What is the best dye to use to obtain a very dark black coating on aluminum?
There are several organic dyes that can be used to achieve a black color; these dyes are available to anodizers from several suppliers. Chemical suppliers can offer advice regarding the specific application. Dye selection depends upon alloy and application. What works well for exterior may not yield good results for interior applications. Another means is an electrolytic coloring, a post-anodic coating procedure where AC current is applied to the anodized part in an electrolyte consisting primarily of tin sulfate, sulfuric acid, and various stabilizing agents. This may not produce the “deepest” blacks, however. Choice of alloy, coloring media, and coating thickness may affect the depth or intensity of color. The surface pretreatment is also important … the eye will perceive a “darker” black on a smooth (buffed) surface than on a heavily etched surface.
