Polarization period, current density, and the cathodic protection criteria

The -850 mV CSE ``instant off\u27\u27 potential and the 100 mV decay potential cathodic protection (CP) criteria applicable to reinforced concrete structures have been studied with the focus on their dependence on the polarization period and current density. Four constant current densities of 1, 3, 20, and 60 ma/ft2 of the steel surface area were maintained on reinforcing steel embedded in mortar specimens, and the ``instant off\u27\u27 potentials as well as the decay potentials were recorded for different polarization periods and current densities. The ``instant off\u27\u27 potential value was observed to increase with polarization time and current density. The same trend has been noticed in the case of 4-hr decay potential. A current density of 1 ma/ft2 of the steel surface area was found to be inadequate to satisfy either the ``instant off\u27\u27 potential or the decay potential criterion, whereas a current density of 3 ma/ft2 is more than sufficient to satisfy the decay potential criterion, but it is inadequate to satisfy the ``instant off\u27\u27 criterion. Complete depolarization in a 4-hr period is possible with 1, 3, 20, and 60 ma/ft2 CP current densities. The aggregate type has no noticeable effect on the ``instant off\u27\u27 potential and the decay potential values