prep/paint how to: new plastic pieces

[Sweet Tea Man]

so you have a new plastic piece that needs topcoating


as with all things, check for damage before continuing. this particular bumper had several scratches that needed to be addressed before topcoating


if your plastics have any type of scratches, you have two options. try to sand them out with 320-400 grit. if that doesnt work, you will need to apply a skim coat of glaze using a razor. once dried, sand off and your scratch will be filled and leveled off. for these instances, you can use a sealer over the top of them and not have to use a primer.

start by prepping the new plastic with a red scotch brite or sanding with 600.


just like when prepping the metal pieces, your surface will become dull and have no shine. most plastics come bare with no coatings over them.

once prepped, wash the part down with soap and water, then dry and move into the booth. with all plastics, before laying on the sealer, first, spray two coats of an adhesion promotor. i prefer DuPont's Plas-Stick, but we had Bulldog at the shop, and it does the job just as well.


allow the first coat to flash for 5 minutes, then spray another coat. let flash for 10, then follow with your sealer


I generally let my sealer get dry enough so i can run a tack rag over it before applying my basecoat. apply your base using a 50% over lap just like anything else you spray. DO NOT hammer the base on. once you get full coverage(normally after 3 coats), you will have a uniform color, with no dark and light patches. be sure to get into all the corners, and sides. even underneath.



tack off once dry and apply your clear coat. generally 2 coats will do fine. 3 if you're doing any buffing.

on your first coat, get into all the little areas first with a medium coat. then go over the whole piece.

let flash and follow with another medium coat. do the harder areas first again on this coat.

if a third coat is desired, let flash for a little longer and apply the third using the same technique.

[White_Stealth]

On plastic pieces, you first need to check and see if they are either "raw" or primed first, because the prep processes for both are diff. For a new raw piece, you need to bake or heat it up to get the mold release agents to come to the surface, followed by a good plastic cleaner, the wash with hot soap and water, followed by another wipe down with the plastic cleaner, then scuff with a scotchbrite pad, prior to adhesion promoting, wipe a anti-static cleaner made for plastics on it, followed by tacking and then your adhesion promoter.

For primed plastic pieces all you need to do is sand and scuff with 600g paper and a scotchbrite pad, then clean the part. If you sanded through any large areas down to the raw plastic then hit those spots with some adhesion promoter, let it dry for 10-15 minutes then seal. Otherwise seal over the primer.

Also, if you are using R-M Diamont products, don't tack the panel off after you seal, it will do more harm than good, let it flash spray your first coat of base, and take care of any trash then. (this comes from an R-M tech rep. who has been painting for close to 30 years.)

[Sweet Tea Man]

good catch. i forgot about the mold release agents

[94383Z71]

Originally Posted by White_Stealth

On plastic pieces, you first need to check and see if they are either "raw" or primed first, because the prep processes for both are diff. For a new raw piece, you need to bake or heat it up to get the mold release agents to come to the surface, followed by a good plastic cleaner.

The lower air deflector I bougth for my Sierra is raw. Not primed, and I do not have an oven large enough. Are there any other ways to get the mold release agents out?

[White_Stealth]

Put it out in direct sunlight for a couple hours, it will warm it up enough to get it them out, follow by cleaning it with a non-wax car soap, and the hottest water you can get.

[Black90Sport]

can aerosol bulldog be used just as effectively or ?

[Sweet Tea Man]

i use it on smaller pieces. i just dont trust rattle cans a whole lot. but thats just me. maybe someone will chime in

[kandyman]

Yes you can you the spray can, we sell it in our store and its the same thing in the cans you spray wit your gun. I havent heard of having to let the parts bake. Not sayin its wrong I just know that I never have and I know the body shops here dont put that much effort into it. All I DO IS TAKE 3M scuff it gel and a scotch brite and go to town.

[Beyond Static©]

I've also heard to bake raw plastic parts before scuffing and painting to release the mold agents. Scuff a bumper, and set it out in the sun. About an hour later, you can feel the mold release agents again, hence the reason of baking before scuffing. The best bumper prep I've used was the Standox plastic prep paste. It worked tons better than 3m scuffit.

[syscobuzz]

I have an 05 silverado thats victory red, I tried to paint the front bumper covers on it that came stock on the truck as that black textured plastic they use. I bought rattle cans which seem to stick real well (i did them a year and a half ago now and they're not chipping) but they've never had much shine. I'm wondering some say I need to sand it smooth and some say they'll never shine because they're plastic. I used two coats of clear and I'm not sure if anyone here knows if there is anyhting else that I can do to get a better shine or not. I'm in the procees of wet sanding by hand my rear bumper covers to try that but don't know if it's worth it. thanks for any help

[Sweet Tea Man]

rattle can clearcoat is no where near the same as urethane clear. the fact that its plastic doesnt matter. its all in what you use.

[syscobuzz]

so what do i need to get to use that uethane clear? is it easy to do? im just getting into everything and have only used rattle cans before.

[Sweet Tea Man]

urethane clear is just whatwe use in the industry. its pretty much all urethane based. ...except canada and california and soon to be nation wide when the waterborne works its way over.

a spray gun and an aircompressor would be first things i'd get.