Redefining passivity breakdown of super duplex stainless steel by electrochemical operando synchrotron near surface X-ray analyses

Research output: Contribution to journalArticle

Abstract

Passivity determines corrosion resistance and stability of highly-alloyed stainless steels, and passivity breakdown is commonly believed to occur at a fixed potential due to formation and dissolution of Cr(VI) species. In this work, the study of a 25Cr–7Ni super duplex stainless steel in 1 M NaCl solution revealed that the passivity breakdown is a continuous degradation progress of the passive film over a potential range, associated with enhanced Fe dissolution before rapid Cr dissolution and removal of the oxide. The breakdown involves structural and compositional changes of the passive film and the underlying alloy surface layer, as well as selective metal dissolution depending on the anodic potential. The onset of passivity breakdown occurred at 1000 mV/Ag/AgCl, and Fe dissolved more on the ferrite than the austenite phase. With increasing potential, the passive film became thicker but less dense, while the underlying alloy surface layer became denser indicating Ni and Mo enrichment. Rapid Cr dissolution occurred at ≥1300 mV/Ag/AgCl.

Details

Authors
Organisations
External organisations
  • KTH Royal Institute of Technology
  • Swerim AB, 16407 Kista, Sweden
  • German Electron Synchrotron (DESY)
  • Justus Liebig University Giessen
  • European Synchrotron Radiation Facility
  • Diamond Light Source
  • CNR Institute SPIN
  • Sandvik Materials Technology
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Corrosion Engineering
Original languageEnglish
Journalnpj Materials Degradation
Volume3
Issue number1
Publication statusPublished - 2019 Dec 1
Publication categoryResearch
Peer-reviewedYes