Degradation Evaluation of Protective Coatings by Scanning Acoustic Microscopy and Current Interrupter Method

Abstract

Coating degradation has been generally evaluated by its surface appearance by visual observation. However, it is impossible to evaluate the inside of the coating, and corrosion beneath coating by the visual observation. The coating evaluation methods by the Scanning Acoustic Microscope (SAM) and the current interrupter method (CI) as the quantitative coating evaluation method with non-destructive technique are discussed. It was found that the SAM can quantitatively detect the interlayer blisters between coating films which were not detected by visual observation, while the CI method can not quantitatively detect the interlayer blisters between coating films. The correlation of SAM and CI was not able to obtain from this experiment.