Penetrant Testing or PT
Surface control method, allowing the detection of discontinuities or cracks that only lead to the surface.
The part to be inspected is covered with a colored penetrant (red or fluorescent) with very low surface tension, which is introduced into the finest cavities and open discontinuities of the material. After rinsing, usually under clear water, a developer is applied by spraying over the entire controlled surface. As it dries, it will deposit a thin whitish layer which, due to the capillarity phenomenon, will cause the penetrant to rise out of the discontinuities and thus mark the defect with a red linear indication.
The method can be applied to many materials such as steels, aluminums, ceramics or composite materials.