Hi everyone,

This is my first post, great forums! I just painted my car and the paint did not bond at all! I need to repaint my car and I was hoping for advice on finding the problem before I repaint with the same material. I am not a professional painter by any stretch, but I have painted many cars and never had a problem like this. Here is what I did and what happened in steps:

1. Strip 1967 Plymouth Fury convertible to bare metal
2. Self etch primer
3. U-pol epoxy primer
4. Rage gold bondo, more primer, block, 3M guide coat, more primer and bondo as needed to get it all dead flat
5. I have used this combo before, but here is the new step. I sanded the U-pol primer with 220 and then followed their tech sheet and mixed it up at 4:1:2 with reducer to use the U-pol as a sealer, otherwise U-pol primer is 4:1: 0-10% reducer - that is a lot of reducer but I followed their tech sheet, sprayed 1 thin coat
6. Sanded with 600 grit per base coat instructions
7. Waited several days, lacquer thinner wipe down, then tack cloth
8. Sprayed 5 coats Valspar 999 based coat mixed 1:1 with matched Valspar reducer
9. Sprayed 4 coats Valspar LVCC3300 on the same day after appropriate flash times. It only took 1/2 a gallon of clear to spray the recommended 2 coats on the entire car, so I thought I needed more and sprayed 2 more coats (big mistake I think)

OK, at this point the car was a show finish, beautiful! One month later, I banged the paint and it chipped which was odd, so I got under the chip to check the bond - uh oh, the paint peeled up in sheets. I knew it was a disaster, so I peeled the entire car off in 30 minutes by hand with a razor blade to get the peels started.

The paint peeled at the base - primer interface cleanly. The base coat was solidly bonded to the clear coat and the primer is bonded to the car very well. It clearly failed between the base and the primer - the back of the base has no primer on it, no bond at all!

Here are two major areas of trouble I think I identified.

1. When I peeled the car I could smell the reducer, it was very strong, it was solvent city, I stunk up the shop there was so much of it and I had to put a mask on it was so strong. Now I know the Valspar base completely degrades with any solvent at any time

2. I measured the paint thickness with a caliper after I peeled it, uh oh, the base-clear was 10 mils thick - to thick for my usual spraying! This was first time spraying this Valspar high solid clear and I did not expect it to go on so thick. The base was about 2 mil and the clear was 8 mil

So I think that by spraying the U-pol primer as a sealer 4:1:2 for the first time in my life, I loaded the car up with solvent. Then I painted to thick of clear adding more solvent and compounding the problem by trapping it with a thick coat. I think the reducer from the epoxy primer got trapped and lifted the base coat right off.

I have enough material to do this again, but do not want to make the same mistake twice. Any thoughts on what to do? In my shop I have more U-pol epoxy, more base and more clear. I also have a gallon of black PCL poly primer (trouble? Never used it?). What should I do next - I am certainly not going to spray 4:1:2 primer and I am not going to spray 4 coats of clear, only two this time - as the Valspar tech sheet states.

Any thoughts on my fun failure?

Thanks,

Jesse

Epoxy Primer over Etch is not always a good thing. In fact, some epoxy primers state right on the label not to use over Etch primer.

I think your problem came with the Lacquer thinner wipe. Lacquer thinner should only be used for cleaning equipment and never on the car since it leaves a film behind.

Flash times vary by temperature so the tech sheet times are approximated based on 70 degrees and could take longer. I normally watch the base flash off and when there are no more glossy spots (solvent evaporating) I wait another 5 minutes and then shoot the next coat.

I agree, the thinners wipe down was not the right thing to do. It may have contributed to the lack of bond by the residue it leaves behind. Possible that it also attacked the primer surface. But that's not the real problem.

5 coats of base? You should be able to get coverage with 2 coats, sometimes 3 for odd colours, but 5 is too much. You say it was 2 mils DFT which is over 50 µm, close to double what it should be. So, this would also have had the effect of holding the reducer in, especially if it was a bit cool or you didn't allow enough flash off time between coats or before your clear.

200 µm clear? That's 2-3 times as thick as it should have been and, of course, if applied too early would have sealed in the basecoat reducer, resulting in your failure.