Evaluation of the corrosion risk in the mortar by monitoring macro-cell current

An integrated macro-cell sensor for monitoring the service condition such as the open circuit potential, mortar resistance and the macro-cell current between the anodes and cathode of the sensor was developed. Through the analysis of the sensor output and the background theory of the macro-cell current, macro-cell current values were confirmed to be sensitive to the mortar resistance, cathode and anode state. Then a quantitive relationship among macro-cell current, cover-zone mortar resistance, open-circuit potential and the corrosion current density was established. For the passive state, macro-cell current was found to be ignorable and totally depended on the lower voltage, higher cover mortar resistance and higher polarization resistance in the sensor electrodes. But for the active state, the regular is completely contradicted. Then the values of R_a + R_c and ln(I_a · I_c) in different mortar could be obtained according to established relationship. Further, such values could be used as indicative parameters to evaluate the service condition of the cover mortar and corrosion state of the anodes. Results also indicate that macro-cell current sensor could be served as an effective technology for monitoring the corrosion risk in concrete structures.