A Galvanic Sensor for Monitoring the Corrosion Damage of Buried Pipelines: Part 2—Correlation of Sensor Output to Actual Corrosion Damage of Pipeline in Soil and Tap Water Environments Available to Purchase

To develop a new corrosion sensor for detecting and monitoring the external and internal corrosion damage of buried pipeline, the correlation of its output to the corrosion rate of steel pipe was evaluated by electrochemical methods in two soils of varying resistivity (5,000 Ω·cm, 10,000 Ω·cm) and synthetic tap water environments. In this paper, two types of galvanic probes were manufactured: copper-pipeline steel (Cu-CS) and stainless steel-pipeline steel (SS-CS). A comparison of the sensor output and corrosion rates revealed that a linear relationship was found between the probe current and the corrosion rates. In the soil resistivity of 5,000 Ω·cm and tap water environments, only the Cu-CS probe had a good linear quantitative relationship between the sensor output current and the corrosion rate of pipeline steel. In the case of 10,000 Ω·cm, although the SS-CS probe showed a better linear correlation than that of the Cu-CS probe, the Cu-CS probe is more suitable than the SS-CS probe because of the high current output. A correlation based on the ratio of the total charge of the pipeline/Cu-CS probe was determined as 0.39 ~ 0.41 in soil environments and 0.76 in synthetic tap water, respectively. This is an indication that the slope parameter can reflect the types of environment.