Corrosion behaviour of ferritic stainless steels in H2/H2O environments

Typ
Examensarbete för masterexamen
Master's Thesis
Program
Materials chemistry (MPMCN), MSc
Publicerad
2023
Författare
Almyren, Isak
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Sammanfattning
Solid Oxide Electrolysis Cells (SOEC) is an emerging technology for green hydrogen production with high efficiency and without a need for precious metal catalysts. SOEC operates at high temperatures which creates some challenges for the system, one being the high temperature corrosion of metal components in the electrolysis cell. During the thesis work, potential steels for use in SOEC have been exposed in simulated fuel side electrolysis environments (H2/H2O), with varying degrees of argon gas dilution. The work found severe corrosion at 650 ℃ , with a large amount of Fe rich oxides forming for both AISI 441 and 22 Crofer APU. Due to samples experiencing breakaway corrosion samples were pre-oxidised for long term exposures. Different preoxidation times was performed and it was found that increasing pre-oxidation time increased corrosion protection. During long term exposures, formation of hematite (Fe2O3) was identified. Hematite was calculated to be thermodynamically unstable at the specified (H2/H2O) environments. A potential cause of the hematite formation was studied; that the Water-Hydrogen-Oxygen reaction did not come to chemical equilibrium and thus causing a shift in p(O2) in the furnace. Platinum was added to catalyse this reaction before reaching the samples. This addition generally diminished the rate of corrosion but was unable to completely stop the formation of hematite. Further work is required for better understanding of the dilution effect and its dependence on temperature as well as the causes of hematite formation. Updated experimental setups should be designed as this method causes difficulties not well understood. environments, dilution, hematite iv
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Ämne/nyckelord
SOEC , Electrolysis , high temperature corrosion , hydrogen , steam , fuel environments , dilution , hematite
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