Analysis of convective mass transfer by potential relaxation. IV. Active, prepassive, and transpassive iron dissolution at a rotating disk

P. N. Pintauro*, S. Roy

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)

Abstract

Liquid-phase effective mass-transfer boundary-layer thicknesses and FeSO4 salt-film thicknesses were determined at an iron rotating disk in 2.OM H2SO4 by fitting short-time overpotential relaxation data after current interruption to a single mathematical model for surface concentration changes. Steady-state liquid-phase mass-transfer boundary-layer thicknesses during active and transpassive iron etching were in good agreement with those predicted by the Levich equation. Steady-state prepassive salt-film thicknesses, which varied between 0.0012 and 0.0039 cm, were found to be dependent on the disk rotation speed to the -0.57 power and the disk potential to the minus one-sixth power. For a short period of time during the initial stages of constant-current transpassive etching, a prepassive salt film was present on the iron surface. When this film dissolved, mass transfer was controlled by a liquid-phase boundary layer which was unaffected by moderate rates of O2 gas evolution. Salt films, which formed at particular current densities during steady-state transpassive iron etching, ranged in thickness from 0.0014 to 0.0016 cm and were independent of the applied potential and disk rotation speed.

Original languageEnglish
Pages (from-to)177-186
Number of pages10
JournalJournal of the Electrochemical Society
Volume139
Issue number1
DOIs
Publication statusPublished - Jan 1992

Keywords

  • convective mass transfer
  • iron dissolution

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