What is Liquid Penetrant Testing (PT)?

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

How does Liquid Penetrant Testing work?

A liquid penetrant is applied to the test surface and allowed to dwell, seeping into any surface-breaking defects by capillary action. Excess penetrant is then removed and a developer is applied, which draws the trapped penetrant back out of defects making them visible under white or ultraviolet light.

What industries use Liquid Penetrant Testing?

Liquid Penetrant Testing is widely used in aerospace, oil and gas, power generation, automotive, rail, marine, and manufacturing industries for detecting surface defects in welds, castings, forgings, and machined components.

Liquid Penetrant Testing NDT - dye penetrant inspection for detecting surface-breaking defects. Inspected by APEC Inspection

LIQUID PENETRANT TESTING BLOG

Learn how Liquid Penetrant Testing (PT/DPI) uses capillary action to detect surface-breaking defects in metals and other non-porous materials

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Liquid Penetrant Testing

Stephen 17 March, 2026

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