Regal 3200 Bowrider, Руководство пользователя

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CHAPTER 7
Typically electrons fl ow from the anode (the aluminum drive unit),via
the external conducting path to the cathode (stainless steel propel-
ler). If there is a very large anode connected to a small cathode, the
anode will corrode very slowly. If a very large cathode is connected
to a small anode, the anode will corrode very quickly. Obviously, if
you do not control galvanic corrosion, over time the aluminum will
corrode away.
The
fi rst sign of galvanic corrosion is paint blistering (starting on
sharp edges) below the water line- a white powdery substance forms
on the exposed metal areas. As the corrosion advances, the exposed
metal will become deeply pitted as the metal is actually eaten away.
Another condition which will increase galvanic corrosion is the re-
moval or reduction in surface area of the sacri
fi cial anodes. Never add
aftermarket products that are connected to the engine ground such as
stainless steel steering aids and trim planes.
Zinc connected to aluminum will form a corrosion cell but the alumi-
num (drive) becomes the cathode and the zinc (anode) corrodes.
Even though your boat may not have shore power aboard current
from nearby vessels with shore power can produce stray current gal-
vanic corrosion. Stray current corrosion occurs when metal with an
electrical current
fl owing into it is immersed in water that is grounded
(lake, ocean, pond). The current can leave the metal and fl ow through
the water to ground. This will cause rapid corrosion of the metal at
the point where the current leaves.
When a vessel nearby is plugged into shore power, they can poten-
tially tie your aluminum drive unit to their boat via the green ground-
ing shore power lead. Your aluminum drive unit could be the receiving
end of a large galvanic cell (a battery) interconnected with nearby ves-
sels or even through the marina’s metal structures via their electricial
system.