Please help me fix this! (adhesion problem)

C

CongaJon

So, I'm completely green at this. Wanted to see what it's like and figured my labor is free and I'll be doing a lot of sanding/polishing. Boy, was that correct!

I'm having a go at both bumper covers from a Miata. I took them down to plastic, sprayed 1 coat adpro, 2 epoxy primer, 1 light coat of 2K, reduced epoxy sealer, 3 coats of activated PPG DBC Green Mica and 2 coats of Universal Clear. Had quite a bit of peel so I started to wetsand with 600 Abralon on a DA in preperation for 2 more coats of clear. Noticed some small wrinkly bubbles that, as expected, opened up while sanding. 3 or 4 per cover, with the worst being pictured. The long one at the top of the front cover (third picture) I got after with a fingernail and that's as far as it went.

Should I have a go with several light coats of base on the bad areas? Primer it first? I don't think I have enough of that costly green stuff to redo them completely, unless it takes quite a bit less the second time.

Also, is the most sanded cover (second and third pictures) almost ready for reclear?

Thank you in advance for any suggestions!

Jon

P1010605 by CongaJon, on Flickr

P1010604 by CongaJon, on Flickr

P1010606 by CongaJon, on Flickr
 
That doesn't look good at all. It would be helpful if you could add more details, like how you sanded and cleaned in between coats, what reducers you used, how long you waited between coats, etc. Right off the bat it looks like you are dry spraying your coats, but there could be other issues as well.
 
Thanks for the replies! I dry sanded to plastic with 150 and used SPI waterborne wax and grease remover. Hit with adpro and after 30 minutes sprayed epoxy, which went well. A week later I scuffed, recleaned with waterborne and sprayed SPI 2K, which DID go on dry. Most of that was sanded off, then sealed with reduced SPI epoxy. The next day sprayed DBC with PPG DT860, which may have been a problem. It's a fast reducer and we hit 78 degrees when I sprayed. (36 hours later: 18 degrees!) It seems that most of the texture was in the base. Sprayed 3 coats with 25-30 minutes between. Waited 2 or 2.5 hours and sprayed 2 coats of UC with fast activator. It did seem like the first coat of that wasn't wet enough so I hit it harder the second coat. It looked pretty good other than texture, but these issues appeared while wetsanding with 600 later that night.
 
I'd be afraid to tell you it is OK because it looks like you may have adhesion problems, possibly due to the products that went on dry. DT860 is really too fast for basecoat in almost any condition over 60 degrees, unless the part is very small. At 78 degrees, even 870 is a bit on the fast side for two bumpers. DBC going onto a flexible part must be activated, this will increase adhesion and chip resistance. I think what you have there will fail rapidly on the front end of the vehicle due to stone chipping. You might get away with it on the rear until something bumps into it.

At the very least you need to feather back those defects and see if the materials are trying to peel off. Those spots will need primer, again at the very least. The best course of action, imo, would be to remove the color coats and start again.
 
So, here's a picture of the front cover now. Basically I took off some of the 2K down to epoxy, trying to keep things flat. Hopefully didn't go down to plastic in too many spots! Do you think it would be okay to hit it with a coat of reduced epoxy and then base?

Just placed an order with James for epoxy, clear and reducer and will make the 2 hour drive for basecoat tomorrow. I only have enough on hand for 1 cover!

P1010608 by CongaJon, on Flickr
 
Looks pretty good, I would spot spray any raw plastic with the adpro, then shoot a coat of epoxy mixed 1:1:25% 0r reducer and then wait 2-4 hours and shoot the base.

It is not uncommon for a bumper to want to peel the first couple of days if you break through while the solvents are still coming out.
In the future a simple test is where you broke through, put it in the sun for a couple of hours and the peeling should stop at the edge it broke through.
 
Thanks again for the help, gentlemen. If I may, I have one more quick question. While at the jobber today, they suggested that I try Shopline Plus. At $60\qt. vs. $180 for DBC and with the possibility of me messing up again, it seemed like a reasonable idea. The tech sheet for this paint makes no mention of activating it, but can it be safely done? My gut feeling is yes, but I thought I should ask those who know! The guy at the store said not to, but I imagine he is going by the tech sheet.
 
Finally, a positive day to report! 65 degrees and sunny. I hit the covers with reduced epoxy as suggested by Barry. Sprayed really well, but my bodywork wasn't up to par and there was just a little lifting on a few edges. Also had barely enough epoxy, so my gun sputtered and ran in a few spots. Sanded that stuff down and sprayed with 2K reduced about 10%. If it doesn't do anything funky overnight I plan to shoot base tomorrow evening. I have more epoxy coming, but with the number of coats on there I think I will skip that.

So, I have enough DBC to do 3 or 4 coats. Would you:
A) Spray the front cover with DBC and the back with Shopline, or
B) Spray a couple coats of Shopline on both covers and finish with a coat or two of DBC?

Thanks again and I hope everyone had a great Easter.

Jon

P1010614 by CongaJon, on Flickr

P1010615 by CongaJon, on Flickr
 
I wouldn't mix the two paints, spray one with one paint and the other with the other paint or order more paint.
 
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