Abstract: Disclosed is a heat-curable powder coating composition that allows the formation of a coating film having outstanding long-term corrosion resistance, as well as outstanding chipping resistance, flexibility, and adhesion. The disclosed heat-curable powder coating composition is characterized by a resin having crosslinkable functional groups that are solid at room temperature (A), a curing agent capable of reacting with said crosslinkable functional groups (B), a fibrous filler (C), and heat-expandable resin particles (D).

Abstract: A powder coating composition for forming a low gloss coating film based on thermosetting polyester resins exhibiting only a little fluctuation of the resultant low gloss value even if an unequality in the mixing proportion of components or in the baking condition exists, comprising three thermosetting polyester resins (A), (B) and (C) and a hardener (D), wherein the weight ratio of the polyester resin (A) to the polyester resin (B) is in the range of 90/10-70/30 and that of the polyester resin (A) to the polyester resin (C) is in the range of 85/15-60/40 and the equivalent ratio of the polyester resin (A, B or C) to the hardener (D) is each in the range of 0.8 to 1.25 and wherein the polyester resins (A), (B) and (C) are selected from those in which the moduli of elasticity E.sub.a, E.sub.b and E.sub.c for the products of the curing reaction of these resins with the hardener (D), respectively, after 3 minutes' curing with the hardener (D) at 200.degree. C.