Anodes

[Killick69]

Apologies, put my last post in wrong forum. As there is no anode on Night Cap, I was wondering if anyone has ever trialled a temporary anode. I will fit an anode on the outside of the keel when the boat is slipped, but for now was thinking of hanging an anode in the outboard well while the boat sits on mooring (stow it away when sailing). I will then run a wire to the seacocks. Does anyone know if a seacock will be protected if the anode it is wired to is on the boat (Not in the water) and if this arrangement did lend protection, will there be a great(er) amount of green muck arising? I assume that wiring from anode to the items to be protected whould be individual wires to each item, rather than a series connection. I assume series connection will link dissimilair items directly and some current will flow between them and not just between these items and the anode. Does one connect the mast step? the mast? to anode, or only items that are in the water?
look forward to suggestions and comments.

[Shaun]

Gday John,
Sounds complicated mate , I dont know if its an issue to protect the bronze(i presume its bronze) thru-hull on NC, im not sure tho' , has anyone here had any corrosion problems on their thru-hulls, in particular if you have an outboard motor & no anodes?
regards
Shaun

[Dolphin]

G'Day John and Shaun,
You don't need to re-invent the wheel. Just copy what has already been done on other boats.

THe shaft anode is there on inboard boats to protect against the corrosion of dissimimilar metals in contact, ie the brass prop and the stainless steel shaft. Outboards usually have an anode under the cavitation (ventilation) plate too.
The brass skin fittings are alloyed to stop corrosion. If you go joining them with wire you are making a long connection in the water that can cause electrolysis by shorting out any earth currents running in the water. This is particularly a problem in the harbour. Earth leakage currents will then enter at the front sea cock and leave at the prop causing "erosion".
You should be able to replace the shaft anode in the water. I've done a few so far. If you find the other half of the one I dropped at Coasters Retreat its mine! Hint, do it in shallow water with a sandy bottom, like Palm Beach.
Connecting the mast to the anode wont do anything as there is no electrolyte (sea water) to connect the mast and complete the circuit back to the anode. Anyway, if you connect a copper wire to the aluminium mast you have just joined two of the worst metals together and you will get "severe" corrosion just using salt spray and dew as an electrolyte.
While on the subject, and corrosion is a very specialised field, Stainless Steel will rust if part of it is sealed in an oxygen depleted or deficient area and the other is in air. If you screw a stainless screw into some timbers and seal it, it will rust! That's because it sets up an oxygen cell. Hot water heaters use enamelled steel tanks because the hot water is deficient in oxygen and you would get severe corrosion in a stainless steel tank. Stainless needs free oxygen around it. Water heaters have an anode in the top of them.
If you're using a battery charger connected to shore power make sure you have an isolating transformer somewhere in the circuit or your boat can become an earth electrode through the engine connection and the propellor.
So again, don't re-invent the wheel.
Usual disclaimer applies re free advise and what its worth. If you find better advise or I need correcting please feel free to tell me. We're all learning.
Greg.

[Miker]

Gday John,
Sounds complicated mate , I dont know if its an issue to protect the bronze(i presume its bronze) thru-hull on NC, im not sure tho' , has anyone here had any corrosion problems on their thru-hulls, in particular if you have an outboard motor & no anodes?
regards
Shaun

All Dulcamara's skin fittings are fine, she was slipped on Monday. No Anodes. Even the outboard is fine, and it sits on the stern bracket permanently. Only damage on the outboard is from a small bit of weed occasionally.

Michael

[storm petrel]

After over 30 yrs in the water, Storm Petrel's bronze skin fittings and sea cocks were replaced a few years ago(they were a bit green, but still OK). It wasn't that expensive to have done it and I have 30 yrs to save up for the next time, so I am not going to lose sleep about them corroding. If it ain't broke why fix it? Better to just go sailing.