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Raman Spectroscopy of Automotive and Architectural Paints: In situ Pigment Identification and Evidentiary Significance

NCJ Number
Date Published
July 2013
149 pages
This study examined whether Raman spectroscopy ever provided discrimination beyond that provided by FTIR spectroscopy in the identification of pigments as they occurred in automotive and architectural paint samples.

The study concludes that Raman spectroscopy provides additional discrimination in paint pigment beyond currently used methods (namely FTIR and/or EDS); however, thus far this additional discrimination has been observed in only a few samples. The researchers believe this additional discrimination will be of particular importance in certain cases that contain layers too thin to examine by FTIR spectroscopy, as well as in cases where no comparison sample is available. Raman microspectroscopy can be especially useful when attempting to determine whether known and questioned paints that appear to be the same based on their infrared spectra and elemental analyses may still exhibit some difference based on an independent chemical property that is not easily observed using EDS and/or FTIR. The automotive paint samples used in this work are "street" samples collected by soliciting local body shops. These shops were asked to remove a small piece of paints, including the substrate (plastic or metal backing) from vehicles requiring body repair; all samples were collected from damaged areas of vehicles. Twenty-eight sources participated, resulting in 328 samples. The sampling kits are described, and the quality index is discussed. Issues in researching color codes are addressed. The collection of automotive paint samples from a variety of sources resulted in a broad distribution of collected samples from 34 manufacturers. 6 figures, 2 tables, and an 86-item bibliography

Date Published: July 1, 2013