The Liquid Penetrant Examination (PT)
This surface examination method allows the visualisation of defects and fissures being open to the surface. While the visual examination is able to reveal fissures having a width in the range of a millimeter or tenth of a millimeter, the detection limit of the liquid penetrant examination is in the range of 0,001 millimeter. The liquid penetrant examination can be applied on specimen consisting of almost all materials with a non-porous surface.
The liquid penetrant examination is based on capillary action. It supports the creation of outstandingly high contrast and strongly magnified indications by special penetrant agents.
Regarding creation of the contrast two main techniques of liquid penetrant examination are known:
- Color contrast penetrant test (red indications on white background)
- Fluorescent penetrant test (bright fluorescent indications under UV-light)