Sea/fresh water anodes

[dcr]

I put this in PBO section earlier today by mistake:-

Hoping to travel the French canal and river system next year to the Med and have a query about the need to change the sacrificial anode on the saildrive leg from existing seawater version to fresh water type (magnesium).

The boat will only be on the tidal Seine for about 2 weeks so would appreciate any thoughts on whether this is considered necessary - ie: leave existing anode on all the way or change to Mag. type, but would this be seriously depleted during the time spent in salt water and not last our journey time of say 6 months in fresh water?

Presume that once down in the Med we will need to have the usual seawater anode.

Thanks,
dcr

 

[tinkicker0]

Nothing happens fast in freshwater so if your leg is electrically bonded to the engine, why not get some cable with crock clips and a mag anode, then just dangle it over the side?


The main problem may be your Zinc anode, they are known for getting an electrically inert coating on the surface in freshwater and this may prevent it from working when you get back to salt water, you may have to give it a wire brush to remedy this.

 

[dcr]

sea/fresh water anodes

Thanks for your reply tk, but where do I connect the croc clips?
dcr

 

[Tranona]

If you are going to use a hanging anode DO NOT CONNECT it to the engine. This is isolated electrically from the saildrive - if it were not your saildrive would already have rotted away! It needs to be connected directly to the saildrive housing inside the boat.

However, a short period such as transiting the canals should not cause you any problems. You can get magnesium saildrive anodes if you are going to spend a lot of time in fresh water. Suggest you fit a new anode before you start your trip and check it when you get back to salt water.

 

[binch]

anodes in FW

Have spent the last 5 years in our steel boat in the canals. No anodes at all. No noticeable corrosion underwater. Corrosion on deck, yes, but not in the water.
I think all the ordures counteract the current.