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Unusual blacking question


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I have a friend who has agreed to take an abandoned and derelict, but floating, hull off CRT's hands.  It's to be used as a sort of floating pond (don't ask).  I think it's to do with a charity.  The boat will be lined somehow before waterlilies etc are added.

 

AFAIK CRT aren't charging her for it and they legally have to crane it out anyway so it can't be reclaimed by the former owner.

 

CRT have suggested that it should be blacked while it's out at the boatyard.

 

Questions:

 

1.  Would you black the the whole boat inside and out?  Or black the outside and vactan the inside?  Or something else?

 

2.  Would you epoxy it?  Is it worth the cost?  The boat is virtually worthless, but once this project is in place, it won't be easy to black it again.

 

3.  Is there any point in putting anodes on it?  The boatyard seem to want to do it, but I've always assumed that the joey boats I see moored up have no anodes.  This is kind of the same thing.  No engine or electrics.  The boat will not move once in place.

 

 

 

 

 

boat.jpg

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Forget the anodes, not needed if no electrics.

It depends on how long you want your project to last, but blacking should suffice, both internal and external to prolong the metal life........however, its structure will probably last for years anyway, and maybe it should be allowed to dissolve into the natural environment on it's own.

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1 hour ago, matty40s said:

Forget the anodes, not needed if no electrics.

It depends on how long you want your project to last, but blacking should suffice, both internal and external to prolong the metal life........however, its structure will probably last for years anyway, and maybe it should be allowed to dissolve into the natural environment on it's own.Useful advice. 

1 hour ago, ditchcrawler said:

She doesn't need to do all that, there is one already done on the Stourbridge canal

I’m not sure that one could be successfully towed anywhere ?

Edited by doratheexplorer
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11 hours ago, ditchcrawler said:

Is it going to be moved?

I'm struggling to think how this will look like anything other than an abandoned hulk with water lillies growing in it (like that one on the Stourbridge you refer to) unless it's moved off the canal. Might be nice on a traffic roundabout. 

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13 hours ago, ditchcrawler said:

Is it going to be moved?

Yes.  The boatyard is about a day's tow from the final resting place.

1 hour ago, Sea Dog said:

I'm struggling to think how this will look like anything other than an abandoned hulk with water lillies growing in it (like that one on the Stourbridge you refer to) unless it's moved off the canal. Might be nice on a traffic roundabout. 

You may be right, but I think I'd quite like the look of an abandoned hulk with waterlilies in it.  My friend is a very capable horticulturist so I'm sure she's got some think great planned.

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15 hours ago, matty40s said:

Forget the anodes, not needed if no electrics.

It depends on how long you want your project to last, but blacking should suffice, both internal and external to prolong the metal life........however, its structure will probably last for years anyway, and maybe it should be allowed to dissolve into the natural environment on it's own.

Thanks for this.  I couldn't see a point to the anodes either.  It seems the boat yard have just sent out a standard blacking quote.  That concerns me, as it implies that they haven't really thought about what's needed here.  I've advised my friend to ask about a DIY option so we can make sure it's done properly.  The charity is not short of helpers and yours truly can oversee the operation. 

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On 23/03/2021 at 17:56, matty40s said:

Forget the anodes, not needed if no electrics.

It depends on how long you want your project to last, but blacking should suffice, both internal and external to prolong the metal life........however, its structure will probably last for years anyway, and maybe it should be allowed to dissolve into the natural environment on it's own.

 

I don't really understand this? Anodes are added to provide sacrificial protection to steel on all sorts of underwater objects, many without any electrical systems. They work by introducing galvanic action between the dissimilar metals to the detriment of the less noble metal. It has nothing to do with the electrical system onboard a boat, unless of course there is a fault with the electrical system involving the hull in which case the anodes might fizz away much quicker.

On 24/03/2021 at 09:11, Dave_P said:

Thanks for this.  I couldn't see a point to the anodes either.  It seems the boat yard have just sent out a standard blacking quote.  That concerns me, as it implies that they haven't really thought about what's needed here.  I've advised my friend to ask about a DIY option so we can make sure it's done properly.  The charity is not short of helpers and yours truly can oversee the operation. 

 

Personally I don't see the point of blacking it. Standard bitumen based blacking suffers from UV damage and after a few years it will be starting to come off anyway. Are you going to drain it, haul it out and re-black it?

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7 minutes ago, blackrose said:

 

I don't really understand this? Anodes are added to provide sacrificial protection to steel on all sorts of underwater objects, many without any electrical systems. They work by introducing galvanic action between the dissimilar metals to the detriment of the less noble metal. It has nothing to do with the electrical system onboard a boat, unless of course there is a fault with the electrical system involving the hull in which case the anodes might fizz away much quicker.

 

 

 

 

If that's right then you're suggesting that some kind of significant current is likely to be found around a boat with no electric system, is not moving and there are no other boats nearby.  If so, what would cause that?  I would have thought that any galvanic corrosion would be minimal and not really worth bothering with new anodes for.  The hull may have some old anodes on it anyway.

Edited by Dave_P
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If you stick any piece of mild steel in water it will corrode.  The steel itself is not homogenous ( there are lots of bits where the composition varies, there are carbon inclusions etc... ) and some parts are more anodic than others.  These corrode fastest and usually form pits.  The chemistry at the very bottom of a pit is complicated but creates the conditions that make the pit grow.

Blacking keeps the water away from the metal.  Anodes provide an anti-corrosive potential so that even the most anodic bits of steel are less anodic than the Anodes.  This means the Anodes corrode  before the steel.  Empirically, the Anodes have an effective range of about  6 feet.

 

In this case the hulk is going to corrode from the inside out, as well as the outside in.

 

The ideal thing to do with the hulk would be to blast it inside and out and then apply an epoxy coating system designed for in water use.  You could then forget it for 20 plus years.

 

N

 

 

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2 minutes ago, Alan de Enfield said:

 

 

Or, just buy a plastic pond liner from the garden centre.

 

Well yes, that's the plan I think.

7 minutes ago, BEngo said:

If you stick any piece of mild steel in water it will corrode.  The steel itself is not homogenous ( there are lots of bits where the composition varies, there are carbon inclusions etc... ) and some parts are more anodic than others.  These corrode fastest and usually form pits.  The chemistry at the very bottom of a pit is complicated but creates the conditions that make the pit grow.

Blacking keeps the water away from the metal.  Anodes provide an anti-corrosive potential so that even the most anodic bits of steel are less anodic than the Anodes.  This means the Anodes corrode  before the steel.  Empirically, the Anodes have an effective range of about  6 feet.

 

In this case the hulk is going to corrode from the inside out, as well as the outside in.

 

The ideal thing to do with the hulk would be to blast it inside and out and then apply an epoxy coating system designed for in water use.  You could then forget it for 20 plus years.

 

N

 

 

This is something I've heard before.  On that basis I ought to have 9 anodes on each of my hull sides and another 9 anodes along the baseplate of the hull.  27 anodes in total.  Typically a narrowboat might get 4 anodes.  2 at the front and 2 at the back.

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I think it would be simpler (and cheaper) to simply get it to where you want it,clean it up and paint it whatever colour you like.

You said you have plenty of helpers,so once in place a couple of days work.

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7 minutes ago, Mad Harold said:

I think it would be simpler (and cheaper) to simply get it to where you want it,clean it up and paint it whatever colour you like.

You said you have plenty of helpers,so once in place a couple of days work.

Couple of things.  Painting the outside of the boat wouldn't be possible if that happened.  And CRT have to lift it out in order for it to be legally seized.

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Rather than anodes, I might be tempted to place a piece of mild steel chain under the boat along its length and connect a small solar panel between it and the hull to give active protection. Make sure the panel is connected the right way round! It won't stop it rotting from the inside though.

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40 minutes ago, Onewheeler said:

Rather than anodes, I might be tempted to place a piece of mild steel chain under the boat along its length and connect a small solar panel between it and the hull to give active protection. Make sure the panel is connected the right way round! It won't stop it rotting from the inside though.

This sounds interesting.  Can you explain more?  How would I know which way round to connect the panel?  Can you draw a diagram?  Would there have to be lots of contact points along the hull or would the whole boat just become a cathode and gradually get thicker?

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6 hours ago, Dave_P said:

If that's right then you're suggesting that some kind of significant current is likely to be found around a boat with no electric system, is not moving and there are no other boats nearby.  If so, what would cause that?  I would have thought that any galvanic corrosion would be minimal and not really worth bothering with new anodes for.  The hull may have some old anodes on it anyway.

 

I'm not suggesting it, it's a well known fact. It's not a significant voltage, it's a very small voltage. What would cause it is the potential difference between two electrically bonded dissimilar metals immersed in an electrolyte. Look it up. Plenty of articles online.

 

https://structx.com/Material_Properties_001.html#:~:text=A typical rule of thumb,(Anodic) class typically corroding.

 

Surely you remember science lessons at school where zinc and copper electrodes on the end of wires were inserted in a lemon and produced enough voltage to illuminate a small light bulb. How do you think that works?

Edited by blackrose
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3 hours ago, Dave_P said:

This sounds interesting.  Can you explain more?  How would I know which way round to connect the panel?  Can you draw a diagram?  Would there have to be lots of contact points along the hull or would the whole boat just become a cathode and gradually get thicker?

 

It is known as impressed current protection. It can be used to protect any steel structure, but is often used to protect steel framed buildings.

 

https://www.mme-group.com/cathodic-protection/iccp/?gclid=CjwKCAjw6fCCBhBNEiwAem5SO3jiYorNDL6aNOzdxE9i5K3b4IK6mwAq82R8bqUagpXZBPnYub10yxoC1OAQAvD_BwE

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4 hours ago, cuthound said:

 

It is known as impressed current protection. It can be used to protect any steel structure, but is often used to protect steel framed buildings.

 

https://www.mme-group.com/cathodic-protection/iccp/?gclid=CjwKCAjw6fCCBhBNEiwAem5SO3jiYorNDL6aNOzdxE9i5K3b4IK6mwAq82R8bqUagpXZBPnYub10yxoC1OAQAvD_BwE

We used it on Gas Pipelines, had to be isolated not to give the divers a nudge

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On 25/03/2021 at 16:01, blackrose said:

 

I'm not suggesting it, it's a well known fact. It's not a significant voltage, it's a very small voltage. What would cause it is the potential difference between two electrically bonded dissimilar metals immersed in an electrolyte. Look it up. Plenty of articles online.

 

https://structx.com/Material_Properties_001.html#:~:text=A typical rule of thumb,(Anodic) class typically corroding.

 

Surely you remember science lessons at school where zinc and copper electrodes on the end of wires were inserted in a lemon and produced enough voltage to illuminate a small light bulb. How do you think that works?

Thanks for the info.  I barely remember school, even less specific lessons regarding lemons.  I do have a vague understanding of galvanic corrosion, anodes and cathodes (not learned from school).  As I wondered earlier, why don't narrowboats have anodes spaced every six feet along the hull?

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1 hour ago, Dave_P said:

Thanks for the info.  I barely remember school, even less specific lessons regarding lemons.  I do have a vague understanding of galvanic corrosion, anodes and cathodes (not learned from school).  As I wondered earlier, why don't narrowboats have anodes spaced every six feet along the hull?

 

Probably because they would get knocked off and/or potentially cause the boat to jamb in narrow locks.

 

I have often thought an additional bolt on magnesium rubbing strake running the length of the hull on each side would provide better galvanic protection than the type and number of anodes normally found on narrowboats, but no one seems to make them. ?

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