ASTM B568-98 (2021) Standard Test Method for Coating thickness measurement by X-Rays Light spectrum provides a sensitive, non-contact, and non-destructive Measuring method for thickness measurement of metals and certain Non-metallic coatings ranging from 0.01 to 75 microns, depending on the coating and substrate material. This method is particularly suitable for coatings that are difficult to measure with Miscellaneous techniques, such as alkali combination coatings. Coating thickness is critical to coating performance, so the implementation of this test method helps to ensure coating mass and performance Stability. The standard does not address X-Rays radiation safety issues, and users need to refer to relevant safety regulations and ensure compliance before use.