What Does Oxygen Concentration Cell Mean?
Oxygen concentration cells occur where an electromotive force (EMF) results due to the concentration differences of reactive constituents involving the electrolyte solution at varying areas on the metal substrate.
Oxygen is the best example of a reactive constituent. The difference results in discrete cathode and anode area formation on the surface of the metal. If oxygen differences are present, the concentration cell is referred to as an oxygen concentration cell.
Concentration cells are also known as galvanic cells, aeration cells, oxygen cells and differential aeration.
Corrosionpedia Explains Oxygen Concentration Cell
Oxygen concentration cells are often caused by lap joints, crevices, insulation as well as debris. Under such conditions, oxygen serves as the anode while areas that are exposed to oxygen are considered cathodic. An oxygen concentration cell can be related to crevice corrosion, poultice action and oxygen screening.
Rates of local corrosion adjust to normalize ion concentration reductions in the electrolyte. When oxygen has access to a damp metal substrate, the corrosion process is hastened. However, it is promoted most in areas where the concentration of oxygen is the lowest. If the area of the electrolyte adjacent to the metal shows low metal ion concentration, the region will turn anodic to the rest of the metal surface. Consequently, this particular area will corrode quickly to boost local concentration of ions.
The removal of oxygen through de-aeration is a convenient way of reducing the incidence of corrosion, such as in steam boilers that work with feed water that undergoes de-aeration.
Galvanic Cell, Aeration Cell, Oxygen Cell, Differential Aeration