Cobalt is an extremely active & most widely used drier in coatings & capable of being used even as a single Drier. It is primarily an oxidation catalyst & acts as a "Surface Drier". It may have a tendency to cause surface wrinkling, hence to provide uniform drying. Cobalt is generally used in combination with other metals, such as Manganese, Zirconium, Calcium & Combinations of these metals.
As quantity of Cobalt Drier used is very small, it minimizes discoloration in paints & enamels as compared with other Driers. Cobalt does not discolor white paints as the deep blue color of the cobalt counteracts the yellow of the oils & resins & thereby enhances the whiteness of the paint. The unique feature of cobalt is that it is least affected by atmospheric humidity. Cobalt is an effective accelerator for polyester.