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Which 2 pack for blacking??


Troyg

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I can see I have opened an interesting discussion.... much more to this than just some paint! lol

It seems there is no clear winner in which product to use! I was hoping for a majority of people to say  - use xx product! But not so....

Last calls now for folk to name their favourite surface tolerant 2 pack :) Let see what we get! 

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On 11/04/2018 at 09:41, Dr Bob said:

Be very carful with that statement. It CAN be used on splash zones and for TIDAL immersion within 30mins of application but not full immersion. This coating contains 15% solvent and this has to come out before full cure is achieved. It will in a tidal situation where the coating will be exposed when the tide goes out. The solvent cannot get out if under water. Don't paint the bottom of a boat and put it straight back in the water. Let it fully cure first.

Yes, as far as I know the curing of any epoxy is temperature dependent. It may seem to cure underwater, but it won't cure properly if it hasn't fully cured before it goes back in the water

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An epoxy will never be fully cured unles postcured at high temperatures viz 100 deg C ish.

The lower the temperature, the lower the cross linking hence lower the cure. Being under water will mean lower temperature but the level of cure may still be ok. The problem of underwater is if there is solvent left in the coating. Under water that won't come out so the coating stays 'cheesey' and gives a path for water ingress. You are right though in saying get it as cured as much possible before immersion. Most epoxy paints don't achieve their potential full cure unless you use a post cure oven. 

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I'm thinking of going with the Jotamastic 87 now. I was put off by the drying times but going with the winter grade gets around that and it seems to be the name that comes up most often. Plus having the main feature of being surface tolerant makes it very appealing for our moist British days....

Would 20L be enough for 3 coats on a 60ft NB??

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16 minutes ago, Troyg said:

I'm thinking of going with the Jotamastic 87 now. I was put off by the drying times but going with the winter grade gets around that and it seems to be the name that comes up most often. Plus having the main feature of being surface tolerant makes it very appealing for our moist British days....

Would 20L be enough for 3 coats on a 60ft NB??

I used a 4L tub per coat on my 60ft nb (not doing upto the gunnels).  

See my post:https://www.canalworld.net/forums/index.php?/topic/77840-using-jotamastic/

Edited by system 4-50
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On 10/04/2018 at 17:19, Rose Narrowboats said:

The EU has recently (ish) banned coal tar based products so lot of two packs have either changed formulation or are no longer available.

I spoke to one manufacturer this morning about what their recommended replacement was for their now discontinued pitch epoxy product, and was told bitumen.

Most manufacturers won't warrant their product on top of anyone else's, so I fear a lot of people are going to end up re-blasting much sooner than intended for peace of mind.

The reality is that some of products will work over the older ones - but it's going to take a few years and some hard lessons to find out which.

A word of caution with Jotamastic 87 - recommended drying time is 7-14 days at UK ambient temperatures.

I've been advised the same. I'm due to recoat later in the year and this raises a big concern, as the hull is coated in two pack pitch epoxy. I'd imagine many are in the same position. 

My (limited) understanding is that overcoating coal tar pitch based epoxies presents a risk of the pitch 'bleeding' due to the the new coating. If the original coats are compromised by whatever I throw on later, it renders the blacking exercise a bit pointless!

However, a search online found a book (Marine Painting Manual by A.M. Berendsen) stating that this risk when overcoating may be addressed by applying a 'sealer' or 'tiecoat'. I've yet to find a suitable product to do this though. 

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25 minutes ago, Arf said:

I've been advised the same. I'm due to recoat later in the year and this raises a big concern, as the hull is coated in two pack pitch epoxy. I'd imagine many are in the same position. 

My (limited) understanding is that overcoating coal tar pitch based epoxies presents a risk of the pitch 'bleeding' due to the the new coating. If the original coats are compromised by whatever I throw on later, it renders the blacking exercise a bit pointless!

However, a search online found a book (Marine Painting Manual by A.M. Berendsen) stating that this risk when overcoating may be addressed by applying a 'sealer' or 'tiecoat'. I've yet to find a suitable product to do this though. 

Overcoating coal tar epoxies is not a good idea. They are designed to be applied to grit blasted steel. You can overcoat with another coal tar epoxy if you abraid the surface back as the new coating will adhere reasonably well but you are risking that the original coating may not be adhered well. In commercial applications, splashzones etc, you would always blast back to steel.

The withdrawal of coal tar epoxies however removes the ability to overcoat. Epoxies will not stick very well at all to a coal tar epoxy. It is not just the 'bleeding' that is an issue but adhesion. It just will not stick properly because of 'tar' residue on the surface. This is going to be a real problem to a lot of narrowboats. When I was involved with these coatings in the 80's, there were sealing paints available that did provide a key for other epoxies. Best bet is to give one of the big suppliers a call and talk to their technical department - Try International or Jotun - and ask  them what they would recommend.

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It's may be a major headache for many - at least I know what the existing coating is!

Haven'thad a chance to get onto a manufacturer yet, just suppliers. But, International intertuf 262 looks like it might be an option to seal the coal tar epoxy before putting the next stuff on.

The datasheet for this product says it's suitable for spot repair and 'upgrading' of substrates including coal tar epoxy, and then needs coating with intergard 263, a tiecoat.

Not a cheap option and haven't found a UK supplier yet, but has to be better than paying to blast it all off and start over :unsure:

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6 minutes ago, Arf said:

It's may be a major headache for many - at least I know what the existing coating is!

Haven'thad a chance to get onto a manufacturer yet, just suppliers. But, International intertuf 262 looks like it might be an option to seal the coal tar epoxy before putting the next stuff on.

The datasheet for this product says it's suitable for spot repair and 'upgrading' of substrates including coal tar epoxy, and then needs coating with intergard 263, a tiecoat.

Not a cheap option and haven't found a UK supplier yet, but has to be better than paying to blast it all off and start over :unsure:

That looks good. Give International a ring and ask for the technical department. You will get an answer pretty quick.

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Pretty good news on the whole from Jotun and International. 

Both people I spoke to confirmed that bleeding was to be expected. but that provided there was an adequate amount of surface abrasion of the original coal tar epoxy the jotamastic 87 or interzone 954 coatings should adhere ok.

Both said that the bleeding should be an aesthetic issue only. This doesn't bother me too much, and the discolouration should apparently be quite limited given it will be against the black of the coating. I was told an aluminium rich primer would seal the tar better. 

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  • 1 year later...
On 10/04/2018 at 13:03, Troyg said:

Hello all.

I am sure this topic has already been discussed several times.....

I am soon having my narrowboat shot blasted and plan to apply 2 pack. I have recently purchased the boat and it has been neglected and not blacked often. This means the hull, although structurally sound has suffered pitting which needs to be halted. Hence the reason for going down the 2 pack route.

However which 2 pack to use?? There seems to be a minefield of choice....Hempel Hempadur 45143, Interzone 954, Intertuf 362 just to name a few.....

I will be applying it myself and will want something suited to adhere well to a pitted hull and provide a good protection. I am happy (and probably prefer) to do a couple or more coats.

Also would anyone have an idea of how many litres would be needed for a 60ft narrowboat hull?

 

 

Afternoon Troyg,

 

Have you carried this work out yet?

 

I have the perfect solution for a pitted hull if you are still on the lookout!

 

Best regards,

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23 hours ago, Dacrylate Paints Ltd said:

Afternoon Troyg,

 

Have you carried this work out yet?

 

I have the perfect solution for a pitted hull if you are still on the lookout!

 

Best regards,

I would be interested in your solution for a pitted hull.

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