Rudder Anodes

[Trident]

I have stainless steel rudders - both shaft and rudder fin are stainless .

They have always been antifouled and always had anodes attached by a bolt in to the stainless "fin" of the rudder

This year when we lift out they will be stripped back to bare metal and given several coats of epoxy before being antifouled. The rudders should have no metal exposed to water due to the multiple coats of epoxy .

I keep getting conflicted information from "experts" - "316 stainless doesn't need anodes bare or painted" , "you must have anodes even on stainless", "why drill through the protective epoxy to attach an anode to the stainless" etc

Does anyone have a definitive answer ? The only other metal below the water line are the SD20 sail drives in aluminium - also coated with about a dozen coats of underwater epoxy - and the bronze propellors . Oh, also the rudder shoes in to which the shafts sit which are also 316 stainless but I sort of include them in "the rudders" though they do have a phosphor bronze bush inside. All seacocks are plastic, no earth plate etc on the plastic hull

 

[vyv_cox]

Millions of 316 stainless steel drive shafts are in use, large numbers of them without paint or anodes. Smooth unpainted 316 stainless steel with no crevices, corners, threads etc will not corrode due to the film of chromium oxide that protects it. Paint gives further protection. It occasionally happens that marine growth, particularly shell, on unpainted SS will create pits and/or crevices but these are unlikely in your case.

 

[rogerthebodger]

I have a stainless rudder on my elf steering gear and never fitted any anodes as the is no dissimilar metals on the rudder so no galvanic corrosion.

My main rudder is stainless steel shaft with a MS hollow rudder which I do have an anode fitted and also filled with old engine oil