Before painting plastic, you must know the type of paint to use. Not all paints can stick to a non-porous surface like plastic. So, can you use enamel paint on plastic?
You can use enamel paint on plastic if you properly prep the plastic surface. Enamel paint is perfect for non-porous surfaces such as plastic, and the paint will protect high-traffic surfaces.
However, you must wash and sand the plastic before painting. This improves paint bonding and smoothness. There’s more to know about using enamel on plastic surfaces, and this post explains everything.
Does Enamel Stick to Plastic?
Enamel paint sticks to plastic. That’s because enamel paint is an oil-based paint, and oil-based paints stick to plastic better than water-based paints. The oil-based nature of enamel paint contains strong chemicals, additives, and alkyd resins that help the paint stick to plastic.
Plastic is a non-porous material with no grain, fiber, or thread. So, most paints don’t stick to a plastic surface. For instance, acrylic enamel doesn’t stick well to a non-sanded plastic surface.
However, most enamel paints are formulated with alkyd resins such as glycerol. These alkyd resins are paint-modified polyester compounds that improve the enamel paint adhesive qualities.
Some alkyd resins contain thermoplastic composition. Thermoplastics are plastic polymers that harden when exposed to cool air. The hardened plastic has similar characteristics to plastic material, allowing enamel paint to stick better to plastic.
To improve the paint adhesion between enamel paint and plastic, apply an oil-based primer before panting.
Engine enamel paint sticks to plastic as long as the plastic surface is clean. Engine enamel paint is designed to be used on car and motor engines. But, the enamel paint will also stick to plastic surfaces.
That’s because engine enamel is designed with perfect bonding qualities, allowing the enamel paint to stick to different parts of the engine.
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 paint 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 Paint Primer
- Polyurethane Sealant
1. Wash The Plastic Surface
First, clean the plastic surface. You must remove dirt and grime that can prevent enamel paint from sticking to plastic. 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 plastic is clean, rinse with clean water and let it dry.
2. Apply Rubbing Alcohol on The Plastic
You can’t remove stubborn stains from a plastic surface with soapy water. That’s because dish soap doesn’t always degrease the surface.
To remove stubborn stains from plastic, use rubbing alcohol or TSD. To do this, douse a rag with rubbing alcohol and wipe the plastic. 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 plastic, 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 the plastic and ruin the finish.
You can leave scratches behind while sanding. And, if you don’t use a primer, scratches will show after the paint dries.
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 enamel paint stick better.
To apply primer over plastic, 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 to the Plastic
After the second coat of primer dries, apply enamel paint. You can use normal enamel or spray paint for plastic. However, you must apply thin coats of enamel paint because you can control the flow of thin coats easier, they dry faster, and you get a smooth finish.
You must apply 2 coats of enamel paint on plastic. After the first coat dries, sand lightly, then apply the second coat. Enamel paint takes 4-6 hours to dry enough for a re-coat.
For normal enamel, you must thin it with mineral spirits before using it on plastic. This helps you to apply thin coats.
6. Seal The Enamel Paint
To seal plastic enamel paint, use a sealant or clear coat after the final coat of paint dries.
A sealer protects enamel paint from damage and helps the paint to 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.
The best sealer for enamel paint is oil-based polyurethane. But, you can also use wax, acrylic clear coat, or clear enamel. Applying 2-3 coats of sealant over enamel is recommended for the best results.
However, sealing enamel paint isn’t always necessary. Oil-based enamel paint is durable even if it’s not sealed. But, for high-traffic plastic surfaces, you must seal enamel paint so it can last longer.
To seal plastic with polyurethane, apply two coats of oil-based polyurethane to the enamel.
Enamel Dry Time on Plastic
Oil-based enamel paint dries within 10 hours on a plastic surface. Water-based enamel paint takes 6 hours to dry on a plastic surface. Water-based enamel dries faster because it uses water as its solvent, and water evaporates faster than oil.
However, the dry time depends on the ambient temperature, moisture level, and surface preparation. For example, in humid conditions, enamel paint takes 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 on plastic 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 plastic, then apply the enamel paint. The best enamel paint for plastic is oil-based enamel.