Propellor and Saildrive Anodes

[Slipperman]

I have just had an interesting conversation with a very knowledgeable lady from Darglow Engineering about propellor and sail drive anodes. I have a Featherstream propellor fitted to a Yanmar SD20 sail drive. Until now I have always ordered an FSL zinc anode from Darglow, and have usually got my anodes from Ambassador Marine, pre-drilled with the necessary hole to take their Stripper rope cutter. A couple of things emerged from the conversation which might be of interest:
- Darglow have changed the design of their zinc FSL anode, the new one being slightly larger, with a deeper base - which requires slightly longer fixing studs. Apparently the earlier version was apt to erode too quickly around the stud holes.
- Secondly, Darglow now offer an aluminium version of the FSL anode. This has come about because apparently some sail drive manufacturers, including Volvo, but I think not Yanmar (yet) have switched to recommending aluminium for their sail drive anodes, and it is sensible to make sure that the propellor anode and the sail drive anode are of the same material.
I also spoke to Ambassador Marine and they confirmed that currently their Yanmar sail drive anodes are zinc.

 

[vyv_cox]

There is an article on this topic at http://coxeng.co.uk/metallurgy/anodes/. The galvanic voltages of zinc and aluminium are very similar, so mixing the two is unlikely to create problems. If there was a reaction, one anode would waste at the expense of the other (assuming they were connected electrically) but would still.protect the components as desired.

 

[Slipperman]

That's great Vyv, good to know, thanks.

 

[Neeves]

If both are applicable in the same location I can see the benefit of the aluminium anodes. I suspect they have a much more acceptable environmental impact in terms of manufacture.

Molten zinc would demand more serious fume management.

Jonathan