Cathodic prevention was implemented with commercial Zn bulk anodes on laboratory columns simulating a reinforced concrete marine system. Two computational models of these laboratory columns were implemented. The results obtained from both models were in reasonable agreement with the experimental observations. One of the models was used to predict cathodic prevention throwing power on field scale structures, as a step towards field application. These predictions suggest that with an immersed anode useful levels of cathodic prevention may be reasonably expected, even under conservative assumptions, in the area immediately above high tide where conditions are otherwise very severe.
Cathodic protection (CP), implemented either as an impressed current or as a sacrificial anode system, has been successfully used to mitigate corrosion on reinforced concrete structures. One relatively recent variation of the CP technique is cathodic prevention (CPrev) [1 ? 7] for new reinforced concrete structures. To date, CPrev has been principally used to protect atmospherically exposed structures (e.g., bridge decks), by means of impressed current systems [1-6]
CPrev delays the onset of corrosion by polarizing the still passive steel reinforcement to a more negative potential at which corrosion is less likely to initiate. Additional benefits may accrue by slowing the migration of chloride ions toward the rebar and by increasing OH- concentration at the rebar surface. Although this technique requires a system similar to that used for CP, in contrast to CP, CPrev is usually applied early in the service life of the structure, before the initiation of corrosion. Thus, the system is usually installed during the construction of a structure, and energized a short time later. Since the rebars are in a passive state, the required applied current is much smaller than that normally needed for CP. Cathodic polarization by approximately 100 mV is said to increase the chloride threshold for initiation of corrosion by as much as an order of magnitude [1-2]. More recent publications [8-12], based on experiments conducted in reinforced concrete or mortar cells, suggest that cathodically polarizing the steel from ?100 to -200 mV (SCE) increases the chloride threshold by at least 1.5 to 3 times.
