Undercoating
Undercoating1. Spraying primer
Primer is used to fill cavities in the putty and primer surfacer.
- Spray primer on the exposed area.
- Spray the 2 to 3 coats of primer over the area you applied putty.
- Apply primer to the back of the bumper if the damage is a tear or hole.
- Bumper primer
- Warm the primer if the ambient temperature is below 50 degrees F (10 degrees C).
- Follow the bumper primer manufacturer's instructions.
- Use a spray gun and a brush.
Drying
NOTE: Take care not to let the heat lamp deform the bumper during the drying process.
Dry the bumper primer thoroughly with an infrared dryer or other suitable method.
2. Filling/Sanding
Apply putty to repair any holes or deep gouges.
- Apply the putty on the damaged area in 2 to 3 steps.
- Glue aluminum tape on the outside of the bumper, and apply putty from the other side of the bumper.
- Remove the aluminum tape after the putty dries, apply putty from the outside, and fill the hole.
Use a special polyester putty and a putty knife.
3. Sanding
Sand the surface evenly particularly at the area where the PP material and putty meet
Use a flexible block and #240 - #400 - #600 sandpaper
4. Air blowing/degreasing
Use alcohol, a tack cloth, and wax and grease remover.
5. Spraying primer surfacer
NOTE: Spray the bumper primer on the area where the PP material was exposed and around the putty.
- Spray the primer surface wider than the putty and painted surfaces of bumper primer.
- Spray 2 to 3 coats to get 20 to 30 microns of thickness.
- Use the 2-component type primer surfacer (gray) and a spray gun.
- Follow the materials manufacturer's instructions.
Drying
NOTE: Take care not to let the heat lamp deform the bumper during the drying process.
6. Sanding
After drying, wet sand the area of the intermediate coat.
Use the #600 sandpaper.
NOTE: Do not use #600 or less.
7. Air blowing/degreasing
Use alcohol, a tack cloth, and wax and grease remover.
Also clean and degrease the surfaces where the masking tape will be attached.