Simultaneous Thickness Measurement of Double-Sided Coatings Using Acoustic Resonant Imaging Technique

In this study, the coating thickness of a double-sided coating processed by cathodic electrodeposition was measured and visualized using the acoustic resonant imaging technique. This method analyzes the resonant frequency and amplitude spectrum of echoes, enabling the visualization of thin coating thickness. Because changes in the coating thickness owing to the characteristics of the electrodeposition process are expected to influence the properties, we experimentally investigated the relationship between the coating thickness and the resonant frequency. An experimentally established relationship between coating thickness and resonant frequency indicated that a 33% reduction in thickness corresponded to an approximate 10% increase in sound velocity. Based on this relationship, the coating thicknesses on both surfaces were simultaneously visualized. Validation through cross-sectional microscopy confirmed the accuracy of the thickness measurements, with an average error of less than 2%, demonstrating the accuracy of this method for precise and simultaneous coating thickness evaluation.