ELECTROCHEMICAL BEHAVIOR AND INTERNAL CURRENT OF THE MOST ANODIC ELECTRODE IN A COUPLED MULTIELECTRODE ARRAY SENSOR

摘要

The current measured from the most anodic electrode of a coupled multielectrode array sensor (CMAS) is often used to derive the localized corrosion rate. This approach is accurate only if the internal anodic current from the most anodic electrode is negligibly small. In this paper, the internal anodic currents on the most anodic electrode in a CMAS probe were evaluated for carbon steel in simulated seawater and a dilute (0.2 wt%) hydrochloric acid solution. In the simulated seawater, carbon steel corroded dominantly in the form of localized corrosion and the internal anodic current only accounted for 7% of the total corrosion current on the most anodic electrode. However, in the dilute hydrochloric solution, carbon steel corroded dominantly in the form of uniform corrosion and the internal anodic current accounted for 44% of the total corrosion current on the most anodic electrode. The CMAS probes are effective tools in localized corrosion rate measurements. In cases where uniform corrosion is dominant, the CMAS probe measures only the localized portion of the corrosion, but not the uniform portion of the corrosion.