Magnetic particle inspection(MPI) is a method used for detection of flaws in ferrous materials, mostly for surface breaking defects.
MPI is relatively fast and easy to apply. Surface preparation is not always as critical as with Dye penetrant inspection. MPI is therefore one of the most widely utilized non-destructive testing techniques. A white contrast paint is often applied, before commencing the inspection, for better defect visibility. Fluorescent inks are used where a high detection sensitivity is required or where the appliance of a white contrast
paint is prohibited.