Blisters in Coopercoat

[MoodySabre]

A friend of mine has just lifted his Konsort out and discovered blisters in the Coppercoat (applied by the previous owner). When popped these blisters have water in them. He has been told that this is because the hull wasn't properly dried out before CC was applied. He has heard that another boat Coppercoated by the same person has a similar problem.

To save money he intends just to sand these blisters off, prime and then antifoul.

Any thoughts?

 

[Gelmaster]

It sounds very much like osmosis.
A typical GRP hull problem. It is quite a common problem with hull bottoms.
It can get to be quite extensive and very expensive to rectify.
In the most extreme cases, a tool called a gel stripper,hand operated, strips off the affected areas. This process is then followed by the use of vaccuum heat pads. Then it is all skimmed over with an epoxy based 2 pack filler. Smoothed over once more, then 3 to 4 coats of gelshield plus are applied prior to antifouling.

Hopefully , in your friends case, it will only be a minor area affected.
In this case, you are correct to sand it back and re-seal. Make sure it is completely dried out first though, or it will simply come straight back!
I just took the liberty of research!
Basically, osmosis, laymans terms...damp over a long period of time....got water in it!
A term used is "Hydrolisis"when water penetrates a membrane.
Different salinities of water contribute to the accelleration of blisters on the hull. It happens as frequent in fresh and brackish waters as it does in salt water! Apparently, there is a natural phthallic acid already present in polyester resin
which when left exposed to the different acids and alkalis in water, rapidly accellerates hull blisters , which hold the water, known as the condition called Osmosis

 

[alan006]

If when you pop the blisters there is a vinager smell then I would suspect osmosis. If not then as you say it was probably not dry enough when applied.
You can use a heatgun to dry out where the blisters were. A piece of tissue paper touched against the blister hole is a simple way of seeing if moisture is present.

 

[Deleted member 36384]

Test The Fluid, If It Is Osmotic Fluid Seek Genuine Expert Opinion

MoodySabre,

A fellow sailor at my marina had a rash of spots below his antifouling. He tested the contents and it was found to be water, not vinegary smelling fluid. Apparently the cause was applying some coating before he applied the antifouling. The underlying reason was poor preparation.

I dont know anymore than this but I remember him being relieved that it was not the pox. It was an older GRP yacht.

Perhaps he hauled his boat, scrubbed the hull and painted instead off washing and leaving it for the winter and painting in spring.

There are certainly cases of preventative epoxy coatings being added to older hulls, which very rapidly develop blistering caused by Osmosis aka Hydrolysis. It would appear, from my amateur perspective, that old GRP hulls should not be Epoxy Coated as a matter of course. I understand that Copper Coat is an Epoxide.

If it was my boat I would test the blister fluid to establish if it is a by product of hydrolysis or water from poor preparation. If it is hydrolysis I would be inclined to seek genuine expert opinion to establish what to expect and take it from there.

Hope this helps.

Regards,

BlowingOldBoots

 

[Elessar]

A friend of mine has just lifted his Konsort out and discovered blisters in the Coppercoat (applied by the previous owner). When popped these blisters have water in them. He has been told that this is because the hull wasn't properly dried out before CC was applied. He has heard that another boat Coppercoated by the same person has a similar problem.

To save money he intends just to sand these blisters off, prime and then antifoul.

Any thoughts?

you need to put some pH paper in the water in the bubbles

If it's acid, it's 99% certain that its osmosis

If it's alkaline, it's probably poor prep and a failure of the coppercoat, but alkaline readings may be encountered if amine accelerators were used in the lay-up.

If it is osmosis, filling the bubbles will give you a temporary aesthetic improvement.

If it's poor prep, grind away the bad areas to get rid of the bubbles and you'll probably find the gelcoat is OK. (not easy though as coppercoat is very hard) then I'd epoxy the bits that are bare gelcoat to maintain osmosis protection. This should be a good repair.

________________

ARC. Antifoul Removal, Epoxy Coatings, CopperCoat

Noisekiller Marine. Automotive acoustic technology now available for your boat

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[Elessar]

MoodySabre,

It would appear, from my amateur perspective, that old GRP hulls should not be Epoxy Coated as a matter of course. I understand that Copper Coat is an Epoxide.

I very strongly disagree.

Yes Coppercoat is an epoxy. 30odd thousand boats have been coppercoated most of them secondhand. I think there would be a bit of noise about it if they all suddenly developed osmosis.

It is true that putting eopxy on a boat with stage 2 osmosis (this is where the hull has absorbed a lot of water and breakdown has started, but has not started blistering yet) can accelerate bubbling, but to say you shouldn't epoxy on old hulls is just wrong - if the moisture levels are good then the epoxy will preserve your hull and stop it absorbing any more water.

A new hull absorbs water from day 1 - get epoxy on as soon as you can and stop it absorbing any more!

________________

ARC. Antifoul Removal, Epoxy Coatings, CopperCoat

Noisekiller Marine. Automotive acoustic technology now available for your boat

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[Elessar]

MoodySabre,

Perhaps he hauled his boat, scrubbed the hull and painted instead off washing and leaving it for the winter and painting in spring.

and why would that matter??

________________

ARC. Antifoul Removal, Epoxy Coatings, CopperCoat

Noisekiller Marine. Automotive acoustic technology now available for your boat

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[Deleted member 36384]

=Elessar;2668079]and why would that matter??

________________

The coating has to be applied to whatever is regarded as an inappropriate level of moisture. The specification for application is designed around levels of moisture in the substrate, amongst other things. It would matter if the level of moisture was out with the coating specification. That level of moisture specification may or may not be reached quickly or it may take longer to naturally reach that specification.

That is all that I mean.

Perhaps we are back to the drying out over the winter discussion, but that is not what I mean, in this case.

I do not claim that all old boats that have any type of epoxy coating will develop blisters, I do think that old grp boats dont need any further protection as the moisture that contributes to the chemistry of Osmosis has already entered the hull. I do believe that the risk of applying an epoxy coating to an old GRP hull is not worth the cost and it may contribute to an increased risk of blister development. I can not quantify this, it is just my amateur opinion.

I understand what you mean by 2 stage osmosis and risk to blistering under epoxy and I accept that an old hull that is not in this stage may be a candidate for Epoxy treatment. I have trouble with the accuracy of defining what are acceptable levels of moisture or quantifying the stage in the Osmosis process that an old hull may be at. This is where my opinion, as an amateur, comes from.

I would like to learn how this is determined but I have not yet done that and from what I can tell so far, moisture readings are not a reliable method either.

 

[Elessar]

________________

The coating has to be applied to whatever is regarded as an inappropriate level of moisture. The specification for application is designed around levels of moisture in the substrate, amongst other things. It would matter if the level of moisture was out with the coating specification. That level of moisture specification may or may not be reached quickly or it may take longer to naturally reach that specification.

That is all that I mean.

Perhaps we are back to the drying out over the winter discussion, but that is not what I mean, in this case.

I do not claim that all old boats that have any type of epoxy coating will develop blisters, I do think that old grp boats dont need any further protection as the moisture that contributes to the chemistry of Osmosis has already entered the hull. I do believe that the risk of applying an epoxy coating to an old GRP hull is not worth the cost and it may contribute to an increased risk of blister development. I can not quantify this, it is just my amateur opinion.

I understand what you mean by 2 stage osmosis and risk to blistering under epoxy and I accept that an old hull that is not in this stage may be a candidate for Epoxy treatment. I have trouble with the accuracy of defining what are acceptable levels of moisture or quantifying the stage in the Osmosis process that an old hull may be at. This is where my opinion, as an amateur, comes from.

I would like to learn how this is determined but I have not yet done that and from what I can tell so far, moisture readings are not a reliable method either.

Thanks for your reply, and agree with most of what you say in this (only slightly) different context.

Modern hulls dry after a couple of days, older resins a couple of weeks but the moisture on the day from dew and humidity is also very important and probably has more impact on poor results than not having left the boat out over the winter before painting.

The rest of the statement on the suitability of hulls all hinges around the definition of "old". Not only is this hard to define, but a boat somewhere cold and salty and spends 6 months ashore is going to get old a lot later in life than one that sepnds its time on a lake 12 months a year. So I understand your statement, but I think it is far too biased against boats that could benefit from a prevention scheme.

What I'd say is measure the moisture levels and if they are reasonably low, keep them low by putting epoxy on.

________________

ARC. Antifoul Removal, Epoxy Coatings, CopperCoat

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[Sans Bateau]

When we bought Galadriel, this is exactly what the surveyor suggested. In his report he said that as the moisture readings in the hull were so low, an epoxy treatment would be of long term benefit to the boat in keeping it that way (low moisture). This we did with two coats of ME100, then Coppercoat.

 

[Bosun Higgs]

When we bought Galadriel, this is exactly what the surveyor suggested. In his report he said that as the moisture readings in the hull were so low, an epoxy treatment would be of long term benefit to the boat in keeping it that way (low moisture). This we did with two coats of ME100, then Coppercoat.

We did exactly the same and have a line of bubbles down the front leading edge of the rudder. My suspicion is of poor prep even though the rudder like most of its kind is wet, because the blisters havent spread and are in a line down the rudder - as if water had run down before the copper coat was applied.

A key question for the OP is " where are the blisters" ? Are they underneath the gel coat ( osmosis) or between the gel and the copper coats ( coating problems)

 

[bluedragon]

Yes, hasn't everyone missed the point here? The way I read the original post was blisters in the Coppercoat...not the gel coat? A survey I've just had found the same thing in one or two isolated places. When the Coppercoat was scraped off the hull gel coat was perfect. No remedial action needed unless it's all coming off.

 

[Seajet]

I am obviously getting too old, I'm amazed at some people paying mega-bucks for boats & treatments / 'analysis'.

The gist is;

Gelcoat is not, as was originally thought in the 'GRP is a wonder' 1960's, impermeable to water.

Some 'older' GRP boats were plain poorly built ( I don't think deliberately ) and some boats/designs simply got lucky.

IF a boat old or new, is thoroughly dry - and this unfortunately means a summer ashore with antifouling stripped, or an expensive time with heaters in a boatyard you can trust, the epoxy 'barrier' is a very sound idea.

The snag with this is, when osmosis first began to rear it's head in the late 1970's, people did just this - with the epoxy treatments of the day, which were in their way jolly good stuff.

It then became apparent that these epoxies contained solvents, which assist moisture spread around the structure of the GRP.

Then the major marine paint suppliers supplied Solvent Free Epoxies - specifically for use as an underwater barrier coat.

All antifouling must be completely stripped - that's A/F NOT Gelcoat !

And above all the boat must be allowed to dry one way or another once all the antifouling is off.

Despite what some say it's worth starting the process in early winter - too cold in the UK Spring - try standing or kneeling under a boat ashore in rain, you'll be surprised how dry she and you remain ( apart from wind driven on you ).

Stripping antifouling is probably the worst job on boats I've ever done and do be careful re. protective gear and catching residue on plastic sheeting ( boatyards get funny about that getting into water supplies etc now ).

Once REALLY sure the hull is dry, apply the barrier epoxy; this must be in good weather ie temperature & humidity.

International make 'Gelshield', Blakes have an equivalent.

I have used Gelshield on 2 boats, it's better than stripping antifouling but still not much fun.

Unless changed recently, one has to apply 5 coats, alternating grey & green colours are supplied so that one may see where one's been before.

After that's been done and thoroughly cured, apply antifouling or coppercoat as one fancies.

Moderately hard slog ( or pretty expensive if getting a yard to do it ) but the satisfaction is enormous, and it does assist boat value - BTW take photo's as often as possible, and include a newspaper showing the headline & keep it, as proof of date - this may be important in future !

 

[Elessar]

It then became apparent that these epoxies contained solvents, which assist moisture spread around the structure of the GRP.

Then the major marine paint suppliers supplied Solvent Free Epoxies - specifically for use as an underwater barrier coat.

---------8<---------

International make 'Gelshield', Blakes have an equivalent.

Unless changed recently, one has to apply 5 coats, alternating grey & green colours are supplied so that one may see where one's been before.

sorry to pick on this bit as I agree with the rest of your post - but gelshield is a solvented epoxy - only 45% solids.

There IS a solvent free gelshield, but it isn't the green/grey/5coats one you describe.

Any epoxy is worthwhile if your boat isn't yet too wet. It will be one day if you don't epoxy it.

________________

ARC. Antifoul Removal, Epoxy Coatings, CopperCoat

Noisekiller Marine. Automotive acoustic technology now available for your boat

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[tcm]

i have cc and agree with bosunhigins questions.

Sounds from original post that the cc itself has a few bubbles. Not a huge deal imho. In fact, it mite show that the epoxy itself is in excellent conditon, and at worst there are just few bubbles-worth of water or whatever trying to get out. Dry out as much as possible, bosh on a bit more cc. I had a head start in appyling my stuff - did the whole thing in canaries.

 

[nigelhudson]

Peeling copper

I’ve just bought a 25 year old Hunter trailer sailer at auction and I was pleased to be told that a) it had a dry hull at its last survey in 2004 and b) it had been coated with copper antifoul in 2005 (brand unspecified). I was therefore astonished to find that, when it was lifted out, it was covered in barnacles (average 1/sq inch). I was further astonished to find that when pressure washed and scraped with hard rubber squeegee chunks of the “magic” antifoul came off with the barnacles! I previously had an open mind on copper antifouls – now I’m very sceptical.

The missing patches of antifoul showed that there was some kind of white coating underneath so the copper was not applied directly to the pale blue gel coat of the hull. Once cleaned I noticed that the antifoul was covered all over in small blisters. I scraped a few blisters and found that they were only in the antifoul – the hull gel coat and layup were not affected at all. The blisters contained liquid which smelled not of acetic acid as osmosis is normally described but of some organic compound. Fortunately my friend has a PhD in organic chemistry so I called him over to examine the fluid and together we reviewed some papers on the chemistry of osmosis. We concluded that there was some kind of osmosis reaction occurring in the white coating and that the liquid smelled of styrene or a similar compound.

I decided that having these blisters in close proximity to the gel coat was not a good thing so I went round and scraped as many as possible. I followed this up with a further pressure wash to flush away the fluid. This resulted in large spots of antifoul falling off round the blister sites – the boat now has a very spotty bottom. The attached picture shows large areas of missing antifoul, some untouched blisters and the pristine gel coat peeping through the white layer.

I would like to keep the gel coat protected as the boat will be launched and recovered several times next season. Ideally I would like clean away the barnacle-magnet copper and the dodgy white layer and apply gel shield directly to the gel coat – I will not using antifoul as the boat will not kept on a mooring. However I’m not sure how to remove the copper and the white layer without damaging the gel coat which is already exposed in places – heat and sanding are out of the question. Is there a chemical stripper that would attack the (presumably) epoxy of the copper antifoul without affecting the gel coat? I would be surprised if there was. Has anyone else had this problem? The original post would imply that this is the case. Let me re-state that the hull lay-up is not affected by osmosis so a suggestion of gel peeling would display a lack of comprehension.

If it is not possible to remove the lifting layers the back up position on this is to scrape every blister on the hull and give it repeated pressure washes over the winter in the hope that more of the copper will fall off. Then attack the exposed white layer with a solvent that will not damage the gel coat if wiped away quickly (eg. acetone) to see if it can be removed. Finally give the hull a light sand down followed by several coats of gel shield or similar. I know that further blistering will occur if I keep the boat on a mooring in the future so I’ll just have to scrape them away and repair the gel shield as necessary.

I would be useful to hear of any practical experience of the above scenario.

 

[nimbusgb]

From the picture that looks very much like poorly applied coppercoat and little to do with the gelcoat at all.

But of course that's from a picture on the internet.