Anode barely depleted

[RJJ]

Hello, just a bit surprised that my ring anode for Volvo 130 saildrive lost only 80g out of 1.49 kg, in the water from March to December last year.

There is no sign of damage to saildrive.

Is that normal? On that basis the old one would do several years. What am I missing?

 

[Easticks28]

I have the same unit. As I sail in fresh water (The Broads) I previously changed to Magnesium. We have been affected by a number of 'salt tides'over the last couple of years, and I felt this may be the reason why my anode was melting like a bar of soap. I therefore last year switched to aluminium as advice I received.
Like the OP, my anode appears 'as new' and the saildrive appeas to be suffering no ill effects - nor does the propeller.

 

[johnalison]

If the saildrive is decently painted, there shouldn't be much work for the anode to do. My prop anodes disappear rapidly but the saildrive ring can look pretty good after two years, when it gets changed. A zinc anode should be abraded before re-immersion to take the crust off, otherwise it may not be effective for a couple of weeks, so I am told.

 

[yotter]

It may be worth checking the electrical continuity between the anode and the saildrive . If the fixing screws corrode, the anode may no longer function, guess how I know this:-(

 

[duncan99210]

I’d have said that the loss is about right. I change mine about every 4 years, mainly because it’s looking a bit ratty. I suspect that it’d probably continue to work for another season or two.
A properly painted drive leg will have very little exposed metal for the anode to protect, hence the longevity.

 

[RJJ]

Ok thanks. Sounds as though I can keep the new one in my pocket for another time. "Every little helps". Abrading the surface and checking the connectivity points makes sense.

 

[pvb]

Yes, the anode on the 130 saildrive is a lot chunkier than previous versions and should last a long time before needing replacement.

 

[vyv_cox]

As johnalison says, good quality painting of the leg reduces the cathode area considerably and the anode has little work to do. I have found that whereas the anode on my bare Bruntons prop barely made it through a season and the shaft anode did two, since I started painting the prop with Velox the prop anode comfortably lasts for two seasons and I replaced the shaft anode after four, although I suspect it could easily have done one or two more.

 

[Catalina36]

I fitted a Featherstream prop some years ago and the anode supplied with it didn't deplete at all in the first year or two. It turned out that they'd come from China and were not pure zinc, ie it wasn't doing the job properly. Darglow supplied a new one FOC which did deplete a bit, but even then nowhere near as much as the shaft anode a foot in front of it. I replace that every year and the prop one about every four years.

 

[Channel Sailor]

As per Catalina 36, I had one of those not very much zinc anodes on a feather stream, inherited from previous owner. Did not seem to deplete at all. I only buy the Darglow ones, which do deplete.