Painting plastic bumper cover ends in lifting paint

Anything goes in the world of fiberglass and plastic



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PostPosted: Sat Aug 08, 2020 10:39 pm
Hi all, new to the site and my first post is to get back on track from my epic fail. Attempting to paint my wife's new bumper cover because I told here I could do it cheaper and better than the professionals (yeah right...) I need to redeem myself after a bad start! I am obviously new to autobody work so any tips welcome.

I have major lifting but I am not sure where the incompatibility is coming from. I have uploaded some photos of the issue and all the products I am using (as recommended by my local paint shop English Color in Dallas, TX). Here are the steps I followed below. Let me know what you think caused it and how to reset and move forward again.

1.) Paid too much for new OEM bumper cover at dealer.
2.) There was no coating on it from the factory. Wet sanded it with 600 paper.
3.) Washed and dried it with clean water.
4.) Wiped it down with a solvent based WAX & GREASE REMOVER - Advantage 190
5.) Wiped down with tack rag from home depot. Noticed all kinds of static electricity at this point and crap sticking to it so I read online about guys spaying the back side with an anti-static spay. I stole a can from our laundry room and spayed a few areas and it seemed to help. Hit it with the tack rag again.
6.) Sprayed two light coats of bulldog adhesion promoter 10 minutes apart.
7.) 30 minutes later I sprayed two primer sealer coats of Advantage 325 primer mixed to a 4:1:2 ratio. Since it was thinner I used a 1.4 tip and it turned out like crap. Very rough surface, almost like sandpaper in spots. I am sure the gun was not setup well.
8.) Since the primer was so rough, I waited 2 hours to let it dry then went to work wet sanding it with 600 grit to get it all smooth. In general, I didn't burn through the primer except on some body lines and ridges. I washed it with clean water, dried it with a towel, and let it sit in the direct sun for about 1 hour to make sure it was dry.
9.) I ran the tack cloth over it again.
10.) Mixed the metallic DBC base coat 1:1 with advantage reducer and started spraying. Lifting started to occur immediately on the first coat so I only spraying a small section and stopped since I knew I would have to sand it back down.

Any guess on what is causing the lifting? What are all the mistakes you see in my "process"? Thanks for the help! I can't handle another "I told you so" from my wife
:cry:
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PostPosted: Tue Dec 01, 2020 11:57 am
Should have been posted in main paint forum sorry you didn't get an answer.

I am gonna guess that the Bulldog wasn't all flashed off before priming may have caused this.
Dennis Barnett
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Line Maintenance A&P Mechanic and MOC Tech specialist.



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PostPosted: Fri Apr 02, 2021 1:47 pm
I can speak from experience.

I’m currently working on a small project where i am using bulldog on plastic.

On my test piece i got a similar reaction. Mine wasn’t as bad as yours but only common product you & I have is the bulldog. So i would agree with Doright.

Allow the bulldog more time to flash. I would say wait til its completely dry to the touch and then proceed with the next step.

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PostPosted: Fri Apr 02, 2021 5:06 pm
Bulldog, or any AP is about 90% thinners, much of which is very aggressive so that it can melt into the top of the plastic.

You've just put it on way too thick and over another layer of paint so the Bulldog has softened that substrate, just as it's designed to do. Your subsequent coat(s) are also way too thick, allowing the thinners to sit and soften what's underneath.

Use AP only on plastic and use light coats.
Chris

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PostPosted: Sat Apr 03, 2021 8:14 am
People need to read what you posted.
(You said Bulldog was only over bare plastic
and 2 light coats sprayed)
30 min to dry was more than enough.

Bulldog was not the problem, you waited long enough and had 2hr dried
primer over it, way more than ample.

It was either the primer or the base coat lifting.
Was it cold when you sprayed and was the reducer
a slow one? That can do it.

I've had a lot of lifting problems myself lately and suspect the reducer
is to hot, I now apply my base a lot lighter coats at first and use a faster one.
Especially in cooler weather.
JC

(It's not custom painting-it's custom sanding)

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PostPosted: Sun Apr 04, 2021 1:25 am
JCCLARK wrote:People need to read what you posted.


:oops: :oops: :oops: Got sidetracked by subsequent posts, but that's no excuse. :(

Bottom line is that fry-ups like this happen when the thinner in the coat being sprayed softens and attacks the layer beneath. Solvent too slow so sits there too long or coats too thick, making evaporation slower - both will give same result.

Lighter coats and faster solvent are the solutions.
Chris

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