Interfacial phenomena during salt layer formation under high rate dissolution conditions

Research output: Contribution to journalArticle

Authors

  • Joshua A. Hammons
  • S. Majid Ghahari
  • Mehdi Monir
  • Nick Terrill
  • Federica Marone
  • Rajmund Mokso
  • Marco Stampanoni
  • Trevor Rayment

Colleges, School and Institutes

External organisations

  • Birmingham University
  • Diamond Light Source
  • Paul Scherrer Institut

Abstract

Interfacial phenomena occurring during high metal dissolution rates, in an environment with diffusion-limited transport of dissolution products, have been investigated using time-resolved X-ray diffraction (XRD), small-angle X-ray scattering (SAXS) and fast radiography. Time resolved SAXS data reveal that highly anisotropic interfacial X-ray scattering always precedes salt nucleation. The correlation between the interfacial scattering the presence of salt crystals indicates that the interface is between the metal electrode and the concentrated NiCl2 electrolyte and can therefore be interpreted as reflectivity or Porod scattering. Using fast radiography, we show that continued crystal nucleation and growth results in formation of a crystal-containing salt layer, which initially extends far from the interface (>20 μm), until the NiCl2 concentration decreases below saturation. Dissolution of this thick salt layer occurs mainly at the furthest boundary from the interface until, the salt layer thickness decreases to a steady state value, resulting in a steady state limiting current. These results show that the presence of a crystalline salt layer at a dissolving interface causes microscopic roughening which has implications for understanding both the role of salt films in pitting corrosion and electrochemical processing.

Details

Original languageEnglish
Pages (from-to)6724-6732
Number of pages9
JournalThe Journal of Physical Chemistry Part B: Condensed Matter, Materials, Surfaces, Interfaces & Biophysical
Volume117
Issue number22
Publication statusPublished - 2013