What is required before applying liquid penetrant testing?

Before applying liquid penetrant testing, surface preparation to remove contaminants is essential. This step is crucial because the effectiveness of liquid penetrant testing relies on the penetrant being able to seep into any surface-breaking defects present in the material. Contaminants such as oil, grease, dirt, paint, or rust can block the penetrant from properly wetting the surface and penetrating the defects. Therefore, a clean surface ensures that the penetrant can adhere effectively and reveal any discontinuities during the inspection process.

Other methods mentioned, like heating the surface, using a magnetic field, or applying ultrasonic signals, are not applicable to liquid penetrant testing. This testing method specifically focuses on the ability of the liquid penetrant to absorb into flaws and requires a clean surface to provide accurate and reliable results.