A thermally sprayed Aluminum-Zinc-Indium (Al-Zn-In) anode was applied to the substructure and superstructure elements of the San Luis Pass Bridge in Galveston, Texas. The anode was developed under a research and development program that was funded by the Federal Highway Administration (FHWA). The Al-Zn-In alloy is applied to concrete using electric arc spray equipment to form a galvanic coating. The San Luis Pass Bridge is a 38-year old concrete structure that spans a 2.1-kin (1.3-mile) distance over the inlet that connects the West Bay of Galveston Strait with the Gulf of Mexico. The structure is situated in an aggressive marine environment and is subject to frequent storm activity, high relative humidity and high chloride content in the concrete from wind and saltwater spray. During 2002 and 2003 Galveston County funded a major rehabilitation project for the bridge in which the Al-Zn-In anode was applied to the prestressed concrete beams and conventionally reinforced concrete bent caps. The total surface area receiving the Al-Zn-In cathodic protection (CP) system is approximately 30,000 m2 (322,000 ft2). To monitor protective current and polarization decay, six beams were instrumented with isolated anode connections, current measuring shunts, on/off switches and embedded reference electrodes. Initial current densities at the instrumented test beams are high and range from 4.4 mA/m2 to 6.9 mA/m2 (0.41 mA/ft2 to 0.64 mA/ft2) of concrete surface. After 39 days of operation, the current densities range from 1.1 mA/m2 to 2.6 mA/m2 (0.10 mA/ft2 to 0.24 mA/ft2) of concrete surface, and the potential measurements exceed the 100 mV polarization decay criterion for cathodic protection at 11 of the 12 reference electrode sites.

Subject
Coating application, Galvanic anodes, Cathodic protection, Rebar, Aluminum zinc indium alloys, Reference electrodes, Concrete surfaces, Wiring, Steel, Bridges, Polarization decay, Concrete, Anodes
Keywords:
galvanic anode, cathodic protection, corrosion control, Aluminum-Zinc-Indium, chloride-contaminated concrete, thermally sprayed anode
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2004
Association for Materials Protection and Performance (AMPP)
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