Electrical & Chemical Action
Electrolytic & Galvanic Action
In Ferro-Cement Hulls
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).
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.
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.
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.
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. amRINA.