Primer before Coppercoat

The Hempel primer came from Coppercoat recommended by them!
"Compatibility/Substrates:
GRP Gelcoats & compatible epoxies: It should not be used over any one pack products. "
Hempel is two pack.
I have all the Coppercoat info but it doesn't help (and it is Saturday!)
 
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After suffering problems with professionally applied coppercoat, where the copper coat popped off leaving circular holes in the copper coat, I was told (by AMC) that the problem was caused by the primer outgassing.

Coppercoat Pox.JPG

You can apply coppercoat over more or less any primer, providing that you leave it long enough for all the solvent to evaporate. For some primers that could be a very long wait.
It is probably best to use a solvent free epoxy as the primer, but it is best to talk to AMC first about the primer you intend to use. They now have many years of experience of what works and what causes problems. Coppercoat is very expensive, especially if you have to do it twice.
I’d make the phone call.
 
We applied our Coppercoat to epoxy primer that was cured but you could still make a mark in with your finger nail. Primer one day, Coppercoat next day. Not had any adhesion issues.
 
Have to comment I talked to coppercoat quite extensively before whimping out and replacing the existing antifoil with millie NCT after blasting off.

We couldn't take the risk that it might fall off.

Interested to seen how the millie performs
 
IMHO it’s the ‘wet on tacky’ you need to confirm with CC. As their epoxy is water based, you wouldn’t want it to react with a solvented primer somehow.
 
I have now been able to contact Coppercoat and their advice is;-

"Hempel Light Primer is a solvent-based epoxy primer, so after applying the final coat, leave that system to fully cure for a minimum of 5 days, before then proceeding with the Coppercoat application. This is to allow sufficient time for the solvent to fully cure out and evaporate."

My test patch on my rudder was applied after only around 30 hours so may need redoing.
 
Graham_Wright said:
My test patch on my rudder was applied after only around 30 hours so may need redoing.
Click to expand...
It depends how many coats, as well as atmospheric conditions etc… It may well be fine.

It isn’t so much direct incompatibility (any sort of ‘reaction’) that’s usually the issue once the paint has gone touch dry. After that, it’s a risk of solvent entrapment (which can cause small blisters after a period of immersion).

You may find that 5 days is a worse case, assuming the maximum coats and minimum temps, etc.

I wouldn’t entertain sanding it off myself (I know you didn’t say that either!).
 
West system epoxy plus barrier coat additive (minimum 6 coats 'wet on tacky' on bare laminate if going the whole hog). Cure for at least 7 days at UK summer temps. Sand with P80, wipe down with iso alcohol (important not to use any other solvent wipe especially acetone) and the Coppercoat with as many coats as the quantity calculated for size of boat allows. Each coat wet on tacky. Make sure you use the iso alcohol as a thinner otherwise it will go on too thick and orange peely if you don't. That will require excessive sanding to activate. Sand with P240 to activate.
The US Coppercoat website has much better information that the UK one.
 
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