Epoxy adhesion?

O

old soul

Member
I don't know if this is a problem or not.
I have a fender in black SPI epoxy primer that was primed in August when it was around 84 degrees. It sat in the sun for 2 days and has had no bodywork done to it. I wanted to check the epoxy adhesion so I sanded a spot with 80 grit (on a block) down to bare metal. The epoxy feathered nicely with a smooth edge. I put a razor blade scraper to it and to my surprise the epoxy just peeled right off, cleanly, leaving nothing behind.
I expected it to put up more of a fight.
Does this sound like a possible adhesion problem or is it normal?
 
You have a problem with your prep. You did mix 1:1 and let it rest for atleast 30min before spraying right?
 
Yeah, I have been using SPI products for over 10 years now so the prep and procedures are well established.
 
Please explain your prep on the fender. Have a 70 Nova trunk lid in epoxy for 2 years and I can't scrap off. Keep us posted..
 
The fender was stripped with a razor blade scraper and a 3M clean and strip disc. The disc was only used on the body lines and wheel opening contours to avoid gouging with the razor blade. The entire fender was then sanded with a DA with 80 grit and hand sanded with 80 in the tight or irregular places.
Cleaned meticulously with SPI waterborne wax and grease remover and sit overnight in the booth. Middle of August in North Carolina so the temps were in the mid 80's. Next day mixed the black epoxy at 1-1 and usually let it sit an hour. First coat at 11:00 am; second coat at 2:00pm, going by my notes of the day. Sat in shop for 6 days and was then put out in the sun for 2 days.

Chevman, no, I have never tried to scrape my epoxy off before. I always assumed that if it feathered nice and smooth with a clean edge, even with 80 grit, than it was OK. I have never had a problem with SPI epoxy. Only after reading the epoxy adhesion thread on here (from Nov. 5) did I think to check. If you have ever tried to scrape your epoxy off, how did it go?
I would assume the epoxy should not be able to be scraped off so cleanly and easily.
Thanks for the replies.
 
I knew I had a problem once and scraped the epoxy off fairly clean, but never have been able to since. In fact, I believe that is Barry's test for proper adhesion.
Maybe you have something you previously put epoxy on that you could check.
 
What are the odds of a bad batch? I assume it's very unlikely. As that's why we buy these products. Just curious, no offence intended.
 
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