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Dots in powder coated profiles

January 10, 2011

We are manufacturers of diffusers for air conditioning.
after powder coating we see some dots spread on the coated surface.

Our process is acid etching - rinse - rinse -DI rinse - chrome free coating - drying

Jose Sachi
coater - United Arab Emirates

I think a photographic image may help us all to help you as your description of the defect could be due to many things... water in the line, back ionisation, gassing etc.
Clarification of the substrate material would also help, although we can make a guess from your description - but is it sheet, casting or extrusion?

Terry Hickling
Birmingham, United Kingdom
January 13, 2011

January 16, 2011

I can only emphasise Terry's comments.
You could be describing powder contamination.
You could be describing inadequate pretreatment, noting that you do not include an organic wash phase in your system.
You could be describing back Ionisation.
Photos would allow us to help better.
Regards,
Bill

William Doherty
Trainer - Salamander Bay, Australia

Is it possibly because of oil in the compressed air?

Jothi Ramalingam
- Chennai
March 28, 2011

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