| 1. |
- Aastrup, T., et al.
(författare)
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Experimental in situ studies of copper exposed to humidified air
- 2000
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Ingår i: Corrosion Science. - 0010-938X .- 1879-0496. ; 42:6, s. 957-967
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Tidskriftsartikel (refereegranskat)abstract
- Three complementary experimental techniques for in situ surface analysis have been combined for the first time in order to explore the chemistry and physics of a copper surface exposed to humidified air. Infrared reflection absorption spectroscopy, quartz crystal microbalance and atomic force microscopy provide a congruent picture of the processes occurring at the surface. At a given relative humidity, cuprous oxide forms according to an approximately logarithmic rate law. In addition, an aqueous adlayer of constant mass physisorbs on the surface. Increased relative humidity stimulates the physisorption of water and enhances the nucleation rate of oxide grains, thereby increasing the formation rate of cuprous oxide.
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| 2. |
- Aastrup, T., et al.
(författare)
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In situ studies of the initial atmospheric corrosion of copper influence of humidity, sulfur dioxide, ozone, and nitrogen dioxide
- 2000
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 147:7, s. 2543-2551
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Tidskriftsartikel (refereegranskat)abstract
- Infrared reflection absorption spectroscopy and quartz crystal microbalance, integrated into a one-surface analytical system, and complemented with tapping mode atomic force microscopy, has been used to explore the metal/atmosphere interfacial region under atmospheric pressure conditions. This unique combination of ill situ techniques, all possessing submonolayer sensitivity, has revealed information on the different accelerating roles of ozone (O-3) and nitrogen dioxide (NO2) on the SO2-induced atmospheric corrosion of copper. The formation of reaction products could be followed quantitatively with respect to chemical identity and kinetics. Exposure in SO2-containing humidified air resulted in CuSO3. xH(2)O-like species, formed atop a cuprous oxide, designated Cu2O, all over the copper surface. O-3 introduction resulted in an accelerated mass gain with an increased formation rate of both Cu2O and of CuSO4. xH(2)O all over the surface. NO2 introduction resulted in less mass gain than observed under SO2 and O-3, with no formation of new Cu2O, an initial oxidation of CuSO3. xH(2)O to CuSO4. xH(2)O, and with sulfite oxidation gradually replaced by copper nitrate formation, possibly as CuNO3(OH)(3) The formation rates of the dominating end products, CuSO4. xH(2)O in SO2/O-3 and Cu2NO3(OH)(3) in SO2/NO2 seemed to be limited by the supply of the gaseous constituents.
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| 3. |
- Adhikari, Arindam, et al.
(författare)
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Electrochemical behavior and anticorrosion properties of modified polyaniline dispersed in polyvinylacetate coating on carbon steel
- 2008
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 53:12, s. 4239-4247
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Tidskriftsartikel (refereegranskat)abstract
- Conducting polyaniline (Pani) was prepared in the presence of methane sulfonic acid (MeSA) as dopant by chemical oxidative polymerization. The Pani-MeSA polymer was characterized by FT-IR, UV-vis, X-ray diffraction (XRD) and impedance spectroscopy. The polyrner was dispersed in polyvinylacetate and coated oil carbon steel samples by a dipping method. The electrochemical behavior and anticorrosion properties of the coating, oil carbon steel in 3% NaCl were investigated using Open-circuit Potential (OCP) versus time of exposure, and electrochemical techniques including electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and cyclic voltammetry (CV). During initial exposure, the OCP dropped about 0.35 V and the interfacial resistance increased several times, indicating I certain reduction of the polymer and oxidation of the steel surface. Later the OCP shifted to the noble direction and remained at a stable value during the exposure up to 60 days. The EIS monitoring also revealed the initial change and later stabilization of the coating. The stable high OCP and low coating impedance Suggest that the conducting polymer maintains its oxidative state and provides corrosion protection for carbon steel through out the investigated period. The polarization curves and CV show that the conducting polymer coating induces a passive-like behavior and greatly reduces the corrosion of carbon steel.
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| 4. |
- Alipour, Yousef
(författare)
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High temperature corrosion in a biomass-fired power boiler : Reducing furnace wall corrosion in a waste wood-fired power plant with advanced steam data
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The use of waste (or recycled) wood as a fuel in heat and power stations is becoming more widespread in Sweden (and Europe), because it is CO2 neutral with a lower cost than forest fuel. However, it is a heterogeneous fuel with a high amount of chlorine, alkali and heavy metals which causes more corrosion than fossil fuels or forest fuel.A part of the boiler which is subjected to a high corrosion risk is the furnace wall (or waterwall) which is formed of tubes welded together. Waterwalls are made of ferritic low-alloyed steels, due to their low price, low stress corrosion cracking risk, high heat transfer properties and low thermal expansion. However, ferritic low alloy steels corrode quickly when burning waste wood in a low NOx environment (i.e. an environment with low oxygen levels to limit the formation of NOx). Apart from pure oxidation two important forms of corrosion mechanisms are thought to occur in waste environments: chlorine corrosion and alkali corrosion.Although there is a great interest from plant owners to reduce the costs associated with furnace wall corrosion very little has been reported on wall corrosion in biomass boilers. Also corrosion mechanisms on furnace walls are usually investigated in laboratories, where interpretation of the results is easier. In power plants the interpretation is more complicated. Difficulties in the study of corrosion mechanisms are caused by several factors such as deposit composition, flue gas flow, boiler design, combustion characteristics and flue gas composition. Therefore, the corrosion varies from plant to plant and the laboratory experiments should be complemented with field tests. The present project may thus contribute to fill the power plant corrosion research gap.In this work, different kinds of samples (wall deposits, test panel tubes and corrosion probes) from Vattenfall’s Heat and Power plant in Nyköping were analysed. Coated and uncoated samples with different alloys and different times of exposure were studied by scanning electron microscopy (SEM), energy dispersive x-ray analysis (EDX), X-ray diffraction (XRD) and light optical microscopy (LOM). The corrosive environment was also simulated by Thermo-Calc software.The results showed that a nickel alloy coating can dramatically reduce the corrosion rate. The corrosion rate of the low alloy steel tubes, steel 16Mo3, was linear and the oxide scale non-protective, but the corrosion rate of the nickel-based alloy was probably parabolic and the oxide much more protective. The nickel alloy and stainless steels showed good corrosion protection behavior in the boiler. This indicates that stainless steels could be a good (and less expensive) alternative to nickel-based alloys for protecting furnace walls.The nickel alloy coated tubes (and probe samples) were attacked by a potassium-lead combination leading to the formation of non-protective potassium lead chromate. The low alloy steel tubes corroded by chloride attack. Stainless steels were attacked by a combination of chlorides and potassium-lead.The Thermo-Calc modelling showed chlorine gas exists at extremely low levels (less than 0.1 ppm) at the tube surface; instead the hydrated form is thermodynamically favoured, i.e. gaseous hydrogen chloride. Consequently chlorine can attack low alloy steels by gaseous hydrogen chloride rather than chlorine gas as previously proposed. This is a smaller molecule than chlorine which could easily diffuse through a defect oxide of the type formed on the steel.
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| 5. |
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| 6. |
- Bahar, Babak, et al.
(författare)
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Corrosion-induced copper release from rain gutters
- 2008
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Ingår i: Metall (Berlin. 1947). - 0026-0746. ; 62:3, s. 129-135
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Tidskriftsartikel (refereegranskat)abstract
- While runoff rates from copper roofs have been extensively studied during the last years, corresponding studies from copper rain gutters have been missing. A laboratory investigation has been undertaken to examine the influence of important runoff water parameters on the copper runoff from rain gutters. At a given rainfall quantity, the release rate of copper increases with decreasing runoff water intensity and decreasing degree of gutter inclination, and with increasing runoff acidity and increasing Cu2+-ion concentration in the runoff water. A comparison of the predicted long-term copper release from the gutter-system compared to the roof on a real building suggests that less than 5% of the total copper runoff originates from the gutter. However, single rain events may result in higher release rates, especially during the initial rain portion.
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| 7. |
- Bahar, B., et al.
(författare)
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The interaction between concrete pavement and corrosion-induced copper runoff from buildings
- 2008
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Ingår i: Environmental Monitoring & Assessment. - : Springer Science and Business Media LLC. - 0167-6369 .- 1573-2959. ; 140:1-3, s. 175-189
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Tidskriftsartikel (refereegranskat)abstract
- Changes in chemical speciation of copper and the capacity of concrete pavement to retain copper in runoff water from external buildings have been investigated at urban field conditions, and in parallel laboratory experiments simulating outdoor scenarios. The research study showed the concrete surface to form a copper rich surface layer (approximate to 50 mu m thick) upon exposure, and a high capacity to significantly reduce the bioavailable fraction of released copper (20-95%). The retention capacity of copper varied between 5 and 20% during single runoff events in the laboratory, and between 10 and 40% of the total copper release during single natural runoff events. The capacity to retain and reduce the bioavailable fraction of non-retained copper increased with increasing wetness of the concrete surfaces, increasing pH of the runoff water and decreasing flow rates. Bioassay testing with bacterial and yeast bioreporters showed the bioavailable fraction of non-retained copper to be significantly lower than the total copper concentration in the runoff water, between 22 and 40% for bacteria and between 8 and 31% for yeast. The application of generated data to simulate a fictive outdoor scenario, suggests a significant reduction of bioavailable and total copper to background values during environmental entry as a result of dilution, and the interaction with solid surfaces, organic matter and complexing agents already in the drainage system.
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| 8. |
- Belonoshko, Anatoly B., et al.
(författare)
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First-principles study of hydrogen diffusion in α-Al 2O3 and liquid alumina
- 2004
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 69:2, s. 243021-243026
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the energetics and mobility of neutral hydrogen in alumina Al2O3 using ab initio density-functional calculations. The mobility of hydrogen was studied in corundum (α-Al2O 3) as well as in liquid alumina. Using both static as well as molecular-dynamics calculations, and applying classical transition state theory, we derive the temperature-dependent diffusivity of hydrogen in α-Al 2O3 as D(T)=(21.7 × 10-8 m 2/s)exp(-1.24 eV/kT). The corresponding diffusivity of hydrogen in liquid/amorphous alumina, derived directly from ab initio molecular dynamics calculations, is D(T)=(8.71 × 10-7 m2/s)exp(-0.91 eV/kT). The computed diffusivity compares very well to experimental data. We conclude that diffusion of neutral hydrogen through the bulk of alumina is a good approximation of the mechanism for hydrogen mobility in corrosion scales. The representation of grain-boundary structures by amorphous alumina is, probably, realistic at higher temperatures.
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| 9. |
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| 10. |
- Bertling, Sofia, et al.
(författare)
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Environmental effects of zinc runoff from roofing materials : a new multidisciplinary approach
- 2002
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Ingår i: Outdoor Atmospheric Corrosion. - 0803128967 ; , s. 200-215
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Konferensbidrag (refereegranskat)abstract
- The objective of this work is to study changes in concentration and bioavailability of zinc-containing runoff water, released from roofing materials, upon passage through soil. The experimental approach is based on simulating the interaction between zinc in artificial runoff water and soil in a column system. The total zinc concentration of runoff was substantially reduced when passing through the soil and suggests marked zinc retention, During a constant flow and supply of zinc into the soil, equivalent to three and a half years of precipitation in Stockholm, a zinc retention capacity of approximately 99% was recorded, Not only the total concentration, but also the bio-available portion of the total zinc concentration was reduced after passage through soil, Most of the retained zinc was located in top 3 cm of the soil core and suggests the total capacity for zinc retention of the investigated soil to be about 140 years per kilogram soil in an isolated system in real systems, changes of temperature, pH, microbial activity, weathering of minerals and deposition of new organic material must be considered. The results form part of the effect assessment, preceding future risk assessment of the environmental effects of dispersed zinc.
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