United States Department of Transportation
i
Effectiveness of cathodic protection : final report, June 30, 2009.
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2009-06-01
[PDF-260.88 KB]
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Edition:Final report.
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Abstract:The report provides a summary of Oregon’s experience with cathodic protection of coastal reinforced concrete bridges.
Thermal-sprayed anodes, foil anodes with a conductive adhesive, and carbon painted anodes are effective in distributing
current to the steel reinforcement in concrete bridges. A resistive layer develops at the anode-concrete interface with
increasing electrochemical age, thereby increasing anode polarization. In impressed current cathodic protection (ICCP)
systems this is reflected in a higher circuit resistance. In sacrificial anode cathodic protection (SACP) systems it results in
lower current output. Periodic wetting of the anode by rain, fog, and dew is an important factor in reducing anode
polarization.
Catalyzed thermal-sprayed titanium anodes under ICCP service develop no significant anode polarization with
electrochemical age. They perform well in both low and high humidity environments, and exhibit stable long-term
performance.
Humectants based on LiNO3 and LiBr promote more effective performance of new and aged anodes in CP systems than
untreated anodes. In SACP tests, LiBr was more effective
than LiNO3. In accelerated ICCP, LiNO3 was more effective than LiBr.
In SACP service, zinc hydrogel anodes produce a stable protection current sufficient to protect reinforcing bar from
corrosion. There was practically no effect of changing moisture conditions on current production and no evidence of aging
effects in an Oregon DOT field trial.
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