Do I Need to Sand Off the Original Paint When Repainting the Bumper?

[VanVivian]

Bumper repainting requires sanding off the original paint. The functions of a car bumper are as follows: Safety aspects: The bumper serves as a buffer during low-speed collisions, protecting the front and rear body of the car. It also provides some protection for pedestrians in the event of an accident. Aesthetic aspects: The bumper is decorative and an important component in styling the car's exterior. It also has certain aerodynamic effects. Impact resistance: It reduces injuries to passengers during side-impact collisions and enhances the door's impact resistance. The bumper increases passenger safety and provides a sense of security.

[Journey]

I've handled quite a few vehicle painting cases. When repainting bumpers, it's indeed necessary to consider sanding the original paint. If the original paint is intact without bubbling, usually only the surface layer needs sanding with sandpaper to roughen it up, allowing the new paint to adhere better. However, if the original paint has cracks, peeling, or severe scratches, the damaged parts must be completely sanded off; otherwise, the new paint will also lift. Nowadays, when 4S shops refurbish bumpers, they first use infrared lamps to check the paint's adhesion before deciding on the extent of sanding. Completely sanding off the paint not only damages the plastic parts but also doubles the labor costs, so don't listen to shops that insist on complete sanding. Last time, I only had the mechanic sand the scratched areas, preserving the rest of the good paint, which saved me over 800 yuan, and the result looked as good as new after painting.

[Jessie]

As someone who enjoys tinkering with cars, I've tried bumper touch-up painting. Sanding the original paint requires careful consideration. If the original paint is smooth and intact, lightly sanding with 1200-grit sandpaper is sufficient to create a matte surface for the new paint to adhere properly. However, areas with body filler must be sanded down to the primer, otherwise bubbles may form later. My neighbor was once tricked by a small workshop into completely removing the original paint, resulting in overheating and deformation of the plastic part during sanding, which ultimately cost him an extra 2,000 yuan to replace the bumper. Actually, for plastic components like bumpers, it's difficult to perfectly replicate the original high-temperature baked paint finish. Preserving some of the good original paint often results in better durability. I recommend having the technician perform an adhesion test with polishing compound before deciding on the sanding approach, to avoid wasting the original factory paint.

[Maya]

Last time I rear-ended someone and cracked the bumper, I specifically asked about the paint job during repairs. You don't necessarily have to completely remove the original paint before applying new paint - it depends on three key factors: first, whether the original paint is bubbling or cracking (damaged areas must be sanded); second, the color difference (partial sanding may show noticeably on dark-colored cars); third, the type of paint (metallic paint is best sanded down completely). The technician used a thickness gauge to check my original paint thickness and found no damage, so they just lightly sanded it with 1000-grit sandpaper, saving three hours of labor costs. Nowadays, many repair shops routinely demand complete sanding for convenience, but actually most minor scratches only require localized sanding within a 30cm area. Remember to insist on preserving the original factory coating - the new paint actually adheres better this way.