Acker Marine Survey Co., Dewey Acker, , Marathon, Florida, USA - ELECTROLYSIS - The most misused and misunderstood word in boating

Marine Surveys by Acker Marine Survey Co., Dewey Acker SAMSŽ AMSŽ, Marathon, Florida, USA Acker Marine Survey Co.
Marathon Florida
Serving The Florida Keys
From Key West to Key Largo
Dewey Acker, SAMSŽ AMSŽ,
Principal Marine Surveyor

ELECTROLYSIS - The most misused and misunderstood word in boating.
This article was published in the Middle Keys Marine Association Newsletter on July 15, 2005

e-lec-trol-y-sis: The passing of an electric current through an electrolyte to produce chemical changes in it (the electrolyte).
Notice there is no mention of the corrosion of submerged metals in this definition. When people use the "E" word they are actually referring to "Electrolytic Corrosion." Electrolytic Corrosion is like Galvanic Corrosion, except on steroids.
Galvanic corrosion occurs when two dissimilar metals are in close proximity and are submerged in an electrolyte (seawater). The less noble of the metals becomes an anode and the more noble metal becomes the cathode. Ions will pass from the anode to the cathode and the anode will actually lose mass through this process. That's why we use sacrificial anodes (zincs, aluminum, magnesium) so the sacrificial anode will lose mass and protect the less noble metal. That's called Cathodic Protection.
When a stray DC electrical current is introduced from an inside or outside source, it causes the galvanic action to be speeded up. This can be from a stray current aboard the affected vessel or from a neighboring vessel. An automotive type battery charger can create a stray current when used onboard the vessel and there are many other causes, such as DC circuits whose breakers trip the negative side. When stray current occurs, the corrosion process is electrically enhanced and speeded up. That's called Electrolytic Corrosion - NOT Electrolysis.
Dewey Acker, SAMSŽ AMSŽ

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