What condition can prevent penetrant from seeping into a flaw during a dye penetrant inspection?

• A. A perfectly clean surface
• B. A roughened surface
• C. Any grease or dirt on the surface
• D. Using high-viscosity penetrant

Answer: (C)

Dye penetrant testing relies on the liquid wetting the flaw surfaces and seeping into tiny cracks by capillary action. If there is a film of grease or dirt on the surface, it disrupts wetting and creates a barrier between the penetrant and the flaw. That contamination prevents the penetrant from entering the opening, so no indication shows up after the remediation steps. A perfectly clean surface allows the penetrant to wet and enter the flaws; a roughened surface doesn’t inherently stop penetration, and while very high-viscosity penetrant can hinder entry into very fine defects, the most direct and common cause of preventing seepage is grease or dirt on the surface.