anodes

[pugsleyaddams]

hi everyone,
can anyone tell me about anodes?
i am aware they protect the stern gear, but what do they actually do?
are they needed on all water craft and why do / or do they need to be wired up to the engine?
I have a wooden hull.. /forums/images/graemlins/smirk.gif

 

[Tranona]

Suggest you look on www.MgDuff.co.uk this company is the biggest supplier of Anodes and they have good information on the properties and uses of anodes on boats.

 

[KenMcCulloch]

Hi Puggsley
A sacrificial anode corrodes instead of the more valuable metal thing it's protecting, usually a rudder or props etc. It works because of something to do with electricity and ions. It's very important that the anode is electrically connected to whatever it's supposed to protect.

My boat had a hull anode fitted when I took her over. This was wired to the engine casing but not connected to the prop because of a non-conducting flexible coupling. The prop looks fine to me (10 years old) and has not deteriorated in the 2 seasons I have had her afloat. The anode hasn't eroded much either, due to not being connecetd to a dissimilar metal underwater.

In wooden boats there can be problems associated with anodes creating an alkaline environment which damages the surrounding timber. I have therefore taken off the anode this winter; I found some softening of the wood around the through hull bolt which I have repaired and will not be replacing the anode.

The point of this story is that just because everyone else has one don't assume an anode is essential. It may have disadvantages as well as benefits.

 

[pugsleyaddams]

thanks guys,
i now know that the "suspected wood rot" i found in the stern ribs of my boat is actually caused by the anodes fixed through the hull there....
i think i'll remove them and attach them to the rudder instead as it is made of mild steel..

 

[KenMcCulloch]

Be careful about assuming you know for sure what's causing deterioration in timber. It may be associated with the anode but not necessarily; the business about electro-chemical decay is, as I understand it, not something that happens not at the anode itself but around anything acting as a cathode. In my own example I suspect the S/S bolt mounting the anode was in contact with water, making a cell and affecting the timber around, fortunately not severely.

If you have a steel rudder you should have an anode on each side, apparently.
Cheers.

 

[monkey_trousers]

this is a useful guide to explain some of the chemistry going on:

http://geminimarinesurvey.com/yahoo_site_admin/assets/docs/Marine_Metal_Corrosion.325111027.pdf


simple electrolysis, in essence, your boats is like one terminal in a battery, a pontoon, or other electrical source nearby is the other, a small electric current passes through the water from one to the other, but is more readily attracted to some metals than others, zinc is very attractive in this process so the anode gets targetted more than the more precious bits of your boat, and this process will slowly eat away the zinc on the anode, but leave your other metalwork relatively unscathed

you in a marina/pontoon mooring by any chance. It can be much worse than out on a swing mooring, lots of stray electrons fleeing about from the power on the pontoons and the shore power being used by other boats

 

[Sandyman]

What I will say if buying new anodes is to shop around.
We recently replaced all 6 of ours. Cheapest I could find on the internet & from chandlers was £45 ish each. Most expensive was £65:00. Got them from an industrial/fishermens chandler for £22:00 each, then got 10% discount for cash.

 

[lesweeks]

Recently stripped down the hull of the 1912 yawl I'm restoring. Pitch pine planks. The only damage to the wonderful Pitch Pine is where there has been an anode bolted though and, I guess, wired to the engine. This area has gone to a complete mush. The only metal I have in the water, other than the cast iron keel, is a couple of through hull fittings for the heads etc. and the prop & shaft. Following previously given advice, I'm minded to put an anode on the shaft but that's all. Then I'll watch carefully to see what happens.

 

[gary3029]

I used to have one fitted to my wooden hull to protect prop shaft etc. Because of concern with wood damage around anode I now hang a anode on wire over the side near the prop....connected to the engine of course. When I move from my mooring just lift and go.

 

[Peterduck]

I have seen that used fairly often at the Yacht club that I used to belong to. It is an excellent way of providing protection without incurring the side-effects, and should be used more often. Not all boats require anodes, and it sounds as though Border Maid is one which doesn't need any. One of my mates has a 25ft Lyle Hess cutter which hasn't had or needed any from the day of launching.
Peter.

 

[pugsleyaddams]

[ QUOTE ]
Recently stripped down the hull of the 1912 yawl I'm restoring. Pitch pine planks. The only damage to the wonderful Pitch Pine is where there has been an anode bolted though and, I guess, wired to the engine. This area has gone to a complete mush. The only metal I have in the water, other than the cast iron keel, is a couple of through hull fittings for the heads etc. and the prop & shaft. Following previously given advice, I'm minded to put an anode on the shaft but that's all. Then I'll watch carefully to see what happens.

[/ QUOTE ]

i was wondering how far the "mush" affected the wood on your vessel, i have the same problem it has mushed up around the bolts coming through the hull, i have dug out the affected wood which is basically the depth of the oak rib is it likely that the teak planking is also mushed i am in a marina mooring and debating wether or not to lift her out?? /forums/images/graemlins/smirk.gif

 

[Kukri]

Teak is in my experience more resistant than oak to electroylic damage (what I understand is happening is that alkali ions gathering at the cathode turn the wood into paper pulp). But not wholly able to withstand it. I had an oak frame go, with the teak planking OK.