Effective yttrium based coating for steel interconnects of solid oxide cells: Corrosion evaluation in steam-hydrogen atmosphere

Abstract

This work describes manufacture, analysis and test of a new well conducting corrosion-protection coating that can be applied on steel types with high chromium content. Electrolytic deposition of yttrium salts is used to form thin (<100 nm) coatings on both flat steel sheets (material: Crofer 22 APU) and its properties are proven on woven wire-meshes (materials from two different sources: SUS316 and SUS316L). The oxide scale on the coated Crofer 22 APU sheet remains intact after 2000 hours operation at 750 °C in H2 with 90% H2O. The corrosion rate at 750 °C of the coated Crofer 22 APU sheets is compared with that of uncoated samples and of samples with a commercial magneton sputtered CGO coating revealing that the coatings reduce the parabolic rate constant characteristic of the corrosion by a factor of 10 and 20 for the CGO and the Y, respectively.The coated meshes also exhibit high corrosion resistance and long-term-stable low electrical resistance at 650 °C, both in 90% H2O in H2, and in air. In addition to the experimental work, Y-Cr-O2 phase diagrams are constructed illustrating the high stability of the YCrO3 phase (that forms during corrosion) over a wide temperature and pO2 range.

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

“…The Y-coating itself was deposited as a hydroxide and was converted to Y 2 O 3 during the first heat treatment of the coating phase. During long-term oxidation, the coating reacts with the Cr from the steel/oxide scale to form YCrO 3 , as shown by Molin et al [43].…”

“…However, the dual spinel-perovskite nature may pose some doubts about the effective stability of the LFO coatings due to the presence of highly reducible mixed Fe-Cr spinel oxides underneath the perovskite layer. Finally, a thin yttrium-based coating has been shown to provide effective protection against corrosion of Crofer 22 APU steel at 750 • C in 90 vol.%/10 vol.% steam-hydrogen atmosphere [43].…”

Characterization of metallic interconnects extracted from Solid Oxide Fuel Cell stacks operated up to 20,000 h in real life conditions: The fuel side

“…As a preliminary explanation, the presence of water vapor in the stream could induce breakaway oxidation of FSSs [32]. This mechanism eventually leads to the formation of superficial Fe oxides [35,50,51].…”

“…Also, the protectiveness of the chromia based TGO varies according to the percentage of Cr in the alloy [21,32] and the morphology and the adhesion of the scale changes according to the percentage of the water vapor [40], in a mechanism that suggests the higher the oxide thickness the lower the adhesion. The sole effect of water vapor, in presence of Ar, was addressed by many researchers that found contradictory results [35e39] in terms of growth kinetics (from 10 À9 to 10 À16 cm $ s À1 ) [32,35] and composition, attributing the evolution of the scale to diffusion phenomena sometimes coupled to chromium volatilization.…”

PASSIVATION OXIDATION OF THE SURFACE OF AMA Al87Ni8Y5 IN THE PRESENCE OF OXYGEN-CONTAINING INHIBITORS

“…Перелік методів і способів формування та модифікування функціональних покриттів на різних матеріалах постійно зростає, що пояснюється неухильним розширенням сфери використання традиційних матеріалів і новітніх розробок у цій сфері, а також генеруванням нових оригінальних наукових ідей і створенням технічних рішень, реалізованих на основі цих ідей [18,19]. Спроби врахувати максимально можливу кількість істотних чинників, що визначають експлуатаційні властивості матеріалів з покриттями, також сприяють розширенню класів і типів покриттів і методів їх формування [20,21]. Існує багато різних варіантів функціональних покриттів, зокрема хімічні, гальванічні, дифузійні та ін.…”