A stamped coin exhibited visible discolored areas, seen as a tan haze on the surface (Fig. 1). In this case, the discoloration was considered merely cosmetic. The nonstained and stained regions were studied using a scanning electron microscope equipped with an energy-dispersive X-ray spectrometer (SEM/EDS). The SEM allows for high-magnification study of surfaces by utilizing electrons instead of visible light. This instrument is equipped with magnetic lenses and Tinting on these copper parts is evident in this photograph Introduction This paper describes several instances where discoloration was a key element in component failure. Discoloration of the surface of a component can be the result of many different factors, and its effect on function can range from simple visual anomalies to complete failure. Discoloration is generally caused either by the presence of adherent contaminants or by chemical changes on the surface. Sometimes discoloration is merely cosmetic, but even cosmetic changes may lead to part rejection in instances where appearance is of great importance. Additionally, discoloration can be an indicator of more serious problems, including adherent contaminants, thermal excursions, and/or corrosion, which could lead to eventual malfunction or complete failure. In any case, it is important to understand the analysis techniques that can be used to characterize surface discoloration and how these techniques can be used to determine the nature, cause, and relevance of the discoloration to the function of the component.