Liquid Penetrant (PT)
Draper NDT offers liquid penetrant testing as a solution for materials that are not ferromagnetic. This is a great method for locating surface breaking defects in aluminum, stainless and almost any other material. First, the test piece must be absolutely clean and dry.
Then a penetrating oil, that has been treated with a dye, is applied to the test piece. The oil remains on the surface of the test piece for a specified period of time. This allows for the oil to enter any defects that are open to the surface.
After the specified time, the dye is removed from the surface of the part. Care must be taken to avoid removing dye from possible defects. When the surface of the test piece is clean, developer is applied. This leaves a thin film of white powder on the test piece, which blots the dye out of defects, back onto the surface of the part. In the image, the crack is made visible (just below 3 o’clock of the hole).