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Do Galvanic protection devices work ?

My narrow boat moored in a marina, is connected to the mains for months at a time to charge my battery bank. As most of the other boats in the marina are also 'plugged in', I am concerned about galvanic corrosion even though I have anodes fitted. I am thinking of installing an earth breaking device, do they work in stopping the corrosion ?

Asked by: David Spencer  | 4.59pm, Tuesday 17 April

WW says:

As with so many things to do with boating, it depends who you ask. Some people advocate galvanic isolators (also called zinc savers) while others dismiss these as rubbish and swear by the more expensive isolation transformers.
A galvanic isolator works like a one-way valve, maintaining a good earth connection for your equipment while stopping stray currents coming the other way. An isolation transformer keeps your 230-volt circuit physically separate from the mains but allows AC current to pass by induction.
There are so many variables in the equation that it is difficult to find a definitive answer as to which is best. However, if you have a boat connected to the mains and surrounded by boats that are similarly connected, I would fit a galvanic isolator as a matter of urgency just to be on the safe side.

Graham Booth  | 6.41PM, Tuesday 17 April

Anodes protect steel immersed in water by setting up a small galvanic potential between the steel and the zinc anode. The problem is that they only really work for a relatively small area immediately around the anode. Joints and areas of slightly different composition of the steel plate will upset the electron flow.
Interrupting the mains earth with a transformer or a galvanic isolator is a good plan. Even a small voltage difference between the local mains earth and the water to which the boat earth connection is made can cause hull corrosion. A simple galvanic isolator isolates the earth for small voltages, but connects it in fault conditions.
There are however many sources of corrosion that affect boats and the only real protection is regular painting of all underwater surfaces.

Rupert Smedley  | 6.43PM, Tuesday 17 April

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