Magnetic particle testing is a nondestructive testing (NDT) method that is used to detect surface and slightly subsurface discontinuities in ferromagnetic materials.

The test is performed by applying a magnetic field to the material and then introducing a fine iron or iron oxide powder, called magnetic particles, onto the surface of the material.

The magnetic particles will be attracted to areas of the material where there are discontinuities, such as cracks, and will form a visible indication that can be easily seen and evaluated.

This method is commonly used to inspect welds, castings, and other ferromagnetic materials for defects that could affect the strength and performance of the material.