Limitations Of MT

1. MT cannot be used on non-magnetic material.
2. The presence of surface coatings may reduce the sensitivity of the test.
3. Flaws that do not break the surface give diffused indications; these indications from flaws become increasingly diffused with an increase in distance below the surface.
4. Structural variations, rough surfaces and certain types of segregation, or metallurgical changes associated with test items, may give rise to misleading indications. This could include non-relevant indications caused by a change of section, too high amperage, a drilled hole near the surface, or a difference in hardness. This can also occur due to dimensional variations sometimes referred to as ‘furring’ or ‘bearding’.