Magnetic Particle Inspection

MPI testing is carried out on carbon steel or other ferromagnetic alloys. Surface and subsurface indications (flaws) are detected by applying ferrous iron particles and a magnet across the part being tested. A flaw in the material will disrupt the magnetic field created by the magnet and it is this disruption which attracts the ferrous iron particles. These particles are fluorescent when viewed under UV (ultraviolet) light and so highlights the flaw to the operator.