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.
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 is such fluids. In general, the more active alloy of the couple corrodes preferentially while the less active (nobler) material is cathodically protected. The rate of galvanic corrosion is a function of several variables including area ratios, the conductivity of the fluid, temperature, nature of the materials, etc.
The best solution to avoid galvanic corrosion and at the same time prevent any unsafe situation is to install an Isolation Transformer to connect to the shore-side supply.