What is a disadvantage of using the liquid penetrant test method?

The liquid penetrant test method is a widely used non-destructive testing (NDT) technique that can detect surface-breaking defects in a variety of non-porous materials. While it is effective for many applications, one of the significant disadvantages is that it cannot find all types of discontinuities. This method is primarily effective for detecting surface defects, such as cracks, porosity, and laps. However, it is not capable of identifying subsurface defects or discontinuities that do not reach the surface of the material being tested.

For example, internal flaws or defects that are situated below the surface cannot be detected using liquid penetrant testing since the penetrant can only reveal issues that are accessible at the surface. This limitation makes the method less suitable for certain critical applications or components where subsurface integrity is equally important. Therefore, relying solely on liquid penetrant testing may lead to undetected defects that could compromise the reliability and safety of the component in question.