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Affordable Sensors for Infrastructure
Final rept. 13 Dec 96-13 Jun 97,
DACCO SCI INC COLUMBIA MD
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An electrochemical impedance spectroscopy EIS based in-situ corrosion sensor has been adapted and evaluated for use with steel heat exchanger tubes in boilers, coated buried steel pipes, and painted steel structures. An excellent correlation was obtained between the logarithm of the ratio of the breakpoint frequencies, as measured by the sensor, and corrosion rate for the boiler tubes. Use of this sensor and appropriate electronics would allow the corrosion of the boiler tubes to be monitored in real time and the inhibitor concentration automatically controlled to prevent excessive corrosion. A separate acoustic sensor was shown suitable for detecting extensive corrosion of boiler tubes. It has the potential to nondestructively and efficiently detect and locate boiler tube damage. The EIS sensor is also sensitive to the quality of coating of a buried steel pipe with and without the application of cathodic protection. Similar results were obtained from a sensor attached to the pipe and from a separate electrode driven into the soil. A hand held version of the EIS in-situ sensor is suitable for inspecting painted metal structures, such as storage tanks and locks and dams, under ambient, service conditions. An excellent correlation was obtained between the sensor measurements and the amount of corrosion on test panels immersed for up to 28 years.
APPROVED FOR PUBLIC RELEASE