Anodes who needs 'em!

[PabloPicasso]

My anode (large pear drop shaped one at the back near the prop/shaft & appropriately bonded to my knowledge) is a year and a bit old and looks like new after cleaning it and the rest of the undersides off last week (with the boat still in the water). Boat lives in a large marina, no corrosion anywhere & I'm a bit confused as to why there is no wear on the anode whatsoever...

It may be that the anode has insufficient conection to the parts its meant to protect. You could check the resistance (in ohms?) between the anode and the metal parts its supposed to be protecting.

It maybe unnecessary, but it may be doing nothing and the important metal parts of your boat are corroding. Best to check with a multimeter, a lot cheaper than, say, replacing a saildrive.

 

[Refueler]

You may well find that the mast is also bonded to the keel as a path to earth for lightning protection.

Doubt it .... but will be one of the checks ..

Lightning ... mmmm ever considered how large a cable you'd need to actually be effective ?

Years ago ... my Company had a VHF antenna clipped to the safety rail on the roof. Co-ax led down to the radio on the window sill.

I was sitting near it with one of my Dept Managers when lightning struck the antenna .... we were both blown out of our chairs ... co-ax was smouldering ... radio was as if a mortar shell had hit it ..
But that was not all ... our network cables ran close to the radio and the shock had travelled along the cables and fried all the hard drives / network boards etc in half the computers ....

When later we went on the roof ... the antenna was like a banana .. the GRP outer peeled back ... the inner black and charred.

It all reminded me of when I was 3rd mate on a ship in Nigeria ... up river at Port Harcourt. Lightning struck our mast ... there also it shredded the VHf antenna ... the cable exiting in wheelhouse charred along with the bulkhead behind it ... the Sailor VHF unit - the boards had liquified and run out the bottom vents and down the bulkhead ...
There were two wives standing outside the accommodation when it happened ... they had the most 'frizzied' hair I had ever witnessed ... and they were shaking - shocked by it all.

 

[vyv_cox]

I've heard it mentioned for fixed mooring protection, I think on Aberlady Bay yacht club website, but it might have been on another of the Firth of Forth club websites.

Yes, I know of anodes on mooring chains but they would be pretty pointless on anchoring gear.

 

[ducked]

Yes, I know of anodes on mooring chains but they would be pretty pointless on anchoring gear.

Pretty similar situation, but I suppose the mooring chains are in "wet" service all the time, so any positive effect of the anodes wll be more significant and quicker.

 

[Tranona]

Doubt it .... but will be one of the checks ..

Lightning ... mmmm ever considered how large a cable you'd need to actually be effective ?

Pretty common on modern boats. My Bavaria had a heavy cable from the mast compression post to a keel bolt. American boats tend to have lightning protection in this way or from chain plates as lightning is far more common there, particularly in southern waters. Not a big issue in N European waters.

 

[ducked]

It may be that the anode has insufficient conection to the parts its meant to protect. You could check the resistance (in ohms?) between the anode and the metal parts its supposed to be protecting.

It maybe unnecessary, but it may be doing nothing and the important metal parts of your boat are corroding. Best to check with a multimeter, a lot cheaper than, say, replacing a saildrive.

Resistance between the anode and its client component should be less than 1 ohm, according to

Reference Cell Testing; Know Thy Corrosion Protection Level – Editorial: Old vs. New | Steve D'Antonio Marine Consulting

 

[PabloPicasso]

Resistance between the anode and its client component should be less than 1 ohm, according to

Reference Cell Testing; Know Thy Corrosion Protection Level – Editorial: Old vs. New | Steve D'Antonio Marine Consulting

That's the info we need. What a great forum, I hoped someone would be along to give the technical gen on that.

 

[ducked]

That's the info we need. What a great forum, I hoped someone would be along to give the technical gen on that.

I'm afraid it gets quite a bit more technical than that.

I made a few other confused/confusing posts on the general topic, dispersed (perhaps fortunately) over three threads running in this general area.

Perhaps I should try and tidy and pull those mumblings together, but meanwhile probably worth reading that article.

My main uncertainty is whether there would be value in measuring the (surface?) potential difference between the anode and its client, as opposed to between a fancy reference half-cell and the client, as per the method in that article.

It seems to me that this might still give some clue as to what was going on, though it would not allow optimisation of the carhodic protection