Manufacturers make plastic car bumpers tough to take the brunt of occasional bumps and minor collisions. A bumper can take a large number of these small accidents without experiencing structural damage. While structurally strong, with every scratch and scruff your bumper begins to look more worn-down. You can return your bumper to good shape by painting over the damage. Painting a plastic bumper requires extensive prep work, including removing the minor damage. Once finished, however, your bumper should look fresh and nearly new.
Remove the plastic bumper from the car. Different makes and models of cars attach the plastic bumper in different ways; to find the attachment points, consult the manufacturer. Generally, you remove the plastic covering bumper by removal of the screws and bolts securing it to the metal portion of the bumper beneath.
Clean the bumper thoroughly using soapy water. Rinse away the soapy residue and then dry it completely with a towel.
Use a plastic prep solvent to clean any ingrained dirt, wiping in the same direction along the entire surface of the bumper. Allow the solvent to dry completely before continuing.
Scuff the surface of the bumper with 80-grit sandpaper to create a roughened surface that helps the new layer of paint bond.
Locate the stamp in the rear of the bumper identifying the plastic type that makes up the bumper in order to determine the repair filler necessary. PP indicates a polypropylene bumper, PPO is polyphenylene oxide, TPE is thermoplastic elastomer, PUR is polyurethane plastic rigid and TPUR identifies the bumper as thermoplastic polyurethane elastomer. Make a note of the bumper type.
Purchase a plastic filler from an auto store that matches your bumper type. Spread the filler over any scratches and scuffs in the bumper, filling them in up to the surface of the bumper. Wait 20 minutes for the filler to harden and then go over it with wet 400-grit sandpaper to smooth the filler out.
Apply flexible part sealer to the bumper in two layers to seal the surface and wait 30 minutes for it to dry.
Paint the bumper with two coats of primer allowing the primer to dry between each coat, about two hours. Use a HVLP (high volume, low pressure) sprayer for applying paint. Make sure to get a paint that's rated for use on your plastic type. Rent a sprayer from a home-improvement store or equipment-rental shop. Sand the primer with the wet 400-grit sandpaper to smooth out any lines or imperfections in the primer paint. Wipe the sanded bumper with wax-embedded tack cloth to remove any dust left from the sanding process.
Paint the base coat of paint onto the bumper. Spray the base coat on, building up the coat of paint in layers until you've achieved a solid coverage of paint in the colour you want. Allow the coat to dry for 30 minutes.
Cover the base coat with clear-coat paint mixed with hardener. Follow the hardener instructions for mixing ratios. Cover the base coat with two layers of the clear coat to protect the new bumper paint from damage. Allow two hours' drying time between coats, and then allow the bumper to sit overnight to dry completely.
Reattach the plastic bumper to the car, securing it with the screws and bolts removed.
Sand the surface of the clear coat smooth with 1500-grit wet sandpaper. Remove any marks left from the painting process. Polish and wax your newly painted bumper as you would normally.
Paint the bumper in a warm, dry, well-ventilated area.