Barrier coat disaster

[KompetentKrew]

West System was applied "wet on wet" in sense that the previous layers were still tacky, but this is according to the instruction.

Do you have a link to the instructions you followed, please?

 

[dankilb]

Wow. The stuff of nightmares. You have my sympathy.

We didn't use acetone after final sanding.

As a few others, I think this is the likely cause. GRP requires a lot of degreasing before any coating / laminating. The laminate itself can release contaminates. Pressure washing is advised precisely as a means of helping release these - so that too may have been a factor. Plus you have a boatyard environment with grease, dirt, contaminates.

Sanding itself - without degreasing - can spread contamination over an entire substrate.

That is why West and others specify degreasing (which I’d argue is the most important for GRP) and some also require acetone (inc. West IIRC).

Contamination, spread over the entire area via sanding - either in addition to / or moisture - are the only possible factors IMHO.

 

[dankilb]

This:

maybe wax had come to the surface

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

Pressure washing forces water into glass fibre, it would take days/weeks to dry in my opinion.

i think it's more likely that the problem was some contaminant on the surface prior to application of the first coat

 

[dankilb]

That’s good, because degreasing with solvent prior to application of epoxy is known to adversely affect bond.

Mike

Really? By ‘prior’, do you mean immediately before application and without allowing time for evaporation ? (if so, I agree) Or do you mean no degreasing/acetone at all?

West say:

 

[mikegunn]

Really? By ‘prior’, do you mean immediately before application and without allowing time for evaporation ? (if so, I agree) Or do you mean no degreasing/acetone at all?

West say:
View attachment 140170

No. I apologise as I should have qualified my statement by adding “without leaving adequate time for evaporation”. This can take a number of hours because solvent can be drawn along the surface of glass fibres by capillary action and be very reluctant to evaporate.
Mike

 

[kko]

Also, I think the contamination could be the reason.

We have used manuals from the West web page. Thus, cleaned the surface before sanding, as they say. However, when we have sanded down through about 4-5 layers of old paints, there could be contamination source.

I am angry on myself, that we just didn't wipe everything with acetone after sanding. This could change everything.

On the other hand, if there was silicone contamination (someone mentioned this when I looked in Google for epoxy/contamination topic), then we should use some special DuPont wax/silicone cleaner, not acetone only (as West recommends in fact, but before sanding, according to the surface preparation manual).

So, is it possible to remove contamination after sanding well enough? Can it be something that even a good cleaner will not remove?

I must really think now if I want to finance experimenting (and possibly scratch down several thousand $ again) or just put cheapest paints and use the boat as is.

 

[kko]

When I go once again through the West surface prep manual, this we did and not suspect the problem:

How do you know whether your surface preparation is truly effective? Wash it with water. This unsophisticated “water break test” works because many contaminants repel water. Simply apply water to the surface with a Scotch Brite pad. If the water sheets off the surface evenly, the part is “clean.”

 

[kko]

And when I think about contamination from old paints... We have also repaired the bow, well above the water line (there was the old gelcoat only in this area, no other paints). It was sanded with fresh discs, on a different day. And also there are big areas with no good adhesion of the barrier coat to the old gelcoat. So we are really confused about this, what went wrong in this expensive and extremally fragile process, as we see it now.

 

[srm]

Regarding solvents for cleaning - it depends on the epoxy base. It does not apply in this case but Coppercoat uses a water based epoxy and IIRC specifically warns against using solvents to clean the surface before application.

 

[kko]

The Coppercoat sticks well to the barrier coat. All the layers are perfect togerher. But when the first layer goes off, it is just the bare GRP to start again :/

 

[kko]

Or just sail as it is until the water will go inside...

 

[Laser310]

Regarding solvents for cleaning - it depends on the epoxy base. It does not apply in this case but Coppercoat uses a water based epoxy and IIRC specifically warns against using solvents to clean the surface before application.

i usually just use denatured alcohol before barrier coat

mostly i just need to get rid of dust from sanding.., and i want something that dries instantly

and, acetone is not good for you - i should know.., i spent years with all kinds of organic solvents in a chemistry lab at graduate school. I'm amazed I am still alive...

 

[dankilb]

So, is it possible to remove contamination after sanding well enough? Can it be something that even a good cleaner will not remove?

A combination of a alkaline degreaser (concentrated ‘garage’/workshop degreasers are suitable and cheap as they dilute at a couple of capfuls per 1L of water) and aforementioned solvents (acetone, alcohol or painters’ ‘panel wipe’/‘prepsolv’) should do the job.

The trick is regular and meticulous cleaning with the above. I would degrease first before starting any work (after the yard have pressured washed) and then regularly, as require, if the substrate becomes dirty and/or before any major sanding/machining.

Then a final solvent wipe, taking care to allow time for evaporation, as instructed above.

Yours is an extreme and sobering failure, but it shows what can happen (and the implications).

As a pure laminating resin, West is towards the more intolerant end of the epoxy spectrum when it comes to prep. If you have another go, I’d recommend a solvent-based paint such as Jotun Penguard or International GelShield.

 

[srm]

As a pure laminating resin, West is towards the more intolerant end of the epoxy spectrum when it comes to prep. If you have another go, I’d recommend a solvent-based paint such as Jotun Penguard or International GelShield.

When I coated my current boat in 2009 in Plymouth I had the antifoul removed by soda blasting, removed old epoxy barrier coat to gel coat with random orbital sander, then water wash with hose to remove dust. A few days latter applied high build industrial epoxy (one coat per day) that was supplied by the Coppercoat people, then a few days later Coppercoat. When I next lifted out in 2019 to touch up the Coppercoat I had some small solvent blisters on one side of the hull that had formed between the first and second coats of the high build epoxy.
According to the tins the high build epoxy was formulated for repainting bridge steelwork and could be applied in damp conditions so it was probably a lot more tolerant of application conditions than most yacht products.

 

[Tradewinds]

Just a final point. Your sanding discs - were they anti- clog? I know nothing about sanding discs and whether this is a valid point. I can’t imagine the manufacturers producing something that leaves contaminants behind.
But as said before, West epoxy is quite prone to getting ’holidays’ in the coating with the slightest contamination on the surface. Jotun is far more forgiving.

 

[dankilb]

I had the antifoul removed by soda blasting

Indeed blasting itself is also cited as an effective means of surface decontamination (based on TDSs - not any personal expert knowledge!).

Was chatting with pontoon neighbour undertaking a massive (20m+) steel boat restoration in the yard about how some blasting was being delayed so that the pros could blast as much of the new steel as possible too (presumably, we figured, to quickly/effectively clean and key the substrate before coating).

Big vote for Jotun from us. Last autumn we did a (maybe…?!) 8 coat barrier on badly degraded gelcoat on our 41’ - after blasting - and I cannot fault the stuff. We used Penguard and Jotamastic (the latter being an ‘off spec’ usage, based on its even greater water resistance). Audaciously, we also applied several coats of laminating resin before the Penguard. It worked (after considerable prior testing) but the anxiety of poor adhesion meant our prep was meticulous. We even tented the boat in tarps just to keep the sun and dust off.

 

[vyv_cox]

Was chatting with pontoon neighbour undertaking a massive (20m+) steel boat restoration in the yard about how some blasting was being delayed so that the pros could blast as much of the new steel as possible too (presumably, we figured, to quickly/effectively clean and key the substrate before coating).

New steel will have mill scale surface deposits. Painting over these will inevitably lead to rusting long-term. The famous SA2.5 standard requires all mill scale to be removed, leaving an even gray surface with no black spots.

 

[Yngmar]

If you're 100% sure you got the mixing ratio of the first layer (West System resin + hardener + 422 barrier additive) right, it must be contamination. That's also in line with some patches sticking better than others (pressure washer removing some of it).

You're right that with this much sanding it's improbable that something was carried through from other coats while removing them. Silicone antifouling is pretty recent and probably wasn't in the mix of old coats either. Sanding disc contamination, maybe.

You probably have some barrier coat left and can experiment a little with that? I.e. do a patch of hull as is, a patch with acetone cleaning and a patch with alcohol cleaning. See how they do.

Can always do a GoFundMe to get this mystery figured out and help with the costs

Personally I would slap on a layer of Interprotect or epoxy (just resin+hardener, no additives), abrade that gently and put Coppercoat on top. It definitely sticks to either of those, although on my hull it also worked fine on plain polyester gelcoat. Do adhesion tests between (stick on duct tape and rip off).

Good luck!

 

[kko]

The sandpaper was just a cheap "no name", three different types which we could buy in local shops.

I did more tests near the craddle support points (where still I need to apply the barrier/coppercoat after moving the boat and I have some resin left). In 5 points from 6 tested it was ok (don't know if it is really good or should be better). Around one which is in the photo, where I could go further and further scratching, I have just sanded the edge to stop delamination (the same with the water line) and applied coppercoat in these places (no barrier).

A friend we met in the shipyard has used Jotun with no problem, but the boat is different and he used acetone after sanding. Other conditions the same.

Now we go sailing, just to have some fun finally After drying the boat another time we will see...

 

[kko]

What about solvent based products water resistance?

We possibly want to keep the boat in water for 2-3 years in the following seasons. That is why we have started the hull renovation. Still, we plan one more season in the shipyard, so there is some time to improve it. Thus, we think about different options.