Interactive Resource icon  Filliform Corrosion Mechanism

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Description: The filament propagates by anodic undermining. This means that the aluminium surface at the front of the filament just below the coating is corroded away. The coating detaches from the substrate and is pushed up by the corrosion products that form in the tail. In this way the filament grows. When the aluminium ions hydrolyse, hydrogen ions are formed, acidifying the tip. The hydrogen ions are reduced at the tip forming hydrogen gas. The main cathodic reaction takes place just behind the anode and is the oxygen reduction on the intermetallics that are present at the surface. Chlorides (or other cations) provide electroneutrality in the tip. The aluminium ions and hydroxide ions form insoluble aluminium-hydroxides in the tail. This animation expalins the mechanism of filiform corrosion.
Keywords: filliform corrosion • fillament • organic coating • anodic undermining • cathodic reaction
Categories: 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: 12 August 2005
Date added: 07 July 2010
Resource ID: 2869