• Rayment, Trevor
• Mokso, Rajmund
• Ghahari, S. Majid
• Tinnes, Jean Phillipe
• Davenport, Alison J.
• Hammons, Joshua A.
• Marone, Federica
• Amri, Mahrez
• Stampanoni, Marco
• Monir, Mehdi
• Terrill, Nick

Abstract

<p>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 (&gt;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.</p>

Topics

• impedance spectroscopy
• x-ray diffraction
• anisotropic
• pitting corrosion
• interfacial
• small angle x-ray scattering
• dissolving