Discrimination of 1990s original automotive paint systems: A collaborativestudy of black nonmetallic base coat/clear coat finishes using infrared spectroscopy

The 1990s saw the introduction of significantly new types of paint binder c hemistries into the automotive finish coat market. Considering the pronounc ed changes in the binders that can now be found in automotive paints and th eir potential use in a wide variety of finishes worldwide, the Paint Subgro up of the Scientific Working Group for Materials (SWGMAT) initiated a valid ation study to investigate the ability of commonly accepted methods of fore nsic paint examination to differentiate between these newer types of paints . Nine automotive paint systems typical of original equipment applications were acquired from General Motors Corporation in 1992. They consisted of st eel panels coated with typical electrocoat primers and/or primer surfacers followed by a black nonmetallic base coat and clear coat. The primary purpo se of this study was to evaluate the discrimination power of common forensi c techniques when applied to the newer generation original automotive finis hes. The second purpose was to evaluate interlaboratory reproducibility of automotive paint spectra collected on a variety of Fourier transform infrar ed (FT-IR) spectrometers and accessories normally used for forensic paint e xaminations. The results demonstrate that infrared spectroscopy is an effec tive tool for discriminating between the major automotive paint manufacture rs' formulation types which are currently used in original finishes. Furthe rmore, and equally important, the results illustrate that the mid-infrared spectra of these finishes are generally quite reproducible even when compar ing data from different laboratories, commercial FT-IR instruments, and acc essories in a "real world," mostly uncontrolled, environment.