Effect of Asymmetric Epoxy Coating/Metal Electrodes on the Electrochemical Noise Measurements Under Marine Alternating Hydrostatic Pressure

摘要

Electrochemical noise (EN) is expected to be an in-situ evaluation method for coating performance in the real deep-ocean environment. The asymmetric factors of working electrodes (WEs) in EN configuration, including coating area, coating thickness, and coating impedance, were considered under marine alternating hydrostatic pressure (AHP) condition. The effect of WE asymmetry was discussed mainly by EN time records, wavelet analysis and shot noise method. The results indicated that coating impedance is the most important factor, and the coating with higher impedance contributes more to current noise in a pair of electrodes. The reason of asymmetry influence on EN measurements is mainly by the variation of average charge of current sources but not the current source frequency during the initial period of coating failure process. When the obvious corrosion of metal substrate happens, the corresponding EN proportion relationship between coating/metal WEs may be not exist.