Development of a novel method to measure the film thickness of cured can coatings

A new technique was developed for measuring the thickness of can coatings applied to a metal substrate. A metal disc with a known radius creates a small indent in the coating, stopping exactly when the coating thickness is cut through. The indent length is employed to calculate the coating thickness. Accurate measurement of thin films is achieved as the indent is much larger than the respective film thickness. The thickness of epoxy phenolic coatings on tinplate were measured and the results were validated by micrographic cross section analysis and by confocal laser scanning microscopy (CLSM). The coating thicknesses measured using the indentation method coincide with the film thicknesses measured by CLSM, whereas discrepancies were observed using the micrographic cross section analysis. The new technique, presented in this paper, uses simple equipment, is inexpensive, fast and easy to use, and is suitable for film thickness measurements in laboratories and production plants.