively. Scanning electron microscopy images and EDS analysis confirmed the formation of SiO2-rich layer beneath the surface oxide scale for the oxidized specimens. The thickness of the formed scale for the de-siliconized specimens was noticeably lower than that of as-received ones. Step-wise electrical conductivity measurements showed that the de-siliconized specimens, compared to the as-received specimens, had higher electrical conductivity (~ 30–40%), implying lower oxidation degrees of the substrate and thus, better electrical performance under cathodic service condition of SOFC.