This inspection method is used to detect surface defects in all metallic or non-metallic materials. In order to detect errors with this method, it must be open to the inspection surface. Defects that are below the inspection surface or whose opening to the surface is closed for any reason cannot be detected by this method. In addition, the fact that the inspection part has a very porous structure also eliminates the possibility of detection by this method.

Penetrant Inspection is probably the most widely used Non-Destructive Testing (NDT) method. The test object or material is coated with the visible or fluorescent dye solution. The surface is cleaned of excess paint and a developer is applied. The developer acts like blotting paper and draws the penetrant from imperfections on the surface. The bright color difference between the visible dye and the penetrant and developer makes the outflow visible. With fluorescent dye, ultraviolet light makes the outflow process brightly, which makes defects easy to see.

Visible Penetrant Liquids
Penetrant liquids are usually red in color. The property of the penetrant liquid is that it can penetrate surface cracks and gaps.

Fluorescent Penetrant Liquids
Fluorescent penetrant (penetrating) liquids can be tested under ultraviolet rays.