Fluorescent Penetrant Inspection (FPI) is a non-destructive testing method used to detect surface defects in materials. It involves applying a fluorescent dye to the surface of a component, allowing it to seep into any cracks or voids. After a specified dwell time, the excess dye is removed, and a developer is applied to draw out the penetrant from the defects, making them visible under ultraviolet light. This technique is widely used in industries such as aerospace, automotive, and manufacturing to ensure the integrity of critical components. FPI is effective for identifying flaws that are not visible to the naked eye, helping to prevent failures and enhance safety.