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Powder Coating Discolors during Autoclaving





September 11, 2012

Q. We are applying a black powder coating to a cast aluminum part that has been conversion coated. After several exposures to an autoclave process, we are seeing circular discoloration on some areas of the coating. See attached picture.

58875

Any thoughts or suggestions?

Thanks,
Nick

Nick Oosting
- Livonia, Michigan, USA



September 13, 2012

A. Hi Nick,
The circles seem like fingerprints to me; if you handle the piece with bare hands and then put it through an autoclave process the fingerprints could become more visible. Have you tried wiping them with a cloth?

Anna Telk
- Berlin, Germany



September 14, 2012

Q. I had thought about fingerprints but it didn't make sense to me that they would only be on the bottom.

Two possibilities we are currently looking at:
- drips from the conversion coating process forming thick spots on the bottom which then react with the powder coat during the autoclave process
- water drops collecting on the bottom of the part during the autoclave process and reacting with the powder coat at the high temperature during autoclave

Thanks for the feedback

Nick Oosting
- Livonia, Michigan, USA


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