Most plastic bumpers can be welded
Most car bumper covers are made of polypropylene, the most common bumper plastic and one that welds well. That's why a cracked or punctured bumper is often repairable rather than a write-off.
Plastic welding is a regular part of Robert Crenshaw's bumper work. He mends cracks and punctures back together with plastic welding rods, then refinishes the area to match the car.
“Most bumpers are polypropylene. Those are the most common and weldable. There are stamps on the backside of the bumper that tell you what type of plastic it is, and I have different types of welding rods for plastic.”
How to tell what your bumper is made of
Plastic car parts are usually stamped on the back with a short code that names the material. On bumpers you'll commonly see codes like >PP< for polypropylene, >PP+EPDM< or >TPO< for rubber-modified blends, and occasionally others such as >PC/PBT<.
You don't need to find it yourself. The stamp is on the inside of the cover, and Robert checks it as part of the repair.
Why the welding rod has to match the plastic
Plastic welding works by melting the edges of the crack together with a filler rod of the same kind of plastic, so the repair becomes part of the bumper. Different plastics don't fuse well with each other, so a rod that doesn't match the bumper won't hold the same way.
That's why Robert carries different welding rods for different plastics, and why the stamp on the back matters.
Bumper damage plastic welding can fix
Welding is for damage where the plastic is cracked or broken but still there:
- Cracks. Most cracks under about 6–8 inches are repairable.
- Holes, if the piece is still there. A trailer hitch can punch out a square about two inches across; if the piece is still there, it can be welded back in place.
- Some broken mounting tabs, depending on the break.
“Most cracks under six to eight inches are repairable. I can repair a hole if the piece is still there.”
When welding isn't the answer
Cracks in plastic tend to grow over time with vibration and temperature swings, so a crack that's comfortably repairable today can get longer if it's left. If you've got one, it's worth sending photos sooner rather than later.
Welding needs plastic to work with. When there isn't enough of it, the cover needs replacing:
- Big rips through the bumper
- Chunks missing, the kind that got left on the highway
- Cracks much longer than 6–8 inches
- Damage to the parts behind the cover, which Robert doesn't take bumpers off to inspect
Not every bumper is plastic
Steel bumpers can be painted, but dents in steel are hard to remove and steel isn't plastic welded. Chrome can't be painted at all. Off-road bumpers are usually powder-coated; Robert refinishes those with liquid paint. Bumper repair or replacement? covers these cases.
What a plastic bumper weld repair looks like
Robert comes to you, ideally at a home with a driveway and a power outlet nearby. Parking decks don't work, because his truck, trailer and lighting don't fit. He works with the bumper on the car, welds the damage, shapes the area, and paints it with a color he mixes on site to match your car. The paint is cured with a heat lamp before he leaves.
Most of his repairs are done in under three hours. Welding cracks takes longer than a simple scuff, so plan for the longer end. Afterward, see caring for a fresh paint repair.
Common questions: Can a plastic bumper be welded?
Is plastic welding the same as gluing a crack?
No. Welding melts plastic of the same type together, using a rod matched to the bumper, so the repair is fused into the bumper rather than stuck on top of it.
Will the weld show after painting?
The welded area is shaped and refinished with paint mixed to match your car, so the goal is a repair you don't notice. Send photos and Robert can tell you what to expect for your damage.
How long does a welded bumper repair take?
Most of Robert's repairs are done in under three hours on site. Welding a crack takes longer than a scuff repair, and painting and curing come after the weld, so plan for the longer end of a visit.
Can a bumper with a piece broken off be welded?
If the broken piece is still there, often yes. If it's gone, or a big section is missing, the bumper usually needs replacing.
Written from Robert Crenshaw's own explanations of how he works. Nearly 30 years repairing bumpers, and 25 years running his own business.