Forming & Fabricating
What is crazing?
Crazing is a typical phenomenon on pre-anodised aluminium and is a micro-cracking of the anodic layer. It occurs after re-coiling the anodised aluminium and the cracks are perpendicular to the rolling direction. The crazing, caused during recoiling, is homogeneous and therefore less visible.
Pre-anodised aluminium is more sensitive to crazing with higher anodic layer thicknesses (> 10 µm) and with higher gauges (> 1.5 mm).
Crazing has no influence on corrosion resistance.
Post-anodising transformation can result in increased and inhomogeneous crazing and, therefore, specific know-how on further processing, such as cut-to-length is very important.
Can pre-anodised aluminium be welded?
Yes, but first you need to remove the anodic layer at the welding areas.
Can pre-anodised aluminium be cut-to-length?
Yes, with the right know-how.
Special attention should be given on the cleaning of the CTL line before processing, including:
- Removal of aluminium particles
- Pull cleaning felt through the line
- Working in production campaigns
During cut-to-length; take into account :
- Use oil or lubricant during leveling.
- Too much pressure can crack the anodic layer
- For higher gauges (> 2 mm) or higher anodic layer thicknesses (> 10 µm), apply protection film after leveling.
Up to which temperatures is continuously pre-anodised aluminium resistant?
- Temperature < 80°C: the anodic layer is not affected.
- >80°C < 180°C: exposure to these temperatures will cause a more pronounced thermal crazing but the influence on visual appearance will be minimal. Some decrease in corrosion resistance may be experienced.
- Temperature > 180°C: exposure to these temperatures will result in a pronounced thermal crazing, a decrease in corrosion resistance and might result in severe damage of the anodic layer.
How scratch resistant is continuously pre-anodised aluminium?
Continuously pre-anodised aluminium is hard like glass, measuring 8 on the Mohs scale; the anodic film is more flexible than batch anodised aluminium permitting easier post transformation.