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Old 09-08-2011, 01:07 PM
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Quote:
Originally Posted by domenic View Post
It's called Electrolysis. Other boats going by give off Electrolysis. This can attack the metal parts of your boat. The Zincs take up most of the Electrolysis. Zincs are sacrificing plates. In a marina you can hang zincs over the side. They don't have to be attached to your metal parts.
Your boat when under power gives off the same Electrolysis. On slow moving boats under power...it's a magnet for sharks.
Eels draw Electrolysis from salt water. It is a power man has not yet learned how to tap into.
Uhm...

I'm not a chemist, but let's see if we can't clear one or two things up here.

Electrolysis is not radiation or something that is "given off" by a boat. In our application, the more technically correct term than "electrolysis" is galvanic corrosion. It is a chemical reaction that occurs between two dissimilar metals when in proximity to each other in an electrolyte. An electrolyte is a solution that conducts electricity. Salt water is an electrolyte.

Different metals have different tendencies to be more or less electrochemically active in an electrolyte. The more "noble" a metal is, the less likely it will be galvanically corroded. The more "base" a metal is, the more likely it will be galvanically corroded.

When you have dissimilar metals (e.g., steel and bronze) in proximity in a conductive solution, the difference in potential between the two metals causes a gradual flow of electrons from one to the other - they essentially are functioning as the anode and cathode in a battery, and cause a weak electrical current to flow. The more base metal between the two will be galvanically corroded. As between stainless steel and bronze, bronze is more base, which is why a bronze propellor on a stainless steel shaft in salt water eventually will look like it has dissolved in acid - the bronze will be subject to galvanic corrosion because it is more base than the stainless steel shaft.

If there is a source of an impressed current nearby - like a bad ground on wiring in a marina - it can greatly accellerate the process.

The rate of the reaction is affected by the difference in "nobility" of the two metals, the distance between them, and the electrolyte.

The reason a zinc works is because zinc is way down at the bottom of the "base" metals, while stainless is much higher up near the "noble" metals. Bronze is a little lower than stainless, but is higher than zinc. Zinc is more galvanically reactive than bronze or stainless steel. So rather than the reaction occurring between the steel and the bronze, with the bronze becoming galvanically corroded, the reaction will occur bewteen the steel and the zinc - and the bronze and the zinc - with the zinc being galvanically corrorded.

I'm completely confounded by the statement that it is a power man has yet to learn how to tap into. Man has been using elecrolysis and various types of electrochemical reactions for at least 200 years. There is evidence that the ancient Egpytians constructed electrolytic batteries - although they might not have fully understood the physics and chemistry behind how they worked.

The principles and mechanics of electrolysis and galvanic corrosion are very well understood today and it is used on an industrial scale to extract very high-purity metals.

Electric eels do not "draw electrolysis" from salt water. Again, electrolysis is not a substance or matter, or even a mysterious energy field. It is a reaction. Electric eels generate a current using highly specialized organs that actually resemble a multi-plate battery. The organs take advantage of these same principles and use sodium, which is a charged ion, to generate sudden short burst of electricity.
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