NH4 + generation: The role of NO3 in the crevice corrosion repassivation of type 316L stainless steel

Takahito Aoyama, Yu Sugawara, Izumi Muto, Nobuyoshi Hara

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)

Abstract

The role of NO3 in the repassivation of crevice corrosion of Type 316L stainless steel was investigated. In crevice corrosion tests, the solution was changed from 1 M NaCl to NaCl- NaNO3. NO3 led to complete repassivation, and after potentiostatic polarization in 2 M KNO3, NH4 + was detected in the crevice solution by ion chromatography analysis. Repassivation of the crevice corrosion was found to take place in two steps. In the first step, the estimated current density inside the crevice gradually decreased from ca. 5 mA cm−2 to ca. 5 μA cm−2. After that, the current density suddenly decreased to less than 0.1 μA cm−2. From the potentiodynamic polarization in acidic solutions simulated inside the crevice (pH 0.2) and in situ observations of the crevice corrosion morphology, the first step was thought to be generated by the suppression of active dissolution by NO3 . It would appear that the generation of NH4 + results in a pH increase and the further suppression of active dissolution, and then repassivation occurs.

Original languageEnglish
Pages (from-to)C250-C260
JournalJournal of the Electrochemical Society
Volume166
Issue number10
DOIs
Publication statusPublished - 2019

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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