Which NDT method uses iron sprinkles to indicate imperfections?

• A. RT (Radiographic)
• B. UT (Ultrasonic)
• C. MT (Magnetic Particle Testing)
• D. PT (Penetrant Testing)

Answer: (C)

Magnetic Particle Testing uses iron particles to reveal flaws in ferromagnetic materials. When the part is magnetized, any defect disturbs the magnetic field and creates a leakage field at the surface. The iron particles are drawn to these leakage fields and cluster around the defect, forming a visible indication that marks the flaw’s location and shape. This makes tiny surface and near-surface imperfections easy to see as patterns or lines on the part.

This approach relies on magnetic fields and ferrous particles, not radiation, sound, or dye. That’s why it’s the method of choice for detecting cracks and other discontinuities in iron- and steel-based components. It requires a clean surface and proper magnetization, and is not suitable for non-magnetic materials or for defects deep below the surface.