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Which 2 pack for blacking??


Troyg

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I zingered mine I looked at two pack but the Zinc looked [and is] a better system I still pull the boat out every two years and apply Keelblack as cosmetic finish, but where it matters any damage to the zinger is confined to just that scratch and is easily repaired. Two pack if damaged will allow rust to creep underneath it which it what I wanted to avoid. I dont think it was anymore expensive than two pack and it also required glass blasting to prepare the surface

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1 hour ago, Bloomsberry said:

Ok, thanks for that.

 

It does say ' continued cure under immersed conditions' which I assumed would be full immersion but it does state tidal which obviously isn't relevant to my situation.

 

It states 18 hours for hard dry at 15C so will stick to this next time. Thanks again.

No problem:)

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2 hours ago, Dr Bob said:

2 pack epoxies should last far longer than 2-4 years on the hull of a NB. Your experience and need to recoat is most likely due to a lack of surface preparation or bad application. You really need to get back to clean steel and preferably SA 2 1/2  if you want it to last.....and apply the coating in line with the manufacturers instructions. If you cannot achieve this level of preparation, which is expensive, then it is a waste of time using a 2 pack and so a 'traditional blacking' single pack system is the best answer.

I do not understand your comment "but at the end of the day it's all blacking no matter what you use" . No it isnt. Prepare the surface very well and use a 2 pack epoxy for 10 years life or just water jet and slap on a bitumen based blacking and repeat every 2 years.

Not in my experience. As regards preparation I follow manufacturers recommendations. Jet wash with water without chemical, abraid the old paint and paint in temperatures above 14 degrees. What else  do you think I should be doing? 

Last year I sandblasted to baseplate and put 3 coats of 45143 on within minutes of the sandblaster finishing. I'll let you know the outcome next year.

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2 hours ago, Dr Bob said:

2 pack epoxies should last far longer than 2-4 years on the hull of a NB. Your experience and need to recoat is most likely due to a lack of surface preparation or bad application. You really need to get back to clean steel and preferably SA 2 1/2  if you want it to last.....and apply the coating in line with the manufacturers instructions. If you cannot achieve this level of preparation, which is expensive, then it is a waste of time using a 2 pack and so a 'traditional blacking' single pack system is the best answer.

I do not understand your comment "but at the end of the day it's all blacking no matter what you use" . No it isnt. Prepare the surface very well and use a 2 pack epoxy for 10 years life or just water jet and slap on a bitumen based blacking and repeat every 2 years.

Not in my experience. As regards preparation I follow manufacturers recommendations. Jet wash with water without chemical, abraid the old paint and paint in temperatures above 14 degrees. What else  do you think I should be doing? 

Last year I sandblasted to baseplate and put 3 coats of 45143 on within minutes of the sandblaster finishing. I'll let you know the outcome next year.

BTW 45143 bought from the trade supplier isabout the same price if not cheaper than most single pack high-end products. I paid less than £7 per litre

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5 minutes ago, Midnight said:

Not in my experience. As regards preparation I follow manufacturers recommendations. Jet wash with water without chemical, abraid the old paint and paint in temperatures above 14 degrees. What else  do you think I should be doing?  

Surly that is for only over sound paintwork.If it has broken down you need to start again

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3 minutes ago, Midnight said:

Not in my experience. As regards preparation I follow manufacturers recommendations. Jet wash with water without chemical, abraid the old paint and paint in temperatures above 14 degrees. What else  do you think I should be doing? 

Last year I sandblasted to baseplate and put 3 coats of 45143 on within minutes of the sandblaster finishing. I'll let you know the outcome next year.

You said in the previous post there was corrosion. Jet washing and abrasion is not good enough to paint over that. Painting over old paint is ok with water jetting and abrasion. If you are painting epoxy straight onto steel then it has to be back to SA 2 1/2 or just about ok onto a slightly rust bloomed surface if a tolerant epoxy is used.

The temperature guidance is also tied into being above the dew point - otherwise there will be moisture on the steel and then you have a problem.

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2 minutes ago, Dr Bob said:

You said in the previous post there was corrosion. Jet washing and abrasion is not good enough to paint over that. Painting over old paint is ok with water jetting and abrasion. If you are painting epoxy straight onto steel then it has to be back to SA 2 1/2 or just about ok onto a slightly rust bloomed surface if a tolerant epoxy is used.

The temperature guidance is also tied into being above the dew point - otherwise there will be moisture on the steel and then you have a problem.

Re-coating every 2 years works for me.
Not had any corrosion or breaking down of the coating the last few times (since 2011). I could leave it a lot longer but as the club dry dock is inexpensive and the paint is cheaper than Comastic or Intertuf I'm quite happy to re-coat every 2 years. Anyway I like the regular inspections and no point in dry docking and not re-coating.

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Two years ago when I dry docked the boat, power washing removed all the weed etc, but the cosmetic coat was only damaged where it had been scratched, this was cleaned up re zingered and then 3 coats of keelblack applied. This year I have no doubt it will be the same, the waterline looks perfik, but my boat is still worth over a 100k so the cost of dry docking is small in comparison to the value of the boat, and if selling is a definite plus point.

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2 minutes ago, peterboat said:

Two years ago when I dry docked the boat, power washing removed all the weed etc, but the cosmetic coat was only damaged where it had been scratched, this was cleaned up re zingered and then 3 coats of keelblack applied. This year I have no doubt it will be the same, the waterline looks perfik, but my boat is still worth over a 100k so the cost of dry docking is small in comparison to the value of the boat, and if selling is a definite plus point.

re-zingered sounds interesting how is that applied?

 

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1 minute ago, Midnight said:

re-zingered sounds interesting how is that applied?

 

I lightly grind the rust off and paint it on its just for the damage that happens in daily boating, two coats does it fine. The problem is that its always the same places that get damaged! My gunnels are also zingered I do the same there as well  but use a semi gloss on it afterwards. The beauty is that the rust never goes beyond the scratch and any corrosion is very light so easily dealt with as the exposed zinc becomes an anode

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2 minutes ago, peterboat said:

I lightly grind the rust off and paint it on its just for the damage that happens in daily boating, two coats does it fine. The problem is that its always the same places that get damaged! My gunnels are also zingered I do the same there as well  but use a semi gloss on it afterwards. The beauty is that the rust never goes beyond the scratch and any corrosion is very light so easily dealt with as the exposed zinc becomes an anode

Thanks. Being the over-cautious type who worries about pitting,  I'll have to look into that

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7 minutes ago, Midnight said:

Thanks. Being the over-cautious type who worries about pitting,  I'll have to look into that

The boat is now 10 years old I have no pitting then again I dont have a landline either which helps.

You can buy tins of zinger from a place in Hull its expensive but goes a long way and will help protect the regular damage areas

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The thing is. If folk with 2 pack epoxy coatings still keep docking the boat every two or three years to check it, or touch it up, whats the point of all the expense. Might as well just black it each time with ordinary bitumen.

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19 minutes ago, Midnight said:

Would I have to sandblast the hull again before Zinga could be applied?

You would, but its great stuff to do repairs where you get damage! In your case its not worth having it done but for me it was

8 minutes ago, bizzard said:

The thing is. If folk with 2 pack epoxy coatings still keep docking the boat every two or three years to check it, or touch it up, whats the point of all the expense. Might as well just black it each time with ordinary bitumen.

I get what you say, but on my old boat at two years the waterline was always rusty so eventually it was going to need replating, for me mine isnt rusty and the boat should do 25 years plus without any corrosion.

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Lots of advice on what paint to use and how to do it. But what can be said about not blacking at all - as I imagine it could be the 'norm'.

Right or wrong, with best intentions every year,  I have not actually got round to having my boat blacked - or having the anodes renewed. but if left I guess the rust will cause pinhole leaks (made worse by shot-blasting prior to blacking) and hoping the holes will be blocked by the paint, and stay blocked. 

So I can see my boat is covered in rusty pits along the water line - but don't know about elsewhere - although I can say the hull is perfectly dry inside, fully painted and clear of any rust.

Not so the superstructure - where keeping the rust at bay is a constant battle (nobody told me about this when I bought the boat) - but that is nothing to do with lack of blacking 

I assume this affects the resale value and I will have to sell at a loss - a break even situation maybe - so is doing nothing a viable economic option.

What eventually happens to steel narrowboats - other than the bottom of the canal - where do they go when they die?

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1 hour ago, Horace42 said:

 

I assume this affects the resale value and I will have to sell at a loss - a break even situation maybe - so is doing nothing a viable economic option.

What eventually happens to steel narrowboats - other than the bottom of the canal - where do they go when they die?

If you are hoping to break even on sale, then that means your boat is going to have to be in reasonable condition......as I assume it was when you bought it ie not leaking like a sieve. If you do nothing then it will corrode and eventually holes will appear and that will wipe a lot of value. Unfortunately re-blacking every few years at a cost of say £600 is one of the costs of owning a steel boat and should be budgetted in the annual cost - unless you want to blow £,000s on a coating to last 10 years. Doing nothing can never be a viable economic option. If you dont black, then in 10 years you will have saved £3000 but the value you have lost on the boat will far exceed that.

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34 minutes ago, Dr Bob said:

 Doing nothing can never be a viable economic option. If you dont black, then in 10 years you will have saved £3000 but the value you have lost on the boat will far exceed that.

Thanks for that. Intuitively it makes sense to have the work done - but I haven't.

I will have to rely on what the surveyor of a potential buyer might say. I suppose someone will take it on at some price if cheap enough.

 

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7 hours ago, 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.

Right, I still need you to educate me more about this. The epoxy will be pretty solid, just a bit tacky, after just a few hours. I would have thought that the solvent would have gone by then? And once its mostly set is it even possible for any more solvent still to escape?   After you told me that epoxy used a solvent I have thought about this quite a bit (especially as I was using epoxy primer last week). I visualise that the solvent goes quite quickly then the remaining time is just the chemical reaction between the two epoxy components????

and whilst on this subject, my epoxy says overcoat between something like 12 hours and three days, but after 24 hours it feels totally dry so is there really any potential for chemical bonding between the coats???

.................Dave

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1 hour ago, dmr said:

Right, I still need you to educate me more about this. The epoxy will be pretty solid, just a bit tacky, after just a few hours. I would have thought that the solvent would have gone by then? And once its mostly set is it even possible for any more solvent still to escape?   After you told me that epoxy used a solvent I have thought about this quite a bit (especially as I was using epoxy primer last week). I visualise that the solvent goes quite quickly then the remaining time is just the chemical reaction between the two epoxy components????

and whilst on this subject, my epoxy says overcoat between something like 12 hours and three days, but after 24 hours it feels totally dry so is there really any potential for chemical bonding between the coats???

.................Dave

Dave, there is no absolute answer as each paint formulation will be different, but let me try.

The two things that happen during cure of a 2 pack paint are i) the evaporation of solvent and ii) the reaction between the two epoxy components. They start happening as soon as the paint is mixed with the first 'rush' of solvent evaporation when it is applied.

Lets talk about solvents first:

For 2 pack epoxies, the solvent system is usually a cocktail of things like xylene, ethyl acetate, n-butanol etc and maybe some exotics. These have a range of boiling points and in a mixture will form azeotropes with water - but for example xylene boils at 140°C (ish), n- butanol at 100°C and ethyle acetate below 80°C. Evaporation is therefore likely to be slow at say 20°C and will be better in windy higher temps or slower on still, humid, cold days. The re-coat time is indicative of how fast the solvent comes out as you would usually expect most to be out before the next coat - but not always necessary. In your case then at 20°C I would expect most of the solvent out in 12 hours. Thickness of coating is important and the thicker it is applied the slower it will come out. Solvent concentrations are usually 10% to 30% - you can tell by looking at the 'solids' on the data sheet. Solids + solvents =100% (ish). In the case of the coating for tidal structures, solvent will evaporate until the tide covers it and then evaporate again once the tide goes down. Maybe a few tides are needed for it all to come out but the paint near the low water mark may never release all its solvent. At these low levels of solvent, think about its action as 'lubricating' the movement of the epoxy chains rather than occupying a big space. In your coating, it will eventually all evaporate but will not leave 'gaps'. If its left in (ie you paint over it too soom) it will mean the epoxy chains can slide a bit more so the coating will not be as strong as envisaged.

The cross linking reaction;

This starts as soon as the 2 components are mixed and starts to form a 3 d network. By the time the paint in the tin goes rubbery, you have about 10-20% of the reaction complete. Crosslinking then continues for days if not months! Full cure is only achieved by raising the temperature - ie to 100°C ( pick a temp!) but typically 2 -3 days it is reasonably well cured. It is best to put another coat on in the first few days as the surface is still very active chemically and it will probably be ok for another couple of weeks but most manufactures say only days as there is less chance of surface contamination taking place. If I had to guess, I would say you will be 70% cured after 24hrs at 20°C for a bog standard epoxy. Lower temps will extend the cure - drop the temp by 10°C and you double the time to cure. Below 15°C and cure slows rapidly - but modified epoxies are available that cure at lower temps- but they are never going to be as good as higher temp cure ones. Feeling totally dry is not a measure of how well cured the epoxy is. Once totally dry, you can put a knife into the coating and see the indentation - that is how paint inspectors check degree of cure. Try it again the following day and the day after that and see how the knife has more difficulty in scratching the surface.

 

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My boat was 10 years old last November, and I will have owned it 4 years in June.

The hull was treated with Zinga and then International Interzone 954 when new.

When surveyed in May 2014 the 2 pack was on excellent condition, and the surveyor advised inspecting again in 3 years time.

Last May I had her docked with a view to reblacking and the 2 pack was still in good condition. The boatyard advised docking again in 2 years to see if it needed reblacking.

So next year she will be docked again, when the original 2 pack over Zinga will be 12 and a half years old.

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21 hours ago, Dr Bob said:

Dave, there is no absolute answer as each paint formulation will be different, but let me try.

The two things that happen during cure of a 2 pack paint are i) the evaporation of solvent and ii) the reaction between the two epoxy components. They start happening as soon as the paint is mixed with the first 'rush' of solvent evaporation when it is applied.

Lets talk about solvents first: ............... (removed to avoid long quote)

 

 

Thanks, this all makes total sense and fits in with my observations, in particular that its better to wait quite a few days after the epoxy feels totally dry before sanding.

I have just done the bottoms of the side hatches in epoxy primer after some welding repairs, so am not doing the entire boat! This meant that they could stay in the saloon next to the stove for a couple of days to keep the temperature at about 20. I used the lovely Armourguard ST that sadly is no longer available, and note that the specification quotes 94% solids.   I think I tend to put the epoxy on a bit too thick at times but in previous use (front and back decks and lockers) it has lasted well so far so I assume I have not compromised its strength too much.

When the boat was done I think we had 48 hours before we went back in to the water but the yard suggested tying up outside for a few more days to let the epoxy get harder before going through locks so that makes sense too.

.............Dave

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29 minutes ago, dmr said:

Thanks, this all makes total sense and fits in with my observations, in particular that its better to wait quite a few days after the epoxy feels totally dry before sanding.

I have just done the bottoms of the side hatches in epoxy primer after some welding repairs, so am not doing the entire boat! This meant that they could stay in the saloon next to the stove for a couple of days to keep the temperature at about 20. I used the lovely Armourguard ST that sadly is no longer available, and note that the specification quotes 94% solids.   I think I tend to put the epoxy on a bit too thick at times but in previous use (front and back decks and lockers) it has lasted well so far so I assume I have not compromised its strength too much.

When the boat was done I think we had 48 hours before we went back in to the water but the yard suggested tying up outside for a few more days to let the epoxy get harder before going through locks so that makes sense too.

.............Dave

Have you looked to see how the water tank is getting on?

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15 minutes ago, ditchcrawler said:

Have you looked to see how the water tank is getting on?

Still No,  I suppose I really should have a look later in the year. It was 2014 and about this time of the year that the water tank was done so its 4 years old now. Maybe I will wait till next year as 5 is a nice number :D Looking back we left 24 hours between coats and the temperature was ok so we met Dr Bobs criteria.

I did inside the side lockers a couple of years ago and noticed that a very small area of that has "de laminated", possibly due to an impact. I suspect this is the weakness with internal epoxy on a narrowboat.

.................Dave

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