Important steps for bumper refinishing job
Bumpers are designed to protect a vehicle, so it is the most common part of the car to be repaired. Unfortunately, however, we see many mistakes made during the preparation of the bumper for the paint job. Below I present four easy but essential steps for a smooth and high-quality repair job on a plastic bumper.
Whether an old bumper or a new unpainted spare bumper from OEM, thorough cleaning is necessary. An old bumper may contain all sorts of contaminations, including dust, dirt, oils and polishing compounds. The new part may have remains of the moulding waxes and dust. Do not skip this critical step. The best way is to apply the cleaner/degreaser with a unique pressure sprayer and two wipes. Use the first wipe to lift the dirt from the surface and the second wipe to thoroughly dry the surface.
Scuff all the surfaces of the bumper properly.
One of the reasons is that the old paint on the bumper was not correctly sanded to create an appropriate surface for the new coating’s adhesion. Use a nonwoven sanding pad, soft abrasive pad or sand with an orbital sander with a soft intermediate pad for better results. Inspect the surface carefully for untreated spots.
Use special putty/filler for the plastic parts.
Keep in mind that the materials common bumpers have been changed from metal and rigid plastics to softer thermoplastics. Consequently, new types of bumpers are subject to shrinkage and expansion much more than the previously used materials. Standard polyester filler is not flexible enough. Make sure that you use a polyester filler.
Always use plastic adhesion promoter.
We have noticed that even some experienced painters avoid using plastic primer/sealer before applying filling primer and paint. However, skipping this vital step is another reason we see so many cars with pilled off paint on the roads. Instead, spray a light coat of the plastic primer on the spots with unpainted or exposed plastic. In case of a new unprimed bumper, spray the whole surface. Usually, the adhesion promoter is transparent, available for spray guns or in an aerosol can.