Over 264K miles of driving we have encountered the need to attempt to repaint both the front and rear plastic bumpers. The paint shop I have used has had difficulty matching the white pearl mica color but has come close enough. However, the paint never seems to stick on very well. We are careful using the car wash, etc. but it just tends to come off in fairly big chunks over time.
I think the plastic has a texture that makes any kind of sanding difficult.
Does anyone know a technique that really works and gives an original quality smooth finish that sticks?

I was reading some articles on painting recently on the Martin Senior Auto Painting website. They have special primers for plastic that attack the plastic so that a permanent bond of paint can be obtained over the primer. Please go to the NAPA auto store and ask about bonding paint to plastic.

I've done a fair bit of research recently into this as i want to get rid of the grey plastic and replace it with white to match the car.
This is the technique that most people have suggested. Both car painters and model painters alike interestingly enough.

It is as follows;

Painting Plastic Parts
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Tools Needed:
1. Whatever tools that are required to remove the part to paint
2. Airbrush
Other Items:
1. Sandpaper, 400-600 grit
2. Tack cloth
3. Plastic adhesion promoter (primer)
4. Color paint
5. Clearcoat
6. Reducer
7. Flex agent if paint requires it
When using an airbrush, many times you are required to thin the paint. Check out a local hobby store for an inexpensive airbrush kit (or a compressor and paint gun for larger projects).

If you're unsure of painting, try a practice piece or the back of the plastic piece you are painting.


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Step 1 - Remove part to be painted

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Step 2 - Clean thoroughly

Remove all grease and wax using a degreaser and a detergent.

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Step 3 - Wet sand

Wet sand lightly, so that the promoter will adhere better.

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Step 4 - Clean again

Clean again with detergent and dry, or use a tack cloth.

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Step 5 - Plastic adhesion coat
• Follow instructions on the can.
• Apply 2 coats and allow for drying time (time on can)
• DO NOT OVERSPRAY!!!
• If you notice imperfections, you can wet sand again and apply another promoter coat.

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Step 6 - Paint
• Follow instructions on the paint can.
• Wipe down lightly with a tack cloth to remove any dust or debris.
• You'll likely have to use a reducer at this point to thin out your paint mix (refer to the can or your airbrush instructions for details).
• Apply about 3-4 thin coats, allow for drying time per instructions on can between coats, in many cases over an hour.
• DO NOT OVERSPRAY!!!
• More coats may be needed, you want a smooth surface.
• Allow to dry for 6-24 hours, the more coats, the longer the drying time.
• FYI - Don't touch while drying, yes it is wet, yes you will leave marks.

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Step 7 - Clear Coat
• Follow instructions on the clear coat can.
• Wipe down lightly with a tack cloth to remove any dust or debris.
• Apply about 2-4 coats, allow for drying time per instructions on can between coats, in many cases over three hours.
• DO NOT OVERSPRAY!!!
• More coats may be needed, you want a smooth, bubble free surface.
• Allow to dry for a full 24 hours.
• FYI - Don't touch!

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Step 8 - READ THE LABELS

Check with the paint and clearcoat maker about waxing information before using any wax. Most recommend not to in the beginning.

The labels will also tell you any additional instructions the manufacturer recommends you follow.

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Step 9 - Reinstall part

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PPG, DuPont, and ColorRite are good paints to use, here is some PPG info:
Plastic Adhesion Promoter - SXA1050
Reducer - DT870
Urethane Clearcoat - DCU2021
Hardener - DCX61