Magnetoscopy

Non-destructive testing by magnetoscopy (symbol MT) is a technique based on magnetic and/or electromagnetic fields. This technique is limited to surface defects but remains very interesting in that it is a global control method, unlike ultrasound or eddy currents which remain local control methods.


Magnetoscopy consists of applying a magnetic field to the part to be controlled so as to saturate it. The presence of surface defects will therefore give rise to fluxes of field leaks which will be highlighted using magnetic developers, colored in daylight or fluorescent under ultraviolet light (UV-A).

There are several ways to magnetize a part to be controlled: by an electromagnetic field (with alternating, rectified or direct current), by direct passage of current or also using a permanent magnet.

The parts after inspection require cleaning (possible elimination of the contrasting white background) and often demagnetization is required.

The main advantages that magnetic particle inspection presents over penetrant testing are the speed of the process and the fact of being able to detect surface defects even if they are closed. On the other hand, the limitation of magnetoscopy is that it only applies to ferromagnetic metals.