Because magnetization of certain metals is possible, it is possible to reveal discontinuities by using a medium (iron powder) having magnetic attraction.

The medium is applied to the surface of the test object after or during induction of a magnetic field.

The sketch below shows a build-up of the magnetic particle medium over the discontinuity in the magnetized part.

Magnetic Particle testing is a relatively easy and simple test method that can be applied at various stages of manufacture and processing operations.

Advantages:

¨    Easy to learn

¨    Easy to be automatized, except for visual observation

¨    Highly sensitive

¨    May be applied on parts slightly layered

¨    Flaw indications are easy to be understood.

¨    Has good accessibility

Limits:

¨    Can be applied only on magnetic materials and can only detect supoerficial or sub-superficial flaws.

¨    Part geometry and dimension may limit the use of some examination techniques.

¨    Demagnetization, if required, may be difficult if very low level of residual magnetism are required.