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Adamwalker64

Blacking

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8 minutes ago, Troyboy said:

I'm fairly certain I once read somewhere that a narrowboat  had a baseplate rust through but maybe I am mistaken . I'll carry on painting mine as the surveyor that last surveyed my boat made a positive comment in his report . 

Corroded through, maybe. It would require something to accelerate the corrosion so to say it "rusted" through is misleading. Surface coatings will protect against rusting but other forms of protection - or more accurately prevention - are necessary to prevent the sort of thing Matty has posted. Just painting alone won't prevent that happening.

 

Corrosion is 99% about environment.

 

JP

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5 minutes ago, Captain Pegg said:

Corroded through, maybe. It would require something to accelerate the corrosion so to say it "rusted" through is misleading. Surface coatings will protect against rusting but other forms of protection - or more accurately prevention - are necessary to prevent the sort of thing Matty has posted. Just painting alone won't prevent that happening.

 

Corrosion is 99% about environment.

 

JP

My mistake I use the term rust as that is what I feel I am trying to combat however as you rightly state the term I should use is corrosion . Most on this Forum are far more learned than me and I am keen to learn so what in your opinion has caused the baseplate in Mattys photo to 'corrode' and what would have prevented it mindful of the fact that the sides did not show similar pitting ? 

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1 hour ago, Troyboy said:

My mistake I use the term rust as that is what I feel I am trying to combat however as you rightly state the term I should use is corrosion . Most on this Forum are far more learned than me and I am keen to learn so what in your opinion has caused the baseplate in Mattys photo to 'corrode' and what would have prevented it mindful of the fact that the sides did not show similar pitting ? 

Sorry if the distinction seems a bit pedantic. I think it's important to recognise that it's mostly human activity that is the more likely problem than natural occurrence.

 

What causes pitting is a bit like the $64 million dollar question on here. What's for sure is that it is not natural oxidisation, that occurs in laminar fashion and wouldn't happen to any great extent underwater anyway. It's also almost certainly nothing to do with the age, origin or type of steel.

 

Pitting is known to be caused by stray current corrosion and by chloride attack. Which it is will depend upon the history of this boat but I see Matty says no GI was fitted. That suggests he knows the boat has been on shore supply. Logically then stray current corrosion is the likely cause. I suspect this is the case with most boats suffering pitting but if I were in a marina I might wonder about the chemicals from cleaning products that are routinely discarded overboard. It does though take quite high concentrations to cause significant problems.

 

It's always worth bearing in mind that there are something like 25,000 steel boats on the canals and you will pass endless rows of 1970s and 80s steel boats on any linear moorings. While there are ways the hull can fail and sink the statistics say this is a rare occurrence. Hence the style of response.

 

Also note that even with the problems with that hull pictured it's still nowhere near sinking.

 

JP

 

 

Edited by Captain Pegg

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2 hours ago, Troyboy said:

Thanks for that Matty I'm not sure if Sea Dog or Captain Pegg  will now believe baseplates can rust through .

You can see from JP's posts what I was driving at though Troyboy, eh?  He's put the issue well - straight forward rusting of the baseplate isn't going to be a sinking issue for our boats. Pitting due to galvanic action is a different matter however, and there's plenty of discussion on here about that should you wish to have a trawl. :)

 

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There's nothing wrong with painting a baseplate if you can get to it. But cleaning the baseplate properly prior to painting is often going to be much more difficult than actually painting it. Most drydocks won't have enough clearance to angle the lance of a decent pressure washer, but if the boat's been craned out and is on hard standing you might be ok. Scraping alone is never going to clean it properly.

 

My baseplate has never been painted and is now 14 years old and last time I looked at it a couple of years ago there was just a bit of light surface corrosion which just brushed off by hand.

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Before I bought my boat it was taken to a dry dock for surveying.

 

As the dry dock drained I was amazed by the number of fresh water mussels protecting the baseplate.

 

Once these were pressure washed off the baseplate was found to be in excellent condition with no loss of metal or pitting.

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15 minutes ago, cuthound said:

Before I bought my boat it was taken to a dry dock for surveying.

 

As the dry dock drained I was amazed by the number of fresh water mussels protecting the baseplate.

 

Once these were pressure washed off the baseplate was found to be in excellent condition with no loss of metal or pitting.

Which rather po po's the thinking that paint would get all scrapped off the base plate, if that were the case so would the mussels. I have watched them do it at Debdale

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4 minutes ago, ditchcrawler said:

Which rather po po's the thinking that paint would get all scrapped off the base plate, if that were the case so would the mussels. I have watched them do it at Debdale

 

Unless of course the mussels are feeding on the baseplate blacking! ?

 

With regard to the mussels not being scraped off, it rather depends on which canals you navigate.

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6 hours ago, cuthound said:

Before I bought my boat it was taken to a dry dock for surveying.

 

As the dry dock drained I was amazed by the number of fresh water mussels protecting the baseplate.

 

Once these were pressure washed off the baseplate was found to be in excellent condition with no loss of metal or pitting.

There must have been lots of little teeth marks, surely?

 

:giggles:

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6 hours ago, cuthound said:

 

Unless of course the mussels are feeding on the baseplate blacking! ?

 

With regard to the mussels not being scraped off, it rather depends on which canals you navigate.

But the same would be true for the blacking

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I've used keelblack on my boat last time, its water based so no issues with a damp surface, dew etc. It's lasted fine, about to redo after 2 years. (timing is just my preference) 

I used a rotoblaster wheel, almost as good as sandblasting, to remove the old bitumen and rust. 

As for the bottom, when I got the boat it hadn't been blacked for 10 years. Moored in one place for about 4. There was a crusty rust layer about 4mm thick to be removed. I blacked it, it had suffered no further rusting. 

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5 hours ago, Jim Riley said:

I've used keelblack on my boat last time, its water based so no issues with a damp surface, dew etc. It's lasted fine, about to redo after 2 years. (timing is just my preference) 

I used a rotoblaster wheel, almost as good as sandblasting, to remove the old bitumen and rust. 

As for the bottom, when I got the boat it hadn't been blacked for 10 years. Moored in one place for about 4. There was a crusty rust layer about 4mm thick to be removed. I blacked it, it had suffered no further rusting. 

Same here Jim I use it as cosmetic protection for my Zinger, it dries fast and in the summer I can spray 4 coats on in the day works well and so far has been durable, let is know how yours has fared will you?

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13 hours ago, Jim Riley said:

I've used keelblack on my boat last time, its water based so no issues with a damp surface, dew etc. It's lasted fine, about to redo after 2 years. (timing is just my preference) 

 

 

7 hours ago, peterboat said:

Same here Jim I use it as cosmetic protection for my Zinger...

So we still don't really have any evidence based opinion on Keelblack, do we.  Jim's has "lasted fine" for two years (like most bitumen coatings) but how do you judge objectively 'til it comes out of the water?  Peter has it has cosmetic protection on Zinger which one has to presume/hope is doing most of the work.  I've had a close up look at a boat out of the water where it had gone bad rather quickly , but this was put down to incorrect prep.  So, anyone think we're know anything stronger than the manufacturer claims wonderful things but hasn't done any testing on narrowboats before market release and there is little real world evidence to support those claims yet?

 

Don't get me wrong - I hope it's fantastic and is the perfect answer to all our blacking needs! 

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10 minutes ago, Sea Dog said:

 

So we still don't really have any evidence based opinion on Keelblack, do we.  Jim's has "lasted fine" for two years (like most bitumen coatings) but how do you judge objectively 'til it comes out of the water?  Peter has it has cosmetic protection on Zinger which one has to presume/hope is doing most of the work.  I've had a close up look at a boat out of the water where it had gone bad rather quickly , but this was put down to incorrect prep.  So, anyone think we're know anything stronger than the manufacturer claims wonderful things but hasn't done any testing on narrowboats before market release and there is little real world evidence to support those claims yet?

 

Don't get me wrong - I hope it's fantastic and is the perfect answer to all our blacking needs! 

Mine has been keeblacked before, and after the 2 years it was found to be ok, it hadnt fell off or washed off so I deemed it a success and very easy to apply

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9 minutes ago, peterboat said:

Mine has been keeblacked before, and after the 2 years it was found to be ok, it hadnt fell off or washed off so I deemed it a success and very easy to apply

I thought I'd covered that?

21 minutes ago, Sea Dog said:

 

Peter has it has cosmetic protection on Zinger which one has to presume/hope is doing most of the work.  

And I don't see how that is evidence that keelblack any more effective than any other blacking.

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I'd suggest the outermost coating is doing the work irrespective of what is beneath it, in the case of a blacking product overlaying Zinga I would also suggest it's doing a bit more than being cosmetic.

 

Zinga - assuming that is the same product as the Zinger referred to above - is 96% zinc in particle form in it's dried state. Zinc has no capability to stick to itself or to steel. Therefore only 4% of the product is actually binding the zinc particles together and adhering them to the steel. Zinc rich paints need to be high in zinc content to be effective but it does limit their ability to behave like a standard paint. This is evidenced in industrial applications where zinc based paints may struggle to be effective if subject to high mechanical forces. I have experience of such a coating formulated by Corus for application at the mill that was never successful for that very reason. We ended up having to send components away to a specialist thermal spraying contractor. More expensive but a better result. Zinc based paints are also incredibly heavy since zinc is about 7 times more dense than water and only slightly less dense than iron.

 

It seems expedient to me to coat a zinc rich paint with a secondary layer for protection as well as aesthetics.

 

JP

 

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2 minutes ago, Captain Pegg said:

I'd suggest the outermost coating is doing the work irrespective of what is beneath it, in the case of a blacking product overlaying Zinga I would also suggest it's doing a bit more than being cosmetic.

 

Zinga - assuming that is the same product as the Zinger referred to above - is 96% zinc in particle form in it's dried state. Zinc has no capability to stick to itself or to steel. Therefore only 4% of the product is actually binding the zinc particles together and adhering them to the steel. Zinc rich paints need to be high in zinc content to be effective but it does limit their ability to behave like a standard paint. This is evidenced in industrial applications where zinc based paints may struggle to be effective if subject to high mechanical forces. I have experience of such a coating formulated by Corus for application at the mill that was never successful for that very reason. We ended up having to send components away to a specialist thermal spraying contractor. More expensive but a better result. Zinc based paints are also incredibly heavy since zinc is about 7 times more dense than water and only slightly less dense than iron.

 

It seems expedient to me to coat a zinc rich paint with a secondary layer for protection as well as aesthetics.

 

JP

 

Hard not to read that as "quite an expensive undercoat" then if it's still the blacking that's doing the job.  Might "belt and braces" be a fairer judgement? 

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1 minute ago, Sea Dog said:

Hard not to read that as "quite an expensive undercoat" then if it's still the blacking that's doing the job.  Might "belt and braces" be a fairer judgement? 

The job will always primarily be done by the topcoat since that's the first line of defence subject to attack. There is good precedence for a zinc based undercoat and while it might not be the most cost effective for inland waterways craft if you look at it in pure commercial terms this is about personal preference and peace of mind for an individual spending their own money. No reason not to do it that I can see.

 

JP

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if you look at pictures on here of boats that have been zingered they are still in great condition after ten years, and that for me is the end goal after 25 years I want to be looking at a boat still having a perfik hull, no need for welding or any other expensive remedy for a rotten boat! whilst it might seem expensive, will it be at the end?

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1 hour ago, peterboat said:

Mine has been keeblacked before, and after the 2 years it was found to be ok, it hadnt fell off or washed off so I deemed it a success and very easy to apply

But you dont know the porosity as you have a good coating underneath it, It may have looked just as good if you had gone over your Zinger (which is doing the work) with a wax crayon so cant say how well it would protect steel

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15 hours ago, Jim Riley said:

I've used keelblack on my boat last time, its water based so no issues with a damp surface, dew etc. It's lasted fine, about to redo after 2 years. (timing is just my preference) 

I used a rotoblaster wheel, almost as good as sandblasting, to remove the old bitumen and rust. 

As for the bottom, when I got the boat it hadn't been blacked for 10 years. Moored in one place for about 4. There was a crusty rust layer about 4mm thick to be removed. I blacked it, it had suffered no further rusting. 

Jim, you may have been just lucky.

Because a coating is water based does not mean it is tolerant of a damp surface. You must follow the manufacturers guidelines and only apply to steel 3 deg above the dew point. Perhaps you did.

You are giving people incorrect info on a rotoblaster. Yes, to you it may be almost as good as sandblasting but how are you 'sandblasting'? Lets get rid of 'sand' as its not allowed any more. 'Grit blasting' is done to a standard ie SA2.5 required by most paint manufacturers for ultimate performance. This gives a cleanliness and profile standard. You will not achieve that with a rotoblaster. Maybe, just maybe, you could get near the clean but surface profile? .....and how long will it take? Mechanical cleaning is much more diffcult than grit blasting. Ok on small areas if you can get the surface profile right.

For applying blacking (not 2 pack epoxies), water jetting is fine as the coating sticks enough to last 2 years so you dont need to get to an SA 2.5 finish.

 

eta. The ability of Keelblack to be applied to a damp surface is not because it is water based - it is because the coating has been formulated to stick to less than perfect surfaces. OK for a 2 year life.

 

eta more: Just checked the application sheet and they dont ask for a temp above a dew point so ok to apply it cold. Having spent the years I have in paint formulation, I would'nt apply it at the temps they say!!!!

Edited by Dr Bob

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I reckon folk use far more blacking than they need to. After the first coat its a devil of a job to see exactly where your brush strokes of paint are with being all glossy especially with the sun shining on it as well and tend to give very large overlaps with the brush to be on the safe side, in the end it ends up with hundreds of varying thicknesses all over the place. There needs to be two types of the same stuff, one black and one a sort of off black, slightly grey or something so you can see where you've bin.

  First coat black second coat grey-black, third coat black again.

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