Adhesion problems with epoxy and 2K, not SPI.

A

angrywombat4

I used Martin Senour CP400 epoxy which adhered very well to the base metal and any remaining old paint underneath. I then sprayed CP440 high build 2K, waiting about an hour after spraying the epoxy. The epoxy tech sheet says the epoxy can be top coated in 30 minutes.

The 2k cured beautifully. But I am having adhesion problems between the 2k and the epoxy. It is peeling off in places very easily, even blowing off in some. And where it comes off, I can smell the epoxy reducer I think.

So I am thinking the 2K cured and sealed in the epoxy and didn't let the solvent evaporate, hence the separation? Does 2K do that? I thought the 2K would allow the solvents to breath out.

Now am afraid to put the 2K over the epoxy? How long should I wait to do it again, and I guess I will be sanding the epoxy before I do?

Any ideas?
 
I have no experience with that epoxy, but it seems to me maybe the 2K was sprayed too soon?
 
angrywombat4 said:
I used Martin Senour CP400 epoxy which adhered very well to the base metal and any remaining old paint underneath. I then sprayed CP440 high build 2K, waiting about an hour after spraying the epoxy. The epoxy tech sheet says the epoxy can be top coated in 30 minutes.

The 2k cured beautifully. But I am having adhesion problems between the 2k and the epoxy. It is peeling off in places very easily, even blowing off in some. And where it comes off, I can smell the epoxy reducer I think.

So I am thinking the 2K cured and sealed in the epoxy and didn't let the solvent evaporate, hence the separation? Does 2K do that? I thought the 2K would allow the solvents to breath out.

Now am afraid to put the 2K over the epoxy? How long should I wait to do it again, and I guess I will be sanding the epoxy before I do?

Any ideas?
Click to expand...

Some questions;
What did you wipe it down with? How soon after you wiped it down did you spray? Did you DA the surface with 80 grit? How many coats of epoxy? Did you allow proper flash time between epoxy coats? What was the temperature that you sprayed it? Did you mix it correctly?

Off Topic:
I am pumped as my New England Patriots just completed the greatest comeback in NFL history to win the Super Bowl.

A true epoxy is never re-coatable in 30 minutes. More than likely the "epoxy" needed more time to set up before you sprayed 2k. So when you sprayed the 2k you trapped the solvents in the epoxy, hence the loss of adhesion. 24 hours @ 65 degrees or higher is considered the minimum when using a true epoxy like SPI, but it is also a good rule to follow with other brands like MS.
 
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Sounds like, the 2K was put over the epoxy to soon and the epoxy solvents are breaking adhesion.
 
sanding 71 corvette ,will epoxy stick to 180 sand scratch, how does your epoxy sand, car is already pretty straight, wouldn't mind skipping 2k primer,
i'm also activating dbc base
 
The 180 scratch should be fine. 80 is recommended if it is metal. I've sprayed the epoxy reduced as a sealer over 400 before. SPI epoxy sands great after drying a couple days. Has built in guidecoat which helps. Shines posts on here have lots of info about Corvette's and avoiding potential problems with them. Hope this helps. Friend had 72 t-top back in the day.
 
Thanks guys. I definitely think it's solvent entrapment. I peeled another small section off today when I got home and it still releases the epoxy solvent smell after about 2 weeks. Guess I'll be razor blading all the 2k off and starting over. How frustrating.
 
angrywombat4 said:
Thanks guys. I definitely think it's solvent entrapment. I peeled another small section off today when I got home and it still releases the epoxy solvent smell after about 2 weeks. Guess I'll be razor blading all the 2k off and starting over. How frustrating.
Click to expand...

True, but the saving grace is you caught it now before the topcoat went on.
 
When it comes to most painting processes, especially involving epoxy, slower IS faster. Everyone that has ever done much body work has had to scrape off something that at the time was thought to be good.
 
Patience has never been a virtue that I possess unfortunately. I have had to start using a timer on my phone to make sure I wait long enough for flash times. I am quickly learning that NOTHING can be rushed when it comes to paint and body work, (unless you want subpar results or want to create further work for yourself). Anybody that ever complains about the cost of a quality paint job, (and I was guilty of that) should have to spend some time participating in the process. Just the first trip to the supply store to buy materials opens one's eyes very quickly. My hat is off to you guys that do this stuff for a living. I wouldn't last a month.
 
If this was my epoxy here is what i would want you to do before you start peeling it off.
Give the car 7 full days in sun and then lets test, if you do this, after 7 full days call me and we will see if we are fine or in deep >>>>.
 
Thanks Barry, I appreciate the offer of assistance. I have almost all the 2k razor bladed off though. I just didn't want to take any chances, so I'll chalk it up to a learning experience and move on.

If I ever do another car, I'm going to foam roller on some rustoleum over anything already on the car and call it "patina". That seems fashionable now. :D
 
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