Magnetic Testing or MT
Surface control method, allowing the detection of through or slightly underlying cracks and discontinuities.
Using magnetic saturation, this method is only applicable to ferromagnetic materials. It can be carried out under UV lighting in a dark room with a fluorescent developer or under white light with a colored developer coupled with a contrasting agent.
The part to be inspected is subject to a magnetic field by direct or indirect magnetization, then sprayed with the developer which will accumulate at the magnetic field leakage lines created by the discontinuity. Detection is almost instantaneous.
The method is used in production (welding, foundry, forging, etc.) as well as in maintenance to detect fatigue cracks.