Anodes

[dak]

Can someone please explain what anodes are and what they do? I keep seeing topics and adverts that mention them and how many there are, but don't understand exacctly what they or their function is. Does a n/b have to have a certain amount of them? Sorry for my ignorance.

[Clivo]

Can someone please explain what anodes are and what they do? I keep seeing topics and adverts that mention them and how many there are, but don't understand exacctly what they or their function is. Does a n/b have to have a certain amount of them? Sorry for my ignorance.

 

Hi dak

 

Please don't apologise, we're all here to learn.

 

Anodes (sacrificial anodes-I believe there full name is) are there to protect your steel hull from premature corrosion due to electrolytic action. Seawater anodes have a different composition to those required for freshwater vessels but their goal is the same. There is a little more info on wikipedia, Here

 

Quantity required depends on the size of the boat.

 

Good Luck, & don't hesitate to keep asking.

[dak]

So is it/they a sort of conductor? How many and where should they be on a 58 - 60 foot n/b. and what do they look like? Sorry i am a woman after all!

[kitman]

So is it/they a sort of conductor? How many and where should they be on a 58 - 60 foot n/b. and what do they look like? Sorry i am a woman after all!

Definition of 'galvanic action' from about.com: "When iron and steel are subject to conditions of aqueous corrosion the incidence and rate at which the corrosion takes place will alter if the steel is coupled with other metals or alloys that are also exposed to the electrolyte. Copper, brass, bronze, lead and nickel are more "noble" and act as auxiliary cathodes to the steel and accelerate its anodic dissolution, that is, its corrosion. Magnesium, zinc and zinc-base alloy are nearly always less noble and tend to divert the attack from the steel to themselves. The galvanic relationship of various metals is an important factor affecting corrosion."

 

____________

 

Narrowboat anodes are made from Magnesium. Saltwater anodes are usually zinc I think

Edited January 16, 2011 by kitman

[dak]

Definition of 'galvanic action' from about.com: "When iron and steel are subject to conditions of aqueous corrosion the incidence and rate at which the corrosion takes place will alter if the steel is coupled with other metals or alloys that are also exposed to the electrolyte. Copper, brass, bronze, lead and nickel are more "noble" and act as auxiliary cathodes to the steel and accelerate its anodic dissolution, that is, its corrosion. Magnesium, zinc and zinc-base alloy are nearly always less noble and tend to divert the attack from the steel to themselves. The galvanic relationship of various metals is an important factor affecting corrosion."

 

____________

 

Narrowboat anodes are made from Magnesium. Saltwater anodes are usually zinc I think

 

 

Many thanks. I think i'm beginning to understand.

[Keeping Up]

Can someone please explain what anodes are and what they do? I keep seeing topics and adverts that mention them and how many there are, but don't understand exacctly what they or their function is. Does a n/b have to have a certain amount of them? Sorry for my ignorance.

 

Most narrow boats have 2 at the bow and 2 at the stern, Here is an excellent photo from the Ashby Boats website showing a stern one:

 

 

[dak]

Most narrow boats have 2 at the bow and 2 at the stern, Here is an excellent photo from the Ashby Boats website showing a stern one:

 

 

 

ah ha, now i know what they look like. Thank you so much.

[terryvanman]

I sugest that you have more than 2 at the front and 2 at the back on a 58 foot boat,,,I have 2 back and front and 8 more [4 sets of 2] at intervals along the lenth of the boat...but thats just me....

[DHutch]

Its also worth noting that they are partially important around the stern, and if you have a bow thruster the bow, as these areas contain other dissimilar metals which without a more anodic metal would cause problems. Typically the (bronze) propeller causing the (stainless steel) propeller shaft to deteriorate very rapidly.

 

If i didnt have bow thruster i think i would only have anodes at the rear and rely on good paint for the rest.

 

 

Daniel

[Keeping Up]

I sugest that you have more than 2 at the front and 2 at the back on a 58 foot boat,,,I have 2 back and front and 8 more [4 sets of 2] at intervals along the lenth of the boat...but thats just me....

 

Most boats have just the 2 at each end. Certainly it would be much much better to have more, but on most boats the ones along the sides would just get wiped off.

[terryvanman]

Most boats have just the 2 at each end. Certainly it would be much much better to have more, but on most boats the ones along the sides would just get wiped off.

 

mine are under the base-plate,,,you would have to hit something real hard to rip them off. most canal bottoms are mud with the odd supermarket trolley and the occasional rockery you would have to be a bit unlucky to hit them

 

you can see them at 8 foot intervals

 

[jonk]

I have often wondered why anodes are lumps at intervals that protect an area round them. Why would not a strip of magnesium along the side, below a rubbing strake, not be a better solution? Surely this would give a wider protection? Must be a good reason but I don't know what it is.

 

John

[deletedaccount]

Make sure you paint them so they don't corrode!

[alan_fincher]

Most narrow boats have 2 at the bow and 2 at the stern, Here is an excellent photo from the Ashby Boats website showing a stern one:

 

If that piece of plywood attached with an elastic strap is an attempt to increase rudder area, then they have not done a robust enough job!

 

OK, I realise it is probably some kind of strap on sign, perhaps because the boat is on the back of a lorry ?

 

As another complete aside, when we bought out boat it had a prop hanging off that kind of length of unsupported shaft, and we were strongly advised by our surveyor to shorten it.

[Heffalump]

Having cleaned and blacked quite a few different boats, I can safely say that actually they do make a difference. A boat coming out with anodes attached has noticibly less corrosion than one without. And a boat with anodes front and back will have very little corrosion at the front and back, getting stronger in the middle. (more corrosion away from anodes)

[LEO]

If that piece of plywood attached with an elastic strap is an attempt to increase rudder area, then they have not done a robust enough job!

 

OK, I realise it is probably some kind of strap on sign, perhaps because the boat is on the back of a lorry ?

As another complete aside, when we bought out boat it had a prop hanging off that kind of length of unsupported shaft, and we were strongly advised by our surveyor to shorten it.

 

Not sure about that, it would be dragged off by the wind as the lorry sped along.

 

When I had my boat transported by road down from Newark the rudder was tied up very tightly, as was anything else externally that would move, including hatches and flue covers. The only thing which flapped about after a while were the unused ends of the securing straps, much to the consternation of a pack of police motorcyclists who passed the lorry.

 

Mike

[blackrose]

mine are under the base-plate,,,you would have to hit something real hard to rip them off. most canal bottoms are mud with the odd supermarket trolley and the occasional rockery you would have to be a bit unlucky to hit them

 

you can see them at 8 foot intervals

 

 

I did the same thing some years ago but was told on the forum that anodes don't work around corners. But if that's true they will still protect your baseplate!

 

I found some thin ones from Amber boats and put them on the sides when the boat came out for blacking last summer. They have tapered ends and are protected by the overhang of the baseplate.

 

Edited January 18, 2011 by blackrose

[jonk]

Make sure you paint them so they don't corrode!

 

Hope no-one takes this seriously though!!!

 

A couple of thoughts.

Why would anodes not protect round corners?

Do the anodes have to be in contact with the steel, or on top of the paint?

Why are strip anodes not used to cover a wider area?

 

John

[deletedaccount]

Yeah, sry bout that

[blackrose]

 

A couple of thoughts.

Why would anodes not protect round corners?

Do the anodes have to be in contact with the steel, or on top of the paint?

Why are strip anodes not used to cover a wider area?

 

John

 

I don't know why they wouldn't work around corners but I was told that they have to be in direct "line of sight" with the steel to be protected. Presumably this would mean they wouldn't work around curves too, so the ones on my bow wouldn't work either?

 

Anodes have to be bonded to the steel to form an electrical connection.

 

I don't know why the range of anode shapes is so limited. Unless you have recesses in the sides of your boat then it's very difficult to find anodes for the sides of a NB.

Edited January 18, 2011 by blackrose

[Strads]

There's probably a couple of degree courses required to fully answer the how and why anodes work, then the type of steel, stainless, bronze in the variou slocations and how they interact/bond...

 

far to technical for me.. however i can see the logic of having them at regular intervals along the hull side but also the isse of knocking them of, particuarily on moving into/out off locks etc...

[Don't tell him Pike!]

I hadn't realised quite how heath robinson-esque the application of annodes was on narrow boats! This question of why they aren't just strips is an interesting one, it seems to me it'd make a lot of sense to have a sort of rut running the lengh of each side with long annode strips tucked safely into them, but then I suppose this rut would constitute a corner, rendering them pointless.

I wonder also if the industry is resistant to change as longer lasting boats = less people needing new boats = less sales.

[kitman]

I wonder also if the industry is resistant to change as longer lasting boats = less people needing new boats = less sales.

We've have boats at our place that are over 75 years old

[blackrose]

We've have boats at our place that are over 75 years old

 

We have a couple that are over a hundred, but they are wafer thin in places!

[canaldrifter]

Having cleaned and blacked quite a few different boats, I can safely say that actually they do make a difference. A boat coming out with anodes attached has noticibly less corrosion than one without. And a boat with anodes front and back will have very little corrosion at the front and back, getting stronger in the middle. (more corrosion away from anodes)

 

That is the first time I've ever seen anyone come up with any comparisons. But, are you taking into account how long the boats have been in the water since the last blacking, how old they are, whether they've been moored for any length of time with a power hook-up, and where they've been?

 

And do you fit anodes?

 

Tone

(still cynical.... sorry)