Measuring coating thickness was one of the first applications of x-ray fluorescence spectrometry and is still one of the most common uses of the technology. So, the majority of analyzer certifications that Eastern Applied Research technicians provide are for coating thickness applications and those certifications actually reference the ASTM Standard B568. This standard is titled ‘Standard Test Method for Measurement of Coating Thickness with X-Ray Spectrometry,” and operators of ED-XRF systems (especially those new to the technology) may find it beneficial to take a few moments to read the standard.
Information That ASTM B568 Provides
While energy dispersive analyzers (ED-XRF) are more commonly used for coating measurements, the standard also covers the use of wavelength dispersive (WD-XRF) analyzers. The document lists the scope of the standard as covering “the use of x-ray spectrometry to determine thickness of metallic and some nonmetallic coatings.”
The benefit to operators is that it details the variations in x-ray spectrometry systems and explains how XRF works with some terminology that may be useful. It also provides an overview of calibration techniques and best practices along with standard-less (fundamental parameters) calibrations.
Most Important: Factors Affecting Accuracy
In the opinion of Eastern Applied Research associates, the most important part for an XRF operator to review is the section on “Factors Affecting Accuracy.” Some variables that most users could guess would affect results are covered – those include measurement time, size of measurement area, coating composition, detector technology, etc. However, the ASTM B568 standard also details some variables that an operator may not think of; such as sample curvature, substrate composition, and surface cleanliness. In all, thirteen (13) factors are highlighted and worth knowing about in case issues occur.
This industry standard (ASTM B568) should be reviewed by all operators of x-ray fluorescence because it offers a beneficial overview and highlights proper implementation of the technology. Associates and XRF Technicians from Eastern Applied Research are always happy to discuss technology concepts and help with any questions relating to this standard or any others that relate to XRF – contact Eastern Applied for a discussion.
NOTE: It is important to note that ASTM B568 does not detail safety procedures relating to operation of x-ray spectrometry and refers the reader to the appropriate governing bodies and regulations. Eastern Applied associates are available to help with safety radiation related questions and training if needed.