Potential drop mapping for the monitoring of corrosion or erosion

Potential drop techniques have been employed in the power generation industry for the medium- and long-term monitoring of corrosion and/or erosion, but little quantitative data are available in the literature. The present work aims to determine how accurately the maximum depth of a defect on the far side of an inspected structure can be estimated from low-frequency potential drop measurements as a function of the shape and size of the defect itself and of the geometry of the probe. Finite Element simulations show that the electrode array configuration commonly used in existing commercial setups can lead to an underestimation of the defect depth. The novel electrode arrangement proposed in this paper overcomes this problem and is shown to give satisfactory estimates of the depth of defects as small as about twice the probe pitch. Experimental results confirm the numerical predictions and show that the quality of the reconstruction does not depend significantly on the relative position of the probe and the defect.