Non-Destructive Testing (NDT) Practice Test

What characteristic do penetrants need to have to function correctly in an inspection?

1. They must be corrosive

2. They must remain solid

3. They need to be fluid and return to the surface

4. They should evaporate quickly

The correct answer is: They need to be fluid and return to the surface

For penetrant testing to be effective, the penetrants need to be fluid and have the ability to seep into the surface openings of a material. This characteristic allows the penetrants to fill cracks, voids, and other discontinuities that may exist on or just below the surface of the material being inspected. Once the penetrant has filled these defects, it can then be drawn back to the surface, where it forms a visible indication of the flaw when developed properly. This ability to return to the surface is critical in allowing inspectors to identify and evaluate defects in the material. The other characteristics such as being corrosive, remaining solid, or evaporating quickly are not conducive to effective penetrant testing. Corrosive materials could damage the surface being inspected, solid penetrants wouldn't be able to infiltrate the cracks, and those that evaporate too quickly wouldn't provide an adequate indication of the defects, as they would not stay long enough to be developed accurately.