Buffing / polishing a plastic enclosure prior to spray painting

[microbug]

Hi,
I have a large transparent tic-tac box (see picture) which I plan to use in my boom box project. It has a few scratches / minor blemishes on it, and I am assuming (I haven't done it before) that these will show up underneath the black spray paint. I have a Silverline rotary tool (Dremel rip-off) which has a buffing tip.

Question 1: Will the scratches etc. show up through the spray paint, and if so what is the best way to remove them before hand?
Question 2: As the plastic is probably fairly soft given its original application, will it be very easily scratched again after the spray paint? Although it is a boom box it probably won't be too abused - mostly used inside...

Thanks!

[CaptnYellowShirt]

I can't see the scratches that well in the pictures.

Paint tends to cover small stuff like that up -- especially with a few coats.

Maybe get a similar piece of plastic and try it out?

[deth502]

itys hard to get any good adhesion to flexable plastics with paint and still expect them to dry to a hard and durable finish.

tht said, id just paint the thing, throw a few coats on it, and if the scratches show through, wet sand them out of the paint and recoat as needed. the paint will fill the scratches in just fine.

[rdl]

Just guessing from the appearance, but that looks like some kind of polyethylene or polypropylene type plastic. If so, you'll probably never find any normal kind of paint that will stick to it. I would test for adhesion before I got carried away with details.

[Joule Thief]

Check out SEM paint products

http://www.semproducts.com/

they do specialize in automotive grade paints and some plastic adhesion promoters. As mentioned above, flexible plastics pose a great challenge to adhesion. Please consider a ROUGH project finish will allow for increased ability of mechanical adhesion of the paint to the plastic. A chemical bond may be difficult to achieve. I would not buff the project as this may embed buffing compound into the surface of the plastic and promote poor adhesion or even a "fish eye" effect.

[microbug]

Thanks for all the replies. I think I will first try painting without adhesion promoter and if (when) that doesn't work I'll buy some.

[Shock]

If you haven't brought the paint already buy some spray paint designed for plastic use.
You should be able to get it online or at major auto stores for roughly the same price as normal paint (or at least it was when I last brought a can).
On youtube you will see many videos on spraying custom paint jobs on game controllers.

The scratches will show up unless you either put a thick enough single coat or multiples which won't look the best.
For a better look use 3M polishing paper or "micro mesh" pads,  it will make dull plastic shine and if you use progressive grits be invisible once painted.
On soft plastic you just need to be careful if it's layered.

As for ultra cheap route you could try toothpaste or car polish but make sure you clean it thoroughly off with plenty of detergent and dry well before painting.

The golden rule is do a test run on something you don't care about first.

[microbug]

Thanks for the information! I will get some micro mesh paper & spray paint for plastic, then test the method on a small (normal) size tictac box - they are made of the same plastic.

[Conrad Hoffman]

For adhesion you certainly don't want it buffed. It should have a medium matte finish like you get with machinists Scotchbrite pads. I think Plastikote or somebody similar recently came out with spray paint specifically made to adhere to plastics.

[microbug]

I found this on Amazon – looks fine. Right next to the plasti-kote stuff in listings, just cheaper. Might switch to a matte one though - which would look better? Decided on matte – looks much more professional and cool! I am planning to go with the micro mesh paper, starting with the coarsest and working down to the finest.