Magnetic particle testing (MT) is a method for detection of surface and near-surface discontinuities in ferromagnetic materials.
When a ferromagnetic material with a discontinuity at the surface is magnetized, a magnetic leak field is created on the surface at the place where the discontinuity is located.
This leak field behaves like a small magnet, which attracts other magnetizable particles. Magnetic testing uses either small powdered ferromagnetic particles or particles in a suspension as a detection agent to visualise the leak fields.
Magnetic particle testing can be applied to all ferromagnetic materials and can be used during the various stages of production to detect production discontinuities, and in the control of parts that have been in service to detect operational discontinuities. It is a fast and effective method that allows discontinuities open to the surface and right underneath it to be detected.