Consumable anodes were evaluated in the laboratory for use in cathodic protection systems for steel reinforced concrete bridges in coastal environments and in areas where deicing salts are employed. The anode materials included Zn-hydrogel and thermal-sprayed Zn, Zn-15Al and Al-12Zn-0.2In. These anodes were evaluated for service in both galvanic (GCP) and impressed current (ICCP) cathodic protection systems. ICCP anodes were electrochemically aged at a factor of 15 times greater than used by the Oregon Department of Transportation in typical coastal ICCP systems (2.2 mA/m2 based on anode area). Increasing moisture at the anode-concrete interface reduced the operating voltage of all the anodes. The pH at the anode-concrete interface fell to 7 to 8.5 with electrochemical age. Bond strength between the anodes and concrete decreased with electrochemical aging. Interfacial chemistry was the critical link between long-term anode performance and electrochemical age. Zn-hydrogel and thermal-sprayed Zn and Al-12Zn-0.2In GCP anodes appear to supply adequate protection current to rebar in the Cape Perpetua Viaduct.

Subject
Scanning electron microscopy, Bond strength, Impressed current cathodic protection, Adhesives, Zinc anodes, Impressed current anodes, Slabs, Current densities, Interfaces, Pastes, Cement, Concrete, Aging
Keywords:
bridge, cathodic protection, ICCP, GCP, reinforced concrete, bond strength, electrochemical aging, thermal-spray, arc-spray, zinc
Government work published by the Association for Materials Protection and Performance (AMPP) with permission of the author(s). Positions and opinions advanced in this work are those of the author(s) and not necessarily those of AMPP. Responsibility for the content of the work lies solely with the author(s).
2000
GOV
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