An intumescent coating in the form of an initially liquid coating which cures to a solid and adheres to a substrate. The coating includes a flexible thermosetting epoxy, such as diglycidyl ether of bisphenol-A (DGEBA), with an aliphatic amine curing agent, expandable graphite flakes with reagent chemicals that react upon heating and decompose into gaseous products, and fumed silica. In the presence of heat or flame, an intumescent layer develops at the coating surface, insulating the substrate. The coating is found to add intumescent characteristics which provide heat resistant and fire retardant qualities.