METHOD FOR DIAGNOSING CORROSION OF PIPE

PURPOSE:To detect the pipe axial direction component of the leaked magnetic flux caused by corrosion and the depth of the diameter of a thin-wall part by magnetizing a pipe to be diagnosed and allowing magnetic detection elements to run through the pipe along with an exciting coil to detect leaked magnetic flux. CONSTITUTION:Magnetic flux is generated in the normal part of a pipe so as to magnetically saturate the same by the exciting coil 4 wound around the small diameter part at the center of the axial line direction of a core 3 composed of a high permeability material. A plurality of magnetic detection elements 5 are arranged on the small diameter part of the core 3 at equal intervals L in the peripheral direction thereof. When there is no thin-wall part due to the corrosion in the pipe 1, the magnetic flux due to the coil 4 entirely passes through the thin wall of the pipe 1 and, therefore, no leaked magnetic flux is generated from the pipe and leaked magnetic flux is not detected by the magnetic detection elements 5. When there is the thin-wall part 6 in the pipe 1, the magnetic flux due to the coil 4 is leaked from the pipe 1 and detected by the elements 5.