Non-destructive liquid penetrant (LP) testing is a method used to detect surface discontinuities in solid and non-porous materials. This technique allows large surfaces to be inspected simply, quickly and with optimum efficiency for most industrial applications.

The LP method consists of applying a colored, low-viscosity liquid to the area to be inspected, which can penetrate cracks, crevices or pores by means of capillarity. The excess liquid must then be removed until the surface is clean. Finally, the developer, usually white, is applied to extract the liquid that has penetrated the discontinuity. In this way, any surface flaw is revealed with high contrast, making it easy to identify.

This type of test is widely used to identify flaws in weld seams, structural components, highly stressed parts, gears, among others. It can be applied to any asset and equipment, as it does not cause damage to the structure.