US Patent 7169480 Clad pipe

A clad pipe includes an external layer and a coating layer made of Ni base anticorrosion alloy. Both end portion areas of the coating layer are formed by a build-up welded layer (Ni base alloy of composition 1) on the inner surface of the external layer. Other areas are formed by a Ni base alloy layer (Ni base alloy of composition 2) fusion-bonded to the build-up welded layers and the inner surface of the pipe, a solidus-curve temperature of the Ni base alloy layer being 1300° C. or below and lower than a solidus-curve temperature of the Ni base alloy formed by build-up welding by 150° C. or more. Composition 1 and composition 2 are adjusted so that, in the same environment, corrosion resistance of the Ni base alloy of composition 1 is equivalent to or superior to that of the Ni base alloy of composition 2.