A simple description of the Alexander Cell is 'a corrosion cell'. This is also a simple description of a dry cell battery. Both produce electrical current by chemical reaction.
We control the discharge by breaking the circuit of a dry cell battery and we control corrosion on pipelines by coating the steel.
We can also control the corrosion reaction of a dry cell battery using a battery charger. This balances the potential of the corrosion reaction and there is no discharge. We can balance the reaction in the Alexander Cell with a CP transformer-rectifier (a big battery charger).
By observing the corrosion reaction at a particular location using the Alexander Cell we establish all of the conditions required by the Pourbaix diagrams...... temperature, pressure pH and condutivity of the electrolyte.
We then connect the Alexander Cell to the pipeline making it a coating fault at this location. The cathodic protection current the comes from mass earth to cause an increase in the potential at both the anodic and the cathodic interfaces between the metal and the electrolyte.
If this potential is sufficient to move the reaction into the passive zone as described by Pourbaix, the Nernst equations and Gibbs free energy et al.... then we have attained protection. This can be seen as predicted by Farraday in the cessation of electrical discharge from the anodic electrode, as is normally set up in a laboratory.
The Alexander Cell is an electrode system as described by Prof Walshe of Southampton Uni and has been evaluated by scientists world wide.
In order to test it in a laboratory it is necessary to understand that open circuit conditions are very difficult to replicate and I have therefore another design for laboratory work which overcomes a minor misunderstanding pointed out by Jim Gosden who was the Chairman of the committee for BSI CP1021 at the time. (all correspondence and documentation from this period is available on request.)
To sum up;
place the Alexander Cell on the ground and charge it with a sample of the electrolyte. Note the corrosion current.
Connect it to the pipeline and note the current again. The changes are due to the pipeline cathodic protection system. If the current has stopped or reversed the corrosion must have stopped....or Faraday was wrong and your dry cell batteries are just an illusion!!!!
Cathodic Protection Monitoring Device.. Alexander Cell
