Dissolution of sputter-deposited iron oxide films used as a model for the passive film on iron

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This paper reports results from XANES (X-ray absorption near edge spectroscopy) studies during polarization of thin sputter-deposited Fe-oxide films in acidic solutions. The dissolution rate of Fe-oxides in acidic solutions was found to be strongly increased by the presence of Fe(2+) in the oxide. During anodic polarization in acidic solutions, a deleterious effect of chloride anions is found compared with sulfates. In HCl solutions of increasing concentration, not only the pH decrease, but also the increasing anion concentration accelerates dissolution. On the other hand, the dissolution rate in sulfuric acid does not depend on the sulfate concentration. During cathodic polarization, ... continued below

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12 p.

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Virtanen, S.; Schmuki, P.; Davenport, A. J. & Vitus, C. M. December 1995.

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This paper reports results from XANES (X-ray absorption near edge spectroscopy) studies during polarization of thin sputter-deposited Fe-oxide films in acidic solutions. The dissolution rate of Fe-oxides in acidic solutions was found to be strongly increased by the presence of Fe(2+) in the oxide. During anodic polarization in acidic solutions, a deleterious effect of chloride anions is found compared with sulfates. In HCl solutions of increasing concentration, not only the pH decrease, but also the increasing anion concentration accelerates dissolution. On the other hand, the dissolution rate in sulfuric acid does not depend on the sulfate concentration. During cathodic polarization, the dissolution rate is not affected by the presence of chloride ions. This could be due to the negative surface charge of n-type oxides at potentials lower than the flat-band potential, retarding anion adsorption on the surface. These results suggest that the detrimental role of chloride anions on the stability of Fe oxide films is due to a surface complexation effect. The dissolution rate is fairly independent of the potential in the anodic range, except at very high anodic potentials. The XANES spectra reveal no changes in the average oxide valency during anodic polarization. Thus in the passive range, the dissolution that takes place is mostly chemical rather than electrochemical. The findings and their relevance to the stability of natural passive films are discussed.

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12 p.

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OSTI as DE96003319

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  • 188. meeting of the Electrochemical Society, Chicago, IL (United States), 8-13 Oct 1995

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  • Other: DE96003319
  • Report No.: BNL--62351
  • Report No.: CONF-951007--12
  • Grant Number: AC02-76CH00016
  • Office of Scientific & Technical Information Report Number: 170589
  • Archival Resource Key: ark:/67531/metadc618511

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Office of Scientific & Technical Information Technical Reports

Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

Office of Scientific and Technical Information (OSTI) is the Department of Energy (DOE) office that collects, preserves, and disseminates DOE-sponsored research and development (R&D) results that are the outcomes of R&D projects or other funded activities at DOE labs and facilities nationwide and grantees at universities and other institutions.

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  • December 1995

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  • June 16, 2015, 7:43 a.m.

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  • Nov. 30, 2015, 7:41 p.m.

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Virtanen, S.; Schmuki, P.; Davenport, A. J. & Vitus, C. M. Dissolution of sputter-deposited iron oxide films used as a model for the passive film on iron, article, December 1995; Upton, New York. (digital.library.unt.edu/ark:/67531/metadc618511/: accessed October 19, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.