A Galvanic Sensor for Monitoring the Corrosion Damage of Buried Pipelines: Part 3—Correlation of Probe Current to Cathodic Protection and Stray Current

In order to develop a new corrosion sensor for monitoring the status of cathodic protection of buried pipelines, the correlation of sensor output to protection abilities (protection potential and current) was evaluated using two types of laboratory tests. The galvanic sensor uses the well-known principle of galvanic corrosion and consists of two dissimilar metals (acting as the anode and cathode) installed in the soil near the pipeline. In this paper, a copper-pipeline steel (Cu-CS) probe was used. The cathodic protection status of the pipeline was simulated by a galvanostatic test. The galvanic current density was measured using a zero-resistance ammeter for the Cu-CS probe with the anode (CS) either connected or disconnected to the pipeline. The results showed a good correlation between the protection potential/current of the pipeline and the sensor output. Especially when the protection current was induced to the pipeline, the measured sensor current was negative (−), whereas when the stray current was removed from the pipeline, the measured sensor current was positive (+). This indicates that the direction of sensor current reflects the status of the pipeline with cathodic protection or stray current corrosion, confirming that the Cu-CS galvanic probe is an effective tool for monitoring the effectiveness of cathodic protection.