Cathodic blistering example

Cathodic Blistering. In the absence of a purposely-imposed defect in the coating, the cathodic delamination phenomenon is known as cathodic blistering. An example of cathodic blistering as a function of time is shown in Figure 1. 

Figure 1. An example of cathodic blistering. The coating was a zinc chromate alkyd primer material. The electrolyte was 0.5M KCl and the potential of the metal was maintained at - 1.0 v vs, SCE.

In more detail, the model of cathodic delamination can be described and understood as follows [3,57] the delamination starts with randomly distributed anodes and cathodes in a defect or at a dalaminated area. When iron is taken as an example, the dissolved Fe " at the anode is further oxidized to Fe + by oxygen and forms insoluble corrosion products in the defect that often adhere to the polymer (in the case of a blister) and at the edges of the defect (where oxygen enters the defect). In what way the defect is blocked and a cap of corrosion products is formed on the top of the blister see Figure 20.7. In this cap oxygen... 

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