Zinc or Magnesium Annodes?

[wakeup]

My boat is based in Cardiff Bay. When I bought it the water was salt water prior to the impoundment of the Ely and Taff rivers. Now it is fresh(ish) water.

I was asked today whether I had changed my annodes from zinc to magnesium becasue zinc would simply fur up and wouldn't work any longer and now that the boat spends 99% of its time in fresh I should change the whole lot to magnessium otherwise it is pointless having annodes and therefore risk corrosion of the leg etc.

I can't remember the periodic table so I am not sure where zinc and magnesium fit.

Has anyone had any expererience of going from salt to fresh water and should i be changing by annodes?

Thanks in advance.

 

[ccscott49]

If it spends 99% in fresh(ish) water, you need magnesium anodes, it's a simple as that.

 

[markc]

If using in both types of water and shaft (not outdrives) you can use Aluminium anodes, they work fine in both. Have used them myself when I had mixed cruising.

Mark

http://www.geocities.com/jinto100/Jintopics.html

 

[Piers]

As has been said, magnesium is your only choice - and it must be done asap.

Remember that anodes are called "sacrificial" for a reason! And if you haven't fitted the correct ones, other metal on your boat becomes sacrifical - normally at a cost to challenge a chap's sense of humour...

Piers du Pré
MBM Cruising Club enthusiast
www.dupre.co.uk/fsPlaydeau.htm

 

[Guest]

Ive used Mag' anodes in the same marina as you for the past 2 years. Think my boat was the first to changeover from zinc.

Some boats have hanging mag' anodes and have fitted zinc on the boat. This doesn't work as the zinc anodes get a coating over them very quickly.

 

[ArthurWood]

Magnesium and its alloys are at the top of the galvanic scale, ie most active, and Zinc is next most active.

 

[ArthurWood]

Wot about in lake water? I had my boat on a lake for 4 yrs w/Zn anodes w/no probs. In fact I think US manfrs install Zn anodes for fresh or salt water.

 

[Guest]

what boat yer got then ?

"The Med is calling me"

 

[KevL]

But that's American water.. It's different

KevL

--
It may be the early bird that catches the worm but its the second mouse that gets the cheese.