Alluminium anodes with aluminium props

[Frontier]

Are aluminium propellers at risk of corrosion if you use aluminium anodes?

My last zinc anodes didn’t last very long and as I am moored in brackish water I fitted aluminium anodes. I also fitted a galvanic isolator a few months later. Recently I noticed the props have lost most of the black paint and look pretty corroded across their surface. I can’t tell if they have stabilised since changing the anodes or got worse. I did just wonder if having aluminium anodes puts the props at risk. The GI indicator always shows no current so I guess its working. Also all of the pontoons have been rewired recently, so lots of variables that only time will eliminate.

 

[tcm]

well, yeah they must be. Tho the ally anodes should be less noble that the ally alloy they use for flaps.

Try a magensium anode perhaps, less noble in fresh?

 

[cliff]

Yep, Magnesium sounds a good deal but they will get eaten away quite quickly.
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[Margem]

Anyone know if aluminium anodes are ok foe s/s props on a vp drive?

 

[Frontier]

I dont think I can use mags, the marina is tidal and when I am out its in the Solent. Just when the lock is closed the marina is fed from marsh land. Ali is supposed to be good for Salt-to-freshish water. But shouldn't the Galvanic Isolator virtually stop all corrosion anyway?

 

[Whitelighter]

[ QUOTE ]
But shouldn't the Galvanic Isolator virtually stop all corrosion anyway?

[/ QUOTE ]

Nope, sadly it still happens. I think the GI just sows it down a little.

 

[Frontier]

Bu@@er that means I need an isolating transformer as well!! /forums/images/graemlins/frown.gif

I suppose you can just get metal to metal corrosion anyway.

 

[Whitelighter]

I have found changing anodes every 6 months easier and less hassle.

 

[Frontier]

What put me off changing them every six months was the £400 to get her out. However I have since found Sealift2, but that is still about £160 I think. (incl the lift and the anodes) I was hoping the GI would stretch it to 2 years, and if I could get the A/F to last that long that would be good too.

I suppose I am letting the side down on this aspect, as I think all this out of the water stuff is a real pain, a waste of good cruising time and at my marina too ruddy expensive.

D