Breakdown mechanism of γ-Al2O3 on Ni2Al3 coatings exposed in a biomass fired power plant

D. L. Wu*, K. V. Dahl, F. B. Grumsen, T. L. Christiansen, M. Montgomery, J. Hald

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

A Ni2Al3 coated tube was exposed in a wood firing power plant for 7100 h. The exposure resulted in protective behaviour in most areas, while corrosion attack occurred in local areas. In areas exhibiting protective behaviour, a 30−50 nm thick γ-Al2O3 layer was found, and a 200−250 nm K–O rich amorphous layer was identified in the corroded area. A corrosion mechanism is suggested: γ-Al2O3 was broken down by reaction with KCl(g) resulting in formation of potassium aluminate. Migration of Cl through potassium aluminate resulted in formation of volatile AlCl3. KCl-AlCl3 then led to alumina fluxing and further corrosion attack.

Original languageEnglish
Article number108583
JournalCorrosion science
ISSN0010-938X
DOIs
Publication statusAccepted/In press - 2020

Keywords

  • Biomass firing
  • FIB/TEM
  • High temperature corrosion
  • Molten salt corrosion
  • Nickel aluminide coatings
  • Power plant testing

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