Which of the following materials may be inspected using the magnetic particle inspection method?

• A. Magnesium alloys
• B. aluminum alloys
• C. iron alloys
• D. zinc alloys

Answer: (C)

Magnetic particle inspection works by magnetizing a part and looking for flux leakage at flaws. Only ferromagnetic materials can be reliably magnetized to create those leakage patterns that attract the magnetic particles and reveal cracks or defects. Iron alloys are ferromagnetic, so when they’re magnetized, any surface or near-surface flaw produces a visible indication as particles gather at the defect. Magnesium, aluminum, and zinc alloys are non-ferromagnetic (or only weakly magnetic), so they don’t produce the same detectable leakage under standard MPI conditions. Therefore, iron alloys are the materials suitable for MPI, while the others are not typically inspected with this method.