Local cell

a local cell is a short circuit galvanic cell. It forms everywhere, where a noble and a unedles metal meet or common electrolyte locally differences produced (see a rusting of iron). The nobler metal forms the cathode, which anode formed by the unedleren metal, which dissolves with the time. Since the overvoltage for hydrogen formation at nobler metals usually is smaller than with the unedlen metal comes it with this to a faster oxidation.

A technical application of this effect is the sacrificial anode.

The following reactions run off:

anode: Oxidation

metal <math> \ rightarrow </math> Metallion + electron

cathode: Reduction

for example in sour environment:
Proton + electron <math> \ rightarrow </math> Hydrogen

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