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Cracking of Powder Coating on Aluminum Window Frame

Q. We are involved in an investigation into the cause of cracking of a powder coated aluminum window frame. The cracks are very fine and go right through to the metal. The edge of the cracks are rounded which may suggest that they have formed in the oven. The cracking pattern is that similar to dried mud. Could you suggest some likely causes of this problem?

Regards,

Dr. David M [last name deleted for privacy by Editor]
- Sydney, NSW, Australia

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The aluminum might have been badly abused, but this normally tends to fail in a tear or series of tears.

My wild guess is that it is a high copper aluminum alloy that was taken to too high a temperature. This causes copper to precipitate in a doily or rosette pattern. If it had extreme precipitation, it might be able to give your mud flat cracked appearance. A metallurgical analysis would answer a lot of questions.

James Watts
- Navarre, Florida