title: Interfacial phenomena during salt layer formation under high rate dissolution conditions.
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.
authors.affiliation: School of Chemistry, University of Birmingham, B15 2TT, Birmingham, United Kingdom.
authors.forename: Joshua A
authors.initials: JA
authors.lastname: Hammons
authors.forename: Alison J
authors.initials: AJ
authors.lastname: Davenport
authors.forename: S Majid
authors.initials: SM
authors.lastname: Ghahari
authors.forename: Mehdi
authors.initials: M
authors.lastname: Monir
authors.forename: Jean-Phillipe
authors.initials: JP
authors.lastname: Tinnes
authors.forename: Mahrez
authors.initials: M
authors.lastname: Amri
authors.forename: Nick
authors.initials: N
authors.lastname: Terrill
authors.forename: Federica
authors.initials: F
authors.lastname: Marone
authors.forename: Rajmund
authors.initials: R
authors.lastname: Mokso
authors.forename: Marco
authors.initials: M
authors.lastname: Stampanoni
authors.forename: Trevor
authors.initials: T
authors.lastname: Rayment