Abstract: The present invention provides methods of forming and detecting non-visible marks and articles marked in accordance with the methods. In accordance with the methods of the invention, a marking material is applied to a substrate to form a mark that is contrastable from the substrate in one or more regions of the infrared portion of the electromagnetic spectrum. The mark is covered with a film, which can be a bonded coating or a non-bonded covering sheet, that comprises an amount of one or more inorganic pigments such that the film appears opaque in the visible portion of the electromagnetic spectrum but is sufficiently transmissive in one or more regions of the infrared portion of the electromagnetic spectrum to facilitate the detection of the mark covered by the film. The non-visible marks can be applied to articles such as automobile parts, aircraft parts and other articles of manufacture to deter counterfeiting.

Abstract: The present invention provides inorganic pigments including cobalt and aluminum having the spinel crystalline structure that exhibit improved color and/or weatherability in paint and polymer applications. Inorganic pigments according to the invention are formed by adding small quantities of a phosphate compound such as aluminum phosphate and, optionally, chromium (III) oxide, to a raw batch that includes a mixture of cobalt-containing and aluminum-containing inorganic pigment precursors, and calcining the raw batch to obtain the inorganic pigment.