Magnaflux

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Magnafluxing, developed originally by Carl E. Betz, is a method of testing ferrous metals for surface and subsurface flaws. The component being tested must be made of a ferromagnetic material such as iron, nickel or cobalt, or some of their alloys. This test is often used on industrial tools, and engine parts during maintenance inspections. It can also be used to diagnose failure, as in crash investigations.

It works by applying a magnetic field to the component under test, using e.g. a permanent magnet. This will cause a high concentration of magnetic flux at surface cracks, which can be made visible by dusting iron powder or a similar magnetic material over the component.

Parts can be tested using one of two methods. The wet method consist of bathing the parts in a solution containing iron oxide particles. The wetted part is then placed in a magnetic field and inspected using a black light (ultraviolet light). The iron oxide particles are attracted to surface discontinuities or cracks, where the magnetic field is discontinuous. The particles flux around the imperfections and the patterns are visible under the black light.

The dry method is based on the same principle. Parts are dusted with iron oxide particles and charged using a yoke. The particles are attracted to the discontinuities and are visible by black light.