ABS parts

metalman

Oldtimer
A customer picked up new mirror covers for his BMW, VW and his Volvo truck. He wants them all painted an accent color and he will keep the originals for when he trades in.
All are new unpainted ABS plastic. Do I need to use adhesion promoter?
The truck covers have a fine texture molded in so I want to get 2 coats of epoxy on them so I can block the surface smooth, then I'll use an epoxy seal coat prior to base/ clear.
 
No need-do not use adhesion promoter on ABS, no need for scuffing. Just clean it well and apply the primer or sealer of your choice.
 
As long as they are really ABS and not something else, I assume you have positive ID of the material.
 
I can't post photos because of some issues with the other computer, so I'll try to describe the parts.
The VW and BMW covers are very similar, both have ">ABS
 
ABS will melt in most reducers, shave off a little sliver and drop it in an ounce of reducer or lacquer thinner and you'll see. No need for adhesion promoter with this type of plastic-don't do it. Give your epoxy plenty of flash time between coats-remember this plastic melts so you don't want anything with solvent to be on there wet for too long. Get the epoxy on, let it cure, sand it smooth, then shoot one thin sealer coat and let it flash good, then your paint with plenty of flash time. I've seen painters melt ABS grilles by applying BC to fast and heavy-melt to the point the grille teeth were sagging.
 
Bob
If the ABS is that sensitive do you think it would be better to use regular 2K primer instead of the epoxy? Faster set and less aggressive, I could let it set a day or two to avoid any sink and shrink. Only reason I wanted to use epoxy is I trust it for adhesion and not shrinking. But it may be overkill on this job.
 
Thank you both for the information. I'll stick (no pun intended) with the epoxy and Let you know how it all worked out.
 
Report: All went well. Bob, I tested the back side with a rag damped in reducer and I could see what you were refering to, melt.
After cleaning I applied 2 coats of un-reduced epoxy to the textured units. This was likely enough but I had other things that needed epoxy so I blocked the first 2 coats with 240 and applied 2 more reduced about 12%. After guide coat I wet blocked with 400, sprayed epoxy 1:1:1 for sealer, de-nibed, 3 coats of base with lots of flash time. I had enough Universal so I did 3 coats vith very slow activator. Last 2 gallons of clear here was 2100 Production, I'm getting good with that but I forgot how nice Universal flows. No cut and buff needed, not worth it for the few dust nubs that it had.
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Love painting small round parts;).texture.jpg

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cleared.jpg
 
Looks great, I have painted ABS and ABS/PC mirror housings with solvent enamels with similar results. I wet sand with 800 to knock off really gloss molded surfaces.
Advise to look at the bare parts for tiny slender molded over flashing "burrs" then trim and wet sand edges with 600. Can help to apply medium wet cut in to edges. Makes edge coverage cover better for first full coating.

Got it down.
 
Finally got the covers swapped out. Not crazy about the look but the customer loves it and that is what matters. It made more sense on the tractor because of the red tanks and frame. Didn't take a photo of the VW, that didn't look that great due to the design of the mirror, kind of half black, half red. Big PITA to get the old covers off with out wrecking the snap tabs. The BMW was the hardest, truck next and the VW's came off easy.
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I have almost always sprayed down a coat of adhesion promoter as a safety net before applying epoxy as a sealer, base, then clear. Is there a reason why adhesion promoter should not be used on abs parts?
 
If you use it make sure to give the part extra flash time before shooting your epoxy, ABS soaks up solvent like a sponge, it will melt if it's wet too long. So the worst thing you could do is shoot the adpro and apply the epoxy to soon trapping in solvent and allowing it to soak even deeper in the abs. I've seen grilles turn into a melted mess. On plastics that don't absorb solvent the adpro has no choice but to evaporate it's solvent and flash off properly. JMO, Hope that makes sense.
 
Bob, Can I ask what you mean by "adpro"? I have never heard of that. Generally i just shoot a dust coat or so of adhesion promoter on a bumper cover and let it sit a good 20-30 minutes. I haven't had any issues that i know of. I would think someone would come back and see me if they had a peeling or wrinkling issue. I never thought about the abs soaking the solvent based adhesion promoter up. Glad you brought that up. I need to really look my plastic parts over and see if they are ABS. Also, if they are i guess i need to just triple check my sanding/scuffing and forget the adhesion promoter. Thanks!
 
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