Join Date: Apr 2012
Location: Raleigh, NC
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Re: Non active zinc suddenly VERY active.
As Jaramaz indicated something has changed either in your vessel or due to moving to a new marina to increase the galvanic action causing your sacrificial anodes (zincs) to corrode faster.
As he said start with your boats electrical system, are all equipment bonding good and clean and in proper working order, are the grounds AC and DC properly connected and in good corrosion free condition. Is the shore power connections in good condition free of chaffing and do the pins properly engage within the plug or is one out of alignment, this is sometimes hard to see by itself, but if you had a know good plug compare them to each other the only difference should be only minor(very) wear. Inspect the female end of the connectors also they should all look the same and be at the same depth, is one pushed further back than another, again comparing to a known good also helps in this.
Lastly, galvanically isolate your boat from the marinas AC power with at least a galvanic isolator, or an isolation transformer, though this is expensive.
To answer why would you suddenly need a galvanic isolator, hmmm keeping it simple without getting into a whole lot of electrical power generation theory. Simply put, while most think of ground as zero volts this is actually not always the case, what we call ground is simply a common reference point to take a measurement from, and this point can differ from point to point depending on a multitude of conditions. Simply put, at your previous marina the AC voltage may have varied around a different voltage reference than at your current marina, resulting in increased zinc depletion you are seeing now. An example is shown in the picture I have included, on top is an AC signal, middle is a DC voltage level, bottom is the two signals combined, or summed together note the AC signal/voltage is riding the DC voltage level, if this is happening on your vessel then this could be the cause of increased corrosion.
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Last edited by CVAT; 08-03-2015 at 03:23 AM.