Put The Metal To The Metal
Galvanic corrosion, electrolysis, stray currents, dissimilar metals ... start spewing off these words around any boater and watch the involuntary twitching begin. While it is currently impossible to prevent corrosion, we at least know how to postpone the inevitable thanks to the magic of science (which we won't attempt to explain in depth here).
For example, and as you probably know, zincs are "sacrificial anodes'" which, by design, attract electrical current away from other surrounding metals. Their underwater job is to protect your through hulls, props and struts from corrosive damage that would otherwise be caused by stray current. Blame other boats, blame the marina, stray current's down there waiting to nibble at your nodes and your zincs are happy to oblige. They corrode for the cause and have to be replaced regularly to keep up the good deflective work.
Out Of Sight, Out Of Mind
Given their underwater location, zincs are easily overlooked and boaters may forget to check them at regular intervals. However, just like your sea strainers, zincs need to be routinely inspected and replaced - after all, they are protecting some very expensive gear. Ignore them and you might not be facing just the loss of a strut or a prop, but a through hull fitting, the thinnest area of metal on your boat's bottom. If one of those gets eaten away, you could sink your boat.
So, remember to check your zincs! (And while you're at it, make sure your through hull bonding is adequate so as not to be even more susceptible to stray current.) You know how it goes: Better safe than sorry.
As for us here at Stanley Yachts, when it comes to the vessels in the fleet we manage and maintain, we always rely on the professionals at Mrs. G Diving for hull inspections, bottom cleanings and zinc replacements - they "dive right in" with prompt and thorough service. Give Maureen a call and tell her we sent you.
Surveying Fiberglass Power Boats | David H. Pascoe
Negative Effects of Corrosion | Southern Boating