How to Get Paint to Stick to Plastic: Step-by-Step Guide

Painting plastic surfaces can be a daunting task, often resulting in poor adhesion if not done correctly. Whether you're looking to rejuvenate outdoor furniture, automotive parts, or household items, keeping paint from peeling off plastic starts with proper preparation and the right products. KBS Coatings offers indispensable products to get paint to stick to plastic: KBS Klean, Fusion SEP Self-Etching Primer and Fusion FPP Flexible Plastics Primer.

Understanding the Challenges of Painting Plastic

Plastic surfaces present unique challenges for paint as they are smooth and non-porous. Traditional paints often struggle to adhere effectively, leading to peeling and flaking. To make paint adhere to plastic, specialized plastic primers are used to create a strong bond between the plastic and the paint, leading to better adhesion and a more durable finish.

What is Plastic Primer?

Plastic primers are typically formulated with special bonding agents that help the paint grip the plastic surface and keep paint from peeling off plastic. These primers may also have flexible properties, which is important since plastics can expand and contract with temperature changes — especially for soft plastics which flex.

For soft plastics KBS Coatings offers Fusion FPP Flexible Plastics Primer. For hard plastics, Fusion SEP Self-Etching Primer is recommended.

What's the Best Primer for Soft Plastics?

Getting paint to stick to soft and flexible plastics, such as rubberized plastics, vinyl, or soft PVC requires a flexible plastic primer. Also known as elastomeric primer or adhesion promoter, flexible plastic primer incorporates a flexing agent that allows the primer to strongly bond to soft plastics and provide a strong yet flexible base coat that will move with the plastic — thereby avoiding delamination, cracking and peeling.

A primer that's not intended for soft plastic won't work well or may not work at all. For example, a self-etching primer designed for materials like metal and hard plastic can't flex with soft plastic to remain adhered, potentially leading to the primer and top coat cracking and peeling.

KBS Fusion FPP — Flexible Plastics Primer

KBS Coatings Fusion FPP promotes a tight bond between flexible plastics and most varieties of top coats. It can also be used on urethanes, wood, fiberglass, and carbon fiber. The gray-colored primer features a fast dry time that allows film thickness to be built quickly and is easy to apply right out of the aerosol can.

Shop Fusion FPP — $27.00 View Full Directions →

What's the Best Primer for Hard Plastics?

Hard plastic primers are made for rigid materials that don't bend or flex. These primers are formulated to form a strong, durable bond with smooth, non-porous surfaces, such as polycarbonate, acrylic, or ABS plastic. They tend to be more rigid once dried, as hard plastics don't need the same level of flexibility as soft plastics.

Primers designed for soft plastic can typically be used on hard plastics as their formulations make them conducive to bonding strongly with both hard and soft plastics. But they may not be the ideal choice — flexible primers are designed to handle movement and stress, so they may not provide the same hard, durable finish as a dedicated hard plastic primer.

KBS Fusion SEP — Self-Etching Primer

KBS Fusion SEP is an adhesion-promoting primer for hard plastics and metals including steel, brass, and aluminum. On metal surfaces, its self-etching ability etches an anchor pattern for best adhesion. It also performs excellently as an inter-coat between multiple surface coatings. Available in aerosol, pint, quart, and gallon sizes.

Shop Fusion SEP — From $27.00 View Full Directions →

Step-by-Step Guide to Get Paint to Stick to Plastic

Before applying primer, thorough surface preparation is essential:

Step 1: Cleaning

• For primer adhesion that will stop paint from peeling on plastic, any dirt, grease, wax, or other contaminants must be completely removed. KBS Klean is designed for this purpose — a strong, concentrated cleaner that doesn't leave residue that can interfere with primer adhesion. Mix with warm water and apply with a sponge, bristle brush, or scouring pad. After contaminants are removed, rinse thoroughly with water and dry completely with a clean lint-free cloth or compressed air.


• Detailed use and safety instructions for KBS Klean can be found here: KBS Klean Directions.

Step 2: Scuff the Surface

• Scuffing or lightly sanding the plastic can help primer adhesion by providing a slightly rough texture the primer can grab onto. This is typically more of a preparation procedure for hard plastics, as flexible primers used on soft plastics often don't require sanding — however, for maximum adhesion, soft plastics can be scuffed.
• Plastic can scratch and gouge easily, which can show through to the final finish. Use fine sandpaper (400-600 grit) or steel wool, applied with light pressure in a back-and-forth motion. Adequate scuffing is indicated when the surface sheen has slightly dulled.
• After scuffing, plastic dust residue must be completely removed. Use hot water and a sponge, or KBS Klean for the most thorough results. Dry completely with a clean lint-free cloth or compressed air.

Step 3: Primer Application

Safety

Always work in a well-ventilated area and wear appropriate respiratory and eye protection when handling primers and paints.

Temperature and Humidity

Ideal application conditions are between 55-82°F with humidity below 85%. Avoid painting in direct sunlight or excessively humid conditions.

Mixing

Before applying primer, ensure it is thoroughly mixed. If stirring, use a paint paddle and mix from top to bottom for at least one minute. For aerosols, shake the can for at least one minute once the mixing ball moves freely, then shake for 10 seconds after every one minute of use.

Fusion SEP Self-Etching Primer Application

• Fusion SEP can be applied by brush, roller, spray gun, or in aerosol form. We prefer spray gun or aerosol for the smoothest and quickest application. Hold the nozzle 10-14" from the prepared surface and apply in steady, even, overlapping strokes.
• Apply a light and even coat. A single coat is generally all that is required, but 2 to 3 light coats can be added, allowing a 3-5-minute dry time between each coat. Keep coats light for proper curing and to avoid runs.
• Fusion SEP will be dry-to-the-touch in 15 minutes. Allow a one-hour dry time before sanding, priming, or top-coating. Always coat over within 7 days. If after 7 days, scuff with 300-grit sandpaper. No sanding needed if coated over within 24 hours.
• Detailed use and safety instructions for Fusion SEP can be found here: Fusion SEP Directions.

Fusion FPP — Flexible Plastics Primer Application

• Fusion FPP is applied in aerosol form. Hold the nozzle 10-14" from the prepared surface and apply in steady, even, overlapping strokes.
• Apply a light and even coat. A single coat is generally all that is required, but 2 to 3 light coats can be added to fill in small imperfections, allowing a 3-5-minute dry time between coats. Keep coats light for proper curing and to avoid runs.
• Detailed use and safety instructions for Fusion FPP Flexible Plastics Primer can be found here: Fusion FPP Directions.

Top Coating Plastic Primers

Both Fusion SEP and Fusion FPP can be top coated with a variety of paints and coatings including KBS BlackTop, KBS MAXX, KBS Top Coater, and KBS Top Coater Aerosol.

Of note, many plastics do not hold up well to UV light, which causes chalking and fading. Applying a solid color top coat provides lasting protection against UV degradation.

Top Coating Instructions

• Allow 1 hour for Fusion SEP or Fusion FPP to dry before applying another topcoat or primer.
• Always coat over within 7 days. If more than 7 days have passed, scuff Fusion SEP or Fusion FPP with 300-grit sandpaper before applying the top coat.
• For exceptionally smooth finishes, lightly sand the primed surface with fine-grit sandpaper (600-800 grit) after it has cured.

Conclusion

The best way to get paint to stick to plastic is using proper preparation techniques and the right products. KBS Klean, Fusion SEP Self-Etching Primer, and Fusion FPP Flexible Plastics Primer offer reliable solutions to ensure your painted plastic projects are durable, attractive, and resistant to peeling or cracking over time. By following these steps and tips, you can transform plastic surfaces into beautifully painted finishes that withstand the test of time.

Questions?