| 1. |
- Långberg, Marie, 1988-, et al.
(författare)
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Lateral variation of the native passive film on super duplex stainless steel resolved by synchrotron hard X-ray photoelectron emission microscopy
- 2020
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Ingår i: Corrosion Science. - Stockholm, : Elsevier BV. - 0010-938X .- 1879-0496. ; 174
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Tidskriftsartikel (refereegranskat)abstract
- A native passive film on 25Cr-7Ni super duplex stainless steel was analyzed using synchrotron hard X-ray photoemission electron microscopy, focusing on variations between individual grains of ferrite and austenite phases. The film consists of an oxide inner layer and an oxyhydroxide outer layer, in total 2.3 nm thick. The Cr content is higher in the outer than the inner layer, ca. 80 % on average. The Cr content is higher on ferrite than austenite, whereas the thickness is rather uniform. The grain orientation has a small but detectable influence, ferrite (111) grains have a lower Cr content than other ferrite grains.
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| 2. |
- Långberg, Marie, 1988-, et al.
(författare)
-
Redefining passivity breakdown of super duplex stainless steel by electrochemical operando synchrotron near surface X-ray analyses
- 2019
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Ingår i: npj Materials Degradation. - Stockholm, : Springer Science and Business Media LLC. - 2397-2106. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Passivity determines corrosion resistance and stability of highly-alloyed stainless steels, and passivity breakdown is commonly believed to occur at a fixed potential due to formation and dissolution of Cr(VI) species. In this work, the study of a 25Cr–7Ni super duplex stainless steel in 1 M NaCl solution revealed that the passivity breakdown is a continuous degradation progress of the passive film over a potential range, associated with enhanced Fe dissolution before rapid Cr dissolution and removal of the oxide. The breakdown involves structural and compositional changes of the passive film and the underlying alloy surface layer, as well as selective metal dissolution depending on the anodic potential. The onset of passivity breakdown occurred at 1000 mV/Ag/AgCl, and Fe dissolved more on the ferrite than the austenite phase. With increasing potential, the passive film became thicker but less dense, while the underlying alloy surface layer became denser indicating Ni and Mo enrichment. Rapid Cr dissolution occurred at ≥1300 mV/Ag/AgCl.
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