Penetrant testing detects surface-breaking defects via what?

• A. Magnetic fields
• B. Radiographic energy
• C. Ultrasonic waves
• D. Penetrant liquids

Answer: (D)

Penetrant testing detects surface-breaking defects by using a penetrant liquid that seeps into tiny cracks and openings that are open to the surface. After allowing time for entry, the excess liquid is removed and a developer is applied. The penetrant trapped in the flaws migrates to the surface, producing a visible indication (often enhanced with fluorescent dye and UV light for greater sensitivity). This method specifically targets flaws that reach the surface, rather than subsurface flaws, and it works by capillary action of the liquid rather than magnetic fields, radiographic energy, or ultrasonic waves.