Measurement of Paint Film Thickness on Prepainted Steel Sheet by Compton Scattered X-ray

A new method for rapid meaurement of paint film thickness on prepainted steel was developed. In the developed method, intensities of Compton scattered X-ray from samples were measured as a indicator of paint film thickness by X-ray fluorescence spectrometer and RhKα from X-ray tube was used for the incident X-ray. It was confirmed by experiment that intensities of Compton scattered X-ray from bulk samples were proportional to the reciprocal of absorption coefficients of X-ray in bulk. Intensities of Compton scattered X-ray from prepainted steel sheets were influenced by chemical composition of paints and amounts of Zn coating on steel sheets, and these influences were corrected by XRF intensities of individual elements measured simultaneously with Compton sacttered X-ray intensitity. Informations on samples such as densities of paints and amounts of Zn coating gave more accurate results. The reproducibility of values by the developed method was 0.15μm and the accuracy (variance of differences between data by the developed method and data by gravimetry) was 0.8 μm.