Electrochemical characteristics of Fe-Cr alloy thin films prepared by ion-beam-sputter deposition

Naoki Iwamoto, Hiroki Chujo, Noboru Akao, Nobuyoshi Hara, Katsuhisa Sugimoto

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)

Abstract

A series of Fe-Cr alloy thin films having various Cr contents (11-34 mass%) and thicknesses (60-550 nm) were prepared by ion-beam-sputter (IBS) deposition. The structure of the films was examined by transmission electron microscopy (TEM), electron diffraction (ED), glancing angle incidence X-ray diffraction (GIXRD), and atomic force microscopy (AFM). The anodic polarization curves of IBS-Fe-Cr alloy films were measured in 1 kmol · m-3 Na2SO4(pH 3.0), 1 kmol · m-3 HCl(pH 0.0) and 1 kmol · m-3 NaCl(pH 5.8) at 298 K, and then compared with those of vacuum-induction-melted (VIM) Fe-Cr alloys containing 10-25 mass%Cr. TEM images and ED patterns of IBS-Fe-Cr alloy films indicated that the films consist of equiaxial bcc microcrystals with an average grain size of approximately 30 nm. The root-mean-square roughness value estimated from AFM images of IBS-Fe-Cr alloy films increases from 0.36 nm for a film 60 nm thick to 0.77 nm for a film 550 nm thick with increasing film thickness. This suggests that the surface microroughness becomes large as the film thickness increases. The critical passivation current density, icrit, of IBS-Fe-Cr alloy films in 1 kmol · m-3 Na2SO4 (pH 3.0) is lower than that of VIM-Fe-Cr alloys: the value of icrit for an IBS-Fe-12Cr alloy film 140 nm thick is less than that for a VIM-Fe-14Cr alloy by a factor of about 100. The value of icrit for IBS-Fe-18Cr alloy films increases with increasing film thickness in the range of 60-550 nm, while it never exceeds that for a VIM-Fe-21Cr alloy. The IBS-Fe-21Cr alloy film 90 nm thick covered with a native oxide film does not show spontaneous activation in 1 kmol · m-3 HCl under the open circuit condition. The alloy film never develops pitting under the subsequent anodic polarization in 1 kmol · m-3 HCl and 1 kmol · m-3 NaCl.

Original languageEnglish
Pages (from-to)877-886
Number of pages10
JournalNippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals
Volume62
Issue number10
DOIs
Publication statusPublished - 1998

Keywords

  • Anodic polarization curves
  • Aqueous solutions
  • Corrosion resistance
  • Critical passivation current density
  • Film composition
  • Film thickness
  • Ion-beam-sputter deposition
  • Iron-chromium alloy films
  • Passive film
  • Pitting

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Mechanics of Materials
  • Metals and Alloys
  • Materials Chemistry

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