Effectiveness of Cathodes and Cell Formation

The cell current is determined by the coating resistance r and the size of the coated surface S. Neglecting the anode resistance, the cell current from these two quantities is given by [see Eq. (2-43)]  

The blister population-potential curves can intersect one another. Thus shortterm experiments at very negative potentials, in the region of cathodic overprotection, give no information on the behavior at potentials in the normal protection range. The susceptibility generally increases strongly with over protection -0.83 V). 

Compared with cathodic blisters, which can be recognized by their alkali content, anodic blisters can be easily overlooked. Intact blisters can be recognized by the slightly lower pH value of the hydrolyzed corrosion product. The pitted surface at a damaged blister cannot be distinguished from that formed at pores. 

In general the population of cathodic blisters increases with cathodic polarization and the population of anodic blisters with anodic polarization. Both types of 

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