Frequency considerations for a system using phase information to detect and image corrosion in steel rebars located at distances of 8–9 cm

Abstract

Professor Gaydecki's group at The University of Manchester have imaged steel rebars using a system comprising of a square DC field generating coil with an array of sensors underneath, which produces an image without using a scanner. A square coil was used to generate an AC magnetic field allowing the skin depth principle to be used to detect corrosion. Also the receiver was placed in an orthogonal position instead of the original vertical position, enabling corrosion to be detected at deeper distances, particularly when using the phase information. When generating images of an area there is an optimum frequency range to enable the changes due to corrosion to be visualized.