Driers for Paints Cobalt
Cobalt is without a doubt the most important and most widely used drier metal in coatings. It is primarily an oxidation catalyst and, as such, acts as a "surface" or "top drier." Used alone, it may have a tendency to cause surface wrinkling; therefore, to provide uniform drying, cobalt is generally used in combination with other metals such as manganese, zirconium, rare earth, calcium and combinations of these metals.
Due to the fact that it is necessary to add only very small amounts of cobalt driers, cobalt minimizes discoloration in paints and enamels as compared with other drier metals. Additionally, cobalt does not discolor white paints, since the deep blue color of the cobalt counteracts the yellow of the oils and resins and thereby enhances the whiteness of the paint. Cobalt is almost always used as a drier in white coatings.
Owing to their high activity, cobalt driers should preferably be added as near to the end of the manufacturing process as possible.