A magnaflux test is used to show what flaw in ferrous metal?

• A. Cracks in the surface
• B. Corrosion pits
• C. Porosity
• D. Inclusions

Answer: (A)

Magnetic particle testing is used on ferrous metals to reveal surface and near-surface flaws by magnetizing the part and applying iron particles. When a crack interrupts the magnetic path, the flux leaks to the surface at the crack, and the particles gather there, making the crack easy to see. This is why cracks on the surface are the defect that this method highlights best.

Corrosion pits are small surface depressions that don’t typically create the same clear flux-leakage pattern as a crack, so they’re not detected as reliably by this method. Porosity is a volumetric internal defect; unless it reaches the surface or creates a leakage path, magnetic particle testing won’t consistently reveal it. Inclusions are internal nonmetallics; again, without a surface-breaking feature that disrupts the magnetic field, they’re not the primary target of this technique.