Liquid Penetrant Examination
Penetrants detect surface flaws by permeating cracks or pores. A small amount of penetrant is applied to a test area. After a specified “dwell time” has elapsed, the penetrant is removed from the surface. A blotter-like developer is applied over the test surface. The developer draws excess penetrant from the defects. The penetrant is either a color that contrasts heavily against the component background, or it is fluorescent. Although simple to use, penetrants can miss defects if the surface is not adequately cleaned, or the flaw is obstructed with smeared metal.