Reduced anode wear...does this make sense?

[dustywings]

Yesterday I went to do my annual anode change on the boat. The set up I have is a main large anode that all at risk things on the boat are linked up to; being a belt and braces man I also have anodes attached directly onto the shafts and rudders (the rudders and shafts are also bonded to the main anode). The boat is kept in Bursledon where anodes do tend to get eaten reasonably fast and each year when she comes out the anodes that are on the shafts and rudders have totally vanished and the main one has worn but there is still some remaining. This year however despite the boat actually having been in the water for a few weeks longer than normal there is actually still plenty of the anodes left which has stumped me rather. The only thing I have done differently is that after the usual polish up of props, shafts and rudders I coated them all with TK Line spray on antifouling (which was recommended by other forumites), can this coating have protected the gear from the water and therefore potential corrosion thereby reducing anode wear?

 

[KevB]

maybe with all the rain we've had the water up that end of the river is less saline, reducing the galvanic effect on your anodes?

 

[longjohnsilver]

Can't help with the anode query, but how did the TK Line prop antifoul work?. I'm just about to spray my props with it.

 

[andy59]

Maybe by spraying over with TK line you have reduced the surface area of metal , that has in turn , reduced the amount of galvanic current wandering about .
BTW did the TK line work ? .

 

[omega2]

I trust you did not paint the areas before you fitted the anodes as this would degrade the contact, and negate the purpose, also no paint on the anodes gives the same result.

 

[dustywings]

Maybe by spraying over with TK line you have reduced the surface area of metal , that has in turn , reduced the amount of galvanic current wandering about .
BTW did the TK line work ? .

That is my thinking Andy just reduced the exposed area of metal.
TK Line certainly made a difference, not perfect but certainly helped and my worry was that it would wear off but there was still a good coat left on.

 

[dustywings]

I trust you did not paint the areas before you fitted the anodes as this would degrade the contact, and negate the purpose, also no paint on the anodes gives the same result.

No I fitted the anodes then masked them off totally before spraying the TK Line.

 

[rafiki_]

My boat lost 50% of the shaft anodes last summer after 1 month at Burlesdon. Have you checked your engine anodes?

 

[kashurst]

I can relate to this. last few years I have had my shafts and props etc coated with an epoxy based primer then antifouled. anode wear rate dropped right down - yes they are connected and yes they still do dissolve but much more slowly. Just changed them after 3 years. One for Rafiki - that sounds too fast to be protecting just your props and shafts. Have you got a galvanic isolator? That would help.

 

[dustywings]

I can relate to this. last few years I have had my shafts and props etc coated with an epoxy based primer then antifouled. anode wear rate dropped right down - yes they are connected and yes they still do dissolve but much more slowly. Just changed them after 3 years.

Excellent thanks, that explains it then. Seems good news all round... reduced fouling to props shafts rudders etc and longer life anodes!

 

[rafiki_]

I can relate to this. last few years I have had my shafts and props etc coated with an epoxy based primer then antifouled. anode wear rate dropped right down - yes they are connected and yes they still do dissolve but much more slowly. Just changed them after 3 years. One for Rafiki - that sounds too fast to be protecting just your props and shafts. Have you got a galvanic isolator? That would help.

I moved the boat to Portishead, so no running water, or big steel railway bridge, and fitted an isolator.

 

[kashurst]

any concrete structures near to your mooring? have you measured the volt drop across the isolator? Ideally there shouldn't be anything but worth checking, may be a shore power issue. Sorry just reread your post - boat is now in a different location.