The Electrochemical Behavior of the AI3Ta Intermetallic Compound and Pitting in Two-Phase Al-Ta Alloys

R. G. Buchheit, K. R. Zavadil

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

To identify the role of β-phase Al3Ta precipitates in pitting of heterogeneous Al-Ta alloys exposed to aqueous solutions, the Al3Ta compound was synthesized in bulk form for study by conventional electrochemical and surface analytical techniques. Under conditions of anodic polarization in chloride-free buffer solutions of various pH, Al3Ta is passive, however the phase is capable of supporting electron transfer reactions like anodic O2 evolution and cathodic H2evolution at enhanced rates compared to pure Al. Correspondingly, Al3Ta is effectively noble with respect to its microstructural surroundings. Facile electron transfer appears to be traceable to the fact that the surface oxide is relatively thin and contains a high fraction (—0.4) of Ta2O5 which has a low electronic resistivity. Since reduction reactions occur at enhanced rates, Al3Ta precipitates are expected to act as local cathodes under free corrosion conditions in aggressive environments. Surface analysis shows that significant Ta enrichment of an air-formed oxide film occurs upon initial exposure to solution. Subsequent anodic polarization up to the O2 evolution potential does not induce further enrichment however.

Original languageEnglish
Pages (from-to)51-58
Number of pages8
JournalJournal of the Electrochemical Society
Volume142
Issue number1
DOIs
StatePublished - 1995

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Renewable Energy, Sustainability and the Environment
  • Surfaces, Coatings and Films
  • Electrochemistry
  • Materials Chemistry

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