Determining the electric-field strength in a passive film via photo-induced electric fields

Research output: Contribution to journalArticle

Authors

  • Feixiong Mao
  • Jizheng Yao
  • Yuting Zhou
  • Chaofang Dong
  • Bruno Kursten
  • Digby Macdonald

Institutes & Expert groups

  • NIMTE - Ningbo Institute of Materials Technology and Engineering
  • USTB - University of Science and Technology Beijing
  • School of Metallurgy, Northeastern University
  • University of California - Berkeley Etcheverry Hall

Documents & links

Abstract

The nature of the electric-field strength in the passive film on tungsten is explored using photo-electrochemical techniques. A theoretical expression for the photo-stimulated growth of the film has been derived. Rotating ring disk electrode (RRDE) experiments indicate that photo-corrosion of a tungsten electrode is negligible under super-band gap light illumination. XPS results show that tungsten is in the maximum possible oxidation state (VI) in the film and hence no higher oxidation state is available. The photo-stimulated transient film growth of tungsten in pH 8.5 +/- 0.1 boric-borax buffer was recorded as a function of film formation potential (1 V-SCE, 2 V-SCE, 3 V-SCE, 4 V-SCE, 5 V-SCE, 6 V-SCE) and light intensities (50, 200, 1000 mW/cm(2)). Steady state passive film thickness measurements of the passive film on tungsten indicate that super band gap, UV light suppresses the electric field in the barrier layer, and hence stimulates anodic oxide film growth. The data obtained in this study demonstrate that the electric field strength in the steady state is independent of the applied potential and film thickness, as postulated in the Point Defect Model.

Details

Original languageEnglish
Pages (from-to)239-245
Number of pages7
JournalCorrosion Science
Volume154
DOIs
Publication statusPublished - 1 Jul 2019

Keywords

  • Passive film, Electric-field strength, Photo-stimulated growth, Point defect model

ID: 5265635