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 replacement becomes necessary. Additional anodes can then be installed without
removal of the mooring. Buoy anodes are not used when the buoy is fiberglass or
polyurethane coated; only the chain and the lower portions of the tension bars on
these buoys must be protected.
8.2 CATHODIC PROTECTION FOR BUOYS
8.2.1 ENVIRONMENTAL CONSIDERATIONS. In designing a cathodic protection
system, the extremes of favorable and unfavorable environmental conditions
Favorable local environmental conditions (low salinity,
should be considered.
minimal tide, quiescent water, low dissolved oxygen content, low temperatures,
and moderate currents) result in longer periods of time between preventive or
corrective maintenance. Unfavorable local environmental conditions (high salinity,
h i g h tidal variations, turbulent water, high dissolved oxygen content, high
temperature, and strong currents) increase the wear and corrosion rates and
decrease the time between required maintenance actions. Cathodic protection is
beneficial in all environmental conditions but especially where unfavorable local
conditions exist.
8.2.2 ANODES. Anodes for use on buoys are readily available. One commonly used
is a zinc casting 36 inches long with a nominal cross-sectional area of 16 square
inches. The anode weighs approximately 150 pounds, and is cast on a 48-inch-long
T h e composition of the zinc is in
3/4-inch-diameter pipe (see Figure 8-l).
conformance with MI L-A-18001. Buoy anodes must be secured in a location where
they will not be subjected to impact by vessels; for example, on the bottom of drum-
type buoys, in a sea chest built into core portions of peg-top riser-type buoys, or
within protective cages welded to the conical side of a peg-top buoy. These anodes
should be located about 4 inches from buoy surfaces.
The new foam buoy hulls do not require cathodic protection and, therefore,
anodes are not attached to it. The lower portion of its steel tension bar member,
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