Which examination method uses dyes to locate surface defects?

Which examination method uses dyes to locate surface defects?

• A. Magnetic Particle
• B. Liquid Penetrant
• C. Radiographic
• D. Ultrasonic

Answer: (B)

Liquid penetrant testing relies on a colored or fluorescent dye that is drawn into surface-breaking defects by capillary action. After a dwell period, the surface is cleaned and a developer is applied; the developer pulls the penetrant out of the defect, creating a visible indication on the surface under proper lighting. This makes it easy to locate flaws that open to the surface, such as cracks or porosity that reach the surface. It’s specifically used for surface defects, unlike methods that inspect internal features, like radiography or ultrasonic, or those that require magnetic properties, like magnetic particle testing.

Liquid penetrant testing relies on a colored or fluorescent dye that is drawn into surface-breaking defects by capillary action. After a dwell period, the surface is cleaned and a developer is applied; the developer pulls the penetrant out of the defect, creating a visible indication on the surface under proper lighting. This makes it easy to locate flaws that open to the surface, such as cracks or porosity that reach the surface. It’s specifically used for surface defects, unlike methods that inspect internal features, like radiography or ultrasonic, or those that require magnetic properties, like magnetic particle testing.