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  • 1.
    Alipour, Yousef
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Davis, C.
    Szakalos, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Henderson, Pamela
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. Vattenfall Res & Dev AB, Sweden.
    Corrosion of the low alloy steel 16Mo3 in the furnace region of used-wood fired boilersManuscript (preprint) (Other academic)
  • 2.
    Alipour, Yousef
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Henderson, Pamela
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. Vattenfall Res & Dev AB, Sweden.
    Szakalos, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Effect of temperature on corrosion of furnace walls in a waste wood fired boiler2015In: Materials at High Temperature, ISSN 0960-3409, E-ISSN 1878-6413, Vol. 32, no 1-2, p. 188-196Article in journal (Refereed)
    Abstract [en]

    One way of reducing the furnace wall corrosion is to lower the temperature of the wall by reducing the boiler pressure. To test this, four coupons of 16Mo3 were exposed in the furnace wall of a waste wood fired boiler for 1075 h. The temperatures of the samples were individually controlled in the range 280-410 degrees C. The corrosion rates and corrosion mechanism were investigated. The deposits were analysed by XRD and SEM/EDS. The corrosion fronts were studied by focused ion beam milling (FIB)/EDS. The environment was modelled by Thermo-Calc. The amount of potassium and chlorine in the deposit decreased with decreasing temperature. The FIB sections showed a distinctive iron chloride layer at the corrosion front, with an outer layer of iron oxide. The corrosion rate decreased with decreasing metal temperature, but the boiler pressure needs to be reduced to a low level to achieve this, which is not beneficial for the electrical efficiency and therefore not a viable way of reducing corrosion.

  • 3.
    Alipour, Yousef
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Henderson, Pamela
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Szakalos, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    The effect of a nickel alloy coating on the corrosion of furnace wall tubes in a waste wood fired power plant2014In: Materials and corrosion - Werkstoffe und Korrosion, ISSN 0947-5117, E-ISSN 1521-4176, Vol. 65, no 2, p. 217-225Article in journal (Refereed)
    Abstract [en]

    The use of waste wood as a fuel in power plants is becoming more widespread in Europe, because it is a renewable energy source with a lower cost than forest fuel. However it is more corrosive than coal and corrosion problems have arisen in the furnace wall area of a low NOx heat and power boiler. The furnace walls are made of a low alloy steel which has been coated in some parts with a nickel alloy to reduce corrosion. In this work, furnace tubes coated with a nickel alloy were compared to the uncoated tubes of the low alloy steel 16Mo3 after 3 years of exposure in the boiler. The nickel alloy coating and uncoated material were also compared with more controlled testing on a corrosion probe lasting for about 6 weeks. The corrosion rates were measured and the samples were chemically analysed by SEM/EDS/WDS and XRD methods. The corrosive environment was also modelled with Thermo-Calc software. The corrosion rates measured from the probe and tube samples of 16Mo3 agreed well with each other, implying linear corrosion rates. The results also showed that the use of nickel alloy coatings changes the corrosion mechanism, which leads to a dramatic reduction in the corrosion rate. The results are discussed in terms of the corrosion mechanisms and thermodynamic stability of the corrosion products.

  • 4.
    Dömstedt, Peter
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Lundberg, Mats
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Szakalos, Peter
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Corrosion Studies of Low-Alloyed FeCrAl Steels in Liquid Lead at 750 degrees C2019In: Oxidation of Metals, ISSN 0030-770X, E-ISSN 1573-4889, Vol. 91, no 3-4, p. 511-524Article in journal (Refereed)
    Abstract [en]

    New ductile experimental FeCrAl alloys, based on the composition of Fe-10Cr-4Al, were exposed to stagnant liquid lead at 750 degrees C for up to 1970h. Two exposures with different test conditions were performed: one with addition of oxygen (as H2O) to the liquid lead and one without. The experimental alloys showed generally good oxidation and self-healing properties. The exposures showed that this specific category of steels has the potential to operate in liquid lead at very high temperatures with only minor oxidation. With this new material development, new energy technologies such as the CSP plants may be able to utilize liquid lead at very high temperatures as heat transfer fluid, thus achieving increased thermal efficiency.

  • 5.
    Ejenstam, Jesper
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Halvarsson, M.
    Weidow, J.
    Jönsson, B.
    Szakalos, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Oxidation studies of Fe10CrAl-RE alloys exposed to Pb at 550 C for 10,000 h2013In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 443, no 1-3, p. 161-170Article in journal (Refereed)
    Abstract [en]

    Five experimental FeCrAl-RE alloys have been exposed up to 10,000 h in stagnant liquid Pb at 550 C. The test matrix consisted of three 10 wt.% Cr alloys, with an Al content ranging from 4 to 8 wt.% (10Cr-4Al, 10Cr-6Al and 10Cr-8Al), one alloy without additions of reactive elements (RE) (10Cr-6Al), and one reference alloy with 21 wt.% Cr and 5 wt.% Al (21Cr-5Al). The evaluation showed a clear difference in oxidation properties, and it was possible to divide the alloys into two distinct groups. A critical Al concentration in the interval of 4-6 wt.% at the given RE content was required to form a thin protective oxide. However, the absence of RE addition in one of the two 10Cr-6Al alloys resulted in a significant reduction in oxidation resistance, comparable with 10Cr-4Al. None of the alloys were severely corroded, however Pb penetrated to a relatively large extent into the porous oxide of the low performing alloys. A 100 nm thick oxide scale, partly consisting of alumina (Al2O 3), was observed for the high performing 10Cr-6Al alloy. The Fe10CrAl-RE alloys showed overall very good corrosion resistance and are hence a promising new alloy category for liquid Pb applications.

  • 6.
    Ejenstam, Jesper
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. Sandvik Heating Technology AB.
    Jonsson, Bo
    Szakalos, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Optimizing the Oxidation Properties of FeCrAl Alloys at Low Temperatures2017In: Oxidation of Metals, ISSN 0030-770X, E-ISSN 1573-4889, Vol. 88, no 3-4, p. 361-370Article in journal (Refereed)
    Abstract [en]

    FeCrAl alloys are proposed candidate materials for liquid lead applications. Chromium is needed to assist the formation of a protective alumina layer, albeit has to be limited to avoid alpha' precipitation. Reactive elements (RE) improve oxidation properties, but little is known about the RE effects at lower temperatures. An alloy matrix based on Fe-10Cr-4Al (wt%), with varying Zr, Y and Ti contents, was exposed to liquid lead up to 1 year in the temperature interval of 450-550 A degrees C. It was found that the formation of protective alumina was dependent on the RE/carbon ratio. All alloys with ratios lower than unity showed poor oxidation properties due to the formation of Cr-carbides in the metal-oxide interface. A sufficiently high amount of Zr and Ti was shown to significantly improve the oxidation properties at both temperatures. The positive effect is related to the suppression of Cr-carbides by addition of stronger carbide formers.

  • 7.
    Ejenstam, Jesper
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Jönsson, Bo
    Szakalos, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Optimizing the oxidation properties of FeCrAl alloys at low temperaturesManuscript (preprint) (Other academic)
  • 8.
    Ejenstam, Jesper
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Szakalos, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Long term corrosion resistance of alumina forming austenitic stainless steels in liquid lead2015In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 461, p. 164-170Article in journal (Refereed)
    Abstract [en]

    Alumina forming austenitic steels (AFA) and commercial stainless steels have been exposed in liquid lead with 10-7 wt.% oxygen at 550 °C for up to one year. It is known that chromia forming austenitic stainless steels, such as 316L and 15-15 Ti, have difficulties forming protective oxides in liquid lead at temperatures above 500°C, which is confirmed in this study. By adding Al to austenitic steels, it is in general terms possible to increase the corrosion resistance. However this study shows that the high Ni containing AFA alloys are attacked by the liquid lead, i.e. dissolution attack occurs. By lowering the Ni content in AFA alloys, it is possible to achieve excellent oxidation properties in liquid lead. Following further optimization of the microstructural properties, low Ni AFA alloys may represent a promising future structural steel for lead cooled reactors.

  • 9.
    Ejenstam, Jesper
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Thuvander, Mattias
    Olsson, Pär
    KTH, School of Engineering Sciences (SCI), Physics, Reactor Physics.
    Rave, Fernando
    Szakalos, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Microstructural stability of Fe–Cr–Al alloys at 450–550 °C2015In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 457, p. 291-297Article in journal (Refereed)
    Abstract [en]

    Iron–Chromium–Aluminium (Fe–Cr–Al) alloys have been widely investigated as candidate materials for various nuclear applications. Albeit the excellent corrosion resistance, conventional Fe–Cr–Al alloys suffer from α–α′ phase separation and embrittlement when subjected to temperatures up to 500 °C, due to their high Cr-content. Low-Cr Fe–Cr–Al alloys are anticipated to be embrittlement resistant and provide adequate oxidation properties, yet long-term aging experiments and simulations are lacking in literature. In this study, Fe–10Cr–(4–8)Al alloys and a Fe–21Cr–5Al were thermally aged in the temperature interval of 450–550 °C for times up to 10,000 h, and the microstructures were evaluated mainly using atom probe tomography. In addition, a Kinetic Monte Carlo (KMC) model of the Fe–Cr–Al system was developed. No phase separation was observed in the Fe–10Cr–(4–8)Al alloys, and the developed KMC model yielded results in good agreement with the experimental data.

  • 10.
    Ekström, Madeleine
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Mechanical Metallurgy.
    Szakalos, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Jonsson, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Mechanical Metallurgy.
    Influence of Cr and Ni on High-Temperature Corrosion Behavior of Ferritic Ductile Cast Iron in Air and Exhaust Gases2013In: Oxidation of Metals, ISSN 0030-770X, E-ISSN 1573-4889, Vol. 80, no 5-6, p. 455-466Article in journal (Refereed)
    Abstract [en]

    Due to an expected temperature increase of the exhaust gases in heavy-duty engines in order to meet future emission regulations, there is a need to develop materials that can operate at higher temperatures. The exhaust manifold in the hot end of the exhaust system is specifically affected since the most common material today, SiMo51, is already operating close to its limits. Accordingly, the effects of Cr and Ni-additions on the high-temperature corrosion resistance of this material in air and exhaust gases were examined. It was found that the addition of 0.5 and 1 wt% Cr improved the oxidation resistance in air at 700 and 800 A degrees C by the formation of an SiO2 barrier layer as well as a Cr-oxide at the oxide/metal interface. However, no Cr-oxide was detected after exposure to exhaust gases, probably due to a water vapor-assisted evaporation of Cr from the oxide. The addition of 1 wt% Ni resulted in a deteriorated SiO2 barrier layer and reduced oxidation resistance.

  • 11.
    Ekström, Madeleine
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Mechanical Metallurgy.
    Zhu, B.
    Scania.
    Szakalos, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Jonsson, Stefan
    An electrochemical impedance spectroscopy study on the effect of condensate on oxides formed on a 25Cr/20Ni cast stainless steel in exhaust environmentsManuscript (preprint) (Other academic)
    Abstract [en]

     Condensation of diesel exhaust gases inside an exhaust- or turbo manifold may occur during cold-start and cooling of an engine, resulting in acidic liquid covering the oxide surfaces inside the manifolds. In the present study, the interaction between a chloride-containing exhaust-gas condensate of pH 2.4 and oxide scales formed on a 25Cr/20Ni cast stainless steel in air and in two different exhaust environments, 10%H2O-5%O2-85%N2 and 10%H2O-5%CO2-85%N2, at 900°C has been examined by means of electrochemical impedance spectroscopy, EIS. Interpretation of impedance spectra was coupled to oxide scale structures, revealed by SEM, EDX, XRD and GDOES, and to metal release studies using ICP. It was observed that the acidic condensate caused oxide spallation, followed by corrosion of the underlying metal surface for all test samples. The metal release rate of the oxide scale and underlying alloy was found to decrease at longer immersion times (>1h), most likely due to precipitation of corrosion products on the surfaces. EIS combined with equivalent circuit fitting showed to be a useful technique in describing the electric properties of the oxide scales, suggesting oxidation in H2O/O2 to result in formation of oxide scales being more resistive compared to the other environments. This was coupled to higher thickness and higher defect density, which correlated well with oxide scale analysis.

  • 12.
    Hedberg, Yolanda
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Karlsson, Oskar
    Szakalos, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Wallinder, Inger Odnevall
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Ultrafine 316 L stainless steel particles with frozen-in magnetic structures characterized by means of electron backscattered diffraction2011In: Materials letters (General ed.), ISSN 0167-577X, E-ISSN 1873-4979, Vol. 65, no 14, p. 2089-2092Article in journal (Refereed)
    Abstract [en]

    Electron Backscatter Diffraction (EBSD) studies clearly revealed a different crystallographic structure of the smallest particle size fraction of gas-atomized AISI 316 L stainless steel powder (<4 mu m) compared with larger sized fractions of the same powder (<45 mu m). Despite similar chemical compositions, the predominating structure of the smallest particle size fraction was ferritic (i.e., has ferromagnetic properties) whereas the larger sized particle fractions and massive 316 L revealed an expected austenitic and non-magnetic structure. From these findings, it follows that direct magnetic separation can be applied to separate very fine sized particles. These structural differences explain previously observed dissimilarities from corrosion and metal release perspectives.

  • 13.
    Hedberg, Yolanda
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Norell, Mats
    Materials and Manufacturing Technology, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden.
    Hedberg, Jonas
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Szakálos, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Linhardt, Paul
    Institute for Chemical Technologies and Analytics (CTA), Vienna University of Technology, Getreidemarkt 9/164, A-1060 Vienna, Austria.
    Odnevall Wallinder, Inger
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Surface characterisation of fine inert-gas- and water-atomised stainless steel 316L powders - formation of thermodynamically unstable surface oxide phases2013In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 56, no 2, p. 158-163Article in journal (Refereed)
    Abstract [en]

    New insights are presented on the speciation of surface oxide phases on fine inert gas atomised (GA, <45 and <4 mu m) and water atomised (WA, <45 mu m) stainless steel AISI 316L powders. X-ray photoelectron and Auger electron spectroscopy, scanning electron microscopy, Raman spectroscopy, and cyclic voltammetry were applied for the characterisation. Oxidised manganese was strongly enriched in the outermost surface oxide of the GA powders (13 and 47 wt-%), an effect increasing with reduced particle size. Manganese and sulphur were enriched in oxide nanoparticles on the surface. Oxidised silicon (59 wt-%) was enriched on the WA powder surface. Tri-or tetravalent manganese oxides were observed on the GA particles in addition to alpha-Fe2O3, and Cr2O3. The oxide of the WA powder revealed in addition the likely presence of a silicate rich phase, mainly consisting of tetravalent Si, di- and/or trivalent Fe, and hexavalent Cr, which was confirmed not present as chromate.

  • 14.
    Henderson, Pamela
    et al.
    Vattenfall Research and Development.
    Andersson, Christer
    Vattenfall Research and Development.
    Szakalos, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Kassman, Håkan
    Vattenfall Research and Development.
    Högberg, Jan
    Pettersson, Rachel
    Reducing superheater corrosion in wood-fired boilers2008In: Novel approaches to improving high temperature corrosion resistance: European Federation of Corrosion Publications number 47 / [ed] M Schütze and W.J. Quadakkers, Woodhead Publishing Limited, 2008, p. 428-444Chapter in book (Refereed)
    Abstract [en]

    In the last few years, there has been a move away from burning fossil fuels through the co-utilisation of biomass and coal and finally to 100% biomass such as wood and waste wood products. Unfortunately, burning of biomass causes widespread fouling of superheater tubes and corrosion can occur rapidly under the sticky alkali chloride deposits. Even at today's maximum steam temperatures of 500 to540°C there are some severe corrosion problems when burning  100% wood-based fuel. It is also desirable to be able to burn other environmental fuels such as straw, demolition wood or other wood-waste products, to reduce production costs and avoid dumping waste at landfill sites. This, however, makes the corrosion and fouling problems even more serious. 

     A complete set of superheaters for a 100 MW combined heat and power boiler costs in excess of 1 MEuro. The durability of superheaters is thus an important factor in determining the long-term production costs. Unplanned outages due to leaking superheaters are also very expensive. As well as causing corrosion problems, the build-up of deposits reduces the heat uptake to the superheaters which leads to lower efficiency. Consequently, ways are being sought to reduce superheater corrosion.

    Most biomass fuels have a high content of alkali metals and chlorine, but they contain very little sulphur compared to fossil fuels. Potassium chloride, KCl, is found in the gas phase, condenses on the superheater tubes and forms complex alkali salts with iron and other elements in the steels. These salts have low melting points and are very corrosive. Vattenfall has developed and patented an instrument for in-situ measurement of gaseous alkali chlorides which gives an indication of how corrosive the flue gases are.  This instrument is called an in-situ alkali chloride monitor (IACM).  Vattenfall has also developed and patented a concept with a sulphate containing compound called “ChlorOut” , which is sprayed into the flue gases after combustion is complete, but before the flue gases reach the superheaters, and effectively converts KCl into potassium sulphate, K2SO4.  This compound much less corrosive than KCl.  In the experiments reported here the sulphate used in ChlorOut was ammonium sulphate. This is also used for the reduction of NOx.

     This study reports on measures taken to reduce superheater corrosion in two fluidised bed boilers burning wood-based fuels, using the ChlorOut additive to control the KCl levels and by using more corrosion-resistant steels.

  • 15.
    Henderson, Pamela
    et al.
    Vattenfall Research and Development.
    Szakalos, Peter
    Swedish Institute for Metals Research.
    Pettersson, Rachel
    Andersson, Christer
    Högberg, Jan
    Reducing superheater corrosion in wood-fired boilers2006In: Materials and corrosion - Werkstoffe und Korrosion, ISSN 0947-5117, E-ISSN 1521-4176, Vol. 57, no 2, p. 128-134Article in journal (Refereed)
    Abstract [en]

    One of the major drawbacks to the combustion of 100% biomass in power station boilers is the increase in the fouling and corrosion of superheaters. Experience shows that conventional superheater steels last no more than 20 000 h or four operating years before they must be replaced, if 100% wood-based fuel is used and the steam temperature is higher than 480C. Rapid corrosion of superheaters leads to increased maintenance costs while widespread deposit formation gives rise to a decrease in efficiency of the turbine and an increase in unplanned outages.

    This paper reports on measures taken to reduce superheater corrosion. Most biomass fuels have a high content of alkali metals and chlorine, but they contain very little sulphur compared to fossil fuels. Potassium chloride, KCl, is found in the gas phase, condenses on the superheater tubes and forms complex alkali salts with iron and other elements in the steels. These salts have low melting points and are very corrosive. The corrosion can be mitigated by use of an instrument for in-situ measurement of alkali chlorides in the flue gases, in combination with the addition of ammonium sulphate.  An ammonium sulphate solution, specially developed for the reduction of corrosion was sprayed into the flue gases and effectively converted KCl into potassium sulphate, K2SO4, much less corrosive than KCl.

    Deposit probe tests and long-term corrosion probe tests have been performed in-situ in two biomass-fired fluidised bed boilers. One boiler, 105 MW tot, 540C steam, is the CHP plant in Nyköping,Sweden. The other producing 98 MWtot, 480C steam, is a bark-fired boiler at a pulp and paper mill in Munksund, also in Sweden. Tests have been performed with a range of steel types, ferritic and austenitic, with ammonium sulphate additive and under normal conditions (no additive). Corrosion rates have been measured, deposit chemistry analysed and flue gas chemistry and KCl content measured. The structure and composition of the oxide with and without ammonium sulphate has been investigated. The results show that ammonium sulphate reduced the KCl levels in the flue gases, removed the chlorides from the deposits and the metal/oxide interface, greatly reduced the deposition rates and halved the corrosion rates for superheater materials. The alkali chloride measuring system and the use of ammonium sulphate for the reduction of corrosion have now been patented.

  • 16.
    Hultquist, Gunnar
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science.
    Anghel, Clara
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science.
    Szakalos, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science.
    Effects of hydrogen on the corrosion resistance of metallic materials and semiconductors2006In: High-Temperature Oxidation And Corrosion 2005 / [ed] Taniguchi, S; Maruyama, T; Yoshiba, M; Otsuka, N; Kawahara, Y, 2006, Vol. 522-523, p. 139-146Conference paper (Refereed)
    Abstract [en]

    For long time it is known that protons in aqueous solutions have a detrimental effect on metallic materials. Relatively recently, it has also been observed in aqueous solution that the pitting corrosion resistance of Cr, stainless steel 304 and 310 decreases and the anodic dissolution rate increases due to the presence of hydrogen in the metal. In gas phase a high oxidation rate has been observed for hydrogen containing Cr and Fe. Hydrogen in the substrate can also enhance the oxidation of Fe in SS 316 and As in GaAs. All these results suggest enhanced dissolution in aqueous solution and enhanced oxide growth at the oxide/gas interface in gas phase oxidation due to hydrogen promoted outward-transport of substrate components. A possible mechanism for such out-transport is an increased metal ion diffusivity in the metal-oxide due to a high abundance of metal ion vacancies generated by hydrogen. In contrast to all the above examples, also positive effects of hydrogen have been identified under certain conditions. In an attempt to understand both the negative and the positive effects the concept of a beneficial, balanced oxide growth is used. In this concept a certain amount of hydrogen can be beneficial in the oxidation by improving the balance between oxygen-ion and metalion transport, leading to more dense and protective oxides. Depending on the temperature, H(2) in air is considered as either a sink or a source for hydrogen in materials.

  • 17.
    Hultquist, Gunnar B.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science (closed 20081231).
    Szakálos, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science (closed 20081231).
    Graham, M. J.
    Sproule, G. I.
    Wikmark, G.
    Detection of hydrogen in corrosion of copper in pure water2008In: Int. Corros. Congr.: Corros. Control Serv. Soc., 2008, p. 2378-2386Conference paper (Refereed)
    Abstract [en]

    Copper is generally assumed to be immune to corrosion by water itself. However, this is not supported by any scientific experimental evidence. Corrosion results from 15 years of exposure are presented here. A transition from O 2-consuming to H 2-evolving copper corrosion is concluded, which implies that copper can corrode by water itself. The complex corrosion product contains hydrogen. We have also measured a hydrogen uptake in the copper metal as a result of metallic copper corrosion by water which implies a sample thickness dependence on hydrogen uptake. The results are described in terms of autoionisation of water which offers an explanation why copper corrosion can take place in pure O 2-free water.

  • 18.
    Hultquist, Gunnar
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science.
    Szakalos, Peter
    Catalysed self-cleaning of air on the earth's surface2006In: Journal of Atmospheric Chemistry, ISSN 0167-7764, E-ISSN 1573-0662, Vol. 55, no 2, p. 131-146Article in journal (Refereed)
    Abstract [en]

    Generally, it is assumed that UV-light, high temperature or reactive molecules like O-3 and OH are needed to activate gas reactions in air. In consequence, the catalytic activity on natural materials such as sand and soil on the earth's surface is assumed to be insignificant. We have measured O-2-dissociation rates on natural quartz sand at 40 degrees C and compared these with O-2-dissociation rates near 500 degrees C on materials with well-known catalytic activity. In terms of probabilities for dissociation of impinging O-2-molecules the measured rates are in the 10(-12)-10(-4) range. We have also measured dissociation rates of H-2 and N-2, water-formation from H-2 and O-2 mixtures, exchange of N between N-2, NO (x) and a breakdown of HNO3, NO2 and CH4 on natural quartz sand at 40 degrees C. The measured rates together with an effective global land area have been used to estimate the impact of thermodynamically driven reactions on the earth's surface on the global atmospheric budgets of H-2, NO2 and CH4. The experimental data on natural quartz sand together with data from equilibrium calculations of air suggest that an expected increase in anthropogenic supply of air pollutants, such as NO (x) or other reactive nitrogen compounds, hydrogen and methane, will be counter-acted by catalysis on the earth's surface. On the other hand, at Polar Regions and boreal forests where the reactive nitrogen concentration is below equilibrium, the same catalytic effect activates formation of bio-available nitrogen compounds from N-2, O-2 and H2O.

  • 19.
    Hultquist, Gunnar
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Szakalos, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Graham, M. J.
    Belonoshko, Antoly B.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Condensed Matter Theory.
    Sproule, G. I.
    Grasjo, L.
    Dorogokupets, P.
    Danilov, B.
    Aastrup, T.
    Wikmark, G.
    Chuah, G. K.
    Eriksson, Jan Christer
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Rosengren, Anders
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Condensed Matter Theory.
    Water Corrodes Copper2009In: Catalysis Letters, ISSN 1011-372X, E-ISSN 1572-879X, Vol. 132, no 3-4, p. 311-316Article in journal (Refereed)
    Abstract [en]

    According to a current concept, copper canisters of thickness 0.05 m will be safe for nuclear waste containment for 100,000 years. We show that more than 1 m copper thickness might be required for 100,000 years durability based on water exposures of copper for 20 h, 7 weeks, 15 years, and 333 years. An observed evolution of hydrogen which involves heterogeneous catalysis of molecular hydrogen, first principles simulations, thermodynamic considerations and corrosion product characterization provide further evidence that water corrodes copper resulting in the formation of a copper hydroxide. These findings cast additional doubt on copper for nuclear waste containment and other important applications.

  • 20. Lambrinou, K.
    et al.
    Lapauw, T.
    Jianu, A.
    Weisenburger, A.
    Ejenstam, Jesper
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Szakálos, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Wallenius, Janne
    KTH, School of Engineering Sciences (SCI), Physics, Reactor Physics.
    Ström, E.
    Vanmeensel, K.
    Vleugels, J.
    Corrosion-resistant ternary carbides for use in heavy liquid metal coolants2016In: Ceramic Engineering and Science Proceedings, 2016, no 7, p. 19-34Conference paper (Refereed)
    Abstract [en]

    A primary concern in the development of accelerator-driven systems (ADS) with liquid leadbismuth eutectic (LBE) spallation target and Gen-IV lead-cooled fast reactors (LFRs) is the compatibility of the candidate structural steels with the heavy liquid metal (HLM) coolant In the accelerator-driven system MYRRHA, the envisaged primary coolant is liquid LBE, a potentially corrosive environment for various nuclear grade steels. The inherent LBE corrosiveness is the driving force behind diverse research incentives aiming at the development of corrosion-resistant materials for specific applications. I3ue to their superb corrosion resistance in contact with liquid LBE, MAX phases are currently being assessed as candidate materials for the construction of pump impellers suitable for MYRRHA and Gen-IV LFRs. In the case of the MYRRHA nuclear system, the pump impeller will be called to operate reliably at ∼270°C in contact with moderately-oxygenated (concentration of dissolved oxygen: [O] ≥ 7×10-7 mass%), fast-flowing LBE (LBE flow velocity: v ≈ 10-20 m/s locally on the impeller surface). Selected MAX phases are currently being screened with respect to their capability of meeting the targeted material property requirements, especially the enhanced erosion resistance requested by this particular application. This work gives a state-of-the-art overview of the processing and characterisation of selected MAX phases that are screened as candidate structural materials for the MYRRHA pump impeller. All considered MAX phases were produced via a powder metallurgical route and their performance was assessed by various mechanical tests in air/vacuum and corrosion/erosion tests in liquid LBE.

  • 21. Piticescu, R. R.
    et al.
    Cuesta-Lopez, S.
    Rinaldi, A.
    Urbina, M.
    Qin, Y.
    Szakalos, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Largeteau, A.
    SUPERMAT – A virtual center for sustainable development of advanced materials operating under extreme conditions2016In: Physica Status Solidi (C) Current Topics in Solid State Physics, ISSN 1862-6351, Vol. 13, no 10-12, p. 1023-1027Article in journal (Refereed)
    Abstract [en]

    The expertise, main experimental facilities and some selected results of the EU SUPERMAT Consortium are described, showing the importance of integrating modelling and simulation, fast sintering and coating technologies and specific characterisation techniques for obtaining high temperature ceramics, oxide dispersion strengthened (ODS) steels or Li-ion batteries with controlled properties for extreme environmental applications.

  • 22.
    Szakalos, Peter
    KTH, Superseded Departments, Materials Science and Engineering.
    Mechanisms and driving forces of metal dusting2003In: Materials and corrosion - Werkstoffe und Korrosion, ISSN 0947-5117, E-ISSN 1521-4176, Vol. 54, no 10, p. 752-762Article in journal (Refereed)
    Abstract [en]

    The mechanisms of metal dusting as it appears on different ferritic stainless steels and pure iron have been described in detail. A mechanism for metal dusting (MD) of chromia-forming as well as alumina-forming steels is proposed, based on results from laboratory exposures of 26Cr-steel and FeCrAl-alloy at 600-650 C for up to 5000 h in a synthesis gas tow, in water vapour, 25%CO + 3%H2O + H-2. Metallographical examinations, FEG-SEM, SEM-EDX analysis and X-ray diffraction. as well as thermodynamic calculations were made in order to identify and describe the different metal dusting processes. The work focuses on the role of carbides and oxides to explain the observations and give a description of the metal dusting phenomenon as it appears in engineering alloys. This mechanism was first observed and identified in a study of an austenitic stainless steel. The driving force for steady state MD on pure iron and low alloyed steels is described and a secondary MD-mechanism, carbon nanotube formation. is described in detail. With these additional results it is now possible to extend understanding of the MD-processes to a wide range of engineering alloys.

  • 23. Szakalos, Peter
    et al.
    Hertzman, Staffan N.
    Pettersson, R. F. A.
    Ivarsson, B.
    The effect of surface condition and cold work on the sulphidation resistance of 153MA at 700 degrees C2000In: Materials and corrosion - Werkstoffe und Korrosion, ISSN 0947-5117, E-ISSN 1521-4176, Vol. 51, no 5, p. 313-316Article in journal (Refereed)
    Abstract [en]

    The normal grain sized 153MA-sample experienced an almost linear weight gain curve in the sulphidizing environment while modified materials, with a finer grain size or cold worked structure, displayed more parabolic behaviour and lower weight gains. These effects may be related to more effective Cr-diffusion in the modified samples with a higher Cr-grain boundary diffusion in the fine grain-sample and a higher Cr-bulk diffusion rate in the cold worked sample. The sand blasted sample performed exceedingly well with a thin protective oxide layer compared to the etched and ground samples which both suffered significant weight loss and spalling. The deformed surface structure on the sand blasted sample enhances the Cr-bulk diffusion thus promoting a protective Cr-rich oxide formation.

  • 24. Szakalos, Peter
    et al.
    Hultquist, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science.
    Wikmark, G.
    Corrosion of copper by water2007In: Electrochemical and solid-state letters, ISSN 1099-0062, E-ISSN 1944-8775, Vol. 10, no 11, p. C63-C67Article in journal (Refereed)
    Abstract [en]

    We have studied copper corrosion in a system comprised of deionized water, absolute pressure gauges, and a palladium membrane. A transition from O-2-consuming to H-2-evolving copper corrosion is observed, which indicates that copper can corrode by water itself. The equilibrium hydrogen pressure in corrosion of copper by water at 73 degrees C exceeds the steady-state atmospheric hydrogen pressure (5 x 10(-7) bar) by a factor of about 2000. The growth of a hydrogen-containing corrosion product in O-2-free water is controlled by the hydrogen removal from the corroding surface. The results are discussed in the perspective of conventional potential-pH diagram for copper.

  • 25.
    Szakalos, Peter
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Lindblom, J
    Lindé, L
    Carburizing of chromia and alumina forming stainless steels at 750°C1999In: 14th International Corrosion Congress (ICC), Cape Town, South Africa, Sept., 1999., 1999, p. Paper 153-Conference paper (Other academic)
  • 26.
    Szakalos, Peter
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Lundberg, M.
    Pettersson, R.
    Metal dusting on an alumina forming Ni-base alloy2006In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 48, no 7, p. 1679-1695Article in journal (Refereed)
    Abstract [en]

    A high-performance commercial alumina-forming Ni-base alloy was studied after a 2 years field exposure at 540 degrees C in a methanol plant with a gas composition of 10-20%CO and 20-40%H2O, with some CO2 and the remainder H-2. The same material was also used in laboratory studies performed at 650 degrees C Using a gas mixture With higher CO and lower H-2,O content: 50%CO + 3%H2O + 47H(2) (carbon activity a(c) = 39). Post-exposure metallographic examinations together with thermodynamic calculations were used to identify and describe the metal dusting processes. A growth mechanism for metal dusting in nickel base alloys, which is independent of metal bulk diffusion, is identified. The process involves it separation of the carbon-saturated metal into a network of discontinuous precipitated carbides and a depleted Ni-austenite matrix followed by selective oxidation of the carbide network. The corrosion product consists of Cr-depleted Ni-particles, Cr-rich oxides and free carbon. The estimated metal dusting corrosion rate in the field exposure was 20-25 mu m/year. based on metallography and it was correlated to a theoretical model based on boundary diffusion processes.

  • 27.
    Szakalos, Peter
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Lundberg, M
    Pettersson, R
    The role of discontinuous precipitation in metal dusting2004In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 461-464, p. 561-570Article in journal (Refereed)
    Abstract [en]

    A high-performance commercial alumina-forming Ni-base alloy was studied after a two years field exposure at 540degreesC in a methanol plant. Comparative laboratory studies were performed at 650degreesC using a different synthesis gas mixture with the composition; 50%CO + 3%H2O + 47H(2). Post exposure metallographic examinations with LOM, FEG-SEM, SEMEDX analysis as well as thermodynamic calculations were made in order to identify and describe the metal dusting mechanisms. An estimate of the metal dusting corrosion rates was per-formed based on metallography and these were correlated to a theoretical model based on diffusion processes.

  • 28.
    Szakalos, Peter
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Pettersson, R.
    Hertzman, Staffan N.
    An active corrosion mechanism for metal dusting on 304L stainless steel2002In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 44, no 10, p. 2253-2270Article in journal (Refereed)
    Abstract [en]

    A mechanism for metal dusting of chromia-forming stainless steels is proposed, based on results from laboratory exposures of 304L stainless steel at 650 degreesC for 1000 h in a synthesis gas low in water vapour, 25%CO + 3%H2O + H. The work focuses on the role of carbides and oxygen to explain the different corrosion mechanisms and give a description of the metal dusting phenomenon as it appears in engineering alloys. Metallographical examinations, FEG-SEM, SEM-EDX analysis and X-ray diffraction, as well as thermodynamic calculations were made in order to identify the proposed metal dusting mechanism.

  • 29.
    Szakalos, Peter
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Åkermark, T.
    Rost & Ratt, Ugglev 32C, S-13141 Nacka, Sweden..
    Leygraf, Christopher
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Comments on the paper "Copper in ultrapure water, a scientific issue under debate" by M. Ottosson, M. Boman, P. Berastegui, Y. Andersson, M. Hahlin, M. Korvela, and R. Berger2018In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 142, p. 305-307Article in journal (Refereed)
  • 30.
    Szakálos, Peter
    KTH, Superseded Departments, Materials Science and Engineering.
    Mechanisms of Metal Dusting2004Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The primary intention with this Doctoral thesis is to fillin the knowledge gaps and raise the level of understandingregarding the different metal dusting mechanisms in general andexplain the process in detail for high alloyed materials.Considerable effort is put into identifying the driving forcesand elucidating the diffusional processes in metal dusting.

    The results are based on a series of long-term laboratory exposures of stainless steels and high-performance commercial alumina-forming Fe- and Ni-base alloys in synthesis gasmixtures, plus a separate shorter study on ultra pure iron. ANi-base alloy was also investigated after a two years field exposure in a methanol plant.

    Post exposure metallographic examinations and analysis aswell as thermodynamic calculations were made in order toidentify and describe the operating metal dusting mechanisms.Two main mechanisms were previously used to explain metaldusting, one on the basis of decomposition of metastable carbides (Type I) the other on graphite formation (TypeII).

    A new metal dusting mechanism has been identified in this Thesis which appears on high alloyed steels and Ni-base alloys,an active corrosion induced by carbon and oxygen, denoted TypeIII. Both the mechanisms and the type of corrosion products were consistent with the thermodynamic conditions of the material under the influence of a carbon and oxygen gradient.It was shown that this mechanism not only accelerates the metaldusting process, in fact, it determines the overall metaldusting kinetics on stainless steels and Ni-base alloys.

    Another feature, which may occur at temperatures where metalbulk and even static grain boundary diffusion is too slow forexplaining the metal dusting corrosion process, was identifiedon a Ni-base alloy. It involves a fast growing cellular structure with discontinuous precipitated carbides whichprovides fast metal dusting kinetics by the Type IIImechanism.

    A Type IV metal dusting mechanism, continued fragmentationby graphitization until nano-sized particles are formed andcatalyse carbon nanotube formation is also described. Thesteady state process and the driving force for metal dusting onpure iron was identified and described.

    With these additional processes it is now possible to extendour understanding of the metal dusting processes to a widerange of engineering alloys.

     

  • 31.
    Szakálos, Peter
    KTH, Superseded Departments, Materials Science and Engineering.
    Mechanisms of metal dusting on stainless steels2002Licentiate thesis, comprehensive summary (Other scientific)
  • 32.
    Szakálos, Peter
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Liu, L
    Mechanisms of metal dusting: Application to alloycomposition, temperature and pressure2002In: 15th International CorrosionConference (ICC), Granada, Sept., 2002., 2002, p. Paper 806-Conference paper (Other academic)
  • 33.
    Wallenius, Janne
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Engineering. LeadCold Reactors, Valhallavagen 79, S-11428 Stockholm, Sweden.
    Qvist, S.
    LeadCold Reactors, Valhallavagen 79, S-11428 Stockholm, Sweden..
    Mickus, Ignas
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Engineering. LeadCold Reactors, Valhallavagen 79, S-11428 Stockholm, Sweden.
    Bortot, Sara
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Engineering. LeadCold Reactors, Valhallavagen 79, S-11428 Stockholm, Sweden.
    Szakalos, Peter
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. LeadCold Reactors, Valhallavagen 79, S-11428 Stockholm, Sweden.
    Ejenstam, Lina
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Design of SEALER, a very small lead-cooled reactor for commercial power production in off-grid applications2018In: Nuclear Engineering and Design, ISSN 0029-5493, E-ISSN 1872-759X, Vol. 338, p. 23-33Article in journal (Refereed)
    Abstract [en]

    In this paper, the conceptual design of a small lead-cooled nuclear reactor intended to replace diesel-power in off-grid applications is presented. In a vessel of dimensions making it transportable by air, the targeted design performance is to produce 3 MW of electrical power for up to 30 years without reloading of fuel. Consequently, the inner vessel can be sealed, delaying malevolent access to the nuclear fuel and improving security. Alumina forming alloys are applied to ensure long term corrosion protection of fuel cladding tubes, steam generator tubes and primary vessel over the operational temperature regime. Moreover, decay heat can be removed in a completely passive manner by natural convection from the core to the primary coolant and by thermal radiation from the primary vessel to the environment. Finally, the source term is such that relocation of population residing beyond 1 km from the reactor will not be required even in the case of a complete core melt.

1 - 33 of 33
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