Opinions on my anode location plans please.

[rsimon]

This phase of the houseboat project has to do with anode placement and bonding. Check out the pics. Comments-criticisms are appreciated.
http://s1216.photobucket.com/albums/...0and%20images/

[CDK]

So you have an epoxy coated aluminum hull with an aluminum outboard....

As long as you keep shore power ground isolated from the hull, all you need is a small zinc nut or ring on the stainless outboard prop shaft.
If the stainless bolts for the 'anodes' are already in place and cannot be removed, coat them with a durable compound and put plastic caps over them. They are the only enemies of your hull.

[gonzo]

Passivated stainless would be better. The difference in price shouldn't be too great.

[michael pierzga]

For placement, mass and mounting its Best to contact an anode specilist such as MgDuff and only use marine anodes.

http://www.mgduff.co.uk/leisure-craf...aluminium.html

[CDK]

Originally Posted by gonzo

Passivated stainless would be better. The difference in price shouldn't be too great.

No Gonzo, annealed, passivated or even TiN coated doesn't matter here, only the chemical composition counts.
The stainless steel is much more noble than the aluminum, so at the first scratch in the epoxy coating, the hull will become the sacrificial electrode.

Of course zinc could be used here, but isolating or removing the bolts is cheaper and more effective.

[gonzo]

It is my understanding that passivated stainless steel is non-reactive.

[CDK]

The process removes traces of iron and carbon left by the cutting tools and yields a homogenous oxide layer. It also enhances the general appearance and makes cleaning easier when used for kitchenware etc.
Electrically connected to a less noble metal and submerged in an electrolytic solution it behaves just as untreated stainless does.

[viking north]

I.E. it's still a conductor regardless and as such will act to complete the closed circuit.