Infrared spectra of North American automobile original finishes. XI: In situ identification of perylene pigments—Analysis of Perylene Maroon (C.I. Pigment Red 179) and alumina-based red pearlescent pigments

Abstract

Four perylene pigments were identified in North American automobile original finishes (1974–2019) and the analysis of Perylene Red Y (C.I. Pigment Red 224) was described previously. Perylene Red Y was not a common automotive paint pigment and is no longer used much. The analysis of a second member of the perylene family, Perylene Maroon (C.I. Pigment Red 179), is discussed in this article, and to determine the commonality of its use, spectra of 143 red or maroon metallic original basecoats were examined. Based on this survey, Perylene Maroon was found to be the most common organic pigment used in these. A large number of different pigment combinations involving this perylene were also identified and representative spectra of some of these are presented to illustrate the wide diversity of infrared absorption patterns that result. The individual pigments composing these combinations can often be identified, and this information can be helpful for both classifying and identifying automotive finishes. For red or maroon metallic basecoats produced after the mid-1980s, red pearlescent pigments based on mica became widely used and their identification was discussed previously. More recently, comparable effect pigments using alumina substrates were introduced and the identification of red alumina-based pearlescent pigments is described in this report. Three very unusual automotive paint formulations were identified and their spectra are presented to aid in vehicle identification.