
Photo credit: @grubn_roht
Using direct or indirect magnetism, MT can detect surface and shallow subsurface discontinuities in steels as well as their alloys.
In order for a material to hold a magnetic field after the passing of electric current, the material must contain nickel, cobalt, and/or iron. Therefore, this technique is not valid where none of these elements are present, such as in:
Aluminum
Inconel
Composite