Thermal-sprayed zinc anodes for cathodic protection of steel-reinforced concrete bridges

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Thermal-sprayed zinc anodes are being used in Oregon in impressed current cathodic protection (ICCP) systems for reinforced concrete bridges. The U.S. Department of Energy, Albany Research Center, is collaborating with the Oregon Department of Transportation (ODOT) to evaluate the long-term performance and service life of these anodes. Laboratory studies were conducted on concrete slabs coated with 0.5 mm (20 mil) thick, thermal-sprayed zinc anodes. The slabs were electrochemically aged at an accelerated rate using an anode current density of 0.032 A/m2 (3mA/ft2). Half the slabs were preheated before thermal-spraying with zinc; the other half were unheated. Electrochemical aging resulted in ... continued below

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Bullard, Sophie J.; Covino, Bernard S., Jr.; Cramer, Stephen D. & McGill, Galen E. (Oregon Dept. of Transportation) January 1, 1996.

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Thermal-sprayed zinc anodes are being used in Oregon in impressed current cathodic protection (ICCP) systems for reinforced concrete bridges. The U.S. Department of Energy, Albany Research Center, is collaborating with the Oregon Department of Transportation (ODOT) to evaluate the long-term performance and service life of these anodes. Laboratory studies were conducted on concrete slabs coated with 0.5 mm (20 mil) thick, thermal-sprayed zinc anodes. The slabs were electrochemically aged at an accelerated rate using an anode current density of 0.032 A/m2 (3mA/ft2). Half the slabs were preheated before thermal-spraying with zinc; the other half were unheated. Electrochemical aging resulted in the formation at the zinc-concrete interface of a thin, low pH zone (relative to cement paste) consisting primarily of ZnO and Zn(OH)2, and in a second zone of calcium and zinc aluminates and silicates formed by secondary mineralization. Both zones contained elevated concentrations of sulfate and chloride ions. The original bond strength of the zinc coating decreased due to the loss of mechanical bond to the concrete with the initial passage of electrical charge (aging). Additional charge led to an increase in bond strength to a maximum as the result of secondary mineralization of zinc dissolution products with the cement paste. Further charge led to a decrease in bond strength and ultimately coating disbondment as the interfacial reaction zones continued to thicken. This occurred at an effective service life of 27 years at the 0.0022 A/m2 (0.2 mA/ft2) current density typically used by ODOT in ICCP systems for coastal bridges. Zinc coating failure under tensile stress was primarily cohesive within the thickening reaction zones at the zinc-concrete interface. There was no difference between the bond strength of zinc coatings on preheated and unheated concrete surfaces after long service times.

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  • InterCorr'96, 1st Global Internet Corrosion Conference, 1996 (held online, spanning the year, no physical meeting, sponsored by Intercorr International, Houston, TX)

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  • Report No.: DOE/ARC-1996-004
  • Grant Number: None
  • Office of Scientific & Technical Information Report Number: 898295
  • Archival Resource Key: ark:/67531/metadc889637

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  • January 1, 1996

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  • Sept. 22, 2016, 2:13 a.m.

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  • Nov. 4, 2016, 2:11 p.m.

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Bullard, Sophie J.; Covino, Bernard S., Jr.; Cramer, Stephen D. & McGill, Galen E. (Oregon Dept. of Transportation). Thermal-sprayed zinc anodes for cathodic protection of steel-reinforced concrete bridges, article, January 1, 1996; (digital.library.unt.edu/ark:/67531/metadc889637/: accessed September 19, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.