Pit initiation at single sulfide inclusions in stainless steel. Part III. Mathematical model

Eric G. Webb, Richard C. Alkire

Research output: Contribution to journalArticlepeer-review


Mathematical modeling was used to simulate the dissolution of a single MnS inclusion within an electrochemical microcell. The model allowed for the evaluation of the hypothesis of mechanism of pit initiation based on a critical concentration of thiosulfate ions in the presence of chloride ions, which results in depassivation of the stainless steel. As a result of inclusion dissolution, the concentration of thiosulfate increased to values consistent with critical concentrations observed experimentally for pit initiation. Dissolution of inclusions led to modest local acidification, but not to the low pH values associated with passivity breakdown. The model defined the dimensionless parameter space under which thiosulfate and sulfide species would be expected to occur as a consequence of inclusion dissolution. Based on the hypothesis of critical thiosulfate initiation mechanism, the predictions of pitting potential for 304 stainless steel in chloride solutions were within experimental variation: the chloride concentration dependence was smaller than observed experimentally.

Original languageEnglish (US)
Pages (from-to)B286-B295
JournalJournal of the Electrochemical Society
Issue number6
StatePublished - Jun 2002

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Renewable Energy, Sustainability and the Environment
  • Surfaces, Coatings and Films
  • Electrochemistry
  • Materials Chemistry


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