Liquid Penetrant Testing (PT) is a non-destructive testing (NDT) method used to identify surface defects in non-porous materials such as metals, plastics, and ceramics. While PT can also be applied to ferrous materials, Magnetic Particle Testing (MPT) is typically the preferred NDT technique for ferrous components. PT is one of the simplest, most cost-effective NDT methods and is widely used across industries including oil and gas, aerospace, refineries, and fabrication shops. This method is effective for detecting surface defects in forgings, castings, and welds, such as cracks and porosity.
Surface preparation is essential for successful PT, which relies on capillary action to draw the penetrant into defects. The penetrant can be applied by dipping, brushing, or spraying. A dwell time is then allowed for the penetrant to seep into the flaws, after which excess penetrant is removed, and a developer is applied. The developer helps to draw the penetrant out of the surface defects, making them visible. PT inspections are typically conducted under ultraviolet (UV) or white light to enhance defect visibility.