Aluminium anodes for VP130 saildrive and VP folding propeller

[yotter]

Our new to us boat has a VP 130 saildrive and VP folding propeller, presumably phosphor bronze. I am being advised to fit aluminium anodes for the saildrive and propeller anodes. The boat will be in mainly salt and occasional salt/fresh bracking water in western Scotland. The saildrive itself should be well protected by paint (it has an aluminium split anode), so its more the propeller which is a concern. My previous propeller was a Kiwiprop so mainly composite and stainless and suffered zero corrosion as far as I could see. Does this make any sense to use an aluminium anode for the prop? These aluminium anode seem to be new to the market?

 

[rotrax]

After extensive research and talking with those in the know we changed to aluminium anodes five seasons ago. No visible change in protection-IE, nothing has corroded-and cheaper. The bow thruster anodes are only available in zinc and degrade faster than the aluminium of the larger pear anode. This is purely subjective, by visual inspection. The Sliepner anodes have large pits while the aluminium pear anode has a far smoother surface when compared at liftout.

 

[vyv_cox]

Aluminium anodes have almost exactly the same galvanic potential as zinc ones but have several advantages over zinc ones. They are also cheaper but at present it seems that this advantage is being retained by the manufacturers!

Chapter and verse here https://coxeng.co.uk/metallurgy/anodes/

 

[Tranona]

Our new to us boat has a VP 130 saildrive and VP folding propeller, presumably phosphor bronze. I am being advised to fit aluminium anodes for the saildrive and propeller anodes. The boat will be in mainly salt and occasional salt/fresh bracking water in western Scotland. The saildrive itself should be well protected by paint (it has an aluminium split anode), so its more the propeller which is a concern. My previous propeller was a Kiwiprop so mainly composite and stainless and suffered zero corrosion as far as I could see. Does this make any sense to use an aluminium anode for the prop? These aluminium anode seem to be new to the market?

The aluminium alloy used for anodes is nothing like the aluminium used in the drive. It has virtually the same potential as zinc. so fine for your propeller as well. Vyv's article in YM explains
yachtingmonthly.com/gear/guide-aluminium-anodes-70157

 

[yotter]

Many thanks to both of you, I will go with aluminium. Its mainly the prop I was concerned about since we are afloat for about 10 months of the year. This change to aluminium seem a bit like when VP changed the saildrive oil from ATP to 15W/40 and also many more moon ago when Seagull changed the fuel/oil mix from something like 8:1 to something like 25:1, when it should most likely of always been that specification. What next I wonder....