Correlation between Terahertz Imaging and Electrochemical Impedance Measurements in Detection of Rust Regions in Coated Steel Plates (特集テラヘルツ波)

概要

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An accelerated aging test has been carried out to reveal correlations and differences between terahertz imaging and electrochemical impedance measurements in the detection of rust regions in coated steel plates. Intensity distribution measurements of reflected THz waves use the absorption characteristics of rust. Therefore, a good correlation between the THz reflection absorption and the proportion of the rust area relative to the total specimen area has been found. Electrochemical impedance gradually decreases with age, which shows the effectiveness of this measurement technique. A good correlation between values of THz absorption and film impedance indicates the possibility that THz measurements can evaluate the extent of degradation. The observed frequency spectra of the complex impedance are similar to what is observed in dielectric materials containing many charges. This is based on the assumption that impedance measurements affect the water blocking ability of the coating.