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A dual surface modification of an SOFC metallic interconnect with a Gd 2 O 3 layer and an MnCo 2 O 4 coating was evaluated. The tested samples were oxidized for 7000 h in air at 1073 K. Oxidation products were characterized using XRD, SEM-EDS, and confocal Raman imaging, and ASR was measured. The effect of gadolinium segregation at grain boundaries in Cr 2 O 3 was evaluated using S/TEM-EDS. Area specific-resistance was measured and fuel cell tests investigating electrochemical performance and Cr contamination of electrodes were also performed. The results show that the proposed dual modification was more advantageous than either modification applied separately. The fuel cell tests performed after aging in humidified hydrogen at 1073 K and involving an actual interconnect made of this dual-modified material showed that after 250 h of aging its electrochemical parameters were nearly identical to those of the non-aged reference electrode. Moreover, the modification protected the electrodes from Cr poisoning. [Display omitted] • Crofer 22 APU underwent single and dual modifications via dip-coating and/or EPD. • Dual modification reduced the oxidation rate to a larger degree than single ones. • Confocal Raman imaging allowed the phase compositions to be identified. • ASR of dual-modified material after 7000 h of oxidation was excellent. • Dual modification effectively protected electrode materials from Cr poisoning. [ABSTRACT FROM AUTHOR]

Most oxidation studies involving interconnects are conducted in air under isothermal conditions, but during real-life solid oxide cell (SOC) operation, cells are also exposed a mixture of hydrogen and water vapor. For this study, an Fe–16Cr low-chromium ferritic stainless steel was coated with different reactive element oxides – Gd 2 O 3 , CeO 2 , Ce 0.9 Y 0.1 O 2 – using an array of methods: dip coating, electrodeposition and spray pyrolysis. The samples underwent oxidation experiments carried out over 100 h in three different atmospheres at 800 °C: air, an air/H 2 O mixture, and an Ar/H 2 /H 2 O mixture. The influence of different atmospheres on the corrosion of the Fe–16Cr steel was determined via oxidation kinetics studies; the corrosion product was evaluated using X-ray diffraction, scanning electron microscopy and area-specific resistance (ASR) measurements. All coated samples exhibited lower parabolic oxidation rate constants than bare steel and most also had lower ASR. The applied modifications were found to be sufficiently effective to allow the investigated low-chromium steel to be considered for application as an interconnect material for SOCs. [Display omitted] • Gd 2 O 3 -based thin layers improved corrosion resistance for all oxidation atmospheres. • Under some conditions RE perovskite phases were formed. • The thinnest scale was observed after oxidation in H 2 –H 2 O atmosphere. • Gd 2 O 3 -based thin layers significantly reduced ASR for all oxidation atmospheres. • Addition of Y to CeO 2 improves its electrical conductivity. [ABSTRACT FROM AUTHOR]