Cobalt octoate is the most active surface drier. Cobalt effects rapid surface drying and is generally used in conjunction with auxiliary driers. It is usually added at 0.05 to 0.4 % based on vehicle solids. It is a strong oxidant It is compatible with all surfaces coating media. Atmospheric humidity does not affect Cobalt drier. This unique feature prevents water vapor present in atmosphere from penetrating the paint film. Cobalt octoate being the most effective drier promotes polymerization of media, hardens the paint film, improves gloss and water resistance and reduces brittleness of film. The careful use of Cobalt octoate gives the paint film a good gloss, free from frosting tendency. This drier is a universal drier, which is essential in all the media and is capable of performing individually giving reasonable properties to the paint film.
In air-drying type insulating varnishes use of Cobalt octoate increases water resistance, but the excessive use of Cobait octoate causes brittleness and early failure of insulation. Cobalt octoate accelerates the catalytic action of Methyl ethyl ketone (M.E.K.) Peroxide to polymerize unsaturated polyester resin.
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