Evaluation of Anodes for Galvanic Cathodic Prevention of Steel Corrosion in Prestressed Concrete Piles in Marine Environments in Virginia

About the report:

Many of the major highway crossings over coastal waters in the Hampton area of Virginia are supported by prestressed concrete piles, some of which are showing signs of reinforcement corrosion. Grout jacketing alone is an inadequate protection against corrosion and should be supplemented with cathodic protection (CP). Recent advances in the development of anodes make it practical to use galvanic CP to protect these types of concrete bridge components. Five anode systems were tested on several piles of the Willoughby Bay Bridge on I-64 in Norfolk, Virginia: (1) an aluminum-zinc-indium alloy applied by arc spraying on the concrete, (2) a zinc foil with conductive adhesive backing, (3) a system of zinc mesh and grout jacket, (4) a system of zinc mesh and compression panels, and (5) a bulk zinc. During the first 14 months of operation, the protection current outputs of these anodes, the closed-circuit potentials of the steel at various elevations on the piles, and the extent of polarization imparted were measured. Attempts to project the life of these anodes and compare the costs of using them were made. The authors conclude that the zinc mesh and grout jacket anode system is the best for applying CP at the tidal and splash zones and the aluminum-zinc-indium anode is the best for use at any elevation above the splash zone.

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