MARCH 2004GALVANIC CORROSION PROTECTION
13.123
MARINE ENGINES INSTALLATION
Assessment of progressive wear and tear indicates the importance of this phenomenon. The anodes
that wear down faster must be replaced by larger ones.
Long-lasting efficacious protection is guaranteed only by periodical zinc anode control and replacement
of the markedly corroded ones.
Instructions:
■ During the first year of use, check the zinc anodes deterioration every three months.
■ Change anodes if their original size has been reduced by 50%.
During prolonged mooring near large vessels or during hull repair operations, controls to check wear
and tear must be carried out at shorter intervals; use additional cathode protection with zinc anodes
hanging on the hull’s edge and immersed in water, if necessary.
13.4 ISOLATED POLES INSTALLATION
The need to limit or eliminate eddy currents in the engine can be solved by using electrical compo-
nents with “isolated poles”, or else with the negative pole isolated from the engine ground connexion.
This procedure requires an electrical line for the negative potential that avoids operating currents cir-
culating inside the engine block (See Section 12, Fig. 1).
In all cases, the engine must be electrically connected to the vessel ground connexion, according to elec-
tric equipotential logic to eliminate the galvanic currents originated by electrochemical phenomena.
The following page contains a topographic chart illustrating an onboard electrical installation with
equipotential ground connexions and protective connexions with disposable anodes.
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