Abstract: A hydraulically efficient metal pipe particularly adapted for use in storm drain and sanitary sewer applications which is adapted for use with a self-supporting interior inert protective lining. The pipe has a channeled wall defining a plurality of outwardly projecting structural ribs and a hydraulically smooth interior surface. The ribs are preferably of a helical configuration and the channels which are formed interiorly thereof are generally either square or rectangular in cross-section and are open along the interior surface of the pipe. The walls defining the ribs can be tapered inwardly to form triangular-shaped channels so as to define an anchor througout the length of the pipe for securing thereto a smooth interior lining of corrosion-resistant protective material.