Volume 35, Issue 5 (September 1990)
Analysis Protocol for Discrimination of Automotive Paints by SEM-EDXA Using Beam Alignment by Current Centering
A testing protocol for elemental analysis of automotive paint by scanning electron microscopy/energy-dispersive X-ray analysis, based on beam alignment by current centering and using an attached optical microscope was developed to improve the reliability of sample comparisons. Six light-green paint samples (three color pairs) from the 1983 Reference Collection of Automotive Paints were used for developing this protocol. X-ray spectral data were acquired using a JEOL JSM-35CF scanning electron microscope with an attached optical microscope and a Tracor Northern energy-dispersive X-ray analyzer and software. The instrumental conditions for the analyses were as follows: 20-kV accelerating voltage, 0.5-nA beam current, 30-mm detector distance, 35° detector take-off angle, 0° sample tilt, and × 200 magnification. The software acquisition parameters were 1 000 000 integral counts per spectrum and a 0.2 to 10-eV spectral range. Statistical analyses were used to examine the reliability of the X-ray spectral data acquired using this protocol. A one-way analysis of variance (ANOVA) indicated that the elemental means of all paint samples were significantly different than the means of the same sample in replicate analyses. Simple visual comparison of data between samples, along with ANOVA, provided discrimination of all paint samples.