High Temperature Oxidation of Ferritic Steels for Solid Oxide Electrolysis Stacks

Abstract

Oxidation rates of ferritic steels used as interconnector plates in Solid Oxide Electrolysis Stacks are of concern as they may be determining for the life time of the technology. In this study oxidation experiments were carried out for up to 1000 hours in hydrogen-side and oxygen-side simulated atmospheres at 800°C. Four commercially available alloys: Crofer 22 APU, Crofer 22 H, AL29-4, E-Brite were characterized in humidified hydrogen. One alloy, Crofer 22 APU was also characterized in pure oxygen both in the as-prepared state and after application of a protective coating. Best corrosion resistance in humidified hydrogen atmosphere was observed for Crofer 22 APU and Crofer 22 H alloys. Corrosion rates for Crofer 22 APU measured in humidified hydrogen are similar to the corrosion rates measured in air. Both coatings of plasma sprayed LSM and dual layer coatings (Co3O4/LSM-Co3O4) applied by wet spraying were found to reduce corrosion rates in pure oxygen significantly.

Low temperature processed MnCo2O4 and MnCo1.8Fe0.2O4 as effective protective coatings for solid oxide fuel cell interconnects at 750 °C

“…Among many possible coatings [14][15][16][17][18][19][20][21], manganese cobalt spinels were studied extensively as protective coatings for SOFC/SOEC interconnects [14,22]. These materials are compatible with contact layer materials in the fuel cells and have also proven to effectively block chromium outward diffusion and evaporation.…”

Evaluation of electrodeposited Mn‐Co protective coatings on Crofer 22 APU steel

“…After 1000 hours, weight gain of this sample is ~0.32 mg cm −2 , whereas for the Co coated sample with the largest weight gain is ~0.5 mg cm −2 , so >50% higher. Weight gain for the uncoated Crofer 22 APU alloy tested in the same laboratory was also 0.5 mg cm −2 . Pure Co coating does not result in lowering the weight gain, whereas other coatings results in a decrease in the measured weight gain.…”

Physicochemical properties of Mn1.45Co1.45Cu0.1O4 spinel coating deposited on the Crofer 22 H ferritic steel and exposed to high-temperature oxidation under thermal cycling conditions

“…The interconnect, which is also known as a bipolar plate, is the basic structural component in both types of devices. It has a number of functions: it connects individual fuel or electrolyzer cells in series, gives the entire construction rigidity, and it supplies the gas reagents to the anode and cathode spaces via the channels located on both of its sides [9][10][11][12][13].…”

“…Interconnects applied in SOECs that operate at temperatures of up to 800 °C are generally manufactured from highchromium ferritic stainless steels (FSS), which contain at least 22 mass% of chromium [9][10][11][12][13][14][15][16]. The thermal expansion coefficient of such steels (11.5-14.0 × 10 -6 K −1 [11]) is similar to the corresponding coefficients of the ceramic components of the electrolyzer, namely the anode (12.8 × 10 -6 K −1 for La 0.69 Sr 0.30 MnO 3 [17]), cathode (11.9 × 10 -6 K −1 for NiO-YSZ [17]), and the electrolyte (10.5 × 10 -6 K −1 for YSZ [17]).…”

“…Their main weakness is their low resistance to oxidation in reaction gas media. A chromia (Cr 2 O 3 ) scale gradually grows on their surface during the operation of the SOEC [9][10][11][12][13][14][15][16][17][18][19][20]. This in turn causes a continuous increase in the area-specific resistance (ASR) of the interconnect.…”