What can a penetrant inspection NOT find?

Penetrant inspection is specifically designed to detect surface-breaking defects through the application of a dye or fluorescent penetrant on the material's surface. This method effectively reveals flaws that are accessible on or just beneath the surface, such as surface cracks, fatigue failures, and other surface discontinuities.

An internal cavity, however, is not detectable by penetrant inspection. This is because penetrant testing relies on the ability of the penetrant to seep into surface-breaking defects. Internal cavities are not exposed to the surface and do not allow the penetrant material to reach them, rendering this method ineffective for locating such internal issues.

In summary, penetrant inspection is highly effective for identifying various surface defects, but it cannot find defects that are not exposed at the surface, such as internal cavities.