Adhesion Promoter cobwebbing?

M

mitch_04

Learnin'
Painting a new front bumper on a '06 Malibu. Scuffed with grey pad, washed with Dawn & water, wiped with waterborne W&G remover, blew off with dry air, let set 30 minutes, tacked off, then sprayed promoter.

It seemed like it wanted to cobweb on the bumper. After time, it sort of soaked in. Is this common or did I mis-step along the way?
 
Hopefully someone else will know the cause of this, as I'm stumped?????

My only guess would be trapped cleaner in pours of bumper but you over did the drying process.
 
If I understand the description right, this can happen if the surface tension of the plastic is high and the promoter goes on a bit too wet. It seems like certain bare plastics are just really greasy and need to be treated "by the book," which is to wash them inside and out with strong Dawn solution, wipe down with #700, use prep paste made for bare plastic and a gold scuff pad, then dry and wipe down with #700 again. This helps get the surface to a point where it will accept coatings without freaking out.
 
Was it a factory or aftermarket bumper? Most bumpers come primed and don't need promoter just sanded and washed. Some aftermarket bumpers (depends on which Tong-Yang family member) have a thin weak primer that reacts with some promoters, sealers and wax greese removers.
 
Aftermarket bumper, CAPA certified. It didn't say anything about being primed or not, is there a way to tell what's coated and what's not? Also, will it cause problems spraying adhesion promoter on primer?

I am thinking I may have sprayed too wet, but I am not sure.
 
Sanded out the bad areas, getting ready to spray base. Is this too much of a burn through, or can I spray base over it? It is coated in epoxy other than the burn through areas.

 
I see what appears to be adhesion loss in your feathered areas there. Something isn't sticking. A primed bumper should not get adhesion promoter. But the primer is usually crappy and soluble. the adpro might have lifted it off the plastic? Too hard to tell from the picture, but there is no way that is ready for paint, imo.
 
So in the case of a new bumper, do you rely on the original primer or...?

I'll rework the bumper, but for future reference, do you normally spot in adhesion promoter on breakthroughs or are small breakthroughs acceptable?
 
Generally we do because there is not time or money available to do anything else. We have found that some of those primers need to be cleaned with nothing stronger than Sprayway glass cleaner because SPI #700 softens it. We will use a sealer on these bumpers before paint just like with a bare bumper, just skipping the adpro step.

I will spot adpro on breakthroughs as large as shown in your photo. If I had one say less than 1/16" wide and only a 1/2" long, I would not.
 
If you don't seal down the cut through bumper primer it could (more then likely) swell the edges of cut throughs causing what we refer to as bullseyes that will show through the base and then more sanding. You will be fine if everything is sticking. You can reprime with 2k or epoxy, wait a day check for any swelling and reprep by scuffing. Also check your edges for any loose primer, the solvent may have creeped under it and loosened it from the bumper. You can use tape to see if it will pull off.
There is always (on ours we get) a sticker on the underside with painting instructions along with a CAPA sticker.
 
I stripped it down to the plastic and I'm starting over. Hopefully things will be better this time around, feeling pretty frustrated at this point.
 
You must log in or register to reply here.
Back
Top