2k Primer scraping off? Need help

Hello,

I primed all my fiberglass parts about 5 months ago and realized i needed more bodywork. I finished the filler work about 2 weeks ago and reprimed over the old primer. I scuffed up the 2k with 180 before i shot it to be sure. I'm using U-tech 2k primer and used it before and it seemed fine.

After i wetsanded this 2nd round of 2k i saw there were little pinholes and minor things i had to fix with glaze so as i was sanding down the glaze, the primer had a hint of i guess you could call it an "edge" where the old/new primer transitioned itself around where i was sanding, only revealing the first round of primer as I used my fingernail scraping aggresivly and it started to come off. The area that i could scrape off was a narrow area like the sides of a hood where the jamb is. Seems to me that the large areas are not scraping off and are bonded quite well.

I even tried that trick that Len mentioned about using packaging tape on and pulling it off quickly and no primer came off.

Could this be due to spraying too dry or not enough material on those areas?

Do i need to sand off the new primer and restart on just that particular piece i experienced this with? I have about 10 other med to large parts i sprayed and have not experienced the problem on the others.

I will need to reprime most of the parts as i did minor repairs on them, so would it be ok to just reprime/wetsand, and topcoat?

Any advice will be appreciated. TIA

Chris


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2K primer sticks to fiberglass very good weather sanded or not, so its not a prepping issue unless the edges were contaminated and thats unlikely.
Since primer is good everywhere else we know you did not have a bad isocyanate.
Gasing would be causing problems elsewhere also.

All I can think of would be three possibility's:
Dry over spray of the primer landing on the edges as you were primering.
Or the first coat was dry sprayed around the edges and never had a chance to stick.
Only other thing can think of is excessive heat on edges when sanding.
I assume you are using the High build or 2k-100 and not their
direct to metal (non iso).

Very unusual for sure!

Of course the very best item for raw glass is epoxy first.