Before painting plastic, you must know the type of paint to use. Not all types can stick to a non-porous surface. So, can you use enamel paint on plastic?
You can use enamel paint on plastic if you properly prep the surface. Enamel paint is perfect for non-porous surfaces and protects them from different elements.
However, you must wash and sand the surface before painting. This improves paint bonding and smoothness.
Enamel paint sticks to plastic because it is an oil-based paint that contains strong chemicals, additives, and alkyd resins that help it stick to non-porous surfaces.
Plastic is a non-porous material with no grain, fiber, or thread. So, most paints don’t stick over it because they can’t penetrate the surface. For instance, water-based paints don’t stick well to non-sanded non-porous materials.
However, most enamel paints are formulated with alkyd resins such as glycerol. These alkyd resins are paint-modified polyester compounds that improve the adhesive qualities.
Some alkyd resins contain thermoplastic composition. Thermoplastics are polymers that harden when exposed to cool air. They have similar characteristics to plastic material, allowing the paint to stick better.
You can also improve the adhesion by applying an oil-based primer before painting.
Engine enamel paint sticks to plastic as long as its surface is clean. It is designed to be used on car and motor engines, but it will also stick to non-porous surfaces because it is designed with perfect bonding qualities.
Car and motor engines though largely metallic, also have a few plastic parts. The engine’s block, cam covers, fuel lines, and oil pump are made from thermoset plastics or thermoplastics (thick plastic materials). You can paint these plastic surfaces with engine enamel as long as you clean and degrease them.
How To Paint Plastic With Enamel Paint?
Applying enamel paint on plastic requires a lot of surface preparation. Without surface prep, the finish will peel off quickly.
Here are the tools you need:
- Dish Soap
- A Soft Sponge
- Fine-Grit Sandpaper
- Rags or Tack Cloth
- Rubbing Alcohol
- Painter’s Tape
- Spray Enamel
- Natural Bristled Paintbrush
- A Can of Primer
- Polyurethane Sealant
1. Wash The Surface
First, clean the surface. You must remove dirt and grime that can prevent the paint from sticking to it. Plastic does well to hide dirt, so even if you don’t see dirt, you still must clean it.
To clean plastic:
- Mix dish soap with water.
- Soak a soft sponge (or rag) into the mixture.
- Use the soft sponge (or rag) to scrub the plastic.
- Once the surface is clean, rinse it with clean water and let it dry.
2. Apply Rubbing Alcohol
You can’t remove stubborn stains from a plastic surface with soapy water. That’s because dish soap doesn’t always degrease the surface.
So, to remove stubborn stains, use rubbing alcohol or TSD. To do this, douse a rag with rubbing alcohol and wipe the surface. For hardened greasy stains, pour rubbing alcohol directly over them, wait a few minutes, and wipe the surface with a clean rag.
3. Sand Lightly
Once the plastic surface is free of dirt, you must sand it. Sanding creates a ridged layer over the surface, allowing the paint to stick better.
To sand plastic, use very fine-grit sandpaper. This includes 220-grit sandpaper upwards. Any sandpaper with a lower grit can damage it and ruin the finish.
Tip: The best way to sand plastic is to sand in swirls or circular motion.
4. Apply Primer
Plastic is a slick and non-porous material, so you must apply primer before painting it. Spray enamel paint will stick without a primer, but oil-based primer will help it stick better.
To apply primer, use a paintbrush or a sprayer. Apply 2 coats of primer. Wait for the first coat of primer to dry before applying the next one.
Tip: Don’t apply more than 2 coats of primer on the plastic.
5. Apply Two Coats of Enamel
After the primer dries, you can apply paint. For plastic surfaces, you can use normal or spray enamel. Apply thin coats as you can control them easier and thin coats can penetrate a surface better.
You must apply 2 coats of enamel paint. Wait until one coat dries before applying the next one. It takes enamel paint 4-6 hours to dry enough for a re-coat.
6. Seal The Finish
Optionally, you can seal the finish to allow it to last longer. A sealer will protect the finish from damage and helps it last longer. The sealant, when dry, forms a thick glossy layer that prevents any liquid from penetrating the surface. Sealed enamel paint is water-resistance, has UV protection, and doesn’t scratch.
You can use oil-based polyurethane, wax, acrylic clear coat, or spar varnish as a sealer.
Enamel Dry Time on Plastic
It takes oil-based enamel 10 hours to dry on a plastic surface, while water-based enamel takes 6 hours. The water-based type dries faster because it uses water as its solvent. Since water evaporates faster than oil from the coating, the water-based type dries faster.
However, the dry time depends on the ambient temperature, moisture level, and surface preparation. For example, in humid conditions, the finish will take longer to dry.
Enamel paint dries faster on plastic because the paint doesn’t have to penetrate the material to stick. So, the paint drying process starts immediately after the paint has been applied. The solvent evaporates faster since all the paint is on the top layer.
Related Read: Can You Use Enamel on Wood Surfaces?
Overall, you can use enamel paint over a plastic surface. To do so, clean, sand, and prime the surface, then apply the paint.
Tony is a professional painter and an author of DIY Geeks. Tony has completed over 1,000 painting projects for his clients. It's safe to say he knows what he Is talking about,