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Old 05-02-2012
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Galvanic corrosion from AC leakage?

I've visited a friends sailing boat and he asked me about a corrosion problem on the propeler "gears" (the teeth part that attach to the shaft), that were completly destroyed.

I did some electrical measurements while the boat was in dry storage:

-There was no AC earth connection.
-There was a leakage current from AC to DC on the battery charger.
-If someone touched the propeler shaft while on ground he would feel a small electric shock from that leakage current.

Since I read that all galvanic corrosion is caused by DC currents, and the only possible current is the AC leakage (since there is no earth connection for the shore power), can this be just regular aging corrosion?

Thanks,
Nuno
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Old 05-04-2012
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Re: Galvanic corrosion from AC leakage?

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Originally Posted by nunojpg View Post

Since I read that all galvanic corrosion is caused by DC currents, and the only possible current is the AC leakage (since there is no earth connection for the shore power), can this be just regular aging corrosion?
There is a major difference between galvanic corrosion and electrolytic corrosion.

Galvanic is between dissimilar metals.

Electrolytic is from electrical issues.
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Old 05-04-2012
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Re: Galvanic corrosion from AC leakage?

Quote:
Originally Posted by Stu Jackson View Post
There is a major difference between galvanic corrosion and electrolytic corrosion.

Galvanic is between dissimilar metals.

Electrolytic is from electrical issues.
THIS.

Also, "electrolysis" is NOT electrolytic corrosion. Two different processes.
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Old 05-07-2012
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Re: Galvanic corrosion from AC leakage?

The "teeth" you describe are the prop shaft splines, I take it?

The AC voltage, and it's likely to be quite a voltage, will corrode.

You don't need DC for it.

DC (of the same voltage) is more efficient, but AC will do it too.

It just takes longer.

Disable that charger immediately, my friend.
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