Critical Issues for Chrome-free Pretreatment of Aluminium Alloys
Critical Issues for Chrome-free Pretreatment of Aluminium Alloys
Critical Issues for Chrome-free Pretreatment of Aluminium Alloys
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<strong>Critical</strong> <strong>Issues</strong> <strong>for</strong> <strong>Chrome</strong>-<strong>free</strong> <strong>Pretreatment</strong> <strong>of</strong> <strong>Aluminium</strong> <strong>Alloys</strong><br />
De<strong>for</strong>med Surface Layers<br />
• Since 1996 a wide range <strong>of</strong> sheet alloys have been examined and<br />
ultra-fine grain sized surface layers have been found on almost<br />
every sheet surface examined to date<br />
• De<strong>for</strong>med surface layers are a generic feature <strong>of</strong> aluminium rolled<br />
products. Typical grain sizes are <strong>of</strong> the order <strong>of</strong> 50 nm and the<br />
layers contain oxide inclusions, carbides and entrapped lubricants<br />
• The layers are <strong>for</strong>med as a result <strong>of</strong> high shear de<strong>for</strong>mation during<br />
rolling, particularly hot rolling, and other mechanical working<br />
processes such as machining and grinding<br />
• The layers are nano-materials with a high density <strong>of</strong> grain<br />
boundaries<br />
International Conference on Environmental friendly <strong>Pretreatment</strong>s fo <strong>Aluminium</strong> and other Metals, Oslo, Norway, June 16-18, 2004
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