SEM study of the early stages of Fe-bentonite corrosion—The role of naturally present reactive silica

•First time short-term corrosion observation using electron microscopy.•First time systematically considering the role of soda soluble silica (SSS).•Short-term SEM corrosion products depend on the amount of SSS bentonite.•Two different reaction pathways were identified leading to different magnetite...

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Bibliographic Details
Published in:Corrosion science 2020-07, Vol.171, p.108716, Article 108716
Main Authors: Kaufhold, S., Schippers, A., Marx, A., Dohrmann, R.
Format: Article
Language:English
Subjects:
Bentonite
Corrosion
Corrosion mechanism
Corrosion mechanisms
High level radioactive wastes
HLRW bentonite barrier
Iron
Iron corrosion
Magnetite
Microbiology
Radioactive waste disposal
Radioactive wastes
Silica
Silicates
Silicon dioxide
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Summary:•First time short-term corrosion observation using electron microscopy.•First time systematically considering the role of soda soluble silica (SSS).•Short-term SEM corrosion products depend on the amount of SSS bentonite.•Two different reaction pathways were identified leading to different magnetite/Fe-silicate ratios. The iron-bentonite interface will be important with respect to the long-term performance of high-level radioactive waste (HLW) disposal sites. Magnetite and Fe-silicates form at this interface due to anoxic corrosion. The corrosion mechanism, however, is still under debate. In the present study two bentonites differing with respect to their content of reactive silica were compared using electron microscopy. The presence of reactive silica immediately led to the formation of Fe-silicates while magnetite prevailed in the other sample. These results confirm recently published conceptual models describing the corrosion and point towards the importance of considering reactive silica in this system.
ISSN:0010-938X
1879-0496
DOI:10.1016/j.corsci.2020.108716