Estimation of Ag coating thickness by different methods using a handheld XRF instrument

• Published in: Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms Beam interactions with materials and atoms, 2021-01, Vol.486, p.73-84
• Main Authors: Brocchieri, J., Scialla, E., Sabbarese, C.
• Format: Article
• Language: English
• Subjects: Ag layers; Handheld XRF; PLS regression; Thickness estimation; X-ray characteristic lines
• ISSN: 0168-583X; 1872-9584
• DOI: 10.1016/j.nimb.2020.11.006

•X-ray technique using an ED-XRF handheld spectrometer is applied.•Silver surface thickness of two-layered metal samples is estimated by different methods.•Kα, Kβ, Lα and Lβ lines of Ag and of elements of the substrate (Cu, Fe, Pb) are considered.•PLS regression model was applied on spectra file without any previous processing.•Reference layers were used to derive the calibration curves of the different methodologies. Precious objects are often made from a thin layer of metal (gold or silver) superimposed on another metal or alloy. Non-invasive XRF analysis is widely used on these objects to determine the composition and thickness of the surface layer. Here, silver surface thickness of two-layered metal samples using an ED-XRF handheld spectrometer is estimated by different methods whose results are compared. These methods involved the relationships between the intensities of the characteristic lines of Kα, Kβ, Lα and Lβ of Ag and of elements present in the substrate (Cu, Fe, Pb) and some of their combinations, as well as the PLS regression. Reference layers were used to derive the calibration curves of each methodology. PLS method was the most accurate, but the other methods were also found suitable for the purpose. Applications have been successfully made on an ancient Roman coin and a modern silver-plated object.