Assessment of Electrical Resistance Sensors Sensitivity to Localized Corrosion

ABSTRACT This paper investigates the sensitivity of electrical resistance (ER) sensors to localized corrosion. Analytical models were developed to simulate the ER sensor response to various geometries of localized attacks. These theoretical predictions were validated against experimental data, including controlled electrochemical dissolution and realistic sodium chloride exposure. The comparison revealed a strong correlation between the models and experimental measurements, highlighting a critical limitation of the resistometric method: ER sensors severely underestimate the actual depth of localized attacks. Specifically, models demonstrate that for a localized attack covering less than 5% of the sensor's measuring area, a defect consuming 80% of the initial thickness yields an apparent overall sensor reading of merely 20% thickness loss. Furthermore, under practical NaCl exposure scenarios, actual pit depths reaching 50 µm resulted in sensor readings of only 11 µm. These findings are essential for the accurate interpretation of ER sensor data and the implementation of appropriate safety margins in industrial applications.