Everlasting anode

[richardabeattie]

I fitted a new hull anode last winter, sailed all summer and hauled out to find little or no wear on the anode. I have checked the resistance between the inboard end of the bolt - the one to which the earthing strap to the engine is attached - and the propshaft and it is zero so I assume I am properly connected. What's going on?

 

[maby]

did you paint it? On our first boat, the anode was in excellent condition - it had received several thick coats of antifouling!

 

[zambant]

Does it have a white crust over it?

 

[richardabeattie]

No! I never use antifouling as I have a bilge keeler and cleaning off the barnacles whilst dried out on a sandbank takes half an hour once per summer.

 

[richardabeattie]

No significant white crust but what would a white crust indicate?

 

[BarryH]

I fitted a new hull anode last winter, sailed all summer and hauled out to find little or no wear on the anode. I have checked the resistance between the inboard end of the bolt - the one to which the earthing strap to the engine is attached - and the propshaft and it is zero so I assume I am properly connected. What's going on?

Give it a bit of a scrub with a wire brush before launching. Thats what I've been told.

 

[superheat6k]

Could just be you have no noticeable galvanic action. Have you checked the resistance from the anode surface itself to the prop ? What is the distance between them ?

What is your mooring - pontoon with / without shorepower; swinging, etc. If on shorepower do you have a galvanic isolator ?

Any pink spots or tinges on your prop, especially near the edges, or serations forming ?

 

[Tranona]

Not unusual to have no erosion of the anode. It is there to protect the propeller, but many props, particularly older ones are quite happy on stainless shafts. Check there is no dezincification of the prop by cleaning it and tapping it with a small hammer. If it rings and there is no pinkness or crumbling of the blade edges then it is OK.

 

[MoodySabre]

My hull anode has hardly changed in 6 years but there is a shaft anode that needs to be changed every year as that obviously sees the action.

 

[Ariadne]

I'd check all the connections and bonding for any stray earth, just in case. I get worried when my anodes appear to stop working!

Give them a good scrub with a wire brush, you have put the rubber backing on them?

 

[VicS]

If you have an anode and it is properly bonded so that there is a good low resistance circuit between it and a copper alloy (eg brass or bronze) prop which is near then it will be consumed to some extent in seawater regardless of whether or not it is actually necessary .......... that's the electrochemistry at work....... dissimilar metals and all that stuff.

It it is not being consumed at all then clean any oxide off the anode and check for a low resistance between the anode itself and the prop.
If you were to have an excessively high rate of consumption of the anode then you would be looking at that possibly being caused by a shorepower connection with no galvanic isolator ... but high rates of consumption are not your current problem.

What you say suggests a bad connection between the anode and the fixing stud(s)