Does your vessel need a galvanic isolator?
- Is your vessel connected to AC shore power?
- Is your vessel moored or slipped near other vessels?
- Is the shore power 50 or 60 hertz and less than 600 volts?
If you answer is yes to any of the above questions, a galvanic isolator is strongly recommended for your vessel.
What does a galvanic isolator do?
Galvanic isolators interrupt the galvanic current flow with other boats at a marina when installed on a boat that is connected to AC Shore Power. This technology maintains AC safety ground, isolates the shore ground, and diminishes the most common forms of corrosion and premature zinc loss within a boat’s bonding system.
Common misunderstandings
When it comes to corrosion, there is some misunderstanding, particularly about the role that shore power connection plays. 120/240-volt AC shore power rarely affects corrosion of the zinc anodes or underwater metals. Corrosion is primarily a DC phenomenon. However, the shore-power cord, with its yellow-green safety ground wire, often plays an accessory role.
By plugging the AC shore-power cord into a dock pedestal, where there are other pedestals and vessels, an electrical connection between the grounding system of the vessel (including the grounded underwater metals, zinc anodes, skin fittings, valves, shafts, struts, etc.) and the dock’s AC safety ground is made. Since the neighboring boats also use the same earth connection, this effectively connects all the boats and their underwater metal parts together via the earth cables in the shore power leads. Unfortunately, as all the boats (and metal pontoons) are now interconnected via the earth cables, any voltage leaks or “galvanically” generated voltages have an easy path between the boats. This often results in ‘stray current’ or rapid loss of sacrificial anodes and increased corrosion of all underwater metals.
In simple terms, a galvanic isolator contains semiconductor devices called diodes that act as a one-way switch for current. It allows current to flow easily in one direction but severely restricts current from flowing in the opposite direction.
Conclusion
Simply put, it is a box on your vessel, separating the shore power ground from the vessel ground, allowing AC grounding to the vessel but suppressing damaging DC current that may be present in the area. If you become aware of the excessive deterioration of your anodes, and signs of corrosion on any underwater metal components, request assistance from your marine corrosion specialist or marine electrician.
