The magnetic particles inspection allows to detect the presence of surface and sub-surface ( a few millimeters) discontinuities inside of ferromagnetic materials by exploiting the phenomenon of ferromagnetism .Consequently to the magnetization of the piece, induced by the special equipment and following the application on its surface of a ferromagnetic product ( liquid or powder ) , the latter will tend to concentrate at the points where the magnetic field undergoes a deviation ( due to ” reluctance “of the material , in correspondence of discontinuity ) allowing to detect the presence and shape of the defects ( eg . cracks) that will become now clearly visible. This control technique can also be used with fluorescent products highlighted by the use of a UV lamp called ” black light ” allowing to obtain a higher sensitivity control.
