Magnetic Particle Testing (MT) is a Non-Destructive Testing method through which the examiner can locate surface-breaking and sub-surface defects in ferromagnetic materials. A magnetic field is applied, creating a flux leakage at the location of any defects. Iron oxide particles are then applied to the inspection surface, either in dry form or in a wet suspension. The flux leakage field will attract the iron particles, forming an indication on top of the surface material. This indication is then evaluated in accordance with required standards.
This test can be performed in daylight or in a darkened room. For daylight testing white paint is used to contrast the black particles, resulting in clearer indications. Alternatively, a dark room with UV lighting can be used in combination with fluorescent particles for increased inspection sensitivity.