Barrier coat disaster

[kko]

Hello,

this year we wanted to make the hull renovation which should last "years". But it failed just when we have removed the masking tape. Our boat is polyester Albin Vega. We have sanded all previous paint layers to the original gelcoat. The Gelcoat was thin, so 70% was actually sanded down to the fiberglass. The hull was washed with karcher afterwards. We have painted one layer of unthickened West System epoxy, next 6 layers of the West System epoxy with the Barrier Coat additive. Afterwards, everything was sanded, washed and the Coppercoat was applied. Over a month of hard work and lot of money...

And when we have removed the masking tape, we have found that there is completly no athesion. We can peel the coat with bare hands down to the old gelcoat or laminate (no difference in adhesion). The epoxy cured perfectly, there were no signs of surface contamination, sanding dust was washed, hull was dried 10 months in the Canaries sun. Any hints?

Best regards.

 

[kko]

This has failed and it is a fact. But what should we do? We will test the Coppercoat without the barrier (still we have one kit left). In a few days we will know the adhesion. But the Coppercoat suggests using a barriercoat underneath. We can try the gelcoat. But we don't want to waste more time and money just to test further products without knowing the true reason.

 

[vyv_cox]

Your photos suggest that the adhesion loss was between the hull and the first coat of West epoxy. How long did you wait after pressure washing? Did the West epoxy cure properly?

When I did my keel I used West epoxy, five coats, then five coats of Coppercoat. No problems at all, stayed in place for 10 years.

 

[kko]

Exactly, it is the first epoxy layer going off with all the further layers. We have put epoxy a day after washing. Its dry here. Cured perfectly.

 

[vyv_cox]

I suspect that one day is nowhere near long enough after pressure washing. Even when vacuum drying Is used it takes weeks to dry a hull out. Sorry.

 

[Boater Sam]

Exactly, it is the first epoxy layer going off with all the further layers. We have put epoxy a day after washing. Its dry here. Cured perfectly.

I reckon it was not dry. Surface dry maybe, but once encapsulated in epoxy the moisture in the glass would come out and prevent adhesion.

 

[kko]

Are you sure this is the reason? The hull was dried 10 months. So, a day in a windy, hot conditions wouldn't be enough after 15min pressure washing? Surface was dry after 5 minutes here.

 

[kko]

There in no rain here at all. A desert all around. And the boat was 10 months in the shipyard before we have started.

 

[Graham376]

We have painted one layer of unthickened West System epoxy, next 6 layers of the West System epoxy with the Barrier Coat additive.

Did you apply all coats wet on wet or one coat followed some time later with the others? From memory, unlike Gelshield which can be left for months between coats, West has to be done in one continuous application.

 

[UK-WOOZY]

was the bare GRP keyed for the epoxy to grip to, maybe wax had come to the surface.

 

[kko]

Yes. The layers were wet on wet and there is no epoxy layers separation on the scratched pieces.

 

[kko]

Old paint layers were sanded with 40 grit paper down to the original gelcoat or bare GRP. I have read now about wax/contamination. But don't know where it could come from on such deaply sanded surface. It was first scratched with the rotary high power machine later sanded with oscillatory machine to make the surface smooth.

 

[srm]

I did much the same some 15 years ago in Orkney on my Prout catamaran. Removed antifoul down to gel coat and abraded during Easter holiday then during July applied one coat of West Epoxy each day after checking temp forecasts for +10C being the lower limit for the hardener. Followed by an imitation of Coppercoat (that was not a good antifouling).

No problem with adhesion despite the cool humid climate other than having to pressure wash one of the West Epoxy coats the following morning as it had formed a wax film overnight due to humidity. All was still sound when I sold the boat some 5 years later other than blisters forming under the West epoxy on the saturated foam filled rudders.

I suspect the most likely cause of your problem was either a contamination on the hull that had not been removed by water pressure washing.

Or . .

If you started the West coating early in the morning there may have been the remains of a film of condensation on the surface; just a thin film in the sanding texture could have been enough to prevent a mechanical bond. I have no experience of the Canaries climate so am happy to be corrected but have observed heavy condensation at night around the desert coast of the Persian Gulf.

 

[kko]

Also we have read not to start early because of possible condensation. So we have started in the afternoon.

Contamination after so deep sanding, also not very probable. Or perhaps something from the sandpaper.

So there is no clear reason. And it would be better to know as we need to repair it (probably next year). We will have just bare GRP in a moment with so weak adhesion of the first layer.

Can it be our polyester gelcoat and GRP chemistry incompatible with the epoxy? It peels off the same from the sanded GRP and original gelcoat as well.

 

[kko]

We start thinking that just a cheap paint is what we need on our old boat. Instead of risking again half value of the boat just to scratch it off. Another boat will be finally less expensive. And better just not to touch many years of old paints.

 

[Boater Sam]

If you don't accept it was still not totally dry, why don't you ask the paint maker, West, for their professional opinion?
Pressure washing forces water into glass fibre, it would take days/weeks to dry in my opinion.

Do you not find it strange that all the coats of paint adhere to the previous coat but your first coat onto the washed grp didn't?

 

[Laser310]

If you don't accept it was still not totally dry, why don't you ask the paint maker, West, for their professional opinion?
Pressure washing forces water into glass fibre, it would take days/weeks to dry in my opinion.

Do you not find it strange that all the coats of paint adhere to the previous coat but your first coat onto the washed grp didn't?

i agree that there is a chance it wasn't dry enough.., but other causes are possible too for the lack of adhesion between the first coat and the gelcoat/grp

it is hardly surprising that the epoxy bonded to itself...

i have done a barrier coat touch-up without worrying too much about dryness and it has been fine - i don't have a dry climate and short of putting the boat indoors there is not much i can do about it

I generally think west system makes great products but i haven't used their barrier coat

i have used interlux interprotect 2000 - worked very well for me

 

[srm]

Can it be our polyester gelcoat and GRP chemistry incompatible with the epoxy?

This seems unlikely if its an old boat with fully cured polyester resins. Various epoxy coatings has been used for many years to make good polyester hulls. However, if you used polyester products to make good/fair the hull before the epoxy coating that may be the cause as chemical reactions continue for a very long time after the polyester is hard and sanding could have spread chemical contamination.

What grade did you use for final sanding? A fine grade may have created a polished surface that prevents the first coat's mechanical bond.

I have sucessfully epoxied two polyester resin boats after cleaning antifoul off, then using random orbital sander with 120 grit and water washing to remove dust. Sanding discs were changed after short intervals to prevent polishing as the grit filled up with dust.

 

[UK-WOOZY]

david johnson of wessex resins and epoxies did the barrier coat on my boat in 2020, it had been sandblasted back to the blakes barriercoat and had west systems barrier coat applied on top by him as a one off private job as he was not working during covid and the yacht club wasnt to far for him to get to, then coppercoat onto the barrier coat by another company. the barrier coat was just abraded with scocthbright pads by myself. May be worth contacting him for advice. He also is on youtube with advice and tips. I had reached out to him as there was a crack under the waterline which was revealed after the sandblasting.

from sandblasted to coppercoat=

 

[mikegunn]

Are you sure this is the reason? The hull was dried 10 months. So, a day in a windy, hot conditions wouldn't be enough after 15min pressure washing? Surface was dry after 5 minutes here.

Did you degrease prepared surfaces with a solvent, such as acetone, prior to applying epoxy?

Mike