Safety and prevention of galvanic corrosion
The Isolation Transformer eliminates any electrical continuity between AC shore power and the boat. It is
essential for safety and eliminates the need for galvanic isolators and polarity alarms.
Safety is taken for granted in case of a normal on-shore installation. A fuse will blow or a GFCI (Ground Fault
Current Interrupter) will trip in case of a short circuit or current leakage to ground. Connecting the ground wire of
the shore-side supply to the metal parts of the boat will result in galvanic corrosion (see below). Bringing only the
live and neutral wire on board results in an unsafe situation because GFCIs will not work nor will a fuse blow in
case of a short circuit to a metal part on the boat.
Galvanic corrosion occurs when two dissimilar metals in electrical contact are simultaneously exposed to an
electrically conducting fluid. Seawater and, to a lesser extent, fresh water are such fluids. In general, the more
active alloy of the couple corrodes preferentially while the less active (more noble) material is cathodically
protected. The rate of galvanic corrosion is a function of several variables including area ratios, conductivity of the
fluid, temperature, nature of the materials, etc.
It is a misunderstanding that galvanic corrosion occurs only in metal and aluminium hulls. In fact it can occur on
any boat as soon as a metallic part (the shaft and propeller) is in contact with water. Galvanic corrosion will
quickly dissolve your sacrificial anodes, and attack the shaft, propeller and other metal parts in contact with water
as soon as the boat is connected to the shore-side supply.
It might therefore be tempting not to connect the ground conductor: this is however extremely dangerous
because GFCIs will not work nor will a fuse blow in case of a short circuit to a metal part on the boat.
