tapping my keels for an anode

Tom Dussek

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My Westerly Jouster has no anodes (except for the one in the Yanmar engine). Her metalwork - prop shaft, P-bracket and prop are all fine, but the keel is seriously pitted. Am I right in thinking that fitting an anode to the keel will help? If so, how do I tap into what I believe to be cast iron?
 

vyv_cox

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pvb is correct. You would need a dozen anodes to make an appreciable difference from a galvanic viewpoint and even then the iron would corrode. Anodes are very rarely fitted on keels, for good reason. Painting, after the best possible treatment, is a far better and more cost effective method. There are many threads on these pages about the best treatment methods but grit blasting followed by epoxy coating is the best. Whether you can justify that on an elderly small boat is a question only you can answer.
 

AntarcticPilot

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I too have a seriously pitted cast-iron keel. But it's probably nothing to do with electrolysis or galvanic action - more likely original flaws in the casting. I roughly smoothed it off with thickened epoxy before applying Coppercoat, but I suspect that the coating on the keel won't last as well as the coating on the hull.

In the grand scheme of things it probably doesn't matter - we're talking about the loss of a few kilos of metal from something weighing a tonne or more!
 

Tom Dussek

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Thank you, one and all. What confused me was a yacht that came in to the yard where mine is yesterday with a nicely corroded anode on its pretty smooth keel. Glad to hear it's something I don't need to do ;)
 

vyv_cox

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The anode will be wasted: it has a big cathode driving the reaction. It might be that it protects a small part of the keel around a radius of about five times the anode diameter but that's all.
 

Pagetslady

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The keel on my corsair has been sand blasted, several coats of primacon but still had rust spots all over it, each year I sanded them off, a couple of years ago I earthed my keel to the engine earth and all the other anodes I am sure there is a very good reason why this is wrong but since doing this there is no longer any rust spots when lifted out, what do the team think are the problems with might this solve the OP problem.
Mike
 
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