CP criteria for reinforced concrete in marine exposure zones

A marine environment may be characterized by tidal, submerged, and atmosphe rically exposed zones. Cathodic protection (CP) of reinforced concrete in t he submerged zone may induce reducing conditions associated with immunity t o corrosion characterized by negative steel potentials. In the atmospheric zone CP induces an improvement in the local environment at the steel, promo ting steel passivity, which may be monitored using a potential decay criter ion in relatively dry conditions. Many protective effects will persist foll owing the interruption of the current, providing a basis for intermittent C P in the tidal zone. However, conventional criteria may not be reliable in this case. The importance of the current-induced improvement in the tidal z one environment provides justification for the use of a protection current density criterion. The integrated current densities required to arrest high initial corrosion rates are relatively low. Protection criteria may also b e based on a positive trend in measured potentials indicative of passivatin g steel and the induced voltage drop through the concrete cover that drives the removal of chloride ions and sustains a high hydroxyl concentration gr adient between the steel and the external environment.