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Dec 20, 2016
Category: General
Posted by: alvin

The proposed gateway to a planned interoceanic canal shows little sign of activity but locals say Chinese experts have visited recently and work will start soon.

Oct 29, 2016
Category: General
Posted by: alvin

EU and 24 countries sign long-awaited agreement to protect 1.1m sq km of water in Southern Ocean, ensuring that fewer younger fish will be caught

Jul 29, 2016
Category: General
Posted by: alvin
The Utila Ferry War is Over.
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Almacen Naval
Roatan, & Puerto Cortes, Honduras, Rio Dulce, Guatemala
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You are here: Home » Cathodic Protection

Cathodic Protection

Cathodic protection should be used to prevent localized corrosion in bearing areas or in other crevices (Refer to Galvanic Series Chart). An impressed current system or Navy-grade zinc anodes should be used for salt water applications; boats which see brackish and fresh water should consider Aluminum anodes as Zincs can become inactive in non salt water applications. If the boat sits idle for extended periods of time, it is strongly recommended the shaft be rotated several turns at regular intervals. For more detailed information, refer to ABYC E-2 "Cathodic Protection."

Stray Current

Stray battery current is the most dangerous cause of corrosion. It can be suspected in cases of rapid and deep pitting, loss of metal, bright discoloration, extensive formation of corrosion products. And weakening of batteries. In older boats without digital electronics, the testing procedure was quite simple. A multimeter with a current range from 10 amperes to 10 milliamperes can be used to check tor possible current leaking while the boat is in the water.

The testing procedure is to first turn off all electrical equipment and

fixtures aboard, then disconnect the positive connector from the boat's battery terminal and connect the positive lead of the multimeter

to the battery post and the negative lead to the connector, Starting at the 10 ampere (or highest current) range of the meter, check to see that there is no current flow, then switch the meter to low current ranges. With perfect boat wiring and equipment, no current should flow at any setting. A normally "clean" electrical system will have a leakage current of less than 1 milliampere (0.001amp). Leakage of a few milliamperes indicates a small amount of corrosion – hardly dangerous - but something to locate and correct if possible. However, if the meter shows a-sizable fraction of an ampere, separate circuits should be switched off one at a time to find which is at fault, and the wire or equipment repaired or replaced promptly. One problem with this type of test is modern electronics will typically consume electricity even when switched off. In this case, some current would always be measured as long as the battery is connected.

A better way to do this test (probably not something your typical owner could do) is to use a reference cell and measure hull potential with batteries disconnected and then measure again connected. Then measure while starting loads one at a time and note the effect on the hull potential. This test requires some specialized equipment and the knowledge of how to use it. There are several ABYC approved corrosion surveyors with the equipment and expertise to conduct a corrosion survey of your vessel and recommend remediation should

stray currents be found.