Coating Thickness Measurement – WDXRF¹ Technology

Coating thickness measurement is an essential factor for manufacturing industries due to coating’s essential role in product quality, process control, and cost control. Defective or substandard coating can lead to corrosion. Too little coating results in inadequate protection, while too much coating wastes chemicals, is costly, and can result in an uneven surface and adhesive issues.

WDXRF (Wavelength Dispersive X-ray Fluorescence)

Each WDXRF test is conducted by first specifying what element is to be measured. The testing uses X-ray energy to excite electrons on the target surface. For example, if we decide to test for the presence of Chromium (Cr) present, with the goal of measuring how much Chromium is present on the sample, this is the process involved:

1. 1. The X-ray tube directs a beam of primary radiation onto the sample of the material. This energy excites the electrons on the sample and frees them from their atomic orbits forcing higher-level orbitals to move to lower orbitals and releasing fluorescence radiation energy.
   2. The primary radiation causes the sample to emit secondary fluorescence radiation that contains a characteristic wavelength for each element present in the sample.
   3. The X-rays are focused using a source collimator which directs and aligns the radiation at a specified angle from the sample.
   4. To eliminate radiation other than the target wavelength, a crystal is used to channel the radiation in a parallel way to arrive at the detector.
   5. The crystal splits the fluorescence spectrum of the electrons into individual wavelengths for each element present in the sample.
   6. The electron energy emitted of each element has a different radiation signature which can be identified by the wavelength of the fluorescence emoted.
   7. The reflected radiation passes through a receiving detector that captures and counts the number of electrons present which meet the specified wavelength criteria.
   8. The resulting count is then converted into a coating weight using predetermined proprietary algorithms.