Applicability of ToF-SIMS and stable oxygen isotopes in KCl-induced corrosion studies at high temperatures

Lehmusto, Juho; Bergelin, Mikael; Sui, Jingxin; Juhanoja, Jyrki; Skrifvars, Bengt-Johan; Yrjas, Patrik

doi:10.1016/j.corsci.2017.05.022

Cited by 10 publications

(3 citation statements)

References 32 publications

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“…Since Cr 2 O 3 reacts readily with KCl and not with NiO, NiO could still be found in the outer scale. Alternatively, chromia and NiO could form from intermediate corrosion products such as CrCl 2 and NiCl 2 , respectively . The equilibrium oxygen partial pressure requirement to convert NiCl 2 to NiO is more than the equilibrium oxygen partial pressure requirement to convert the CrCl 2 to chromia, indicating NiO would be stable on top of Cr 2 O 3 /K 2 CrO 4 .…”

Section: Discussionmentioning

confidence: 99%

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KCl‐induced corrosion of Ni‐based alloys containing 35–45 wt% Cr

Malede

Simon

Jonsson

et al. 2019

Materials & Corrosion

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Ni–(35–45)Cr–4Nb alloys containing different fractions of α‐Cr were exposed to potassium chloride (KCl)‐induced corrosion. The corrosion exposures were carried out for 168 hr at 600°C in a 15% (vol/vol) H2O (g) + 5% (vol/vol) O2 (g) + N2 (g; balance) atmosphere using KCl‐free (reference) and predeposited KCl samples. To mimic the KCl deposition in real boilers, 24 hr exposures where KCl vapor condensed continuously onto samples were also performed. The corrosion attack of the studied materials increased significantly when KCl was present compared to the KCl‐free samples. For the KCl exposures, the corrosion attack drastically increased when a significant α‐Cr fraction was present. α‐Cr was either selectively attacked or dissolved through solid‐state diffusion and a layered build‐up of the outer external scale of K2CrO4 and chromia could be observed. For the in situ condensed KCl exposure, severe corrosion was observed already within the 24 hr exposure, indicating a higher corrosion rate compared with when KCl was predeposited.

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Section: Discussionmentioning

confidence: 99%

“…The outer corrosion product of the solution‐treated alloy consisted of K 2 CrO 4 on top of Cr 2 O 3 (Figure ). Hence, the 24 hr exposure was enough to initiate accelerated corrosion . At the corrosion front, the solution‐treated Ni35Cr4Nb sample was internally attacked resulting in a 10 µm porous region (Figure ).…”

Section: Discussionmentioning

confidence: 99%

KCl‐induced corrosion of Ni‐based alloys containing 35–45 wt% Cr

Malede

Simon

Jonsson

et al. 2019

Materials & Corrosion

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“…In addition, traces of potassium chromate (K 2 CrO 4 ) were found on top of some of the oxide scales. K 2 CrO 4 is a solid intermediate, which is known to be rapidly formed in the reaction between KCl and the protective chromium-rich oxide, impairing the corrosion resistance of the alloy through chromium depletion [27]. In the case of a pure chromium oxide scale, the reaction would proceed according to Eq.…”

Section: Oxide Scale Composition and Structurementioning

confidence: 99%

Pre-oxidation as a Means to Increase Corrosion Resistance of Commercial Superheater Steels

2019

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This study addresses the effect of pre-oxidation on the corrosion resistance of the following three commercial steels: a low-alloyed ferritic 10CrMo9-10 steel; a Nbstabilized austenitic AISI 347 steel; and a high-alloyed austenitic Sanicro 28 steel. Samples of these three steels were pre-oxidized under various conditions and then exposed to potassium chloride (KCl) for 168 h at 550 °C under dry conditions. In the case of the ferritic 10CrMo9-10 and the austenitic AISI 347 steels, despite differences in oxide scale composition and structure, their corrosion resistance could not be improved by any of the studied pre-oxidation procedures. In contrast, preoxidation conditions resulting in chromium-enriched oxides improved the corrosion resistance of the high-alloyed austenitic Sanicro 28 steel in terms of oxide scale growth during exposure to KCl.

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