Typical sequence of operations to inspect a weld:

Clean area to be tested

Apply contrast paint

Apply magnetism to the component

Interpret the test area

Post clean and de-magnetize if required

Apply Ferro-magnetic ink to the component during magnetizing

Main features for Magnetic Particle Inspection:

Surface and slight sub-surface detection

Relies on magnetization of component being tested

Only Ferro-magnetic materials can be tested

A magnetic field is introduced into a specimen being tested

Methods of applying a magnetic field, yoke, permanent magnet, prods and flexible cables.

Fine particles of iron powder are applied to the test area

Any defect which interrupts the magnetic field, will create a leakage field, which attracts the particles

Any defect will show up as either a dark indication or in the case of fluorescent particles under UV-A light a green/yellow indication


Simple to use


Rapid results

Little surface preparation required

Possible to inspect through thin coatings


Surface or slight sub-surface detection only

Magnetic materials only

No indication of defects depths

Only suitable for linear defects

Detection is required in two directions