This is the destruction of one metal (the anode) by another (the cathode) when connected via an electrolyte (any liquid which carries electrically charged particles from the anode to the cathode), like water. This is speed up if the water is hot or acidic. These elements are found in the electromotive series:
* Those higher on the list will destroy the lower, e.g copper will destroy zinc.
Corrosion caused by moisture and gases in the air. When oxygen mixes with the surface of a ferrous metal it forms an oxide, commonly known as rust. As this brittle skin flakes off it reveals fresh metal and the process continues until destruction.
Non-ferrous metals are attacked by gases like carbon dioxide and sulphur dioxide, but this surface doesn't flake like rust. It instead acts as a skin called patina and protects from further corrosion. (Think of when copper turns green.)
Prevent or Cure?
In the case of electrolytic corrosion we have power flushing machines and chemicals to add to your system to prevent this from happening. Whereas atmoshperic corrosion is treated by putting a protective coat on and removing moisture from coming into contact with the subject.
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