Sprayed-Zinc Galvanic Anodes for the Cathodic Protection of Reinforcing Steel in Concrete

Corrosion of reinforcing steel bars (rebars), due to penetration of chloride ions from seawater affects the substructure of many bridges in marine service. In a new, low cost control method, sacrificial anodes of arc-sprayed zinc are being applied to the surface of substructure members of Florida bridges. The zinc and underlying rebar are in electronic contact, and the intervening concrete acts as a conducting electrolyte. Field tests of this concept have been in progress for over two years. Laboratory investigations are being conducted to test the limits of applicability (necessary concrete conductivity, polarization characteristics, durability). The results to date are encouraging, showing that the systems retain physical integrity in harsh marine environments. Considerable protective current delivery can be achieved within the limitations of potential available from the galvanic couple and the concrete resistance. This paper describes the field installations with procedures used for the anode application, and highlights the results from the laboratory experiments.