A galvanic sensor for monitoring the corrosion damage of buried pipelines: Part. 2. Laboratory electrochemical testing of sensors in soil

To develop a new corrosion sensor for detecting and monitoring the corrosion of buried pipeline, the correlation of sensor output to corrosion rate of steel pipe, and its sensitivity and durability, were evaluated by electrochemical methods in two soils of varying resistivity. Two types of electrochemical probes were used, i.e., galvanic cells containing pipeline steel-copper and pipeline steel-stainless steel (SS) (Type 304). Galvanic corrosion sensors were highly successful in assessing environmental corrosivity and real corrosion rate. The results showed a good linear correlation of the actual corrosion rate of pipeline steel and the sensor output with different soil resistivity. A good linear quantitative relationship was observed between the Cu-carbon steel (CS) probe current and the corrosion rate of pipeline steel coupons in the soil resistivity of 5000 ohm-cm. In the case of 10,000 ohm-cm, although the SS-CS probe showed a better linear correlation than that of Cu-CS probe, the Cu-CS probe was more suitable than SS-CS probe, due to the high current output. However, several problems still remain to be solved in the practical application of this galvanic probe sensor system to structures in field, e.g., data logger system, stray current, and coating and cathodic protection.