Electrolytic &
Galvanic Action In Ferro-Cement Hulls.
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Most problems associated with electrical action evident
in a hull, are compounded by not knowing what inherent built-in
electrolytic and galvanic action your vessel possesses. Unfortunately
many builders as a matter of course fit anodes in various positions
in the underwater areas of a vessel, before launching when new,
and leave the rest to chance (or a new owner). |
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The fitting of anodes in most cases will....a/ create a
battery and start an electrical action. b/ in some cases cure
part or all of an electrical action. Whatever course it takes,
the inherent electrical flow (if there is any at all), is an
unknown factor. And any attempt at curing a still active detrimental
action becomes a hit or miss situation. |
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If the builder intends taking a continued interest in his
craft he will launch her without anodes, and try to keep her
well clear of any large steel or ferroboats (a ferroboat in many
instances, must be given the same considerations as a steel vessel
because of it's steel matrix armature). And also in water with
at least 6ft beneath her. Then haul her out after between 3 to
6 months (depending on the type and proximity of the bottom sediment),
and look for signs of electrical action. Then strategically place
anodes and link any necessary items that need readjustment of
inherent electrical action. It is not uncommon for a ferro-cement
hull to have no or little inherent action. |
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If a vessel has been well adjusted for quite some period
of time and there is then a sudden change, it is most likely
a new proximity problem. Either a close vessel, or more often
than not a highly polluted sediment bottom. The proximity of
electric welding is another important consideration, either onboard
the vessel with the problem or almost as important, on another
vessel nearby. |
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These comments do not apply to a large steel craft,
which apart from electrolytic will have galvanic action (a 'pd'
or voltage is measured naturally from one part of the surface
to another). This will not happen on a ferro hull if properly
sealed, which to all intents and purposes, as stated previously
must be treated as a steel hull, especially if considering the
use of metalised paints or anti-foulings.
Colin Brookes. mSNAME, advIFIC. etc |
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