Technical Article

Utilizing Galvanic Isolators to Protect Your Vessel

A yacht or commercial vessel is an important asset worthy of the best corrosion and safety grounding protection available. While protective coatings and anodes can help protect your boat, a more reliable method is required to deal with the galvanic corrosion circuit created by the shore power connection.

The Galvanic Corrosion Problem:

Whenever a boat is connected to shore power, the hull and drive system are connected to the shore grounding system and to other adjacent vessels (also connected to shore power) via the grounding conductor in the shore power cable. This connection, while required for safety, creates a galvanic corrosion cell involving the dissimilar metals between boats and between a boat and the shore grounding system.

boat diagram 03


  1. Anode – a metal surface which gives up metal ions (corrodes)
  2. Electrolyte – a medium which conducts ionic current between the anode and cathode
  3. Cathode – a metal surface that picks up metal ions
  4. Metallic Bond – a continuous metallic path that allows current to flow from cathode to anode


Dairyland Galvanic Isolators Address Galvanic Corrosion

A simple method which virtually eliminates this galvanic corrosion problem is to insert an appropriately rated and certified Galvanic Isolator in series with the grounding conductor of the ship-to-shore power cable. The function of the Galvanic Isolator is to provide AC continuity of the grounding conductor (required for safety in the event of an AC fault) and to block the flow of corrosion-causing galvanic current.
 This effectively removes the galvanic corrosion circuit while retaining safety grounding.


Product Selection:

Dairyland Galvanic Isolators are typically applied using an industry standard method of matching the device to the steady-state current rating of the shore power service. In order to select the best product for your vessel you must know the size of the shore power service on your boat and choose the Galvanic Isolator accordingly.

marine selection


Alternate Product Selection Method – AC Fault Current

Dairyland Galvanic Isolators are typically sized to match the steady-state AC rating of the shore power service, which typically also provides an appropriate associated AC fault rating. If an alternate location is planned or higher fault current is expected, there are other methods available for rating the products. This can include sizing the products based on known fault currents, coordinating with upstream circuit breakers, or coordinating with grounding conductor size and ampacity. Contact us if additional information is needed.

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