Paint didn't adhere to 2k Regular Build Primer

A

Albtross

Last Spring I purchased a hail damaged car for my son. I repaired the hail damage used 2K primer over the repaired areas, then repainted the entire car. About a month and a half after painting, noticed a chip in the paint on the A-pillar. As I was preparing the spot for touch up, I noticed that paint had not adhered to the primer. I was able to pull off dollar bill sized pieces of paint. I was able to peel off all the paint on the A, B and C pillars. I did a quick repaint of the pillars, but its time to actually go back an do it right. I'm trying to figure out what I could have done wrong, so that I don't repeat my mistake.
  • Evercoat Rage Ultra body filler
  • 2 or 3 coats of 2K Regular Build Primer
  • Sanded with 400 grit
  • Cleaned with both 700 & 710 Grease & Wax Remover
  • 2 Coats of paint
  • 3 Coats of production clear
I assume that I should sand down to the primer all the areas that I am concerned about. But then what, just clean and repaint?
 

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IN addition to what 68 asked, here are the questions that pop into my head at the moment. Are you experienced at this or was this your first one? The 2k is a quality product so I'm pretty certain it was something on your end. How long did you wait from final sanding of the primer before you painted? Are you sure you activated the primer correctly? Are you certain it was completely cured? Are you sure you sanded those areas? Did you give the W&G removers enough time to flash off before you sprayed your basecoat? What was the weather like when you shot it? Temperature? Are you certain that the ground coat (existing finish) was sanded in those areas before you sprayed primer over it? Looking at your peels gut feeling is that you had solvent trapped in either your primer, or possibly your base and you recoated before everything escaped which then caused the lifting. Tell us what you did in detail.
 
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Maybe primer sit too long and not resanded before color. Was base allowed to flash properly between coats and before clear?
 
Waiting to hear on the timeline of spraying and what the answer is...
 
Sorry for the delay in responding.

I'll do my best to answer your questions, but on some of them I can't say for certain. My father was in out of the hospital around the time I purchased the car, so on at least 3 occasions I had to leave town expectantly. In fact, I had painted the car and was preparing to clear coat on the morning of 5/18, when I received notice that he wasn't doing well. So when I got back to town the next week, I had to sand and repaint before I could clear. That being said, as many times as I stopped and started, I could have done anything. My main goal is to make sure I don't repeat any mistakes.

68:
  • Paint: PPG Shopline, medium reducer
  • I guessing 30min on the W&G remover, which I now realize probably isn't long enough.

Chris:
  • I'm not expert, but this is not my 1st time to paint, but it is my 1st time to use SPI primer.
  • I agree that it is probably something that I did.
  • I allowed the primer to cure overnight.
  • I am as sure as I can be that I sanded before shooting the base coat.
  • I guessing 30min on the W&G remover.
  • Since this was late May, I would say mid-70s to mid-80s.
  • I'm fairly certain that the existing paint was sanded before priming. Since, the primer is not peeling, is it safe to assume that this is not the issue.

Elwood:
  • The primer was allowed to sit overnight, but I'm almost positive that it was sanded before painting.

Additional info that may be helpful.
When it became clear that I was not going to be guaranteed enough time to complete the entire car at once, I ended up doing it in sections. The last item to be painted was the roof. I was prepping the roof for painting, when I noticed the chip on the A-pillar. So I was extra careful when prepping the roof. I know for certain that the roof was sanded and I know that the W&G was given at least an hour to dry.

The roof came out looking good, but after a day or two in the sun I noticed what looked like quarter sized air bubble under the paint in one spot. After several days, the air bubble went away and the roof now looks fine, but I assume this means that the paint did not adhere to the roof either.
 
The paint chips appear to have texture on them to me, which could indicate poor sanding. Primer that's not sufficiently sanded plus reducer that flashes too fast can cause delamination. Or, solvent trapping can cause it, too. If there is a perceived solvent smell when the paint is peeled off, that's a sign of solvent trapping.
 
basecoat does take a long time to gain full adhesion. it wont be fully stuck until 100% of the solvents are out of the paint film. depending on the environment when you sprayed and how long you gave the base to flash will depend on how long that process will take. generally with no clear on, base will generally take about 24 hours for all the solvent to come out. if you cleared in 30 min or as soon as the base flashed dull or felt dry then it can take months. not saying this is what happened. just offering that up because clearing too soon and trapped solvents is the biggest mistake painters make.....or are forced to make to keep a production schedule.
 
I didn't smell anything when I peeled the paint off, but I wasn't really sniffing it either.

Jim, I'm little confused by your comment. Could you clarify? I generally clear an hour after spraying the base coat. After 24 hours, I would have to scuff the paint before clearing wouldn't I? Are you saying that you should wait as long as possible to clear? If so, then I've been doing it wrong all along. I thought you could clear as soon as the base flashed. I wasn't in a hurry, I just thought that was the way it was done.
 
just because the base feels dry doesnt mean its hardened up and the solvents are all gone. you have to remember that 50% of the solvents flash and the other 50% soak in. many of these are tail solvents which are super slow. you DO NOT have to scuff base after 24 hours. base is not a catalyzed finish so your clear will bite into it even after it has say for days. the best thing you can do for a paintjob is let it sit in base a day before you clear. bodyshops dont really have that luxury but they have less of a problem because they are spraying in super high flow booths with heated purge cycles. my previous paint system was diamont and i know with that system the base would flash dull really quick but it would not really harden up for 24hrs. now i could clear it in a hour and be ok but the adhesion would suck. if i for instance didnt score the clearcoat where i had my masking tape i would be guaranteed to peel the base right off the primer like you did. if i let the base flash overnight then clear.....no issue with adhesion. what it boils down to is if the base is soft then full adhesion has not been reached. the clear will trap those solvent making the base soft for months so best to let the base harden up a bit before to seal it in.
 
Had a peeling door one time that I removed 90% of paint with air nozzle. Could still smell reducer they used.
 
Jim C said:
just because the base feels dry doesnt mean its hardened up and the solvents are all gone. you have to remember that 50% of the solvents flash and the other 50% soak in. many of these are tail solvents which are super slow. you DO NOT have to scuff base after 24 hours. base is not a catalyzed finish so your clear will bite into it even after it has say for days. the best thing you can do for a paintjob is let it sit in base a day before you clear. bodyshops dont really have that luxury but they have less of a problem because they are spraying in super high flow booths with heated purge cycles. my previous paint system was diamont and i know with that system the base would flash dull really quick but it would not really harden up for 24hrs. now i could clear it in a hour and be ok but the adhesion would suck. if i for instance didnt score the clearcoat where i had my masking tape i would be guaranteed to peel the base right off the primer like you did. if i let the base flash overnight then clear.....no issue with adhesion. what it boils down to is if the base is soft then full adhesion has not been reached. the clear will trap those solvent making the base soft for months so best to let the base harden up a bit before to seal it in.
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JimC, you need your own section called Jim's Tips. You're an encyclopedia of info.
 
68, yes and no. even though you put catalyst in the base, there is usually very little reactivity. in other words it doesnt really crosslink making a chemical resistant coating. im sure you have noticed if you activate bese that it really doesnt gel and harden in the cup like a clear or primer does. the activator does harden from the moisture in the air just like it does in the threads of the cap that you need channel locks to remove, lol. basically activated or not you can still let the base sit for a week, grab a rag soaked with lacquer thinner and wipe the base off. this means the clear will still bite in and bond to it. best thing to do though if you activate your base and know its going to sit for 3,4,5......days is not activate the last coat and make sure you use clear with a slow activator and add 10% reducer so it stays wet on the surface longer and has time to bite in.


aae....thanks lol
 
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Jim C, thanks for the info. I'll make sure to give the base much more time to harden before clear coating going forward.
 
Jim nailed it, any all over or resto we do sits in base coat for a minimum of 24 hours with booth temp around 80 ( the 240 volt forced air heaters from home depot are fantastic,and for the peace of mind making sure temps are up are worth every penny). With certain basecoats you will want to look into the tech sheet for maximum allowed topcoat time, some have to be done within 24 hours, some can sit for a long time and still adhere. When it comes to repairs or a bumper or whatnot, I give the base 2 or 3 hours before clear, but a big job will sit and just flash off until the following day. One thing I've learned with spi primers especially, rushing them will cause disasters, other production brands are a bit more forgiving and are seemingly made to rush rush rush rush, but not spi. rushing the epoxy or the urethane will simply compound on top of everything else and create a nightmare, so the saying slower is faster is 100 percent accurate.
 
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