Liquid Penetrant Inspection (LPI), also known as Dye Penetrant Inspection (DPI) or Liquid Penetrant Testing (PT), is a non-destructive testing method used to detect surface-breaking defects such as cracks, porosity, seams, and other discontinuities in non-porous materials including metals, plastics, ceramics, and composites.

The inspection process involves applying a penetrant liquid to the test surface, allowing it to enter any surface defects through capillary action. After excess penetrant is removed, a developer is applied to draw the penetrant from discontinuities, creating visible indications for evaluation by a qualified inspector.

LPI/PT is a reliable and cost-effective inspection method commonly used in industries such as construction, manufacturing, oil and gas, aerospace, automotive, and industrial fabrication to help ensure the integrity and quality of components and structures.