Magnetic particle testing is a non destructive testing method for detection of surface and near surface discontinuities in ferromagnetic materials.
It is one of the most widely utilized NDT methods since it is fast and relatively easy to apply and part surface preparation is not as critical as it is for some other methods.
This method uses magnetic fields and small magnetic particles (i.e. iron filings) to detect flaws in components.
The only requirement from an inspect ability standpoint is that the component being inspected must be made of a ferromagnetic material (a materials that can be magnetized) such as iron, nickel, cobalt, or some of their alloys.