Magnetic particle inspection is typically used on which class of materials?

• A. Magnesium alloys
• B. Aluminum alloys
• C. Iron alloys
• D. Zinc alloys

Answer: (C)

Magnetic particle inspection relies on magnetizing a part and using small iron particles to reveal defects where the magnetic field leaks at cracks or flaws. This technique only works well on materials that can be strongly magnetized, i.e., ferromagnetic materials. Iron alloys fit this requirement, so MPI is typically used on steels and other iron-based materials. Non-ferrous alloys like aluminum, magnesium, and zinc do not become significantly magnetized, so they do not produce the visible leakage patterns MPI relies on.