A Real-Time AC/DC Measurement Technique for Investigation of AC Corrosion of Pipelines and Its Effect on the Cathodic Protection Effectiveness

摘要

In this work, a real-time AC/DC (alternating current/direct current) signal data acquisition (DAQ) technique was developed, which enabled separation of AC and DC components from the recorded total voltage during the AC corrosion measurements. Mechanistic information about the steel corrosion in the presence of AC interference was obtained. Furthermore, the effects of AC on the performance of cathodic protection (CP) and the CP potential readings were determined by the developed DAQ. It was found that the presence of AC decreased the CP effectiveness. Moreover, the AC would shift CP potential from the designed value, generating mis-leading information on the CP performance. Under a mild CP potential, e.g., -0.85 V (saturated calomel electrode, SCE), the AC would shift the DC potential of the steel negatively due to an enhanced dissolution of steel upon the AC application. When the CP potential was sufficiently negative, e.g., -1 V (SCE), the DC potential of the steel was shifted positively, but the AC application would not be able to affect the steel corrosion at a detectable level.