A duct section and system, including a laminated shroud, acting as a secondary duct, for aerospace and other applications, and a method for constructing same. The duct structure incorporates a metallic primary duct tube, with a laminated shroud surrounding the primary duct tube and separated therefrom by an annular gap. The laminated shroud includes a metallic inner layer and a polymeric outer layer. Preferably, the thin metallic layer is a corrosion resistant material such as corrosion resistant stainless steel or titanium. In one embodiment of the invention, the outer polymeric layer is a polyimide material, such as polyimide resin-impregnated fiberglass cloth.