Macrocell Effects on Potential Measurements in Concrete Cathodic Protection Systems

The electrochemical situation that arises in reinforced concrete structures equipped with a cathodic protection (CP) anode when CP is not energized was studied. A macrocell effect between anode and cathode was shown to arise even in the absence of a direct connection, inducing alterations in potential measurements. In chloride (Cl-)-contaminated structures where CP was not energized, the presence of the anodic system enhanced localized corrosion. In structures where CP was in operation, potential monitoring, namely of instant-off potential and 4-h decay, was affected.