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  • hot corrosion  (4)
  • Biochemistry and Biotechnology  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Role of platinum in the Na2SO4-Induced hot corrosion resistance of aluminum duffusion coatings (1984)
    Springer
    Oxidation of metals 22 (1984), S. 59-81 
    Details
    ISSN: 1573-4889
    Keywords: Al-diffusion coating ; platinum ; hot corrosion ; acidic and basic fluxing ; sulfate melt
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Electrochemical corrosion measurements have been carried out with Pt-containing and Pt-free Al-diffusion coatings on IN 738 LC in a 90Na2SO4+ 10K2SO4 (mol%) melt at 1173 K. Pt improves the resistance to basic fluxing while there are no significant differences between both coating types in their resistance to acidic fluxing. The corrosion resistance of the Pt-containing coating is also higher in the passive potential region where protective scales rich in Al2O3 are formed. The reason for the different behavior of both coating types appears to be related to the high corrosion resistance of the Pt-rich surface layer of the coating and an increased Al2O3 content in the scale of the Pt-containing type.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00659249
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  • 2
    Electronic Resource
    Electronic Resource
    The corrosion of Ni3Al in a combustion gas with and without Na2SO4-NaCl deposits at 600–800°C (1994)
    Springer
    Oxidation of metals 42 (1994), S. 265-284 
    Details
    ISSN: 1573-4889
    Keywords: Ni3Al intermetallic compound ; combustion gas ; hot corrosion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The corrosion behavior of Ni3Al containing small additions of Ti, Zr, and B in combustion gases both with and without Na2SO4−NaCl deposits at 600–800°C has been studied for times up to four days. The corrosion of the saltfree Ni3Al leads to the formation of very thin alumina scales at 600°C but of mixed NiO−Al2O3 scales containing also some sulfur compounds at higher temperatures, while the rate increases with temperature up to 800°C. The presence of the salt deposits considerably accelerates the corrosion rate, especially at 600 and 800°C. The duplex scales formed at 600°C are composed mostly of a mixture of NiO and unreacted salt in the outer layer and of alumina and aluminum sulfide with some nickel compounds in the inner layer. The scales grown at 700°C contain only one layer of complex composition, while those grown at 800°C are similar but have an additional outer layer containing similar amounts of nickel and aluminum. At 600 and 700°C NiSO4 can be detected also in the salt layer. The samples corroded at 700°C and 800°C also show an Al-depleted zone containing titanium sulfide precipitates at the surface of the alloy. The hot corrosion of Ni3Al involves a combination of various mechanisms, including fluxing of the oxide scale as well as mixed oxidation-sulfidation attack. At all temperatures Ni3Al shows poor resistance to hotcorrosion attack as a result of the formation of large amounts of Ni compounds in the scales.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01052027
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  • 3
    Electronic Resource
    Electronic Resource
    The corrosion of Nb-modified Ti3Al in a combustion gas with and without Na2SO4−NaCl deposits at 600–800°C (1994)
    Springer
    Oxidation of metals 42 (1994), S. 393-408 
    Details
    ISSN: 1573-4889
    Keywords: Nb-modified Ti3Al ; combustion gas ; hot corrosion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The corrosion behavior of a Nb-modified Ti3Al intermetallic compound containing 11 at.% Nb in a simulated combustion gas with and without deposits of a Na2SO4−NaCl mixture was examined at 600–800°C for times up to four days. In the absence of salt deposits the corrosion rates were rather low and increased only slightly with temperature, producing very thin scales of mixed oxides of Ti, Al, and Nb without sulfides. The presence of the salt deposits produced higher weight gains during an initial stage of one to two days at 600 and 700°C, after which the reaction stopped. A more important and longlasting effect was observed instead at 800°C, when the kinetics of hot corrosion became nearly linear. The scales formed by hot corrosion were complex mixtures of various corrosion products at all temperatures and showed a porous outer region containing a mixture of unreacted salts with oxides (mainly TiO2), an intermediate region of a mixture of variable composition of oxides of the three metals, and a TiO2-rich layer beneath it. At 800°C the scales tended to form a thin, discontinuous Al2O3-rich layer in the middle and contained an additional innermost region presenting a large concentration of sulfur, very likely as Nb and Ti sulfides. The high rate of hot corrosion at 800°C is attributed to the appearance of sulfides in the inner region of the scale and to a more efficient scale fluxing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01046757
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  • 4
    Electronic Resource
    Electronic Resource
    Acidic and basic fluxing of Ni-base superalloys in a 90Na2SO4-10K2SO4 melt at 1173 K (1983)
    Springer
    Oxidation of metals 19 (1983), S. 201-229 
    Details
    ISSN: 1573-4889
    Keywords: Acidic and basic fluxing ; hot corrosion ; sulfate melt ; superalloys
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The influence of the electrode potential on the corrosion behavior of a series of Ni-base superalloys has been investigated in a (mole %) 90Na2SO4-10K2SO4 melt at 1173 K. Acidic fluxing occurs at positive potentials and basic fluxing at negative potentials. A protective scale is formed in an intermediate (neutral) potential range on high chromium-containing alloys such as IN-738LC, IN-939, IN-597, and IN-657. The breakthrough potentials for acidic and basic fluxing depend on the composition of the alloy. Alloys with low chromium contents such as IN-100 and IN-713LC do not form stable protective scales at any potential. Numerous sulfide phases have been identified in the scale and subscale, depending on potential, severity of attack, and material composition. NaCrS2 only forms under basic fluxing conditions. Its presence can therefore be considered as an indication that basic fluxing conditions have existed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00666645
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  • 5
    Electronic Resource
    Electronic Resource
    Diffusion of acetophenone and phenethyl alcohol in the calcium-alginate-bakers' yeast-hexane system (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 1217-1227 
    Details
    ISSN: 0006-3592
    Keywords: acetophenone ; phenethyl alcohol ; Saccharomyces cerevisiae ; diffusion coefficient ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The intrabead diffusion coefficients of acetophenone and phenethyl alcohol were measured at 30°C in the triphasic immobilized yeast-water-hexane system. Saccharomyces cerevisiae cells were deactivated with hydrochloric acid and entrapped in calcium-alginate beads. Measurements of dry cell loss during deactivation, shrinkage of the beads during deactivation and the final porosity of the beads were made for various cell loadings. Final concentrations of wet cells in the beads ranged from approximately 0.25 to 0.30 g/mL. Mass transfer in the hexane phase, external to the beads, was eliminated experimentally. The estimated error of 5% to 10% in the diffusion coefficients is within the experimental error associated with the bead method. The effect of significant sampling volumes on the diffusivities was estimated theoretically and accounted for experimentally. The intrabead concentration of acetophenone and phenethyl alcohol was 150 to 800 ppm. The deactivated cells were shown to be impervious to acetophenone so that the measured diffusivities are extracellular parameters. The cell volume fraction in the beads ranged from 0.70 to 0.90, significantly higher than previously reported data. The effective diffusion coefficients conform to the random pore model. No diffusional interaction between acetophenone and phenethyl alcohol was observed. The addition of 2 vol% ethanol or methanol slightly increased the diffusivities. The thermodynamic partition coefficients were measured in the bead-free water-organic system and found to be an order of magnitude lower than the values calculated from the analysis of the diffusion data for the organic-bead system, suggesting that bead-free equilibrium data cannot be used in triphasic systems. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260441009
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  • 6
    Electronic Resource
    Electronic Resource
    Reductive dechlorination of PCB-contaminated raisin river sediments by anaerobic microbial granules (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 55 (1997), S. 182-190 
    Details
    ISSN: 0006-3592
    Keywords: dechlorination ; bioremediation ; PCBs ; sediments ; anaerobic granules ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A polychlorinated biphenyl (PCB)-dechlorinating anaerobic microbial consortium, developed in a granular form, demonstrated extensive dechlorination of PCBs present in Raisin River sediments at room (20° to 22°C) and at a relatively low (12°C) temperature. Highly chlorinated PCB congeners were dechlorinated and less chlorinated compounds were produced. The homolog comparison showed that tri-, tetra-, penta-, hexa-, and heptachlorobiphenyl compounds decreased significantly, and mono- and dichlorobiphenyl compounds increased. After 32 weeks of incubation at 12°C, the predominant less chlorinated products included 2-, 4-, 2-2/26-, 24-, 2-4-, 24-2-, 26-2-, and 26-4-CB. Among these, 24- and 24-2-CB did not accumulate at room temperature, suggesting a further dechlorination of these congeners. Predominantly meta dechlorination (i.e., pattern M) was catalyzed by the microbial consortium in the granules. Dechlorination in the control studies without granules was not extensive. This study is the first demonstration of enhanced reductive dechlorination of sediment PCBs by an exogenous anaerobic microbial consortium. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 182-190, 1997.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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