Maybe you've been there, trying to drive your car into a corner too quickly or simply putting it in Reverse and cringing at the crunch. The resulting damage used to mean a quick trip to the auto-parts store for some inexpensive body filler and a can of spray paint, but modern plastic bumper covers-such as those used on C5 Corvettes-require an entirely different arsenal of products.
Fortunately for your bruised bumper, plastic-repair and -refinishing materials are widely available and reasonably simple to use. The repair job will involve grinding, sanding, sculpting, and painting, but it's well worth the effort considering that the entire process should cost considerably less than your insurance deductible.
We recently had the opportunity to meet Dick Jacobs, founder of Duramix, a plastic-adhesive company that was purchased by 3M. Jacobs described the four main categories of plastics used in the automotive industry, noting that not all plastic bumpers are made from the same material. The type used on your vehicle should be easy to identify, as it is normally stamped on the inside of the bumper.
Replace or repair? Fixing...
Replace or repair? Fixing your damaged bumper should take only two hours or so once you've removed it from the vehicle. We chose to go this route.
1. PUR (Polyurethane Plastic Rigid): Most Corvette bumpers are made of this material. It sands to a powder, does not melt when subjected to high-speed grinders, and is easy to repair.
2. PP (Polypropylene), PPO (Polyphenylene Oxide), and TPE (Thermoplastic Elastomer): These materials smear easily during sanding and melt like butter under a high-speed grinder.
3. TPUR (Thermoplastic Polyurethane Elastomer): These plastics powder when ground or sanded.
4. SMC (Sheet Molded Compound): Today's Corvette body panels are made from this material. It looks like fiberglass, exuding a similar white powder. We will cover SMC repair in another article.
The repair process begins...
The repair process begins with cleaning both sides of the bumper cover using a mild dish soap and water. Dry with unoiled compressed air and finish with a general-purpose adhesive cleaner to remove any remaining oil and wax. We used 3M's General Purpose Adhesive Cleaner (PN 08987).
Which adhesives you need depends on the type of plastic in your bumper. Be sure to consult the counterperson at the auto-parts store so you know you get the right stuff. It's also a good idea to stick with a single brand to ensure compatibility.
Believe it or not, the hardest part of this repair job may be removing the bumper. The screws that hold it on can be tricky to locate, hiding out under the taillights, behind the wheelwells, inside the decklid area, and above the exhaust opening. Once the bumper is off, be sure to do your work in a warm, dry place so the repair adhesives can cure properly. Our next projects will include an SMC repair and information on how to paint your newly repaired panels.
Prepare the front and back...
Prepare the front and back of the bumper using a pistol-grip die grinder with a 50-grit Roloc sanding disc (PN 01396). Prep these areas by "U" grinding and cutting away any excess material.
You may need to use a 700-...
You may need to use a 700- to 1,000-watt handheld heat gun to relax the torn pieces and aid in realignment. When you're done, quench the area with cold water.
Final sanding before repair...
Final sanding before repair should be done using an 80-grit dual-action sander to remove any particles and assist with adhesion. We used the 3M Hook It II System due to the flexibility of the pad.