Tracer study of pore initiation in anodic alumina formed in phosphoric acid

A. Baron-Wiecheć, M. G. Burke, T. Hashimoto, H. Liu, P. Skeldon*, G. E. Thompson, H. Habazaki, J. J. Ganem, I. C. Vickridge

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

39 Scopus citations

Abstract

Arsenic species are utilized as tracers in a study of pore initiation in anodic films that were formed at constant potentials on aluminium in phosphoric acid. The films were grown first in sodium arsenate solution and then in phosphoric acid, and examined using ion beam analysis and scanning and transmission electron microscopies. The analysis of the arsenic content of specimens indicates that the growth mechanisms of incipient and major pores involve mainly field-assisted dissolution and field-assisted flow of the alumina, respectively. The transition between incipient and major pore formation is suggested to be initiated by preferential growth of certain incipient pores, leading to a locally increased current density at the pore bases. The major pores subsequently develop by the flow oxide away from the pore bases, which is evident from the behaviour of the arsenic tracer. The results suggest that the flow is associated with the non-uniform distribution of ionic current and a relatively low volume of formed film material compared with the volume of oxidized aluminium.

Original languageEnglish
Pages (from-to)302-312
Number of pages11
JournalElectrochimica Acta
Volume113
DOIs
StatePublished - 2013
Externally publishedYes

Keywords

  • Aluminium
  • Anodizing
  • Mechanism
  • Porous film

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