Coating composition containing metal-coated microspheres exhibiting improved resistance to environmental attack of metallic substrates

Abstract

A coating composition for the protection of metallic substrates against environmental attack comprising, in weight percent, from about 10% to about 30% of at least one film-forming polymer such as epoxy resins having an epoxide value of about 250 to about 2500, vinyl chloride resins copolymerized with polyisocyanates, polyurethane resins, and polyester resins; from about 40% to about 55% particulate metallic zinc; from about 4.75% to about 7% zinc-coated hollow glass-like microspheres having diameters ranging from about 2.5 to about 60 microns, the volumetric ratio of the metallic zinc to the microspheres ranging from about 0.8:1 to 1.2:1; from about 1.5 to about 3% of at least one particle size grade of pyrogenic amorphous silica having an average particle size ranging from about 0.007 to about 0.04 micron; and not more than 30% solvents compatible with the film-forming polymer. A dried coating of this composition, having a thickness of at least about 4 mils (about 100 microns), is cathodic and electrically non-conductive.

Dependencies are inferred from the claim text.