Bare Bumper Prep

Q

Quazz209

I have been having issues with my prep on bare plastic bumpers the last 2 times I have attempted. (Subaru, and aftermarket). I start with a scuff pad and scuff paste to clean. Hose everything down and wipe with waterborne wax and grease remover. I think shoot epoxy that has been reduced about 25% to limit sanding and to get the primer to lay down smooth in the odd shapes in the bumpers grill. This most recent time I even left the bumper out in the sun for at least 1 hour with temps in the mid 80s. Then proceed to wax and grease, tack cloth and shoot my base. I shoot DBC base exclusively with the DT series reducers.

I shoot 1 or 2 light base coats before the problems arrive. Everything looks perfect then on usually the 3rd coat of base I start getting wrinkling of the primer in sparodic locations on the bumpers. Some very small (1/4") while another may be in a line 2" long.

The first time it happened the temps were cold and i thought i rushed the epoxy and the solvent in the base caused the wrinkling. this time however the temps were greate and I had a suface temp well over 100F before i brought the bumper back inside.

What do you guys use for a procedure on these bumpers. I was taught to scuff, seal, base, and clear. Especially for these production style jobs but the epoxy as a sealer does not seem to be working out well for me.

I am open to any suggestions or recommendations on what I am doing wrong or other methods/products. It is obviously related to something I am doing since I have been able to replicate twice in a row now.

Thanks
 
Are you sure these are bare plastic? The epoxy shouldn't be wrinkling unless there's a soluble product under it.
 
i agree with bob. epoxy doesnt halfway kick off in that amount of time where it would be solid enough to wrinkle. these bumpers probably already have a primer applied. most do these days and sometimes its hard to tell. most of the primers are waterbased as well so they can be a bit sensitive to harsh solvents. sounds like the primer underneath is wrinkling. with all that said you dont need to wait an hour for the epoxy. treat the reduced epoxy as if it was your first coat of base. spray 1 coat, let flash 10 min then go right to base. once all your base is on then let it set up and flash.
 
I had that happen with adpro under epoxy, but the OP doesn't mention adpro?

I had to stop using epoxy as sealer when I switched to Standox. It's much "hotter" than the Ultra 7000 I used before. I understand from this forum that it is impossible to wrinkle the epoxy, yet apparently I am able to achieve the impossible.
 
Crash, how long did the epoxy sit before you based on it? Also how much adpro? More than one super thin coat and you can cause problems and make adhesion worse
 
I honestly don't remember, Jim. It's been a couple of years now. But it wasn't anything too out of the ordinary, I believe 30 min was typical for adpro, and another 30 min for epoxy. I was also able to lift fresh epoxy on new ecoat parts with my Standox Basislack.

It's possible I could use epoxy reduced even more, and jump on it right as it flashes, but that just doesn't suit my style, and I can't afford living on the edge. From now on I stay all within brand when doing wet-on-wet processes, for instance I would feel fine about spraying SPI base wet-on-wet with epoxy.
 
Most of the replacement bumper covers we have been receiving (OEM replacement and aftermarket CAPA certified) have a primer already on them. They also have a tag/sticker on the inside that has prep and paint instructions on them (not saying it is the best primer or the only way), but usually it will say something along the lines of "this bumper cover has been primed with *****. To prepare for paint, lightly scuff with a gray scuff pad or scuff paste, clean with waterborne W&G remover, then proceed to base color and clear" So far we have not had any problems with those type covers following the paint instructions. We occasionally get one of the greasy, slimy feeling ones that don't have a primer on them already. For those we usually wash with something like purple power, wet scuff with a red pad and Comet then, W&G remover, coat with 2K or epoxy, then base/clear. I'm not saying this is recommended by anyone or the correct way, but it has served us well for several years with no failures. Best wishes

Kelly
 
I must respectfully disagree with the above recommendation.

Bare plastic bumpers found on modern vehicles need a product specifically designed for them. SPI makes adhesion promoter, and Standox, for instance, makes a 2K plastic primer that is specifically designed for bare plastic. All paint makers have products designed for this, and none would recommend skipping them.
 
Crash, I apologize, I did forget to mention the use of adhesion promoter on the bare/unprimed bumpers. On the covers that come from the factory/supplier with a primer in place we follow their prep instructions that come with the bumper. Again my apologies for the over sight. My biggest point I was trying to make is to be sure it is well scuffed and clean, clean, clean before going any further. If you or anyone else feels the information given was bad or should not be recommended, then feel free to have it removed. I have no problems and would not get upset if that is the case. I would never intentionally mislead anyone or offer up any advise or knowledge that I was unsure of. I was simply trying to offer some information that may be useful to the OP. Best wishes

Kelly
 
JMO....Adpro is a soluble product and any time a soluble product is under a 2K or epoxy there is a chance of wrinkling and it's more suseptable to happening during the early part of cure. Production shops use mostly wet on wet urethane sealers and since the paint process is so fast it's done before they reach that temper mental stage of cure. But epoxy is more durable IMO. JimC probably sprays more plastic here than anyone and if he says to shoot the sealer coat of epoxy quickly followed by base then that's probably some advice you can take to the bank. Clear doesn't have much solvent-less chance of issues. I haven't had any lifting problems using any SPI products but years ago I have had it happen with urethane sealers and adpro when the cure time was extended before base was applied-thought I was doing good by letting the sealer kick longer-wrong.
 
Well I did forgot that one critical step when i wrote my first post...I am using Adpro before the epoxy sealer coat. The first time I did one I talked to Barry about it before shooting and followed the 30 minute flash times exactly. After the issues that time I let the epoxy cure much longer, perhaps that was a mistake. These bumpers had no stickers indicating proper procedure and I am 99.9% sure they were bare.

So from what I am gathering it appears that I should not allow the epoxy to flash and simply: clean, adpro,30 min wait, seal(25 - 50% reduced epoxy), and immediately base?

I apologize for omitting the adpro step in my original post. I usually use bulldog adpro for convenience however it is hard to get uniform coverage of the adpro on the bumper and it ends up spotty. I usually leave it that way for fear of applying it to heavily or applying multiple coats. Do you think this could play into my problems as well?
 
well for wrinking to happen a coating has to be cured or half cured. it need to be kinda hardened or solidified. an uncured or wet film cant wrinkle. another factor as bob said is the adpro. adpro is non catalyzed so it absorbs solvents and will rewet or liquify when a solvent coating goes overtop of it. its like a sponge. if the epoxy sits and solidifies enough and your adpro is thick in some areas when you shoot the basecoat the adpro becomes wet again. the half hardened epoxy has nothing to hold onto not to mention the solvents in the base are attacking the epoxy from both sides now so it wrinkles up. the key to adpro is one super thin coat. the aerosol type may not be the best way to apply it. i always shoot from a gun. if you shoot it from a gun putting a little catalyst in it just like you would with your basecoat makes a big difference. as for the epoxy, mix it and reduce 25-50%. spray one coat and when done just let it flash until dull same as a basecoat. dont spray on it when its actually wet. once its flashed dull, usually 10 min just apply your base as normal. when all your base is on then allow everything to sit and flash, harden, cure or whatever before you apply your clear. doing it this way will keep any wrinkling from happening and it allows all the layers to melt in together while still allowing a good flash or purge before the clear coat.
 
Appreciate the help with this and will be sure to switch to the adpro that i can shoot from a gun also activate it and my basecoat. Activation of basecoat and now the Adpro is something that I have heard about and knew was good to do but have yet to do myself. What ratio do you recommend when adding activator and also which activator is well suited for this? I usually shoot the Euro clear since most of my stuff is production work, is that activator well suited?
 
Jim, I have a lot of respect for you, your procedures, and advice. I may need to revisit my epoxy sealer process at some point. I know when I changed basecoats and bad stuff started happening I was too busy to play around with it. I had to fix it fast and move on, and for me that meant switching to Standox Non-Stop sealer, at least for now. Don't get me wrong, I still use epoxy, but if it is used as a "sealer," I wait til the next morning to base it and all is well.
 
Quazz209;29201 said:
Appreciate the help with this and will be sure to switch to the adpro that i can shoot from a gun also activate it and my basecoat. Activation of basecoat and now the Adpro is something that I have heard about and knew was good to do but have yet to do myself. What ratio do you recommend when adding activator and also which activator is well suited for this? I usually shoot the Euro clear since most of my stuff is production work, is that activator well suited?
Click to expand...

It's SPI adpro that can be activated with SPI 2K primer hardener. Don't try that with Bulldog. In fact, save the Bulldog for quickie repairs that don't matter too much. It's not all they say it is.
 
on all the aftermarket covers i recieve they already have Primer on them.

no reason to add any kind of adhesion promoter!

i do loads of them the way it was explained

sand with paste clean with WB and seal with my choice of sealer and base/clear.

on slick un primed bumpers,Mirrors i use a Adhesion promoter for plastic(either SPI or SW) and then seal and shoot.

i had a major problem with this method(ADpro) when using PPG sealers.)

i have learned to not mix ADpro with someone else sealers since.

if i use SPi ADpro i use SPI epoxy or 2k sealer

is i use SW i use there Adpro and sealer.

but on primed factory or Aftermarket i never use it.

Travis
 
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