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Cracks on the parts which are anodized

I have anodized some Aluminium spare parts and cracks have formed on it. My question is,
1)Is this cracks formed due to the wrong anodizing procedure used or
2) Is it due to the poor quality of the parts or
3) Is it because of a crack which was already there in the part.
4) if it is because of the wrong anodizing procedure, how can we avoid it?

Gopinath Rao
DVD Dealers - Dubai, UAE
2007

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2007

Not enough information. With no description of the anodizing procedure, who can say it's wrong?
Possible crack causes:
Sharp edges and corners -- need some radius of curvature, especially with hard anodize.
Flexing of the aluminum substrate -- anodize is about 5x as brittle as aluminum.
Thermal shock. If anodize from low temperature is placed into a hot liquid, crazing occurs.
Surface cracks are found occasionally on extruded material but should be evident prior to anodizing (after etching).
Machining, casting and welding problems should also be evident prior to anodizing.
High residual stress in the aluminum may cause anodize defects, but rarely in my experience. May happen around punched holes in cold rolled sheet.

Ken Vlach [deceased]
- Goleta, California
Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from.