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Oldngrumpy

Baseplate corrosion concern

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Getting back to basics, if steel is used to build a boat it is going to corrode once put in the water. It is expected. Boats are built out of steel thick enough to last a few decades with only token attempts at delaying the corrosion, e.g. blacking.

 

The OP seems to want a boat that will last indefinitely rather than one that degrades over the decades, in which case a Sea Otter (made from aluminium) might be a better choice, or a GRP boat. 

 

 

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21 minutes ago, catweasel said:

This three letter acronym corrosion thing (I hate three letter acronyms, or TLA's as I call them):
Does it only live in fresh water, or is it found in salt waters? Does salt water kill it?

Marinas fed by rivers are another risk area and, in salt and brackish water environments, it is well known that harbour muds are highly contaminated by the sulphites supporting these creatures, leading to catastrophic steel pile failure.  MIC can occur on any ferrous and non-ferrous surface including aluminium.

MIC is a highly unpredictable process but the corrosion progress can be rapid, serious damage happening in as little as a matter of months. The oil, gas and mining industries spend millions protecting and repairing their pipelines and equipment but whilst the threat is the same, little is understood and even less done about it in the freshwater boating world.

MIC can destroy steel at four times the rate of electrolytic or galvanic corrosion and must not be ignored.

12 minutes ago, Mike the Boilerman said:

The OP seems to want a boat that will last indefinitely rather than one that degrades over the decades, in which case a Sea Otter (made from aluminium) might be a better choice, or a GRP boat. 

 

MIC can occur on any ferrous and non-ferrous surface including aluminium.

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31 minutes ago, Alan de Enfield said:

Marinas fed by rivers are another risk area and, in salt and brackish water environments, it is well known that harbour muds are highly contaminated by the sulphites supporting these creatures, leading to catastrophic steel pile failure.  MIC can occur on any ferrous and non-ferrous surface including aluminium.

MIC is a highly unpredictable process but the corrosion progress can be rapid, serious damage happening in as little as a matter of months. The oil, gas and mining industries spend millions protecting and repairing their pipelines and equipment but whilst the threat is the same, little is understood and even less done about it in the freshwater boating world.

MIC can destroy steel at four times the rate of electrolytic or galvanic corrosion and must not be ignored.

 

MIC can occur on any ferrous and non-ferrous surface including aluminium.

Cheers for the info. 

44 minutes ago, Mike the Boilerman said:

Getting back to basics, if steel is used to build a boat it is going to corrode once put in the water. It is expected. Boats are built out of steel thick enough to last a few decades with only token attempts at delaying the corrosion, e.g. blacking.

 

The OP seems to want a boat that will last indefinitely rather than one that degrades over the decades, in which case a Sea Otter (made from aluminium) might be a better choice, or a GRP boat. 

 

 

It's same as what they say; nowt is forever.
Alarming that there are claims of serious damage in a few months though. That said there will be some (expensive) miracle cure around the corner...
 

Edited by catweasel

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48 minutes ago, catweasel said:

Cheers for the info. 

It's same as what they say; nowt is forever.
Alarming that there are claims of serious damage in a few months though. That said there will be some (expensive) miracle cure around the corner...
 

It is indeed alarming at how quickly serious damage can occur, given that some underwater parts of a boat hull are often made in steel that is far less thick than the base plate - I am thinking of two areas that might be a problem - bow thruster tubes are rarely blacked and are often created out of a thinner steel. Also the drain for the gutter below the engine cover on a cruiser or semi-trad boat. This is often made out of thinner tube and yet the base of it is often permanently submerged and never sees any blacking. 

 

The first time I became aware of MIC was when Madeline - the Eckington School boat that is based on the unconnected end of The Chesterfield Canal, was diagnosed with it. The boat was only launched in 2014 and yet has had to have welds in the pits on the base plate where it had become very thin in places.  

 

http://www.chesterfield-canal-trust.org.uk/madeline/

 

I came across this graphic when browsing for info on the net and, while it is explaining ordinary corrosion rather than MIC I found it very helpful in understanding how pitting can occur 

 

 

3-s2.0-B0080431526001017-gr4.jpg

Edited by cheshire~rose
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12 minutes ago, cheshire~rose said:

It is indeed alarming at how quickly serious damage can occur, given that some underwater parts of a boat hull are often made in steel that is far less thick than the base plate - I am thinking of two areas that might be a problem - bow thruster tubes are rarely blacked and are often created out of a thinner steel. Also the drain for the gutter below the engine cover on a cruiser or semi-trad boat. This is often made out of thinner tube and yet the base of it is often permanently submerged and never sees any blacking. 

 

The first time I became aware of MIC was when Madeline - the Eckington School boat that is based on the unconnected end of The Chesterfield Canal, was diagnosed with it. The boat was only launched in 2014 and yet has had to have welds in the pits on the base plate where it had become very thin in places.  

 

I came across this graphic when browsing for info on the net and, while it is explaining ordinary corrosion rather than MIC I found it very helpful in understanding how pitting can occur 

 

 

3-s2.0-B0080431526001017-gr4.jpg

 

 

Is that illustration that the anode is actually contributing its magnesium to the chemical 'broth' and helping to support the growth of the little blighters ?

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M is for Metal, in this case. There is no sacrificial anode shown, just the common corrosion process.

 

It would be Mg if it were Magnesium and the 2e- produced would substitute for those produced from the Metal.

N

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2 minutes ago, BEngo said:

M is for Metal, in this case. There is no sacrificial anode shown, just the common corrosion process.

 

It would be Mg if it were Magnesium and the 2e- produced would substitute for those produced from the Metal.

N

Thank you. (I'm no chemist)

 

Why have they annotated the drawing with "Anode" above the 'formula ?

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25 minutes ago, Alan de Enfield said:

 

 

Is that illustration that the anode is actually contributing its magnesium to the chemical 'broth' and helping to support the growth of the little blighters ?

That would be a turn up for the books! Must be 20 years ago when we had the anodes renewed on first nb during blacking. Guy at the boatyard said " It is your money and I will weld them on for you, but you might as well weld them on your garden gates." I did have them fitted but often wonder if he knew something that I didn't.

Edited by catweasel

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More reading ?

 

MIC value of corrosion equates to 0.6% of the Worlds total GDP  

 

 

 

Alessandra Bonfanti, ... Jason S. Lee, in Reference Module in Materials Science and Materials Engineering, 2018

Although little attention is given to corrosion, the annual cost of corrosion due to damages and fixings has been estimated to be over 3% of the world’s Gross Domestic Product (GDP) (Hays, 2010). Studies suggest that 20% of the corrosion damages are caused by Microbiologically Influenced Corrosion (MIC). Therefore, MIC represents a serious problem in several fields. MIC is corrosion due to the presence and activities of microorganisms. Several alternative terms are also used to denote the phenomenon, for example, microbially induced corrosion, microbial corrosion, and biocorrosion.

 

https://www.sciencedirect.com/topics/materials-science/microbiological-corrosion

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On 12/07/2019 at 17:01, Machpoint005 said:

 

That's a good argument for not blacking the baseplate in the first place. Another one is that on shallow canals (ie most of them) you polish the baseplate as you cruise along, so any surface treatment would get scraped off (yes, epoxy too).

 

I'm with you in the "don't black the bottom" club.

Funny mine still had black from when it was done at Fox Narrowboats in 2012 but then as you know I dont move much

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38 minutes ago, catweasel said:

That would be a turn up for the books! Must be 20 years ago when we had the anodes renewed on first nb during blacking. Guy at the boatyard said " It is your money and I will weld them on for you, but you might as well weld them on your garden gates." I did have them fitted but often wonder if he knew something that I didn't.

I had a similar comment from a boat builder down on the Chesterfield who fitted a new gearbox for me. He said the only time he fitted them was when he sold one of his boats. I think he use to launch them in the basin at West Stockwith so his yard was close to there

 

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43 minutes ago, Alan de Enfield said:

Thank you. (I'm no chemist)

 

Why have they annotated the drawing with "Anode" above the 'formula ?

In the electrolytic  corrosion process there is an Anode, where electrons leave the metal and enter the electrolyte, and a Cathode where the electrons leave the electrolyte (labelled oxygen containing water in the piccy). 

N

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10 minutes ago, BEngo said:

In the electrolytic  corrosion process there is an Anode, where electrons leave the metal and enter the electrolyte, and a Cathode where the electrons leave the electrolyte (labelled oxygen containing water in the piccy). 

N

Thank you - I understand it is AN anode, not THE anode,

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1 hour ago, cheshire~rose said:

It is indeed alarming at how quickly serious damage can occur, given that some underwater parts of a boat hull are often made in steel that is far less thick than the base plate - I am thinking of two areas that might be a problem - bow thruster tubes are rarely blacked and are often created out of a thinner steel. Also the drain for the gutter below the engine cover on a cruiser or semi-trad boat. This is often made out of thinner tube and yet the base of it is often permanently submerged and never sees any blacking. 

 

The first time I became aware of MIC was when Madeline - the Eckington School boat that is based on the unconnected end of The Chesterfield Canal, was diagnosed with it. The boat was only launched in 2014 and yet has had to have welds in the pits on the base plate where it had become very thin in places.  

 

http://www.chesterfield-canal-trust.org.uk/madeline/

 

I came across this graphic when browsing for info on the net and, while it is explaining ordinary corrosion rather than MIC I found it very helpful in understanding how pitting can occur 

 

 

3-s2.0-B0080431526001017-gr4.jpg

Had the bottom plate on Madeline been blacked ? 

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31 minutes ago, Alan de Enfield said:

Thank you - I understand it is AN anode, not THE anode,

 

31 minutes ago, Alan de Enfield said:

Thank you - I understand it is AN anode, not THE anode,

Yes.  On a typical piece of steel plate, because the blast furnace,  conversion plant and rolling mill between them turn out steel that is not identical every where, and because we then work it, bend it and weld it to make things worse, there are lots of places that become anodes and an equal number of places that are cathodes.

 

N

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@oldngrumpy

I'd just like some more on that 'Chine' looks fairly close to the weld from the pic there.

 

Some things boatbuilders can't do, ie. know how the boat will corrode over years, depends greatly on the owners.

But giving enough of something to start with, i.e. extra steel, builders can do, that is more rub protection where needed. There isn't enough there, for me anyway.

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On 14/07/2019 at 14:54, Troyboy said:

Had the bottom plate on Madeline been blacked ? 

I don't know, I was not involved with the build. CCT only got involved around the time of the launch when a great partnership began.

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On 14/07/2019 at 05:48, blackrose said:

 

Yes, unfortunately it's the Second Law of Thermodynamics. Energy flows from order to disorder and everything eventually decays.

 

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3 hours ago, 70liveaboard said:

@oldngrumpy

I'd just like some more on that 'Chine' looks fairly close to the weld from the pic there.

 

Some things boatbuilders can't do, ie. know how the boat will corrode over years, depends greatly on the owners.

But giving enough of something to start with, i.e. extra steel, builders can do, that is more rub protection where needed. There isn't enough there, for me anyway.

I specified an extra band the length of my hull and the builder said, "I put one there as standard" some cheaper huls dont have one at all

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