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Galvanic corrosion


sailor mcgee

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5 hours ago, sailor mcgee said:

ice.

you can use GRP if you so wish to (but, that puts me out of a hobby..) and you MUST MUST MUST remove from the water by 1st of november  if in england - ice will crush grp if thick enough and you guys have had canals freeze over completly.

There are lots of GRP boats on our canals, a lot are lived on full time as its a cheap way (compared to a steel narrowboat) to get a home on the canal. Many of these are quite old and get zero hull maintainance.  Most of these Never come out of the water.  Maybe small plastic cruisers are relatively stronger then the larger boats that you are familiar with. Our winters are a lot tamer than yours, but I have seen ice four inched thick and have never heard of a GRP boating sinking due to ice. I am aware of one old steel narrow boat possibly sinking due to ice.

 

A possibly unique feature of are canals is that quite hard impacts with lock sides and canal banks, and items of junk on the canal bottom, are routine for many boats.

 

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

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we get ice thats a lot thicker for a lot longer here. i saw the union canal between edinburgh  and falkirk had frozen a in 2011/2010 it was frozen to the point where someone drove along the ice... in those conditions it can break grp i think.

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4 minutes ago, Alan de Enfield said:

I've corrected that for you.

and I should have said impacts with other boats too!  Remember we are narrow and share locks with other boats, even hirers, so impacts are inevitable even if not of our own making.

 

After a winter on the Rochdale we really are going to have to come out next year and repair the epoxy. Sloping stone wash walls and ledges in places have so far defeated my attempts at impact free mooring.  I can't get the back in so have to moor on a loose back rope which allows some swinging. The only good thing is that there are not many boats moving, and a wonderful absence of stag and hen boats speeding past.

 

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

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27 minutes ago, sailor mcgee said:

we get ice thats a lot thicker for a lot longer here. i saw the union canal between edinburgh  and falkirk had frozen a in 2011/2010 it was frozen to the point where someone drove along the ice... in those conditions it can break grp i think.

Sent you a message Sailor

 

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9 hours ago, Chewbacka said:

Coming back to the op question about copper sheeting - copper sheets were attached with copper nails sometimes brass but never iron/steel, as the iron nails rapidly corrode and the sheets fall off.  Mr Eiffel (of the tower) was well aware of this and came up with an elaborate fixing system so that the copper sheets of the Statue of Liberty ? did not touch the steel structure.

Steel/iron fastenings were generally avoided in favour of copper/bronze in wooden sea going boat construction because of corrosion issues. The wooden boat I sail on had her 2000 odd original bronze fastenings replaced, with one size larger, in her original hull timbers just short of her 100th birthday . 25years later still actively racing.

 

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10 hours ago, Flyboy said:

Isn't osmosis a big problem with GRP ?

Ha Ha Ha, that old chestnut 

It has been said that any boat with Osmosis will outlive it's owner. I moored on the Broads (The GRP capital of England) for 10 years and never came across anybody who had trouble with Osmosis.

Phil

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Silly aluminium car wheels can corrode and seize badly onto the steel hub too, and can be a pain to remove. I think most cars look daft with them on anyway, especially prestige cars showing all their rusty old brake calipers and gear.  The wheels could be fitted with big Mc Duff anodes whirling round for driving in the rain and through puddles.

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2 hours ago, Phil Ambrose said:

Ha Ha Ha, that old chestnut 

It has been said that any boat with Osmosis will outlive it's owner. I moored on the Broads (The GRP capital of England) for 10 years and never came across anybody who had trouble with Osmosis.

Phil

Quite right, Phil.  Nobody on the Broads has ever heard of a boat sinking due to Osmosis.

  • Greenie 1
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7 hours ago, sailor mcgee said:

we get ice thats a lot thicker for a lot longer here. i saw the union canal between edinburgh  and falkirk had frozen a in 2011/2010 it was frozen to the point where someone drove along the ice... in those conditions it can break grp i think.

But the ice under the bridges wasn't quite thick enough ... ?

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On 04/12/2018 at 23:37, Boater Sam said:

For corrosion in fresh water, ZINC is not reactive enough, we use Magnesium anodes,

 

 

Is the correct answer...

 

Fresh water isn't as "effective" an electrolyte as salt water so you need a more dissimilar and less noble anode.

 

galvanic_series.jpg

Edited by blackrose
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8 hours ago, blackrose said:

 

Is the correct answer...

 

Fresh water isn't as "effective" an electrolyte as salt water so you need a more dissimilar and less noble anode.

 

 

 

Narrow botes docked in brackish waters often report seeing bubbles rising from their anodes - evidence of the more concentrated electrolyte.

 

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10 minutes ago, mark99 said:

 

Narrow botes docked in brackish waters often report seeing bubbles rising from their anodes - evidence of the more concentrated electrolyte.

 

Salthouse dock in Liverpool is great for fuzzing anodes. I made a mistake of watering the plants with water from the dock. Stopped when I saw a jelly fish swimming lazily past. Sad to say some of the plants succumb to a saline flush

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1 hour ago, DandV said:

Salthouse dock in Liverpool is great for fuzzing anodes. I made a mistake of watering the plants with water from the dock. Stopped when I saw a jelly fish swimming lazily past. Sad to say some of the plants succumb to a saline flush

I was there for a week in September and saw lots of small jellyfish about 50mm diam.  The brackish water cleaned all the green slime off the hull as well. Salthouse is a great place to stay and would  recommend it as a must do trip.

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15 minutes ago, Flyboy said:

I was there for a week in September and saw lots of small jellyfish about 50mm diam.  The brackish water cleaned all the green slime off the hull as well. Salthouse is a great place to stay and would  recommend it as a must do trip.

It does wonders for hull prep for blacking, which is why we are booked in to both Liverpool and then Wigan dry dock next year. :D

 

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  • 8 months later...

As an offshore oil industry engineer with over 40 years experience in galvanic corrosion who is looking to purchase a retirement narrowboat. I make the following observations:

 It is my view that British canal water is neither fresh water or brackish water (slightly salty) but better described as industrial water. Industrial because its environmental chemistry has been greatly influenced over many years by the continual inclusion of ferrous corrosion by-products. Clearly online flowing waters are somewhat diluted when compared to the stationary enclosed marina waters. These multiple corrosion mechanisms, I have only seen in the enclosed waters of the massive Lake Maracaibo oil fields. Very similar waters in terms of corrosion, especially to those of an offline British canal marina! So the rules and methods applied by the oil industry fall somewhere between freshwater and brackish water but are no less valid.

There are ways to definitely measure the ability / potential of a metal to corrode in water and show if external forces are influencing the corrosion rate at any time or any location.

Also you can quickly answer questions like:

Are the anodes I have purchased actually functioning and are magnesium ?

Are the anodes on my hull damaging my paint / coatings?

Is the boat next door corroding my hull?

Is the marina that I am moored to corroding my hull ?

There is an excellent website that explains the galvanic corrosion problem in simple terms and recommend any boat owner to view.

https://www.galvatest.eu/

An industry standard British made Silver/Silver Chloride  half-cell, tested for use in these industrial canal waters Type BC (British Canal) is available for cost of around £70.00 from:

www.silvion,co,uk

I am happy to assist, even loan equipment to anyone with a question here or at chrisandpj@gmx.co.uk

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4 minutes ago, Chris and PJ said:

As an offshore oil industry engineer with over 40 years experience in galvanic corrosion who is looking to purchase a retirement narrowboat. I make the following observations:

 It is my view that British canal water is neither fresh water or brackish water (slightly salty) but better described as industrial water. Industrial because its environmental chemistry has been greatly influenced over many years by the continual inclusion of ferrous corrosion by-products. Clearly online flowing waters are somewhat diluted when compared to the stationary enclosed marina waters. These multiple corrosion mechanisms, I have only seen in the enclosed waters of the massive Lake Maracaibo oil fields. Very similar waters in terms of corrosion, especially to those of an offline British canal marina! So the rules and methods applied by the oil industry fall somewhere between freshwater and brackish water but are no less valid.

There are ways to definitely measure the ability / potential of a metal to corrode in water and show if external forces are influencing the corrosion rate at any time or any location.

Also you can quickly answer questions like:

Are the anodes I have purchased actually functioning and are magnesium ?

Are the anodes on my hull damaging my paint / coatings?

Is the boat next door corroding my hull?

Is the marina that I am moored to corroding my hull ?

There is an excellent website that explains the galvanic corrosion problem in simple terms and recommend any boat owner to view.

https://www.galvatest.eu/

An industry standard British made Silver/Silver Chloride  half-cell, tested for use in these industrial canal waters Type BC (British Canal) is available for cost of around £70.00 from:

www.silvion,co,uk

I am happy to assist, even loan equipment to anyone with a question here or at chrisandpj@gmx.co.uk

 

Thank you for taking the time - and - for your offer.

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