Liquid Penetrant Testing refers to the process of using a liquid to coat a material. And then looking for breaks in the liquid to identify imperfections in the material. Inspectors conducting a Penetrant Test will first coat the material being tested with a solution that contains a visible or fluorescent dye. Inspectors then remove any extra solution from the material’s surface while leaving the solution in defects that “break” the material’s surface.
After this, inspectors use a developer to draw the solution out of the defects, then use ultraviolet light to reveal imperfections (for fluorescent dyes). For regular dyes, the color shows in the contrast between the penetrant and the developer. This process is ideal for detecting discontinuities open the surface in non-ferrous, and ferrous materials such as aluminum, copper-nickel, steel, or stainless steel. With the different methods of liquid penetrant, it can be done on just about anything including welds, castings, machined surfaces, and threaded surfaces. See More