What Does Concentration Cell Corrosion Mean?
Concentration cell corrosion is the deterioration of parts of a metal surface at different rates, due to the parts of the surface coming into contact with different concentrations of the same electrolyte. These differing concentrations result in some parts of the metal acquiring different electric potentials.
Study of this form of corrosion is important because this type of corrosive damage is observed in critical applications, such as pipes buried in soil, due to variable characteristics of the soil.
Corrosionpedia Explains Concentration Cell Corrosion
Concentration cells occur when the concentration of electrolyte in contact with the metal is different in two contact locations. The extent of this corrosion reaction is proportionate to the difference in concentrations at contact points. It also varies with the type of electrolyte.
If an area of the electrolyte close to the metal shows a lowered concentration of metal ions, the region has to turn anodic in comparison to different portions of metal surface. Thus, this part of the metal corrodes faster, so as to increase the local ion concentration in electrolyte.
Concentration cell corrosion is most prevalent in the presence of oxygen. When pure oxygen comes into contact with a wet metal surface, corrosion action is enabled. However, the corrosion is most severe in areas that have minimal oxygen contact.
Parts of metal that are covered by scale will corrode faster because the contact with oxygen for these parts is restricted. Concentrated pitting can result due to this cumulative reaction.