Aeration electrochemical mechanisms

The electrochemical mechanism of filiform corrosion is described by a differential aeration cell between the front (low oxygen concentration) and the back (open to air through the cracked/porous tail of dry corrosion products) of the filament s active head . Therefore, the head is the local anode and the tail the local cathode, the opposite to the cathodic delamination described earlier. This is shown in Fig. 7-67 where an optical photograph of the filiform head is compared to the potential distribution in air (center) and in nitrogen (right) (Schmidt and Stratmann, 1998). 

However, as previously described, this ennobling mechanism is only based upon steady-state considerations, and it does not adequately take into account electrochemical kinetics, which, depending on the experimental conditions (polymer, substrate, aeration of the environment... [41]), makes the protection efficiency vary considerably. 

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