Abstract: A primer composition for coating a substrate prior to application thereon of an intumescent fire protecting coating composition, the primer composition being a powder coating composition consisting of an extruded and subsequently ground mixture of binding agents, hardening agents and optionally one or more of optional pigments, optional filler, and optional additives, and a porous material in a proportion of one to twelve percent by weight of the powder coating composition. The porous material is mesoporous or microporous.

Abstract: The present invention proposes an expandable powder coating composition for formation of a coating layer on a metallic article, comprising epoxy resin and a curing agent for curing said epoxy resin, wherein said expandable powder coating composition further comprises heat expandable polymeric microstructures with a weight ratio within the range of 0.5-10% (w/w) with respect to the total mass of the expandable powder coating composition, said heat expandable polymeric microstructures having a shell comprising a thermoplastic, encapsulating a fluid core and the glass transition temperature of said thermoplastic is within the range of 90 to 180° C. The present invention further proposes a method for powder coating on a metallic article.