It is difficult to avoid nicks and scratches on a plastic bumper. One reason for this is that the bumper's job is to protect the body of the car against damage. When a stray shopping trolley rolls through a car park, your vehicle's bumper serves as the first line of defence. Scratches and nicks on a bumper are unsightly and annoying, however, they are easily repaired. Repairing minor scratches at home is much less expensive than taking your car to a professional.
Wash the bumper with a mild soap and warm water. Scrub off dirt, grease and other contaminants with a sponge. Rinse the bumper with clean water, and dry it with a lint-free towel.
Sand the scratches with 120-grit sandpaper. Continue sanding until the scratched areas are smooth to the touch.
Wipe the bumper with a clean cloth and denatured alcohol. Wiping the bumper will remove sanding dust and fingerprints.
Protect the surrounding surfaces of the car with masking tape or blue painter's tape.
Apply several light coats of automotive primer to the damaged area. Hold the nozzle of the can 8 inches above the bumper, and apply the primer by moving the can back and forth. Applying the primer in light coats prevents it from running or developing heavy spots. Allow one coat to dry before applying a second coat.
Lightly sand the primed area with fine grade sandpaper to make it smooth. Wipe the bumper with a clean cloth and denatured alcohol. Dry it with a lint-free towel.
Apply several layers of automotive paint to the repaired area. Follow the same procedure in applying the primer. Allow the paint to dry between coats.
Buff the bumper with a polishing compound and soft cloth. Read the instructions for the polishing compound. Apply it to the bumper. Buff the bumper to a nice sheen.
Park your vehicle in the shade. Painting the bumper in direct sunlight may cause the paint to dry unevenly.