Sprayed Zinc Galvanic Anodes for Concrete Marine Bridge Substructures

摘要

A low-cost method for galvanic cathodic protection of reinforcing steel inconcrete was examined. In this method, arc-sprayed zinc is deposited on the external concrete surface of steel-reinforced marine substructure bridge components, which are normally subject to corrosion of the reinforcement as a result of chloride ion contamination of the concrete. The concrete cover of corrosion-damage substructure components is removed, exposing the reinforcing steel. After sandblasting, the zinc is arc-sprayed over the exposed steel and surrounding concrete, creating a 1/2 mm thick galvanic anode which is in electronic contact with the steel and in electrolytic contact with the water in the concrete pores. In this investigation, the ability of the system to deliver protective current was examined by experiments in the laboratory and at field installations at bridges in the Florida Keys. The field tests showed that the anodes retained physical integrity over at least 4 1/2 years in a subtropical environment. The method can be viewed as a competitive alternative to impressed-current cathodic protection systems, and also as a considerable improvement over simple gunite repair of corrosion-damaged substructure concrete.