A galvanic sensor for monitoring the corrosion damage of buried pipelines: Electrochemical tests to determine the correlation of probe current to internal corrosion damage in synthetic tap water

In order to develop a new corrosion sensor for detecting and monitoring the internal corrosion of water distribution pipeline, the selection of sensor elements and the correlation of sensor output to corrosion rate of steel pipe were evaluated by laboratory test methods in synthetic tap water. In this paper, two types of electrochemical probes were used: galvanic cells containing of pipeline steel-copper and pipeline steel-stainless steel (UNS S3 0400). The electrochemical behavior in synthetic tap water for the sensor elements was investigated by potentiodynamic test. Linear polarization resistance (LPR) and electrochemical impedance spectroscopy (EIS) measurements were conducted to obtain the corrosion rates of pipeline steel in synthetic tap water. The galvanic current density was measured by a zero resistance ammeter for Cu-CS and SS-CS probes. The correlation between the galvanic current of sensor and the corrosion rate of pipeline was evaluated in terms of the cumulative charge value. The results of the potentiodynamic test indicated that copper and pipeline steel exhibited active corrosion behavior, whereas stainless steel demonstrated spontaneous passivation. A good correlation was obtained by LPR and EIS measurements for corrosion rates of pipeline steel. In galvanic corrosion tests, the galvanic current of Cu-CS probe was higher than that of SS-CS probe. A comparison of the sensor output and pipeline corrosion rate revealed that Cu-CS probe showed a more reliable linear relationship than SS-CS probe. Consequently, it is proved that the copper was suitable for corrosion sensor element to detect the internal corrosion damage of water pipeline.