sacrifical annodes and battery

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pine island fred

Lieutenant Junior Grade
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Dec 20, 2002
Messages
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While working on friends 290DP outdrive, friend commented on how fast the prop anode disappeared. It was replaced last time we worked on it and spent about 3 months in salt water. I am having difficultes keeping his battery bank charged while the boat is out of service on the lift. Question, can a small draw on his electrical system react on the anodes? thanks fred
 
chuckz

chuckz

Chief Petty Officer
Joined
Aug 22, 2004
Messages
625
Re: sacrifical annodes and battery

Normally the anode is sacrificed to galvanic corrosion. The interaction between disimilar metals in a electrolyte.<br /><br />If an electric current is passed through the solution electrolysis occurs as well as galvanic corrosion. This will accelerate the anode "dissapearance". The question is, where is the battery current flowing? I suspect that if you are having a hard time keping the batteries charged, there is enough current flow to produce electrolysis.
 
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pine island fred

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Re: sacrifical annodes and battery

Thanks guys, props are aluminum and show no corrosion. Will definately have to trace down where the current is going. Right now my priority is somehow draining the tank and engine of fuel before it turns to mud and creates even more problems. Also thought, boat has fresh bottom paint, would the metals in the paint react with the anode? thanks again fred.
 
Dunaruna

Dunaruna

Admiral
Joined
May 2, 2003
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Re: sacrifical annodes and battery

Originally posted by pine island fred:<br /> spent about 3 months in salt water.
Click to expand...
You may be looking at more than one problem, was it in a marina with shore power? <br /><br />Aldo
 
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pine island fred

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Dec 20, 2002
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Re: sacrifical annodes and battery

Was parked at the seawall behind his house. What a convenience. Boat only has a 12 volt system. Strange, he is an electrician (working)and i am an aircraft mech(retired) and i am the one running around with a SIMPSON 260 milli amp meter. Keeps my mind active. fred
 
chuckz

chuckz

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Re: sacrifical annodes and battery

What is the seawall made of?
 
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umblecumbuz

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Sep 25, 2004
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1,062
Re: sacrifical annodes and battery

Be thankful the anode has sacrificed. That's its job. <br /><br />If the hull stays wet while out of the water (rain, brackish bilge water or salt spray for instance)then galvanic action will continue.<br /><br />And if the current from the battery bank is leaking, this will accelerate the sacrificial rate of the anode. <br /><br />Salt water anodes have a high proportion of zinc, so they will - thankfully - sacrifice before harming the aluminum props. Replace them when half eaten, and keep the anode surfaces free of powdery build-up - or the props might suffer next.
 
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