Self Steering Excessive Anode Wear

[kiwiaviator]

We have recently fitted a self steering vane to our GRP vessel. Also replaced other anodes while it was on the hardstand (these weren't worn much at all)

The self steering is primarily stainless steel and has two coin type anodes approx 50mm in diameter. After approx 3 months they are nearly worn away. The self steering assembly is electrically isolated from the vessel ground.

Any thoughts/ideas on how to reduce this wear rate?

Photo attached.

[Orion Jim]

It will be interesting to see what replies you receive. I’ve had a Monitor windvane on my boat for seven years and never had an anode on it, nor is one recommended.

[Ambler]

There must be some dissimilar metals at play or the welding of the trim tab arrangement causing the anode to fizz. I think it better to increase the anode size to cope with your haul out intervals. Or
you could immerse an annode on a cable wired to the vanes rudder when you are not underway.

My stainless rudder on a previous boat started coming apart at the welds due to the anode not being big enough between haul outs.

[atoll]

bigger anodes
lift it out the water when not in use
change the servo to a composite,glass epoxy

[Mike Banks]

It is the negative rail that causes problems--there should be NO electrical connections of any kind on a self-steering system. The usual culprit if fitted would be the electric rudder position indicator switch. Another trap for young players is having the negative of the battery supply permanently connected to the Anchor windlass--for the same reason--the anchor chain being galvanised then becomes an electrode via the windlass drum. In some areas the loss of zinc from anchor and chain is rapid and blamed on the chain manufacturer--and of course thicker galvanising will endure electrolytic corrosion for longer.

[ArmyDaveNY]

Are you at a marina most often and if so, is it the same marina? If so, it is possible that there is stray current at your marina. If on the other hand you are out and about most often, then Mr. Banks advice is very worth considering.

[kiwiaviator]

Thanks for all the replies. Very helpful. I think we have found the issue with dissimilar metals in the assembly. Added a photo which shows a steel bearing surface. We will probably add a substantial 'berth only' anode connected via a wire that easily disconnected.