It is crucial to test any machine or material consisting metal in order to prevent major discontinuities.
Magnetic Particle Inspection (MPI) is a nondestructive testing process that detects discontinuities (seams, laps, grinding and quenching cracks) on surfaces and subsurfaces of iron, nickel, cobalt, their alloys and other ferromagnetic materials.
A magnetic field is put into the ferromagnetic part and is magnetized by direct or indirect magnetization. If the ferromagnetic part has a discontinuity, then it will interrupt the magnetic field flow and a leakage field will occur. An application called magnetic media is then used to coat the part and form a mark over the discontinuity. The mark can only be visible under proper lighting conditions.
Wet– More sensitive since it gives the magnetic particles more mobility because it is a liquid. There are two types of wet particles: One is visible and can be viewed under normal white light while the other is fluorescent and can only be viewed under black light.
Dry– More of a dust that is light and more portable. It comes in a variety of colors so that a color can be chosen that produces a high level of contrast against the background of the ferromagnetic part
