Pitting initiation in Fe-based amorphous coatings

C. Zhang, Kang Cheung Chan, Y. Wu, L. Liu

Research output: Journal article publicationJournal articleAcademic researchpeer-review

93 Citations (Scopus)

Abstract

Amorphous metallic coatings, especially Fe-based amorphous coatings, are thought to have promising potential for industrial applications in aggressive environments due to their excellent corrosion resistance. The intersplat regions in the coating have been suspected to be the preferential locations for pitting initiation. However, no direct evidence has been provided so far for pitting initiation at the regions. In this study, the pitting behavior of a high-velocity oxy-fuel thermally sprayed Fe-based amorphous coating of composition Fe48Cr15Mo14C15B6Y2in a 6 M NaCl solution was studied in detail via high-resolution transmission electron microscopy (TEM) coupled with nanobeam energy-dispersive X-ray spectroscopy (EDX). It was found that pitting was always initiated in a narrow region ∼100 nm wide near the intersplat regions, but not exactly at the expected regions. Nanobeam EDX indicated that a Cr-depleted zone exists near the intersplat due to the oxidation effect. More interestingly, pitting was found to occur only on one side although Cr depletion is equal on the two sides of the intersplat. This can be well explained in terms of the galvanic effect between the Cr-depleted zone and the Cr-rich intersplat regions. The findings provide a new insight into the corrosion mechanism of Fe-based amorphous coatings.
Original languageEnglish
Pages (from-to)4152-4159
Number of pages8
JournalActa Materialia
Volume60
Issue number10
DOIs
Publication statusPublished - 1 Jun 2012

Keywords

  • Fe-based amorphous coating
  • Nanobeam EDX
  • Pitting initiation
  • Transmission electron microscopy (TEM)

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Polymers and Plastics
  • Metals and Alloys

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