Sanding Plastic?

Question

My Motorcycle has two plastic removable sides to make it look cool while adding access to the oil and battery. Well i am repainting it and i sanded the gas tank with 400 grain sandpaper. It looks great but i wanna paint those plastic sides. Can i sand the plastic with the 400 grain sandpaper? there are scraches i wanna sand out but dont wanna mess it up more. Can i do it?

Answer 1

Best Answer - Chosen by Asker

Yes we, er, you can!

Since it sounds like this is your first time, I would highly recommend sanding only by hand because it is VERY easy to cut all the way through plastic with any sort of spinning sander. Treat it like an experiment because different types of plastic will sand differently. Start with your 400 grit and see if that is getting the job done. If it creates scratches bigger than the ones you are trying to remove, go to finer paper; if it looks more like you are polishing the plastic than sanding it, go to a coarser grit - CAREFULLY. Don't jump from 400 grit to 80 grit!

If you have any scratches that are more like gouges or that go very deep, you should consider filling them with filler before sanding. This process involves preparing the "scratch" to hold on to the filler by cleaning it and "roughing it up" with a course grit sandpaper. There are lots of fillers, but good 'ol Bondo will work fine. Try to use no more than necessary and push it into the gouge really good so there are no air bubbles. Don't let it dry too long before sanding (directions on Bondo can) and you might want to use a VIBRATING (not spinning!) sander or even a set of fine files to do the initial forming/smoothing before hand sanding.

One more recommendation - use a primer before painting the plastic, especially if you had to use filler. Besides giving you a better surface finish, it will also keep you from having to use as many coats of your finish paint to get full coverage.

O.K., one more - be very careful what chemicals you use on your plastic parts. Test everything (thinner, stripper, even the Bondo) on an "inconspicuous" spot on the inside where it won't be seen before you use it.

Asker's Rating:

Asker's Comment:

Very informative i will try this thanks!

Answer 2

For plastic i'd recommend a light bondo cover just for a filler and sand it smooth and repaint...or fiberglass resin...straight plastic would chip even with proper sanding...but make sure it is sanded before you place bondo or resin over it...cheap and easy :]

Answer 3

I would clean the scratches out just a little with 200 or even 300, not touching anything else, wash and dry then put a skim coat of bondo to fill and even out the scratches.
Then hand-sand all over with 3M Wet/Dry 400 with frequent dunks in soapy water. They're small; don't use a power tool. I would leave as much original paint on there as possible, just rough it up enough for the new paint to stick.
My biggest frustration with bare ABS plastic bits is that the paint does not stick and lay down like it does on metal. Having an existing layer of paint on there already helps; using good paint instead of the lawn furniture paint in a spray can also helps.
USE LIGHT COATS AND BE PATIENT.

Answer 4

use the 400 wet sandpaper it'll be less apt to scratch and take ur time

Answer 5

Same process. When you paint the plastic, you need to add the plastic additive,called (flexitive), to the new paint or it will crack.

Answer 6

You need to use a very fine sand paper and do it very lightly so that you don't add deep scratches to the plastic.