What Does Differential Aeration Cell Mean?
A differential aeration cell causes corrosion of metals as a result of the formation of an oxygen concentration cell, which is caused by an uneven supply of air on the metal surface.
This uneven level of oxygen creates anodic and cathodic sites in the corrosion cell.
A differential aeration cell is also known as an oxygen concentration cell.
Corrosionpedia Explains Differential Aeration Cell
When a metal surface is exposed to differential oxygen concentration levels, the part of the metal exposed to higher oxygen concentration becomes cathodic and the part exposed to lower oxygen concentration becomes anodic.
For example, two iron electrodes are connected in an electrochemical cell having sodium chloride (NaCl) as an electrolyte. One electrode is subjected to oxygen supply and another electrode to nitrogen. A potential difference is created because of the difference in oxygen levels, and as a result current flows through the circuit. An oxidation reaction takes place at the electrode where nitrogen is supplied while these electrons flow through the circuit and are reduced at the electrode where there is more oxygen.
The following reactions occur at the respective electrodes:
At the anode (lower oxygen level): Metal --> M+ + n e-
At the cathode (higher oxygen level): H2O + ½ O2 + 2e- --> 2OH-