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 8.0 CATHODIC PROTECTION SYSTEMS
8.1 GENERAL
8.1.1 SCOPE. Shore activities responsible for the operation and maintenance of
fleet moorings expend considerable time and money maintaining moorings in a
safe, reliable condition. The highly corrosive effect of seawater necessitates a
continuous program of preventive and corrective maintenance. The frequency of
maintenance actions is directly related to the rate of corrosion and wear of the
mooring chain and other components. Recent analysis of the maintenance of fleet
moorings, with and without cathodic protection over extended periods of time,
indicates that the use of an effective cathodic protection system (CPS) can
significantly reduce the corrosion rate of mooring chain, yielding an attendant
savings in maintenance costs.
8.1.2 APPLICATION. Cathodic protection of steel submerged in seawater is achieved
by impressing a negative electrical potential on the surfaces exposed to the
seawater. Several systems have been developed to supplement protective coatings
in an effort to reduce corrosion of fleet mooring chain and accessories. Typically,
the required electrical potential is provided by sacrificial zinc anodes which are
gradually consumed while catholically protecting the steel components. Cathodic
protection of the submerged portion of the buoy may also be provided by sacrificial
anodes attached to the hull. Anchors normally do not require cathodic protection
because bottom mud isolates the anchors from the corrosive effects of the
seawater.
8.1.3 EFFECTIVENESS. The cathodic protection system and the protective coatings
on the mooring components work together to keep the underwater portion of the
buoy and the chain assembly from corroding. It is estimated that such a system,
properly installed and maintained, can provide complete protection for
years in
IS
aggressive environments, and for longer periods at milder locations, before anode
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