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Air bubbles

 

We are coating Heavy Equipment with steel thickness of 1/2 to 1 inch steel plating. We are having a problem with fine air bubbles being trapped in the powder. If we lengthen our Gel time could this fix our problem. This is happening with all of our colors and suppliers. We had a powder supplier in and they eliminated our process. Sandblast then Iron Phosphate.

Jim Gabe
Clank Powder Coating LLC - Baraga, Michigan

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Jim,

A longer gel time will help, however be careful not to lengthen it too much or the powder will flow off your workpiece.

Powder coatings cure from both sides of the film i.e. from the metal surface and the outer surface. The problem with thick gauge material is the length of time it takes to heat up. This causes the powder to start to cure from the outer surface first and ìskinî, which, by the nature of powder, causes air to be trapped inside the coating. When the metal heats up the air expands and escapes through the outer surface, causing the air bubbles you have. Try to preheat the steel before applying the powder this should eradicate the problem. (Presuming your pre-treatment is ok).

Hope this helps,

Drew Devlin
- Lincolnshire