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Problems Painting Brand New Bumper Cover

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PostPosted: Thu Feb 19, 2009 1:26 pm
I am having fits painting a brand new bumper cover. Started by scuffing with fine scuff pad and then light sanding with 400 grit with soapy water. After thoroughly drying, applied 2 coats of an adhesion prompter (Bull Dog) , per discussions with manufacturer. Manufacturer didn't say Bulldog, just an adhesion promoter. Unfortunately the Bull Dog ran because I had the gun set up for 2K primer and I didn't set it up for the Bull Dog.

After letting it dry overnight, I wet sanded it out with 400 grit and soapy water, thoroughly dried, and applied 2 light coats of Bulldog, flashed for 5 minutes, and applied a light coat of 2K high fill primer. The primer crazed first at the edge of anywhere I sanded through the first BullDog coat, and by the time the primer dried, all over the place.

My current plan is to throughly strip the bumper using "bumper/plastic stripper" and repeat. This is absolutely crazy (no pun intended). Any Ideas of what went wrong or what I'm doing wrong? Is it too cold in the garage (50 degrees)

Note: I am not a professional painter (obviously) but I've successfully painted a dozen or so cars in the last 20 years.

Any, any, any, ANY help would be appreciated.

jmd_forest
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PostPosted: Thu Feb 19, 2009 3:34 pm
Hey,

Sounds like you might be "overthinking" the whole process....

First off is it an OEM or Aftermarket bumper? Usually aftermarket bumpers are already adhesion promoted/primered and all you need to do is scuff with ajax and grey scuff pad...

If its an OEM bumper then typically all you need to do is scuff with ajax and grey scuff pad, then spray light coat adhesion promoter then base/clear...You dont need to primer as the bulldog acts as a primer...

I've had the same exact problem in past, I had horrible experiences with bulldog adhesion promoter causing lifting when trying to redo it...

Here is what you need to do, dont strip it all, as you will create even more of a mess with bumper stripper. Sand the whole thing smooth with 320 i'd do it with dry paper....Sand, sand, sand get it smooth. Then you should use a waterbourne primer it will not react. Or if you dont wanna spend the money on it, shoot couple layers of clearcoat down to create a new surface. Otherwise your going to beat your head in because its going to keep giving you problems



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PostPosted: Thu Feb 19, 2009 3:59 pm
Paintdevil,

Thank you for the reply.

It is an aftermarket bumper, via the internet. I talked to the vendor's paint shop (they offer a paint service for $165) and they said to use an adhesion promoter before painting. My paint shop suggested Bulldog.

Regarding the "do not strip" suggestion ---- sorry too late, just got back in the house from stripping it. The stripper pulled off both the primer and the Bulldog and I've wet sanded it clean with 400 and plenty of water to neutralize the stripper. The bumper is nice and clean now, pure clean black plastic.

Are you saying there is no need for the adhesion promoter? Should I prime this or go straight to base coat?

Note: This is for a higher end car (2007 Lexus) I plan to keep for the next 10 years. I don't want the bumper peeling in a year or so. The finish coat is a 3 stage base, mica, clear finish. I'm using PPG 3 stage for the finish and generic 2K primer.

Again, thanks for any advice



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PostPosted: Thu Feb 19, 2009 4:22 pm
Anytime there is RAW plastic you HAVE to use adhesion promoter or it will peel off in sheets in no time...

If you have the bumper completely sanded smooth as glass now, all you need to do is spray a couple coats of adhesion promoter, let it sit, then spray basecoat/clearcoat. No need for a primer

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PostPosted: Fri Feb 20, 2009 6:55 am
If you want to avoid future rock chips, apply a coat of epoxy primer
before painting.
I started doing that for all my bumpers and it definetly makes
a big difference in less rock chips. 8)
JC

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



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PostPosted: Fri Feb 20, 2009 8:51 am
JCClakrk,

Thank you for the reply.

Regarding the epoxy, should a flex additive be added to the epoxy prior to spraying since my understanding is epoxy paint is prone to cracking and this bumper is quite flexible? If so, the Bulldog container notes you can add 1/3 volume as a flex additive, would that be appropriate?

I'm also assuming that even if added to the epoxy, I should spray the bumper with Bulldog first, let flash, followed by the epoxy, let epoxy dry overnight wet sand the epoxy, and then the 2K primer (see below for 2K primer reasoning)?

Paint Devil,

Thank you again. The main reason I'm primering the cover is to help it match up with the hood and fenders that are also being painted. They are in primer that color matches the base coat of the 3 stage paint and I want the bumper to match as closely as possible.

Thank you both for any help you may be able to provide.

jmd_forest



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PostPosted: Fri Feb 20, 2009 9:08 am
If you use the Bulldog 2 in 1 Adhesion promoter/Sealer you wont have any color match problems. I literally paint about 7-8 bumpers a day 6 days a week and I always use bulldog 2in1.

Priming the bumper is only really needed if there is pinholes, flaws etc that you wanna fill them in



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PostPosted: Fri Feb 20, 2009 10:16 am
PaintDevil,

I bought Bulldog 3 in1 Bond-Flex-Tie Coat. Didn't even know there was a 2 in 1, the 3 in 1 was recommended by my paint shop, probably because that is what they stock.

I was primering to help ensure color match since this is my first time painting a 3 stage paint and I've read several articles noting to ensure both the base and mica coats match with original (somehow). I figured at the very least they should match each other as best as possible.

Thanks again, nice to hear from a local guru, I'm in South Jersey (Medford).

jmd_forest



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PostPosted: Fri Feb 20, 2009 10:23 am
They stopped making the 3-1 awile ago "Bond Flex Tie" because it had issues. The new product that replaced it is the 2in1 there website is

http://www.kleanstripauto.com/

Just so you know its REALLY REALLY hard to match a tristage paint job. Even for an experienced painter its not easy. You should defidently get some spray cards, and see how many coats of the midcoat you will need in order for it to match rest of car. Then paint the bumper. Otherwise its going to stickout like sore thumb, expecially on 07 lexus!

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PostPosted: Fri Feb 20, 2009 1:25 pm
Epoxies are different.
I use SPI epoxy on bumpers because it does stay flexible,
any other brand I would definetly recommend a flex agent in it.
When in doubt, use it.
If you let the epoxy dry only overnight there's no reason to sand it.
You can paint right over it (check the recoat window).
Most all epoxies have a window of at least 24 hrs before needing sanded.

Sand if you just want a smoother surface.
I usually do but I wait 24 to 48 hrs before sanding epoxy.
(It sands so much easier after 48 hrs)

No need for 2K primer unless you're filling for scratches or bodywork.
Epoxy is far superior to 2K in regards to sealing and increased adhesion.
If the bumper is smooth, skip the 2k.
If I have to use 2k on a bumper, I will still cover it with epoxy just for the
increased adhesion against rock chips. 8)
JC

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