Anodes for fresh and salt water???

[viva]

Why not

Whatever you do DO NOT MIX ANODE MATERIALS. Chose one or the other. Andrew

Why not? This is what M G Duff recommend when going between salt and freshwater for short period. E.g a permanent mag anode when in freshwater and hang a zinc one over the side for a foray into seawater

 

[vyv_cox]

How long would you need to be in fresh water before the zinc anodes wouldn't work in salt? I am thinking about a canal passage.

My boat was kept in fresh water, with fairly frequent trips to the sea, for seven years when we lived in Holland. We used zinc anodes throughout. Yes, they developed zinc hydroxide films very slowly but an annual trim up with a file and wire brush were sufficient to keep them active.

 

[coreng]

Why not? This is what M G Duff recommend when going between salt and freshwater for short period. E.g a permanent mag anode when in freshwater and hang a zinc one over the side for a foray into seawater

Though I am not a native english, this is not what I read in MGDuff answer :

1) "Essentially what we are saying is that ideally you would have magnesium anodes fitted the whole time you are in fresh water and then have the boat lifted and zincs fitted when you change to salt."

2) "By using hanging anodes instead of hull mounted anodes..."

With a (-) 1600 mV potential [vs about (-) 1000 mV for zinc and aluminium], magnesium anodes will not last long in sea water... Even for a few days.

 

[SHUG]

My reading of the MGDUFF response is that it is a good idea to hang a Magnesium anode over the side in fresh water.
It will have a limited lifetime and the Zinc anodes will become coated but when you move to saltwater , freshen up the Zinc, remove the Magnesium and and on you go!

 

[vyv_cox]

I cannot see any reason why an additional magnesium anode hung over the side would not consider everything else to be more noble than itself and helpfully corrode to protect them. Always assuming it can 'see' any other anodes and whatever is being protected and that electrical paths are correct.

 

[[3889]]

A very useful thread. Would 10m of 2.5mm copper strand be a suitable conductor for a hanging Mg anode in fresh water or do I need lower Ω ?

 

[VicS]

A very useful thread. Would 10m of 2.5mm copper strand be a suitable conductor for a hanging Mg anode in fresh water or do I need lower Ω ?

The hanging anodes which MGDuff supply are on stainless steel wire but they dont say what diameter

 

[Cloven]

A very useful thread. Would 10m of 2.5mm copper strand be a suitable conductor for a hanging Mg anode in fresh water or do I need lower Ω ?

Re post #5 of this thread, yes you can buy a hanging Mg anode ready made but if you read my original reply you will see what I do and its much cheaper. The Mg anode is bolted to a length of stainless rigging wire approx 5mm diameter with a rigging eye on the end. That is bolted to a stud which passes through the transom. Internally, another wire connects to the internal hull anode fitting so all is connected electrically. Just check electrical continuity when fixing. I hang the anode off the pushpit so it hangs approx in line with the prop etc. which is the main thing I am protecting.

 

[viva]

Re post #5 of this thread, yes you can buy a hanging Mg anode ready made but if you read my original reply you will see what I do and its much cheaper. The Mg anode is bolted to a length of stainless rigging wire approx 5mm diameter with a rigging eye on the end. That is bolted to a stud which passes through the transom. Internally, another wire connects to the internal hull anode fitting so all is connected electrically. Just check electrical continuity when fixing. I hang the anode off the pushpit so it hangs approx in line with the prop etc. which is the main thing I am protecting.

+1. This is exactly what I do