Gelcoat on Epoxy: Will it work, or disaster?

sculpin

Super Anarchist
So I've got a patch of deck to repair, and have to decide on the method.

The West literature claims that gelcoat will stick to epoxy.  Standard industry wisdom says this is like crossing the streams in the movie Ghostbusters.  Who is right?

I do admit a few years back I filled some un-used screw holes with epoxy and then put gelcoat over top of it, worked fine - but a tiny repair, not under stress.  This is some core repair, smooth area (not anti-skid).  About a square foot.

 

Zonker

Super Anarchist
9,714
5,669
Canada
Wash the cured epoxy well with warm water and a green scrubby. The residual amine on the surface is what seems to inhibig the Gelcoat cure. 

 

Overbored

Anarchist
711
59
So. Cal
when you remove the peel ply you are removing the amine when you sand you remove the amie. gelcoat over epoxy or polyester works best if there is a lot of tooth for it to hold on to. I use 80 grit before gelcoat. there are additives the make gelcoat adhere to epoxy better. I have used Duratec and it works good it also thins the gelcoat for spraying but does make the color a bit more see thru.

 

Gouvernail

Lottsa people don’t know I’m famous
38,010
5,544
Austin Texas
My best understanding  of those whose gelcoat applications over epoxy have not been personally disastrous has to do with faith,  believing, and never allowing doubt to cause investigation. 
    




 

sculpin

Super Anarchist
Thanks Gouv!

So - remove amine, 80 grit prep, possibly "duratec".  And faith.

Well, it isn't structural and worst case it looks bad for a season, I guess I will go for it.

 

Slowboat

Super Anarchist
Really, really, really (yes really) scrub to remove the amine blush. I have had significant issues due to amine causing the gelcoat not to harden. I might think about using a non-blushing epoxy as well if it makes sense for the type of repair. 

Other than that, it can work pretty well. 

 

PeterRoss

Member
215
45
Rhode Island
Wash it down with water, water only. I wipe first with cloth towel and warm water to remove most of the blush. You can feel the surface difference right away. Next, scrub with a soft scrub pad. Then sand with 80 grit without goofball kneeling to the gel coat gods or leaps of faith. It simply works and if done properly will not fall off in 6 months.

 Mixing Duratec additives works beautifully but that doesn't answer the gel coat over epoxy question. I was a disbeliever and never bought into the water only blush removal, until I actually tried it. Do not use soapy water. Nice clean bottled drinking water works great.

 No blush epoxy is a bad alternative imho.

 
Last edited by a moderator:

European Bloke

Super Anarchist
3,407
826
Years back Winder in the UK has some problems with gel coat over epoxy peeling after a year or two.

Then they worked out what to do and now all is well. So as we as know it can be a problem, but when done properly it's fine.

 

Gouvernail

Lottsa people don’t know I’m famous
38,010
5,544
Austin Texas
The most amazing thing about those pushing application of polyester over epoxy are generally the same folks who insist Epoxy over old polyester is “better because of the epoxy’s super duper adhesive properties. 

Counting on adhesion when applying polyester over well cured epoxy is an invitation to Mr Murphy to show up.

The failure to adhere is NOT 100% ABOUT AMINES.

There are a myriad of reason the bond snd / or the cure can fail to happen as you wish

You may be working on your own boat where the consequences of surprise failures are nothing more than an opportunity to enjoy working on your own toy. 

Those of us who sell our services to other people have two options:’

**Do it properly so it lasts until we die.

**Not do it at all. 

I haven’t knowingly applied polyester over epoxy this century. I have no intention of ever doing do again. 
 

If a person employed in my  shop is caught deliberately applying polyester over epoxy he is given three days off unpaid or fired on the spot.

 It is an offense  that ranks up there  with applying epoxy over antifoulant , applying hard antifoulant over ablative, using non-stainless fasteners,  stealing beer or alcohol from a customer’s boat, or other absolutely  inexcusable  bullshit. . 

.

 

PeterRoss

Member
215
45
Rhode Island
The most amazing thing about those pushing application of polyester over epoxy are generally the same folks who insist Epoxy over old polyester is “better because of the epoxy’s super duper adhesive properties. 

Counting on adhesion when applying polyester over well cured epoxy is an invitation to Mr Murphy to show up.

The failure to adhere is NOT 100% ABOUT AMINES.

There are a myriad of reason the bond snd / or the cure can fail to happen as you wish

You may be working on your own boat where the consequences of surprise failures are nothing more than an opportunity to enjoy working on your own toy. 

Those of us who sell our services to other people have two options:’

**Do it properly so it lasts until we die.

**Not do it at all. 

I haven’t knowingly applied polyester over epoxy this century. I have no intention of ever doing do again. 
 

If a person employed in my  shop is caught deliberately applying polyester over epoxy he is given three days off unpaid or fired on the spot.

 It is an offense  that ranks up there  with applying epoxy over antifoulant , applying hard antifoulant over ablative, using non-stainless fasteners,  stealing beer or alcohol from a customer’s boat, or other absolutely  inexcusable  bullshit. . 

.
Bullshit!! You are clueless.

Sometimes, your inane rants are hilarious because they are so far out in left field. That collection of words is far from constructive. It's mean spirited ignorance at best and it's nonsense.

 OP asked a question. Some replied with working solutions to his question. You........typed bullshit as usual.

 
Last edited by a moderator:

MiddayGun

Super Anarchist
1,179
442
Yorkshire
Bullshit!! You are clueless.

Sometimes, your inane rants are hilarious because they are so far out in left field. That collection of words is far from constructive. It's mean spirited ignorance at best and it's nonsense.

 OP asked a question. Some replied with working solutions to his question. You........typed bullshit as usual.
The OP asked if gelcoat will stick to epoxy, Gouvernail is just saying that as a professional he can't take that risk which I totally get.
For what its worth none of the professional repair guys around here will put gelcoat over epoxy either, and they all subscribe to his philosophy that in nearly all cases a repair in Polyester is perfectly adequate. 

 

PeterRoss

Member
215
45
Rhode Island
The OP asked if gelcoat will stick to epoxy, Gouvernail is just saying that as a professional he can't take that risk which I totally get.
For what its worth none of the professional repair guys around here will put gelcoat over epoxy either, and they all subscribe to his philosophy that in nearly all cases a repair in Polyester is perfectly adequate. 
 He takes risks everytime he touches a boat. Your comment about polyester does not apply. OP noted epoxy was used some time ago. 

 In his case there is nothing wrong with gel coat over epoxy. Any "Professional" who runs away from that repair due to inexperience uses the term "Professional" lightly.

 




Top