Interactive Resource icon  Intergranular Corrosion: Depleted Solute Zone

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Description: Precipitates at grain boundaries are not the only entities responsible for intergranular or intercrystalline corrosion (IGC). During grain boundary precipitation, solute atoms (i.e. Cu, Mg) diffuse towards the grain boundary, creating a so-called depleted zone adjacent to the grain boundary. For example, in the case of 2xxx alloys this zone, which is mainly depleted in Cu, has a lower corrosion potential compared with the adjacent aluminium matrix and the cathodic intermetallics at grain boundaries. Consequently IGC alloys is driven by microgalvanic coupling, in which the Cu-depleted zone dissolves preferentially. This zone is also depleted in vacancies and is free of precipitates. The animation schematically illustrates this.
Keywords: intergranular corrosion • corrosion potential • grain boundaries • depleted zone • microgalvanic coupling
Categories: Science approaches > Structure, bonding & defects > Grain boundaries
Science approaches > Corrosion & degradation
Science approaches > Corrosion & degradation > Forms of corrosion
Materials > Metals & alloys > Aluminium & alloys
Created by: MATTER, The University of Liverpool
Steven Meijers, Corus
Carlos Caicedo-Martinez, Corus
Contributions: Andreas Blistein, Alcan
Herman Terryn, Vrije Universiteit Brussel (VUB)
Iris De Graeve, Vrije Universiteit Brussel (VUB)
Marc Ryckeboer, Sapa
Published by: European Aluminium Association, Brussels
License: This resource is released under the Creative Commons Attribution Non-Commercial No Derivatives license (2.0 UK: England & Wales).
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Date created: 24 January 2005
Date added: 07 July 2010
Resource ID: 2872