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Penetrant testing (PT)

Penetrant testing (PT) is a widely applied and low-cost inspection method. This NDT method detects discontinuities, e.g. cracks, laps, porosity, lack of fusion, lamination, fatigue failure which are open to the surface of the material to be tested. It is mainly applied to metallic materials, but can also be performed on other materials, provided that they are inert to the test media and not excessively porous (castings, forgings, welds, ceramics, glass, etc.)

Prior to penetrant testing the surface to be inspected shall be cleaned and dried. Penetrant can be applied to the part to be tested by spraying, brushing flooding, dipping or immersion.  Suitable penetrants are then applied to the test area and enter into discontinuities open to the surface. The appropriate penetration time depends on the properties of the penetrant, the application temperature, the material of the part to be tested and the discontinuities to be tested. The penetration time is between 5 min and 60 min. After the appropriate penetration time has elapsed the excess penetrant is removed form the surface and the developer applied. The developer absorbs the penetrant that has entered and remains in the discontinuities and may give a clearly visible enhanced indication of the discontinuity.