Magnetic Particle Inspection
Magnetic Particle Inspection uses a magnetic field to locate surface and near-surface discontinuities in ferromagnetic materials. When very fine ferromagnetic particles are applied to the surface of the part and the magnetic field encounters a discontinuity the particles will be drawn into the discontinuity, producing a visible indication on the surface of the part.
Florescent Penetrant Inspection
Florescent Penetrant Inspection uses a very low viscosity fluorescent liquid which is applied to the surface of a part, it penetrates into defects on the surface. Once the excess penetrant is removed, the penetrant trapped in those defects will flow back out, creating an indication which can be seen under black light. Penetrant testing can be performed on magnetic and non-magnetic materials, but does not work well on porous materials.