Painting new aftermarket plastic parts

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PostPosted: Wed Mar 31, 2021 9:27 pm
Im in the process of painting new after market grill & lower fascia.

Both parts are bare plastic, with the exception of the grill rings, which i have sanded down to plastic. The lower fascia is the textured kinda plastic.

This is a small project so i bought all rattle cans.

Bulldog adhesion promoter
Prep all
Spray max 2k epoxy
Spray max 2k clear
SEM black trim paint
SEM high build primer
1 pint of 1k urethane brilliant black to match the grill with body paint.

From all the info i have gathered on this forum, my process should go as follow:

Clean all parts with prep all. Then let air dry and wipe one more time with a clean tack cloth.
Spray a coat of bulldog and let dry for 30 min
Spray 2 light coats of epoxy primer, 5 min between each coat. Then wait 15 min
Spray a coat of high build primer, wait 5 min, sand with 320 grit then spray second coat
Wait 15 min and spray base coat until good coverage waiting 5 min between coats.
Wait 15 min then spray clear.

If this process is correct, my next question is for the lower fascia that is textured. I would like to keep the textured look, so skipping epoxy & primer would be ideal. This area would be the highest exposure to rock chips so would just spray bulldog and then base give me good rock chip protection?

Or would forgetting about the textured look and instead stick to epoxy & primer be the best for the protection against rock chips?



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PostPosted: Wed Mar 31, 2021 11:01 pm
Cant offer any advise as I have NO experience with Rattle bombs.
One of the Rules of the forum No experience don't reply.

Pay special attention to #4

chris wrote:Credit goes to Han for this suggestion:

There are a few fundamentals that folks new to auto body / painting and new to using resources like this board should know. I'd like to document these in this thread and after a period of time I'll pull all the key points into the first post, and we will sticky this. So, here are a few to get the ball rolling:

1. Everyone here comes from different backgrounds. In this field there are often many ways to achieve the same end result. Sometimes the difference in advice is based on the perspective of an experienced technician who is "on the clock", versus a serious hobbyist or restoration expert who is going for a "six nines" (.999999 perfection) result. Sometimes the difference in advice is based on the way we were taught. The new person here needs to read and examine all advice given, and decide for himself which is the lowest risk/highest reward approach. If someone posts advice that is flat out wrong, the community here will quickly (and hopefully, kindly) point out the flaw, and offer alternatives.

2. You can hurt yourself doing this stuff. Anything learned here is to be employed at your own risk. Research and learn how to protect yourself -- especially when it comes to your lungs. If you are unsure about any safety aspect of what you are about to attempt, ask/research first. Lungs are very expensive to replace.

3. There are three things you need to have under control when spraying (assuming your prep work was done correctly): The environment, the material, and the gun. If you don't get all three right you will likely have a problem. Good lighting is a must. Reading and understanding the tech sheets for the products you are using is a must. Dialing in your gun and your technique is a must. This is not a venture you want to rush into. Spend 90% of your time preparing and 10% of your time applying.

4. Rattle can products at your local auto parts retail store are best to be avoided. We see a lot of guys here mistakenly use aerosol primer under a catalyzed color coat, then wonder why they have adhesion problems later. That rattle can stuff is a type of lacquer (that's the only way it can have a shelf life for so long). It can work if used under acrylic enamel or other rattle-can finishing products -- but typically not what the community here gets involved with. No time like the present to get rid of those aerosol cans and move up to a real spray gun and compressor, and learn how to use a modern urethane (or waterborne) finishing system.

5. Sandpaper. Leave the home improvement stuff at the big box store, and get yourself a variety of top quality automotive sandpaper. Norton makes great paper, as well as 3M. It may seem expensive at first but the time savings and lifespan of the paper will more than pay for itself. There a thread here that discusses the various grits and usage.

6. Rust-stop, Rust-conversion, Rust-anything. Some people will swear by this stuff, most people will say that it's a joke and causes more problems than it's worth. I'm in the latter camp. I can see where maybe on an old truck frame you might want to try it -- but I'd never recommend it on sheet metal. If you are doing a restoration the right answer is to remove and replace the bad metal. If you are doing a $50 quickie for the used car lot down the street...then let your conscience be your guide.

7. Metal Prep, Etch, Soda Blast. Any of these things introduce a layer of unknown chemistry on the surface of your sheet metal. I say "unknown" because the pH and penetration of this stuff is never really under your control. Best bet is to avoid any metal prep or etch products -- modern epoxy primers don't need them. For soda blasting...it can be done but you need to have your blackbelt in neutralizing the stuff afterward -- and pray that you got it out of every nook and cranny on the car. I don't touch anything that has been soda blasted and I wouldn't do it to any car I'm working on.

8. You can never have enough compressed air. If you are using an HVLP gun or a D/A sander, you will quickly find out if your wheeled Craftsman tire inflater is up to the task (it won't be). Be sure to determine the greatest CFM (Cubic Feet per Minute) tool you have, and then pair that with a compressor that has at least 25% headroom above that number. It doesn't matter how many horespower, gallons, cylinders, color or weight of the compressor -- the critical spec is the delivered CFM rating at the PSI you need.

9. You've learned everything, prepped your car, have a new gun and compressor, garage is all set up - you are ready to paint, right? No! Practice on a couple of old hoods and fenders from the junkyard, first. Your prized car project is not the place to work out kinks in your technique...trust me on this one. Shoot the junk parts first and you'll be much more confident moving to your real project. Some junkyards will give away stuff that is unlikely to sell. Make friends with your local salvage yard. Practice priming, sealing, color, clear...anything involving your spray gun.

10. Learn how to use a mixing cup. Click on this thread for a great discussion regarding this topic.

11. Get the tech sheets or product (p) sheets for the paint products you are using! Every manufacturer I've come across has these product sheets available for download from their respective websites. These sheets boil down years of product development and research into the environmental and mixing conditions the chemical engineers intended for their products -- don't play "junior chemist" -- follow the directions, instead.

12. Finally, if anything begins to go wrong while you are painting - stop. Fisheyes will not get better with time. Drips coming out of your gun will not magically fix themselves. If you are getting orange peel, try to dial the gun in (first step - increase pressure a notch) before you continue with your clear. There are a ton of things that can go wrong when painting -- don't feel bad if any one (or a few) happen to you. That's what the website is here for, to help you sort this stuff out. A wise man once said "A true mark of a craftsman is his ability to fix mistakes". That's very true when it comes to auto body and paint!

Don't forget to check out the articles we've assembled -- especially the "newbie" and "beginner" articles under the General Articles section found at the page here: AutoBody 101 Info Center
Dennis Barnett
A&P Mechanic, FCC General radio Telephone Operator
Line Maintenance A&P Mechanic and MOC Tech specialist.

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PostPosted: Thu Apr 01, 2021 3:36 am
I'd say your flash times are a bit short. Double the between coat times, at least, more if you put it on heavy - which is likely with spray cans.

Was the original lower textured section painted? Is the replacement just black plastic? Can't leave it unpainted?

The thinner the total paint thickness the better the paint will stand up to stone chipping. I can't imagine why you'd want to put four coats of primer on a brand new part, covering and filling in the texture.

If it must be painted then, if it were me, I'd use 1.5 coats of Cromax 901R/907R (TDS here, then base and clear. Wet-on-wet, the whole job finished in under an hour.
Chris



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PostPosted: Thu Apr 01, 2021 9:33 am
NFT5 wrote:I'd say your flash times are a bit short. Double the between coat times, at least, more if you put it on heavy - which is likely with spray cans.

Was the original lower textured section painted? Is the replacement just black plastic? Can't leave it unpainted?

The thinner the total paint thickness the better the paint will stand up to stone chipping. I can't imagine why you'd want to put four coats of primer on a brand new part, covering and filling in the texture.

If it must be painted then, if it were me, I'd use 1.5 coats of Cromax 901R/907R (TDS here, then base and clear. Wet-on-wet, the whole job finished in under an hour.


The original lower textured isn’t painted. I got the idea of painting it from a previous experiment i did last year. The plastic wheel fender & rear bumper plastic had faded due to exposure to sun rays. So i used the SEM trim paint directly on them after cleaning them, and they looked alot better and has held up well so far with no chipping, a year later.

So as i am modifying my front area with an upgraded look like the newer models, i wanted to have the same black look instead of the factory dark grey that it is.

Only reason i thought 4 coats was because the TDS says apply 2 coats of each. I’ve read many posts where people would put high build primer on top of epoxy primer. So after your advice, i’m assuming the 2k epoxy primer is best because it has flex agent and no high build premier is needed on top of that?

For future reference, i’ll purchase the product you recommended as it is of a higher quality. But for now i’ll use what i got.

So for the grill it would be, bulldog, epoxy, base then clear.
For the lower fascia, bulldog, base, clear?



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PostPosted: Thu Apr 01, 2021 10:49 am
If the parts are new and or sanded with fine grit, 400,then i would just use your bulldog. i believe you can go right over the Bulldog with your color, note i said believe. or use the Bulldog then use your epoxy like a sealer then your color on that. really no need for the primer layers, as Chris said less is better sometimes. i like to prep my plastics with a gray or maroon scratch pad wet with comet cleaner then a wash with soap and water.
Jay D.
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