Monitoring and control - internal surfaces in contact with liquid

When the introduction of a reference electrode is possible, the efficiency of a cathodic protection installation is monitored by measurement of the potential of the structure with regard to a reference electrode put in the structure. In order to eliminate the effect of the ohmic fall, this potential is preferably measured just after the protection current has been turned off.

The value of the potential to be reached depends on the constitutive material of the structure and on the liquid inside. It also depends on the type of reference electrode. Chart 4 gives the example of a non-alloy steel structure containing water.

Chart 4 : Potection potential (volt) of a non-alloy steel immersed in waters with various chloride rates