Help With Sanding and Painting Interior Plastic

**xhazn** · 05-04-2005, 07:33 PM

I have a few questions. Should I sand down my interior plastic? I'm painting the dashboard, console, and trim. I've heard of people using 600-800 grit, and then go over it with 1500 grit to help adhese the paint. Should I use metal or wood sand paper? Has anyone had experiences with unsanded and sanded painting work? Also, should I put an adhesion promoting primer down on the plastic? I've heard of people doing work without it, and it turned out fine. Has anyone had experience with non-primered and primered work? I just don't want any chipping in 100 degree, Fahrenheit, temperatures. Can anyone share their plastic painting experiences? Also, should each coat of paint cover the entire object, or have splotches of unpainted surface? I know to paint lightly, but I don't know if I should paint until the entire object is painted for the first coat, or let each coat paint a bit more of the object. Does anybody understand my concern? Thank you all for your input. This is my first interior project, which I'm sure is apparent.

-One more thing: Should I use wax and grease removing spray on the plastic?

**shotgunefx** · 05-04-2005, 08:41 PM

I would say 100% use adhesion promoter.
I'm going to refer you to this post I wrote on 2gstratus.org (I really should write a howto instead of posting directions over and over

)

One step I omitted in that post is cleaning. I'd use Prep spray, but mineral spirits work as well. I'd avoid alcohol. I had it melt part of mine.

I think mine turned out ok.

**xhazn** · 05-04-2005, 09:42 PM

Did you design the RGB light control board yourself? And, what kind of lights are you using? Do you know of any bright LED lights (for uses such as under-dash lighting, a nice omni-directional light). Awesome job on the dashboard and lighting. Seems that you've written quite a bit in the forums. Thanks for helping me out. You've covered my questions as well as made me think about buffing the finished product.

**shotgunefx** · 05-04-2005, 10:05 PM

Originally Posted by xhazn

Did you design the RGB light control board yourself? And, what kind of lights are you using? Do you know of any bright LED lights (for uses such as under-dash lighting, a nice omni-directional light). Awesome job on the dashboard and lighting. Seems that you've written quite a bit in the forums. Thanks for helping me out. You've covered my questions as well as made me think about buffing the finished product.

No prob.
The boards are custom. The leds are rgb leds from superbrightleds.com Most of the leds you're going to find will have a rather narror view angle. Usually the brighter the narrower. Luxeon star and a few others have wide angle ones, that are really bright (maybe too bright for your interior depending on your tastes). As far as led replacment interior bulbs, I haven't used them so I can't really speak to how wide the view angle is. I've heard other people say they are a bit directional.

Hope that helps.

**gothate** · 05-04-2005, 11:19 PM

That is a really nice piece of work, you should definitely just make up a guide. Picked up a lot of tips.

**Altimat** · 05-05-2005, 01:34 PM

1000 grit is a bit fine for good paint adhesion. I'd stay down around 600. You can even get away with 400 if you're spraying a semi-gloss or textured finish. Coarser grit = better adhesion as long as scratches don't show through.

Wax and grease remover is a must before you even begin sanding and especially if silicone (Armor-All etc.) was ever used in your interior. After that you can use alcohol, soapy water, etc, to remove sanding dust prior to painting as long as the part remains wax, grease, and silicone-free throughout the preparation process. Alcohol won't melt plastics.

Adhesion promoter is required with polypropylene-based plastics (labeled "PP" on the back), but not necessarily with ABS (labeled "ABS" on the back). Paint sticks well to properly prepared ABS.

**shotgunefx** · 05-05-2005, 05:21 PM

Originally Posted by Altimat

Wax and grease remover is a must before you even begin sanding and especially if silicone (Armor-All etc.) was ever used in your interior. After that you can use alcohol, soapy water, etc, to remove sanding dust prior to painting as long as the part remains wax, grease, and silicone-free throughout the preparation process. Alcohol won't melt plastics.

I'd quibble with you on that point. When i got my first dash kit for this car, I was told to use alcohol. I had rubbing on hand, asked the seller if it was ok.
"Sure it is."
It wasn't

YMMV.

**Altimat** · 05-05-2005, 06:06 PM

I've never seen alcohol dissolve plastic and I'd have to see it to believe it. Yours must have been laced with something lol.

**Harlanc03** · 05-05-2005, 06:50 PM

If you look around at the stores theres actually a spray paint product that advertises use with plastics now... Check it out!

http://www.krylon.com/main/product_t...roduct_details

**shotgunefx** · 05-05-2005, 07:25 PM

Originally Posted by Altimat

I've never seen alcohol dissolve plastic and I'd have to see it to believe it. Yours must have been laced with something lol.

I'm reluctant to destroy my spare to convince you

Anyway, looking at the body repair manual it says the piece was talc filled polypropelene. Either way, it can't hurt to do a test on an inconspicous spot.