520 Express Series
5-19
A Word About Galvanic
Corrosion
Galvanic corrosion is the decomposition of
compounds, such as metals, exposed to an
electric current. For boat owners, galvanic
corrosion is a common occurrence. The
shore power AC electrical system on the
yacht includes an earth ground circuit that
“grounds” all onboard metal parts to the
earth on shore. This circuit provides the
protection against hazardous shock, but
unfortunately it can also create stray DC
currents which cause the decomposition of
all submerged metal.
SOLUTIONS TO GALVANIC
CORROSION
IMPORTANT
It is your responsibility to periodically
inspect and replace the sacrificial
zinc anodes. Damage resulting from
galvanic corrosion is not covered by
the warranty. Additional zinc anodes
may need to be installed on your
yacht as recommended for your
region.
Sacrificial zinc anodes
, installed at the
factory, protect the hardware that is exposed
to the water. Galvanic corrosion attacks the
least “noble” metals first. Because zinc is a
less “noble” metal it will decompose before
the more “noble” metals. Your Cruiser Yachts
Dealer may install additional zinc anodes
based on your boating location. Check these
zincs periodically, and have them replaced
as needed. See your Cruiser Yachts Dealer
for parts and service.
A Galvanic Isolator
is installed in the green
bonding wire between the yacht and the
dockside ground to prevent the flow of
relatively low electrolytic stray currents. It
will, however, provide a path for catastrophic,
short-circuit currents which are sufficient to
actuate circuit breakers.
GALVANIC ISOLATORS
The Galvanic Isolator(s) installed in Cruisers
Yachts comply with the ABYC A-28
standard. Section A-28.13 requires status
monitoring of the galvanic isolator. The
conditions monitored are:
A-28.13.1.1 shorts or open condition of any
diode;
A-28.13.1.2 failure to block galvanic current
at 1.1 volts DC;
A-28.13.1.3 circuit continuity of the shore
grounding circuit;
A-28.13.1.4 operation of the status
monitoring device.
Yachts with single docksides have one
galvanic isolator. Yachts with dual docksides
have two galvanic isolators. The galvanic
isolators have status indicating LEDs (light
emitting diodes) which indicate the
conditions required in A-28.13.
Further, ABYC A-28.13.2 requires the status
indicating device for the galvanic isolator
shall be mounted in a location readily
apparent to the vessel operator. Because
the galvanic isolators are not located where
these diodes are readily apparent, a status
indicating panel has been installed in the
AC/DC panel area to duplicate the
indications of the LEDs on the galvanic
isolator(s), L1 and L2 for dual docksides.
Each galvanic isolator dockside circuit has a
red and green status indicating diode. The
following information describes the
monitoring functions.
GREEN
- When the dockside power is
connected and the green LED is on
continuously, the galvanic isolator is
functioning normally and the dockside
connection is correct. When the dockside
power is disconnected, it will take a minute
or more for the red LED to start blinking.
RED
- If the red LED is ON continuously, it
indicates a faulty condition internal to the
galvanic isolator. The galvanic isolator must
be replaced.
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