Fluorescent penetrant inspection (FPI), also called liquid penetrant inspection (LPI) or penetrant testing (PT), is a widely applied inspection method used to locate surface-breaking defects in non-porous materials (metals, plastics or ceramics).
LPI is used to detect casting, forging and welding surface defects such as hairline cracks, surface porosity, leaks in new products, and fatigue cracks on in-service components.
