Which testing method uses a liquid to reveal surface-breaking defects on non-porous materials?

Which testing method uses a liquid to reveal surface-breaking defects on non-porous materials?

• A. Eddy current inspection
• B. Magnetic particle inspection
• C. Ultrasonic inspection
• D. Liquid penetrant inspection

Answer: (D)

Liquid penetrant testing relies on a liquid that wets and enters any open surface cracks. After allowing time for capillary action to pull the liquid into flaws, the surface is cleaned and a developer is applied. The developer draws the liquid out of the cracks, creating a visible indication that can be seen with the naked eye or under UV light. This method is ideal for surface-breaking defects on non-porous materials because the penetrant only reveals flaws that reach the surface, giving a clear surface indication without being obscured by porosity. Other methods use different physical principles—eddy current uses electromagnetic fields, magnetic particle uses magnetism with iron particles, and ultrasonic uses sound waves—so they don’t rely on a liquid showing surface defects in the same way.

Liquid penetrant testing relies on a liquid that wets and enters any open surface cracks. After allowing time for capillary action to pull the liquid into flaws, the surface is cleaned and a developer is applied. The developer draws the liquid out of the cracks, creating a visible indication that can be seen with the naked eye or under UV light. This method is ideal for surface-breaking defects on non-porous materials because the penetrant only reveals flaws that reach the surface, giving a clear surface indication without being obscured by porosity. Other methods use different physical principles—eddy current uses electromagnetic fields, magnetic particle uses magnetism with iron particles, and ultrasonic uses sound waves—so they don’t rely on a liquid showing surface defects in the same way.