A galvanic sensor for monitoring the corrosion damage of buried pipelines: Part. 1. laboratory tests to determine the correlation of probe current to actual corrosion damage

In order to develop a new corrosion sensor for detecting and monitoring the corrosion of buried pipeline, sensor element design and the correlation of its output to corrosion rate of steel pipe, were evaluated by laboratory test methods in synthetic groundwater. The sensor uses well-known principles of galvanic corrosion and consists of two dissimilar metals (anode and cathode) installed in the soil on the pipeline. In this paper, two types of electrochemical probes were used: pipeline steel-copper, and pipeline steel-stainless steel (Type 304) galvanic cells. The corrosion behavior in synthetic groundwater for the different electrodes was investigated by potentiodynamic test. Weight loss and galvanic corrosion tests were conducted to obtain the correlation between galvanic current and corrosion rate. The results of the potentiodynamic test indicated that pipeline steel and copper exhibited active corrosion behavior, but stainless steel demonstrated spontaneous passivation. In galvanic corrosion tests, the galvanic current of copper-steel couple was higher than those of other couples. The comparison of the sensor output and corrosion rates revealed that a linear relationship was found between the probe current and the corrosion rates.