Dye penetrant inspection (DPI), also called liquid penetrant inspection (LPI) or penetrant testing (PT), is a widely applied and low-cost inspection method used to locate surface-breaking defects in all non-porous materials (metals, plastics, or ceramics). The penetrant may be applied to all non-ferrous materials and ferrous materials. Dye penetrant inspection 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.
Penetrant FLUXO P125 (or fluorescent FLUXO 8702) may be applied to the cleaned with FLUXO S190 test component by dipping, spraying, or brushing. The excess penetrant is removed and a developer FLUXO R175 is applied. The developer helps to draw penetrant out of the flaw so that an invisible indication becomes visible to the inspector. Inspection is performed under ultraviolet or white light, depending on the type of dye used – fluorescent or nonfluorescent (red).