Interactive Resource icon  Pitting Corrosion Mechanisms

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Description: It is generally accepted that there are two steps to the mechanism of pitting corrosion of aluminium: pit initiation and pit propagation. The initiation of pitting corrosion is often linked to the presence of local defects at the metal surface such as flaws in the oxide or segregates of alloy elements, and the presence of aggressive anions such as chlorides in the environment. The chlorides are believed to locally disrupt the oxide, preferably at pre-existing weak spots, resulting in microfissures of several nm in diameter. Amongst the many initiated pits only a few will propagate. This animation presents the mechanism of pitting corrosion as a discontinuous process. The overall reaction equation can be described as follows: 2•Al + 3•H2O + 3⁄2•O2 → 2•Al(OH)3.
Keywords: pitting corrosion • pit initiation • pit propagation • defects • precipitates • aluminium hydroxide
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: 21 January 2005
Date added: 07 July 2010
Resource ID: 2873