Before taking on a painting project that involves a powder coat, there are some important things to find out. Like: can you prime or paint over a powder coat? And what kind of paint will stick to the powder coat?
Although paints may have trouble adhering to it, you can paint over a powder coat. I’ll discuss which kinds of paint will stick to powder coats and how to prime and paint over a powder coat.
Many different kinds of materials can be powder coated. I’ll be focusing on the most common one to be powder coated, which is metal.
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Can Sanding Alone Fix Defects?
In some situations, the only reason a new paint job is considered is due to a very small localized surface defect. If this is the case for you, sanding alone may be enough to repair it.
Try sanding the spot over with 1000 or 2000-grit sandpaper, keeping the repair area as small as possible. Finish by using a polisher and wool bonnet on it with automotive rubbing compound and wax.
For bigger damages, it is best to remove the powder coating and start over.
Powder coating itself is an excellent paint base, provided that no slip agents were added to it. Slip agents make it impossible for the paint to adhere to it properly.
Because of this, I recommend you lightly sand the surface with 180-grit sandpaper and work your way to finer grades until the surface is smooth to the touch.
Epoxy, thermosetting acrylic, polyester or polyurethane enamels will adhere to the prepped powder coat just fine. Aerosol spray paint cans and other air-drying enamels will also adhere.
A “slip agent” (like wax) can be added to powder coats to increase the metal’s mar resistance.
Mar is defined as a very light abrasion that’s just enough to drive a perfectionist crazy.
If your metal was powder coated without the need for added mar resistance (like in situations where scuff marks don’t matter), there’s a chance a slip agent wasn’t added to it.
It may be impossible to tell for sure if the powder coat had a slip agent added to it or not. If you feel so inclined, you could try adding primer to a small section of the metal to see if it dries and sticks.
Primer Over a Powder Coat
If the powder coating had a slip agent added to it, you must solvent-clean, abrade, or bake the object so that the surface regains adhesion for the new layer of paint.
I recommend a two-component epoxy primer. These two components cross-link to create a chemical, moisture, and abrasion-resistant film.
Be sure to use the best primer for the type of metal you’re working with and the environment it will be in.
If you’d like, you can test your selected primer on a portion of the object to see if it dries and adheres properly.
Paint Over a Powder Coat
I do not recommend painting directly over a powder coat. Even if no slip agent was used, the paint won’t adhere to the surface as flawlessly as it would if it was properly prepped and primed.
For most situations involving metal with primed powder coat, epoxy-based paint is the best option and won’t have trouble adhering. Enamel paints also adhere well to metal primers.
You can use brushes, rollers, or sprayers to apply paint to a prepped and primed metal surface.
No matter which painting method you choose, use long and steady horizontal strokes. Take your time to avoid unnecessary dripping or mistakes. Painting is an acquired skill, and it may help to do some practice strokes to get the hang of it.
Removing Powder Coat
In most situations, starting fresh is the best option. In order to do that, you must remove the powder coat. There are many easy ways to do this.
Solvent-cleaning or chemical stripping involves using chemical strippers (like Benco B17) and should be done in a well-ventilated area. This method is usually very quick, taking around 20 minutes for the coat to be stripped away.
Media-blasting uses high-pressured media to break down and remove paint and rust. The media could be aluminum oxide, crushed glass, sand, glass beads, silicon carbide, water, etc. To break down and remove paint and rust on metal, aluminum oxide is the best choice.
Sanding (wet or dry) is the most common and very reliable option. Starting with 180-grit sandpaper, sand the entire surface evenly. Work your way through finer sandpaper until you finish with 800-grit to ensure the surface is adequately prepared for primer.
Thermal stripping is when you use heat to turn the powder coat into ashes.
Baking off the coat entails baking the object at 650 – 750 degrees Fahrenheit for 3 to 6 hours. The ashes must be washed away lest they stick to the surface again.
Using a blow torch at 1000 – 1200 degrees Fahrenheit is probably not a realistic option for those of you at home. Regardless, this “burn off” method removes the powder coating in a matter of minutes.
If you’d like to use one of the thermal methods, make sure the type of metal you’re working with can withstand the temperature.