Most aftermarket and replacement bumper covers come unpainted and have a dull black finish. This finish cannot be painted without properly preparing it first. If painted without preparation, the paint will flake and peel within a matter of months or even weeks. There are a few tips for painting raw plastic bumper covers, however, so that they will look good and last.
Begin by placing the bumper cover on a stand or a set of sawhorses. This is to help hold the bumper cover in place. They are awkward to hold and control with one hand, so you may need assistance if you don't have a stand to sit them on.
Use 300-grit sandpaper to sand the entire outer bumper cover. Use a dual-action sander to speed the process, but for bumper covers with multiple designs and shapes, hand sanding is the only option. The paint will not stick to areas that aren't sanded. Make sure to sand inside any crevices and along the edges of all sides and openings.
Once the raw plastic has been sanded and wiped with a wax and grease remover, spray it with a sealer. Allow the sealer to dry for an hour before moving forward. An automotive plastic sealer can be found at automotive paint supply stores. This helps make the paint adhere easily and more even.
Spray a thin coat of automotive primer on the bumper cover. Apply the primer evenly on the entire bumper cover so that the surface is consistent. Allow the primer to dry for about an hour before spraying the paint.
When applying the paint, begin on one side of the bumper cover and move to the other side in smooth, even strokes. If starting on the left side, paint the entire height of the bumper cover as you move to the right. Use thin coats so that there are no runs in the paint. In total, apply three to four thin coats of paint. Allow each coat 30 minutes to dry between layers. Once the paint has dried, apply clear coat paint in the same pattern, using the same drying time between coats. Wait one full day before touching or moving the bumper cover.
Once the bumper cover is dry, bring it into the sunlight to inspect it for imperfections. If there are any runs or small bumps in the paint, sand them out. Use 600-grit sandpaper and water to sand only the areas with problems. The area will become dull, but this is what is supposed to happen. Sand until the area is smooth and the imperfection is gone. Sand the same areas again, using 1200-grit sandpaper and water. Rinse the bumper cover clean, and either dry it with a chamois or allow it to dry.
Once dried, apply liquid rubbing compound to the bumper cover. Use a dual-action orbital polisher on the flat areas to bring a shine to the bumper cover. On areas the polisher can't reach, use your hand and a microfiber cloth. Use a dry cotton towel to buff the bumper until it shines.
