Stray-current corrosion detection

The causes and common means of detecting and mitigating stray current interference effects that result from direct current sources are reviewed in this Sect. [1, 40-44]. Alternating current, while creating a potential safety ha2ard, may contribute to corrosion of ferrous structure [42]. Extensive research is in progress in this regard. 

Half-cell potential measurements Simple to conduct May act as a screening mechanism for more expensive methods Well established as method to detect corrosion activity in buried objects Factors such as stray currents and soil conditions may affect readings Accuracy of results depends on distance between readings Small areas of localized corrosion can not be detected... 

Apart from the above design improvements in more modem transit systems, several other remedial measures can be considered. Regular rail inspections are important for detecting problems with electrical continuity and faulty insulators. In addressing stray current problems of this nature, communication and cooperation between different organizations and stakeholders is most beneficial. Corrosion control coordinating committees are usually established for these purposes. 

The in-service cable plant is tested to establish the presence or absence of stray direct currents, the galvanic corrosion effect of "foreign plants, the corrosivity of local environmental conditions, and the corrosive effect of long cells formed by the changes in the environment. The corrosion of the in-place plant is detected through potential surve5fs, current tests, soil resistivity tests, redox potential tests, and pH tests. 

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