GALVANIC CORROSION
Galvanic corrosion results whenever two or
more dissimilar metals (like those found on
the sail-drive) are submerged in a
conductive solution, such as saltwater,
polluted water or water with a high mineral
content because a chemical reaction takes
place causing electrical current to flow
between the metals. The electrical current
flow causes the metal that is most
chemically active, or anodic, to erode. If not
controlled, galvanic corrosion may corrode
Sail-Drive components.
CORROSION CONTROL
It is the boat designer’s responsibility and/or
the re-powering engineer’s responsibility to
design the proper systems and equipment
to control and reduce the possibility of
galvanic corrosion.
However, it is essential that the owner/
operator frequently monitor the anodes for
wear, inspect the sail-drive for corrosion and
replace the anodes often enough to provide
a sacrificial surface for the electrical current
to attack. Galvanic isolators and isolation
transformers are also available from the
aftermarket (not supplied by Yanmar). The
Galvanic isolator is a device that is installed
in series with the (AC) grounding (GREEN)
conductor of the shore-power cable to
effectively block low-voltage DC galvanic
current flow but permit the passage of
alternating current (AC)
*
.
The rate of corrosion depends on numerous
factors, such as:
• the number, size and location of sacrificial
anodes on the sail-drive and vessel;
• the marina environment, such as stray
current in the water, fresh or salt water and
use and isolation of shore power;
• improper application of marine paint or
antifouling paint;
• failure to repaint damaged areas; and
• how the vessel is bonded.
Please check with the boat builder, dealer or
other professional to determine if your
vessel and/or Sail-Drive is adequately
protected from galvanic corrosion.
NOTICE: The anode of the Sail-Drive is only
calculated for the Sail-Drive. Changing the
material of the propeller may require
additional anodes to be installed on the Sail-
Drive.
“The Boatowner's Guide to Corrosion”, by Everett Collier.
PRODUCT OVERVIEW
SD Operation Manual
11
© 2009 Yanmar Marine International
