Corrosion Behavior of Crofer 22APU for Metallic Interconnects in Single and Dual Atmosphere Exposures at 1073 K

To determine the impact of an oxidizing Ar-H₂-H₂O/air dual atmosphere on the kinetics and mechanism of oxidation of the Crofer 22APU steel as compared to oxidation in a single atmosphere (Ar-H₂-H₂O or air), the oxidation kinetics of this steel were investigated both in single and dual reaction atmospheres at 1073 K during 100, 250, 500, and 1000 h of oxidation. Detailed morphological observations and the results of chemical composition analyses carried out using transmission electron microscopy combined with energy-dispersive X-ray spectroscopy revealed the presence of Fe in the scale formed on the cathode side in the dual atmosphere. Based on morphological observations (scanning- and transmission electron microscopies) and chemical and phase composition analyses (energy-dispersive X-ray spectroscopy and X-ray diffraction, respectively) of the products of oxidation of the Crofer 22APU steel, and on the determined oxidation kinetics, a mechanism describing scale growth on both sides of the steel during its oxidation in conditions involving a gradient of the chemical potential of oxygen and hydrogen was proposed.