The magnetic field can be introduced into the test specimen by either direct or indirect magnetization. Direct magnetization occurs when the electric current is passed through the test object and a magnetic field is formed in the material. Indirect occurs when no current is passed through the test specimen, but a magnetic field is applied from the outside source. When the magnetic field is disturbed by surface or near-surface discontinuities the magnetic powder forms around an indication which can be seen quite clearly.
- Wet continuous method by AC/DC Yoke
- Wet continuous method by Permanent Magnet
- Fluorescent Magnetic Particles Inspections
- MPI by Dry Powder Technique
