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Will post-anodizing punched holes discolor?

January 19, 2010

I am working in the production & construction department of a fabrication company that is working in building curtain wall.......My question is : we have punched some holes to an anodised aluminium sheet , will there be any dark patches(oxidation) resulting from the mill pockets since it was done after the anodizing process?

The anodized panels are meant for external use and are subject to weathering.

Andy Teng
facade manager - Kuala Lumpur, Malaysia

January 21, 2010


You have exposed bare aluminium and this will almost certainly corrode. The level of corrosion will depend on the level of exposure to the elements and what those elements are.

If used in Malaysia then the surface is going to see hot wet conditions, ideal for rapid corrosion. If you are installing these anywhere near the coast then the corrosion potential jumps again.

If possible you should protect all cut edges. You could consider a trivalent chrome conversion coating as a start and then maybe touch up with a paint of some sort for added protection.

The ideal way is to punch the holes prior to anodising, but I am aware this is not always possible. If it is in your case then I would suggest that it is your best solution.

Brian Terry
Aerospace - Yeovil, Somerset, UK

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