From Corrosion Properties of Materials

Electrochemistry of Corrosion

Corrosion is most visible when the corrosive substance is moisture or water. When the metal surface is exposed to water or moisture, it reacts with the water in a process called oxidation, which means the reaction of a substance with Oxygen. This reaction produces electrons in the metal while a reduction reaction consumes electrons. Together, they form a Corrosion Cell.

Note

A reduction reaction consumes the electrons produced by an anodic reaction.

During an oxidation reaction, the metal dissolves to form a soluble metal compound or an insoluble oxide depending on environmental conditions. In the oxidation reaction, the flow of electrons is necessary for the completion of the corrosion reaction.

An example of a typical anodic oxidation reaction that occurs on a metal surface in a "Corrosion Cell" is:

Fe ==> Fe 2+ + 2e

An example of a cathodic reduction is:

O 2 + 2H 2O + 4e - ==> 4OH

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