Disclosed is a rigid or flexible conduit usable particularly for transporting fluids and enabling to limit the permeability to transported fluids. According to the invention, the conduit comprises at least an inner flexible sheath (1) made of thermoplastic, elastic, or rubber material and an outer sheath (10) comprising a metal layer (3) and arranged around said inner sheath (1). Said metal layer comprises at least a layer of flat metal band (3) which is spirally wound with a winding angle alpha higher than 50o and lower than 90o with respect to the axes of the conduit. For rigid conduits, said metal layer (3) is adhered to said inner flexible sheath (1) on the major part of the width of the band (3). For flexible conduits, the turns present superposition areas so as to provide for a complete covering of said inner sheath (1), the superposition areas (30) of the band turns on one hand and the areas comprised between said superposition areas on the other hand, having each a width at least equal to amplitude of the deformation imposed to the outer sheath by the maximum bending or traction of the conduit. Application particularly to the transportation of corrosive fluids under pressure, to the oil industry at the drilling site or the production.