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High Gloss Powder Coat Losing Its Gloss

We are attempting to coat die cast aluminum boxes with high gloss black powder coat. We are baking the box at 450 °F for 20 minutes after cleaning with a chlorinated solvent. The coating is going on well. When we place it in the oven the powder coat is very glossy on flow out. When we attempt to cure it for the prescribed 20 minutes at 400 °F it dulls out and looks patchy. What should I try?

Robert Hilton
- East Hampton, Connecticut, USA
February 5, 2010

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First of two simultaneous responses --

Make sure that you have good airflow around the parts. Check to see if one or more vents are blowing directly in the same spot the entire time that the part is in the oven, and if so does it correspond to the dull areas. Also, are you painting these hot and then curing them for the full cycle? If so you are seriously over curing the paint.

Sheldon Taylor
supply chain electronics
Wake Forest, North Carolina
February 12, 2010

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Second of two simultaneous responses --

Dear Rob, Unfortunately, you do not inform us what method of cure you are using gas/electric or the type of powder, epoxy, hybrid or poly.
If it is gas and epoxy powder you could be getting a form of gas checking. This can be caused by the vapours of the solvent you are using being pulled into the oven and being converted to an acid vapour by the gas flame.... or you could be just getting out-gassing from the casting.

Terry Hickling
Birmingham, United Kingdom
February 12, 2010