What are the common limitations of Magnetic Particle Testing?

Magnetic Particle Testing (MPT) is fundamentally designed to detect defects in ferromagnetic materials. This is due to its reliance on the magnetic properties of these materials to generate a magnetic field that can reveal surface and near-surface discontinuities. Ferromagnetic materials, such as iron and its alloys, can be magnetized sufficiently to allow the detection of defects through the accumulation of magnetic particles at the sites of magnetic flux leakage created by cracks or other flaws.

While other options present some aspects of the technique or its effectiveness, they do not hold true when discussing the limitations specific to MPT. For instance, it's essential to note that MPT primarily reveals surface and near-surface defects, and not subsurface defects, which is a limitation in terms of penetrating below the surface. Additionally, surface conditions are crucial in MPT; rough or contaminated surfaces can hinder detection. False positives can occur due to various reasons, including the magnetic properties of the material itself, which could lead to misleading interpretations. However, these points do not challenge the fundamental reality that MPT is confined to ferromagnetic materials, which is the most definitive limitation in its application.