The glass flower vase with the water is placed in the large plastic container.



It is in an empty section and on the level, in relation to the bottom of the large container.

This could be likened to three places where the coating on a pipeline has 'disbonded' from the metal.

Each has included some material that results in each 'blister' having a different electromotive force at its anodic interface.

The coating is not penetrated and there is not conductive path to allow corrosion to proceed.

We cannot gather any of this information in the case of a real cathodic protection as we can only measure between to electrical potentials that themselves can be at any level in the system.