Penetrant testing is another test method used globally to detect surface discontinuities. Parts can be locally or fully inspected. It can be used on all metals and other non-porous materials such as ceramics, some plastics and composites. PT can be can be performed manually in situ during maintenance (MRO), or automated close to a manufacturing line (OEM).
How does PT work? A dye solution is applied to the surface to penetrate any surface breaking cavity. Once the excess solution is removed, a developer is applied to draw out any unseen penetrant. With visible dyes, a colour contrast between the penetrant and developer makes the ‘bleed-out’ easy to see. With fluorescent dyes, UV light makes the ‘bleed-out’ fluoresce brightly, allowing imperfections to be seen.