Dye penetrant testing reveals what type of defects?

• A. Surface-breaking defects revealed by capillary flow into cracks.
• B. Internal voids inside the material.
• C. Cracks near the surface but not open.
• D. Surface-breaking defects revealed by applying dye and developer and inspecting for capillary flow into cracks.

Answer: (D)

Dye penetrant testing is used to find defects that are open to the surface. The process relies on capillary action: a dyed liquid is applied to the part and is drawn into any cracks or surface-connected flaws. After removing the excess dye, a developer is applied. The developer pulls the retained dye back to the surface, producing a visible indication where flaws exist. This makes the method effective for revealing surface-breaking cracks, seams, or porosity that reach the surface. It cannot detect internal voids completely enclosed within the material or cracks that do not connect to the surface. So the description that matches is the one stating surface-breaking defects revealed by applying dye and developer and inspecting for capillary flow into cracks.