02265 CARBON PAINT ANODE FOR REINFORCED CONCRETE BRIDGES IN COASTAL ENVIRONMENTS

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Solvent-based acrylic carbon paint anodes were installed on the north approach spans of the Yaquina Bay Bridge (Newport OR) in 1985 and performed well after 15 years. Anodes were inexpensive and repairs easy. Depolarization potentials are consistently above 100 with long-term current densities around 2 mA/m 2. Bond strength remains adequate.

Product Number: 51300-02265-SG

ISBN: 02265 2002 CP

Author: S. D. Cramer, S. J. Bullard, B. S. Covino, Jr., G. R. Holcomb, J. H. Russell, C. B. Cryer and H. M.

Publication Date: 2002

Industry: Highways & Bridges

Member Price: $0.00

Non Member Price: $20.00

Price: $20.00

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Solvent-based acrylic carbon paint anodes were installed on the north approach spans of the Yaquina Bay Bridge (Newport OR) in 1985. The anodes continue to perform satisfactorily after more than 15 years service. The anodes were inexpensive to apply and field repairs are easily made. Depolarization potentials are consistently above 100 mV with long-term current densities around 2 mA/m 2. Bond strength remains adequate, averaging 0.50 MPa (73 psi). Some deterioration of the anode-concrete interface has occurred in the form of cracks and about 4 % of the bond strength measurements indicated low or no bond. Carbon anode consumption appears low. The dominant longterm anode reaction appears to be chlorine evolution, which results in limited further acidification of the anode-concrete interface. Chloride profiles were depressed compared to some other coastal bridges suggesting chloride extraction by the CP system. Further evidence of outward chloride migration was a flat chloride profile between the anode and the outer rebar.

Keywords: cathodic protection, bridges, reinforced concrete, solvent-based acrylic carbon anode, bond strength, service life, depolarization, circuit resistance, chloride, pH, interracial chemistry, SEM