Magnetic testing is a non-destructive testing process for detecting surface and slightly subsurface discontinuities in ferromagnetic materials such as iron, nickel, cobalt and some of their alloys.
The process induces a magnetic field in the part. The presence of a surface or subsurface discontinuity in the material allows the magnetic flux to leak. Ferrous iron particles are applied to the part.
The particles may be dry or in a wet suspension. If an area of flux leakage is present the particles will be attracted to this area. The particles will build up at the area of leakage and form what is known as an indication.
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