Define Limitations of Underwater Magnetic Particle Testing?

As with any non-destructive test method, UWMT has some limitations as under:

i. Underwater magnetic particle testing has limited surface capability. It is refferd to be strictly a technique for detecting and measuring surface discontinuities. It is not an approved method for detection of flaws below the surface.

ii. UWMT technique can only be applied to ferromagnetic materials. For most applications, a simple test with a magnet is sufficient to ascertain suitability for UWMT.