Pipe corrosion inspection is another application of in-line inspection technologies: based on the magnetic flux leakage (MFL) principle, install magnetic induction probe, electronic recorder and battery pack on the pig, so as to convert it into a corrosion inspector; if the inspector encounters metal defects  on the pipe wall when running in the pipe, the magnetic induction probe will detect and record the distorted leakage magnetic field; after taking out the inspector, read the technical data on the recorder, and analyze with data analysis software, so as to confirm the metal loss area, depth and position of the pipe.