It is an inspection method used to detect surface defects. Errors do not have to be obvious to the inspection surface


Scientific Basis 
If a magnetic flux is applied to the inspection surface, leakage flux occurs on the discontinuities on the surface, depending on the positioning on the surface. In the meantime, if ferromagnetic dusts are sprinkled on the inspection surface, these dusts are drawn by the stray fluxes and collected on discontinuities. Thus, the locations of the discontinuities can be determined.

Scope of application 
It can be applied to all ferromagnetic materials.
It cannot be applied to non-ferromagnetic materials. If the discontinuity is not positioned at an angle appropriate to the applied magnetic field direction, it cannot be determined. Very high magnetizing currents may be required for large parts. Too rough examination surface affects the result negatively. If there is a paint or coating on the inspection surface, its thickness directly affects the inspection result. Generally, additional operations such as demagnetization and final cleaning are required after the inspection.