Anode

[BODs SR2]

Does this anode need changing. Very rarely connected to shore power. Will it last another 2-3 years before the next blacking. Cheers. 

[dmr]

Its hard to answer that as different boats appear to consume anodes at very different rates.

Do you know when it was last replaced?

[matty40s]

That's 2/3 gone, I would add another about 2 feet away and leave that one to finish.

[blackrose]

1 hour ago, BODs SR2 said:

Does this anode need changing. Very rarely connected to shore power. Will it last another 2-3 years before the next blacking. Cheers. 

 

It's not really a question of being connected to shore power or not. If you were connected to shore power then you should be properly isolated in which case your anodes wouldn't be doing anything other than their normal sacrificial rate of decay. 

 

To me that anode looks like it would last another few years. Give it a quick wire brush before the boat goes back in.

[BODs SR2]

On 22/09/2023 at 11:03, dmr said:

Its hard to answer that as different boats appear to consume anodes at very different rates.

Do you know when it was last replaced?

Been on about 8 years 

[Chewbacka]

25 minutes ago, BODs SR2 said:

Been on about 8 years 

So roughly a third every 4 years, probably last another 3 years or so - depending on who you moor next to etc.  I would change it next time.

Some may tell you they get less effective as they get smaller, but I suspect the opposite as all the pitting greatly increases the surface area to make them more effective.  But I don’t suppose there is any real data to prove either view.

[Alan de Enfield]

1 minute ago, Chewbacka said:

So roughly a third every 4 years, probably last another 3 years or so - depending on who you moor next to etc.  I would change it next time.

Some may tell you they get less effective as they get smaller, but I suspect the opposite as all the pitting greatly increases the surface area to make them more effective.  But I don’t suppose there is any real data to prove either view.

 

Do a Google search and you'll see that every article feature about anodes says they should be replaced when they are about 50% depleted, after that they lose effectiveness.

 

Whilst you might thing they increase the surface area with the pitting, you will find that as it changes colour it becomes coated with a sort of 'rust' that, in effect coats the anode and stops it working.

 

 

 

 

A boat which did not renew its anodes - this is after an estimated 18-24 months without protection.

 

[ditchcrawler]

7 minutes ago, Alan de Enfield said:

 

Do a Google search and you'll see that every article feature about anodes says they should be replaced when they are about 50% depleted, after that they lose effectiveness.

 

Whilst you might thing they increase the surface area with the pitting, you will find that as it changes colour it becomes coated with a sort of 'rust' that, in effect coats the anode and stops it working.

 

 

 

 

A boat which did not renew its anodes - this is after an estimated 18-24 months without protection.

 

Lot of dissimilar metals there, will a magnesium anode protect aluminium on a steel narrowboat ?

[Tracy D'arth]

I would just weld a new one next to the existing.

 

There is a school of thought that on a fully epoxy coated hull and base plate the anodes have not much to do. They certainly last longer in that application.

 

Zinc for salt water.

[Alan de Enfield]

1 hour ago, ditchcrawler said:

Lot of dissimilar metals there, will a magnesium anode protect aluminium on a steel narrowboat ?

 

Yes as Magnesium is further along the scale and is less Noble (more active) than Aluminium.

 

 

 

 

 

 

45 minutes ago, Tracy D'arth said:

 

 

Zinc for salt water.

 

 

And Aluminium for 'brackish' water (tidal rivers, estuaries etc)

Edited September 23, 2023 by Alan de Enfield