A GALVANIC SENSOR FOR MONITORING THE CORROSION DAMAGE OF BURIED PIPELINES: PART Ⅳ. ELECTROCHEMICAL TESTS TO DETERMINE THE CORRELATION OF PROBE CURRENT TO CATHODIC PROTECTION CONDITIONS

摘要

In order to develop a new corrosion sensor for monitoring the status of cathodic protection of buried pipeline, the correlation of sensor output to protection abilities (protection potential and current) was evaluated by laboratory and field tests. It uses well-known principles of galvanic corrosion and consists of two dissimilar metals (anode and cathode) installed in the soil near the pipeline. In this paper, the copper-pipeline steel (Cu-CS) probe was used. The cathodic protection status of pipeline was simulated by galvanostatic test. The galvanic current density was measured by a zero resistance ammeter for Cu-CS probe with connecting or disconnecting the anode (CS) to pipeline. The results showed a good correlation of the protection potential/current of pipeline and the sensor output. Especially, when protection current was induced to pipeline, the negative(-) sensor current was measured, whereas stray current was left from pipeline, the positive(+) sensor current was measured. Thus, it can be known that the direction of sensor current reflects the status of pipeline with cathodic protection or stray current corrosion, so that the Cu-CS galvanic probe is an effective tool for monitoring the effectiveness of cathodic protection.