| 1. |
- Karlsson, Sofia, 1982, et al.
(författare)
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A Laboratory Study of the in Situ Sulfation of Alkali Chloride Rich Deposits: Corrosion Perspective
- 2016
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 30:9, s. 7256-7267
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Tidskriftsartikel (refereegranskat)abstract
- The initial corrosive effect of small (1.35 mu mol/cm(2)) and large (13.5 mu mol/cm(2)) amounts of KCl on 304L has been investigated. The investigations were performed in both the absence and presence of 300 ppm of SO2 at 600 degrees C. The results showed that in the absence of SO2 KCl accelerates the rate of corrosion by means of two types of corrosion attack: a general attack and a steel grain boundary attack. The general attack has been proved to be initiated by K2CrO4 formation. Meanwhile, the steel grain boundary attack is suggested to be accelerated by HCl released due to the chromate formation which increased with higher amounts of KCl. The presence of KCl and SO2 resulted in the simultaneous formation of K2SO4 and K2CrO4. The chromate formation resulted in a general corrosion attack. However, the oxide growth was significantly reduced due to the very fast sulfation reaction. In contrast, the steel grain boundary attack increased in the presence of SO2. It is suggested that the attack is accelerated by HCl released from the sulfation reaction and by sulfidation of the steel grain boundaries.
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| 2. |
- Larsson, Erik, 1983, et al.
(författare)
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A Comparative Study of the Initial Corrosion of KCl and PbCl2 on a Low-Alloyed Steel
- 2017
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Ingår i: Oxidation of Metals. - : Springer Science and Business Media LLC. - 1573-4889 .- 0030-770X. ; 87:5-6, s. 779-787
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Tidskriftsartikel (refereegranskat)abstract
- Heat exchange surfaces in biomass- and waste-fired boilers are exposed to corrosive species due to the considerable amounts of alkali chlorides and PbCl2 which are released during combustion. The corrosivity of alkali chlorides toward superheater alloys exposed at high temperature has been studied extensively. However, at lower material temperatures, i.e., at waterwall conditions, considerably less research has been performed. In order to investigate the effect of small amounts of KCl and PbCl2 during the initial stages of the corrosion attack, a Fe–2.25Cr–1Mo steel was exposed for 24 h in an atmospheres consisting of O2 + H2O + N2 at 400 °C. Both KCl and PbCl2 resulted in an increased corrosion rate compared to the reference. The aim of the present paper is to investigate the influence of KCl and PbCl2 on the initial oxidation of a Fe–2.25Cr–1Mo steel. The work involves a detailed microstructural investigation as well as thermodynamic equilibrium calculations.
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| 3. |
- Larsson, Erik, 1983, et al.
(författare)
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The Influence of KCl and HCl on the High-Temperature Oxidation of a Fe-2.25Cr-1Mo Steel at 400 °C
- 2020
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Ingår i: Oxidation of Metals. - : Springer Science and Business Media LLC. - 1573-4889 .- 0030-770X. ; 93:1-2, s. 29-52
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Tidskriftsartikel (refereegranskat)abstract
- The influence of alkali- and chlorine-containing compounds on the corrosion of superheater alloys has been studied extensively. The current paper instead investigates the corrosive effects of KCl and HCl under conditions relevant to waterwall conditions. A low-alloy (Fe-2.25Cr-1Mo) steel was exposed to KCl(s), 500 vppm HCl(g) and (KCl + HCl) in the presence of 5%O2 and 20% H2O at 400 °C. The results indicate that alloy chlorination by KCl occurs by an electrochemical process, involving cathodic formation of chemisorbed KOH on the scale surface and anodic formation of solid FeCl2 at the bottom of the scale. The process is accompanied by extensive cracking and delamination of the iron oxide scale, resulting in a complex, convoluted scale morphology. Adding 500 vppm HCl to the experimental environment (KCl + HCl) initially greatly accelerated the formation of FeCl2 at the scale/alloy interface. The accelerated alloy chlorination is attributed to HCl reacting with KOH at the scale surface, causing the cathodic process to be depolarized. A rapid slowing down of the rate of chlorination and corrosion in KCl + HCl environment was observed which was attributed to the electronically insulating nature of the FeCl2 layer which forms at the bottom of the scale, disconnecting the anodic and cathodic regions.
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| 4. |
- Cantatore, Valentina, 1986, et al.
(författare)
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Oxidation Driven Permeation of Iron Oxide Scales by Chloride from Experiment Guided First-Principles Modeling
- 2019
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 123:42, s. 25957-25966
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Tidskriftsartikel (refereegranskat)abstract
- In this comprehensive investigation, it is demonstrated how chloride ions may permeate a crack-free oxide scale, thus providing hitherto missing mechanistic insight as to the impacts of KCl(s) or HCl(g) exposures on the high-temperature corrosion of biomass- and waste-fired boilers. Guided by dedicated experimental analyses, mechanistic understanding is gained by means of density functional theory. Chloride ions, being accommodated in oxygen anion vacancies that are generated at the receding magnetite/alloy interface, are driven through the oxide scale by the oxidation process. Intermediate stabilities of quasi-homogeneous transient iron oxychloride species are found, employing potassium ferrite and goethite as complementary cation sinks for the KCl(s) and HCl(g) reactants, respectively. Spontaneous disproportionation of the supersaturated oxychlorides into two different types of chloride decorated magnetite grain boundaries is demonstrated. These motifs are proposed to explain loss of scale integrity as well as accelerated oxidation by offering short-circuiting transient pathways for ion diffusion.
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| 5. |
- Eklund, Johan, 1991, et al.
(författare)
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Field exposure of FeCrAl model alloys in a waste-fired boiler at 600°C: The influence of Cr and Si on the corrosion behaviour
- 2019
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Ingår i: Materials and Corrosion. - : Wiley. - 0947-5117 .- 1521-4176. ; 70:8, s. 1476-1485
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Tidskriftsartikel (refereegranskat)abstract
- Materials and Corrosion WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim The aim of this study was to examine the performance of FeCrAl model alloys in a waste-fired boiler and investigate the influence of chromium and silicon content on the corrosion behaviour. The investigation was executed by utilising an air-cooled probe, giving a material temperature of 600°C throughout a 672 hr exposure. The material loss measurements were performed by utilizing an ultrasonic thickness gauge in combination with scanning electron microscopy analysis. It was found that increasing the chromium content significantly reduced the overall material loss of the FeCrAl model alloys but further accelerated the corrosion attack on the windward side. Simultaneously, the increased chromium content caused embrittlement of the material. Minor additions of silicon drastically reduced the material loss of the FeCrAl model alloys, whereas the sample ring with no silicon present was completely deteriorated. The trends observed in this field study correlated well with what has been observed in previous laboratory studies. A state-of-the-art alloy in the present environment, Inconel 625, was simultaneously exposed and showed similar performance to the silicon-containing FeCrAl model alloys with ≥10 wt% Cr.
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| 6. |
- Eklund, Johan, 1991, et al.
(författare)
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The influence of silicon on the corrosion properties of FeCrAl model alloys in oxidizing environments at 600 °C
- 2018
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Ingår i: Corrosion Science. - : Elsevier BV. - 0010-938X. ; 144, s. 266-276
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Tidskriftsartikel (refereegranskat)abstract
- The present study investigates the influence of Si on the high temperature corrosion behaviour of FeCrAl model alloys in O2, O2+H2O and O2+H2O + KCl at 600 °C for up to 168 h. The investigation by SEM/EDX showed that all alloys displayed a protective behaviour in dry O2. In the more corrosive environments (O2+H2O and O2+H2O + KCl) the addition of Si affected the oxidation properties in two ways; Alloys containing Si resisted breakaway oxidation caused by Cr-evaporation (O2+H2O) and the thickness of the oxide formed after breakaway oxidation decreased with increasing amount of Si (O2+H2O + KCl).
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| 7. |
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| 8. |
- Folkeson, Nicklas, 1981, et al.
(författare)
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The influence of small amounts of KCl(s) on the high temperature corrosion of a Fe-2.25Cr-1Mo steel at 400 and 500 degrees C
- 2011
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Ingår i: Materials and Corrosion - Werkstoffe und Korrosion. - : Wiley. - 1521-4176 .- 0947-5117. ; 62:7, s. 606-615
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Tidskriftsartikel (refereegranskat)abstract
- This paper reports the oxidation behaviour of a low-alloyed steel (Fe-2.25Cr-1Mo) in the presence of small amounts of KCl(s) at 400 and 500 degrees C. Cleaned and polished sample coupons were exposed in a horizontal tube furnace with exposure times ranging from one hour to one week. The flue gas composition was 5% O(2) with 40% H(2)O in N(2), and 0.1mg KCl/cm(2) was deposited on the samples prior to exposure. X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis were used to characterize the samples. Cross sections were prepared by means of focused ion beam (FIB) and broad ion beam (BIB). At 400 degrees C there was a modest mass gain in the absence of KCl. In the presence of KCl, mass gain is significantly increased and a rapid attack is evident already after short exposure times. At 500 degrees C, the mass gains in the absence of KCl were considerably higher than at 400 degrees C, especially after 168 hours of exposure. KCl had an effect at shorter exposure times, but after one week the samples exposed with and without KCl had mass gains of comparable magnitude.
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| 9. |
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| 10. |
- Hellström, Kristina M, 1971, et al.
(författare)
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Oxidation behaviour of a (Mo, W)Si2-based composite in dry and wet oxygen atmospheres in the temperature range 350–950◦C
- 2009
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Ingår i: Journal of the European Ceramic Society. - : Elsevier BV. - 1873-619X .- 0955-2219. ; 29:10, s. 2105-2118
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Tidskriftsartikel (refereegranskat)abstract
- The oxidation of a (Mo, W)Si2-based composite was investigated in the temperature range (350–950 °C). The influence of temperature and water vapour on the oxidation was examined. The kinetics was studied using a thermobalance whereas the morphology and composition of the oxides were examined using X-ray diffractometer (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and energy dispersive X-ray (EDX). Focused ion beam (FIB) milling was performed on some of the oxide scales which allowed us to look at a non-mechanically disturbed scale/oxide in cross-section. Rapid oxidation was found to occur in the 550–750 °C temperature range. The mass gains were significantly larger in O2 than in O2 + 10%H2O. The different mass changes in the two exposure atmospheres were attributed to the higher vapour pressure of the volatile MoO2(OH)2 and WO2(OH)2 species in O2 + 10%H2O than that of (MoO3)3 and (WO3)3 in dry O2. The peak mass gain was found to occur at a temperature of about 750 °C in O2 and 650 °C in O2 + 10%H2O. At temperatures above 850 °C, especially when water vapour is present, the removal of Mo and W from the oxide scales is rapid enough to allow partial healing of the silica, causing the oxidation rate to drop. At 950 °C in O2 + 10%H2O, a protective SiO2 scale could be re-established quickly and maintained, causing the oxidation to essentially cease.
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