Epoxy functional acrylic coating powders and powder coatings therefrom having improved filiform corrosion resistance

Abstract

The present invention provides coating powders that enable improved filiform corrosion resistance in clear or tinted clear coating comprising an epoxy functional acrylic copolymer component having a Tof from 40° C. to 90° C. and chosen from a copolymer or copolymer mixture that comprises, based on the total weight of copolymerized monomers in the epoxy functional acrylic copolymer component, i) from 10 to 40 wt. % of one or more epoxy functional unsaturated monomer, e.g. glycidyl (meth)acrylate; ii) from 2.0 wt. % to 13 wt. %, preferably 12 wt. % or less, or, more preferably, 6 wt. % or less, of one or more hydrophobic acrylic monomer that has a mass solubility in water of 3.5 g/L or less and which would itself form a homopolymer having a glass transition temperature (T) of 50° C. to 175° C., e.g. a bicycloalkyl(meth)acrylate, and iii) the remainder of one or more nonionic comonomer that is not a hydrophobic acrylic monomer ii), e.g. methyl methacrylate; one or more crosslinker for the thermosetting acrylic copolymer; and, optionally, one or more adhesion promoter, e.g. epoxy resin, a light stabilizer, an ultraviolet (UV) absorber, and/or a hydrophobic submicron particle.