Magnetic Participle Inspection is a common method for inspecting welds for discontinuities located on or just below the surface. A thin layer of white contrast paint is applied, and the item is magnetized using a hand magnet (yoke). A magnetic particle fluid is sprayed over the item, and any cracks or irregularities disturb the magnetic field, causing the magnetic particles to accumulate and form a visible indication of the defect.

Advantages:

• Quick and relatively easy to perform.

• Suitable for complex shapes and welds.

Limitations:

• Only applicable to ferromagnetic materials.
• Detects only surface and very shallow defects (up to about 3 mm deep).
• The orientation of the defect relative to the magnetic field is crucial.