Magnetic particle inspection, also known as Magnaflux testing, allows to detect and locate superficial and sub-superficial defects. This technique can be used only for ferromagnetic materials. The pieces to be inspected are magnetized, then a wet suspension or a dry powder containing fine iron oxide particles with high magnetic permeability are spread on their surfaces. Discontinuities distort the magnetic field and magnetic particles are attracted in these areas. Final inspection may be performed under natural light, if visible dry method has been applied, or in a dark environment, under the Wood’s lamp, in case of fluorescent magnetic particles.