Name a drawback of dye penetrant testing compared to other NDT methods.

Dye penetrant testing (PT) has a notable drawback, which is the necessity for surface preparation, as this can potentially lead to contamination on the part being tested. The preparation process typically involves cleaning the surface to remove any dirt, grease, or other contaminants that could interfere with the detection of flaws. If not performed adequately, contamination can obscure the indications of defects, leading to false negatives or missed detections.

In contrast to other NDT methods, this requirement emphasizes the vulnerability of dye penetrant testing to issues that may arise from improper surface conditions. While other methods may have their unique limitations, dye penetrant testing's reliance on pristine surface cleanliness is a distinctive factor that places it at risk of compromised results if not handled with care.

The sensitivity of various NDT methods also varies, with dye penetrant testing often being limited to surface-breaking flaws, which further differentiates it from methods like ultrasonic testing that can detect subsurface defects without requiring the same level of surface preparation.