Very rapid anode wear

Dazedkipper

Dazedkipper

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When I hauled out end last season I discovered my 2kg pear shaped anode had completely erroded away, complete with the steel strap, nuts and most of the hull fixing studs too. This was a brand new anode at the begining of the season, I normally use an anode every three years so something has drastically gone wrong.
Over winter I fitted a fresh water cooling system (Martec) that has an electric circulation pump, a calorifier with immersion heater and polished the prop rather than paint it with a/f.
I was on shore supply of a max of 5 days, and engine hours probabally no more than 20.
So what has gone wrong? I'd appreciate some advice...
 
If the the problem is related to shore power then 2kg in 5 days is a massive wear rate. Not only would bubbles be pouring off the anode in streams you might even get some steam!

It looks like something else has gone wrong. I'd suspect that circulation pump first but the calorifier water circuit 'should' be isolated from the ocean except of course the path back from the calorifier via the engine and that's scary!

I'd disconnect all the new stuff, get a good digital meter in line with the replacement anode and start reconnecting and looking for stray current sources.
 
[ QUOTE ]
then 2kg in 5 days is a massive wear rate. Not only would bubbles be pouring off the anode in streams you might even get some steam!

[/ QUOTE ]

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2kg in a season, rather than 3 seasons is what I read.
 
It is unlikely, but I was warned that there are some conterfit 'branded' anodes in circulation which are a bit short on longevity. You didn't by chance get the anode from a different supplier or for a 'bargain' price?
 
[ QUOTE ]
[ QUOTE ]
then 2kg in 5 days is a massive wear rate. Not only would bubbles be pouring off the anode in streams you might even get some steam!

[/ QUOTE ]

??? /forums/images/graemlins/confused.gif


2kg in a season, rather than 3 seasons is what I read.

[/ QUOTE ]

Aha! I see what you mean - it's unlikely to be due to shore power, or there would have been a boiling mass - sorry!!
 
I had the same problem. New saildrive with folding prop. Anode disappeared in 6 months. No shorepower or other electrical problems. I had a walk round the yard. It seemed to be that boats with folding props and a large amount of exposed bronze had more erosion on their anodes than those with non folding or alloy props. Mine was a new prop. I suspected that the new surface was very active and the zinc was being wasted by the bronze in very close proximity. Your polishing may have had the same effect. Would appreciate comments on this theory as £90 per season is going to knock a hole my the budget. I was thinking of changing back to an aluminium alloy prop this season.
 
quote] Not only would bubbles be pouring off the anode in streams you might even get some steam!

[/ QUOTE ] Rubbish. Lets see your version of the electrochemistry that explains that and your calculations that support the volumes of gas you suggest would be produced.

My version would be for the anode to dissolve quietly away as magnesium salts and for hydrogen to be produced perhaps at the cathode, what ever that is and where ever it is, at a rate of less than 0.3cc per minute. No steam either!

Of mcw739 I'd ask if the shorepower was connected, but not in use, for considerably more than 5 days.

If not then i think I would be looking at the installation of the cooler and in particularly the wiring of the pump since that is the major change. I'd be looking for a stray positive feed to the anode.

You've not made any connection to the bonding between the anode and the stern gear?
How is the anode bonded to the stern gear for that matter?

Cleaning the prop rather than painting it may be a factor but .... ????
 
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