steel boat/ electric discharge/reaction

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masterofnone

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Could someone please explain why if I measure the voltage from salt water to a s/s deck bollard I have a 0.74v reading on a multimeter.
I have disconnected all possible elec supplies, bats, solar, bat charger, etc.
 
If you are in a marina, check all the yachts and motorboats within 15 metres of your boat and make sure that none of them have their pontoon mains electrical supply trailing in the water as this can set up small voltages which eat skin fittings and outdrives.

Check also that you are not near a yacht with an aluminum hull as there can be a high probability of an electrolysis action between the steel and aluminum hulls.

Also check on another stainless steel part of your boat down to the sea water and note the readings?



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masterofnone said:
Could someone please explain why if I measure the voltage from salt water to a s/s deck bollard I have a 0.74v reading on a multimeter.
I have disconnected all possible elec supplies, bats, solar, bat charger, etc.
Click to expand...

Galvanic cell.

The bollard is connected to the hull with zinc anodes presumably?

The anodes are one electrode, the water is the electrolyte. The other electrode is what ever you dip into the water. If that's copper wire you'd expect a difference up to around 0.7 volts.

Dissimilar metals, galvanic series and all that jazz
 
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