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Q&As since 1989


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Is a powder coat finish moisture proof?

We manufacture a steel product that is used outdoors. In some situations it may be used with ACQ treated wood. ACQ will corrode steel unless there is a moisture proof barrier separating the two. We are having the steel powder coated to provide a moisture proof barrier. I'm looking for generic information that confirms that a powder coat finish is moisture proof. Can anyone provide direction on where I may find such information?

Jeff Lentsch
steel product manufacturer - St. Paul, Minnesota, USA
2004

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Decorative powder coatings will all pass moisture to some extent, although much less than liquid coatings in the same price range. FUNCTIONAL powder coatings are designed to be almost completely impermeable, and are used on things like natural gas line fittings and the "stubs" the come up through the ground to attach to the meter. If you really need high quality look to your powder vendor for a functional coating with the color and gloss you want.

Jeff Watson
- Pearland, Texas
2004

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I've never seen a generic statement that specifically mentioned moisture barrier as a quality of powder coat, but when you spec'd that to your supplier, he gave you a paint with those qualities. The best place to find that info would be the paints TDS or general description which is available at the manufacturers website. Most websites also have a number to call for technical support and questions.

Sheldon Taylor
supply chain electronics
Wake Forest, North Carolina
2004