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Adhesion problems between powder paint and liquid field ctgs.

2004

I am currently trying to help solve a problem concerning the field painting of epoxy powder coated steel handrails and stairs.

The topcoat we are using is an alkyd enamel. The paint is peeling off in sheets almost over 100% of the surface.

I feel that if we are going to powdercoat this specific product, it needs to also be finished with a powdercoat. The application of most liquid coatings in the field over powdercoat is a recipe for disaster.

Jimmy Zientek
field painting - Austin, Texas

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2004

Dear Jimmy,

Please check that you are correct, it is unusual to use an epoxy for outside work as their resistance to the weather is very poor. Check on the base metal - is it galvanized? Check the pre-treatment used, if any!

Poor adhesion to the epoxy may be due to that some epoxy powders use a wax additive to obtain very low gloss levels.

A suggested process: Start with galvanized metal - clean - pre-treat with zinc phosphate - heat without coating to remove any entrapped air. Apply a POLYESTER type powder (ACRYLICS if you can obtain one would be even better) - bake. If you can find a powder primer apply that then your final powder coat.

Terry Hickling
Birmingham, United Kingdom