Painting Over Powder Coatings

Q. I am a manufacturing engineer for an electrical equipment manufacturer in Asia. I came across your clinic while searching the Internet. We make pole mounted distribution transformers for outdoor environments. We powder coat our transformer tanks with pure polyester powder. One of our customers is demanding we paint identification patches on transformer in different colors. Basically, they intend to identify transformers from ground level for rating, project, guarantee period, etc. by painting identifying markings on some portion of the tank.

As you know paint does not adhere to powder coated articles. I can’t remove the powder completely due to requirements of corrosion protection. Can you suggest some means to paint the powder coated surface. V. K.

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A. I’m sorry V. K., you are misinformed. It’s news to me that paint doesn’t adhere to powder coatings. That’s also news to people who use powder coatings as a primer for multi-coat systems, and to people who supply spray cans color matched to the powder coating for use as touch-up.

Indeed, there are problems recoating certain powder coatings formulated with a slip agent to inhibit mar resistance. These slip agent come to the surface during cure. Many of these slip agents can be removed by solvent wiping or surface scuffing the powder coating. On the other hand, your supplier can provide powder coating without a slip agent. I don’t know what your requirements are, but I believe a coating for pole mounted transformers don’t require much mar resistance. The best solution to your problem is to start coating your transformers using a powder coating having no slip agent.