Corrosion Protection; Galvanic Corrosion - Nanni N2.10 Operator's Manual

Corrosion
protection
The engine and all metal item in the
boat that are exposed to water or
damp can be damaged by corro-
sion.
There are two main categories of
corrosion, which can be cumulative:
galvanic corrosion and electrolytic
corrosion. Both corrosion pro-
cesses are a result of electric cur-
rent that flow between metal items
in an electrolyte such as water.

Galvanic corrosion

Galvanic corrosion is an electroche-
mical reaction that create electrical
current between dissimilar metals
exposed to water. This current will
corrode the more anodic metal.
Several factors, cumulative or not,
can worsen this effect:
• High saline and/or mineral
concentration in water.
• High water temperature (>25°C).
• When cruising at high speed or
when there's a strong current.
• Important relation difference
between the cathode and anodic
surfaces.
Anodes in magnesium or zinc are
generally used to protect the boat
against galvanic corrosion. Due to
their intrinsic nature, these anodes
54
will wear down in place of other
metallic components.
During the first year of use, check
the anodes deterioration every 3
months. During prolonged moo-
ring near other boats or dock side,
control the wear and tear of the
anodes at shorter intervals. In that
case, the use of additional corro-
sion protection might be necessary
during prolonged mooring.
Depending upon operating condi-
tions and water properties, it might
be necessary to check and/or
replace the anode more frequently.
I CAUTION
The anodes must never be
painted or damaged. They must
be changed as soon as they are
corroded of more than 50%.