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Corrosion Information | Common Types of Corrosion
Galvanic Corrosion -
common type of
corrosion caused by dissimilar metals.
This can occur for a variety of reasons
including dissimilar fittings and fasteners
in direct contact with bare aluminum, or
even loose items like sinkers and old
hooks that find their way into the bilge or
an inconspicuous area. These dissimilar
metals cause galvanic corrosion when
immersed together or while in contact
with saltwater, brackish or even
contaminated freshwater.
Crevice Corrosion -
lack of oxygen
can be another reason why aluminum
corrodes. Standing saltwater, brackish,
and even contaminated freshwater sitting
in the hull of your boat over a long period
of time can cause tiny areas where the
oxide layer slowly gets deteriorated. Not
having that natural hard protective
coating of oxide will cause the aluminum
to become pitted over time and could
potentially evolve into microscopic
pinholes through the hull.
Electrolysis Corrosion -
when an
electrical component in either the AC or
DC system is incorrectly installed or has
an electrical fault which leads to ground.
This fault doesn’t necessarily need to be
on your vessel to cause an issue. It
could be located on a neighboring vessel
or a boat on the other side of the marina
connected to the same AC grounding bus
on the marina supplied shore power
connection. These faults will turn your
boat and every other boat in the marina
into a battery, with the saltwater as the
conducting electrolyte.
Poultice Corrosion –
accumulation of
debris can create a highly corrosive
condition. Combined with aluminum, this
debris creates an acidic solution called
aluminum hydroxide that can corrode
through the parent metal. These areas
tend to seriously aggravate aluminum
when there is wet-dry cycling.
