Coating Measurement Using Handheld X-Ray Fluorescence

McDowell, Dillon; Olympus Scientific Solutions America; United States

Faulkner, P.; Olympus; USA
Paklin, K.; Olympus; USA

ID: ECNDT-0111-2018
Session: Surface Methods 1
Room: R2
Date: 2018-06-14
Time: 10:00 - 10:20

Handheld X-ray fluorescence (HHXRF) can be used to measure coating thicknesses, with advantages in precision and portability compared to other technologies. Analyzing coatings applied over large surface areas often requires destructive procedures for benchtop analysis. HHXRF overcomes this limitation and provides a nondestructive coating thickness testing capability.

A simple, user-friendly calibration built into the instrument interface enables the use of a certified standard to determine up to three layers of accurate and precise coating thicknesses. HHXRF coating measurements, which are independent of the substrate material, provide a user freedom to analyze any deposited coating comprised of elements Ti through Pu. Due to the large elemental range of analysis, many corrosion, wear, and adhesion coatings determined from labs near the site of action can benefit from the precise results returned by HHXRF.

The physics behind the coating analysis is driven by the Lambert-Beer law of absorption, where the intensity of the X-ray entering a sample is highest upon the first layer and the intensity of the X-ray exiting the layer decreases. Upon entering a second layer, the intensity of the X-ray entering the sample has decreased because a portion of the intensity was absorbed by the previous layer. The intensity of the X-ray entering the sample will continue to decrease as it is absorbed by the layers in an exponential relationship, the quantity of which is dependent on the physical properties of the sample.

Lambert-Beer Law of Absorption
I_t = I_0 〖exp〗^(((-MAC)*ρ*t))

I_t = intensity of the X-ray exiting the sample
I_0 = intensity of the X-ray entering the sample
MAC = mass attenuation coefficient of the sample
ρ = density ofthe sample
t = thickness of the sample