Penetrant testing (PT) can also be identified as liquid penetrant inspection (LPI). It is a widely applied and low-cost inspection method used to locate surface-breaking defects in all non-porous materials (metals, plastics, or ceramics). Penetrant may be applied to all non-ferrous materials, but for inspection of ferrous components magnetic-particle inspection is preferred for its subsurface detection capability. PT is used to detect casting and forging defects, cracks, and leaks in new products, and fatigue cracks on in-service components.