Measuring Atmospheric Corrosion is Hard – AC vs DC Methods

Abstract The aspiration of atmospheric corrosion monitoring is to develop an electrode capable of accurately measuring the corrosion rate of metal in a given environment, ideally by detecting changes in electromagnetic properties. This study begins by reviewing the available techniques, including alternating current (AC) impedance measurements, direct current (DC) resistance measurements, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). For AC-based methods, different approaches using low- and high-frequency measurement techniques are considered. For DC-based methods, a Wheatstone bridge-based approach for measuring corrosion is explored. This analysis includes data collected both in the laboratory and in the field. The field measurements involve over 50 custom IoT sensors utilizing AC-based impedance measurements, deployed in various environments. The results indicate that while the sensors can detect some changes in the electrodes due to corrosion, confounding variables make interpretation challenging, especially in environments with highly volatile corrosivity. Additionally, the study demonstrates improvements in electrode design using a Wheatstone bridge-based approach and enhancements to impedance techniques through cyclic voltammetry.