Magnetic Particle Inspection

Magnetic particle inspection (MPI) is a non-destructive testing (NDT) process for detecting surface and slightly subsurface discontinuities in ferromagnetic materials such as iron, nickel, cobalt, and some of their alloys.

Advantages of Magnetic Particle Inspection:
  • Can find both surface and near sub-surface defects
  • Some inspection formats are extremely portable and low cost
  • Rapid inspection with immediate results
  • Indications are visible to the inspector directly on the specimen surface
Limitations of Magnetic Particle Inspection:
  • The specimen must be ferromagnetic (e.g. steel, cast iron)
  • Paint thicker than about 0.005" must be removed before inspection
  • Maximum depth sensitivity is typically quoted as 0.100" (deeper under perfect conditions)