Penetrant Testing (PT)
Penetrant testing makes surface cracks visible by liquid penetration and developer.
Physical-Chemical Mechanism of Action
A capillary-active liquid is applied to the surface to be examined. The liquid penetrates cracks because it can move due to surface energy. After the liquid has penetrated, the material is dried with a developer. This medium reacts with the liquid and provides a visible marking of the cracks.
Metallurgical Relevance & Welding Risks
Penetrant testing is especially important for detecting surface cracks in weld areas. These cracks can occur from inadequate cleaning or incorrect welding parameters and lead to brittleness or corrosion. A negative result indicates that the surface is not clean or that there are microscopic cracks that could be dangerous with continued use.
Workshop Practice & Instructions
1. Prepare the surface to be examined carefully: remove all dirt and paint residues.
2. Apply a capillary-active liquid (e.g., water, alcohol) to the surface.
3. Let the liquid have a little time to penetrate.
4. Spray or brush the developer over the liquid.
5. Observe whether visible markings of the cracks appear.
6. Document the result and take further cleaning or repair measures if necessary.