Magnetic particle inspection methods are recognized as superior to liquid penetrant techniques when?

Magnetic particle inspection methods are recognized as superior to liquid penetrant techniques when parts are painted. This is because magnetic particle inspection can identify surface-breaking defects on ferromagnetic materials even when the components are coated or painted. The magnetic field penetrates through non-magnetic coatings, allowing for detection of any discontinuities below the surface.

In contrast, liquid penetrant testing is significantly affected by coatings. The dye penetrant may not effectively reach defects beneath a layer of paint, as the fluid relies on capillary action to invade cracks and surface flaws. Therefore, the presence of paint can compromise the efficacy of the liquid penetrant method, making it less reliable in such cases.

When considering other scenarios, large defects could be detectable by both methods, and neither method may have a distinct advantage based solely on defect size. Cost concerns could be a factor in choosing between different inspection methods, but it doesn't inherently determine effectiveness. Similarly, while different textured surfaces may complicate inspections, the primary advantage of magnetic particle testing lies in its ability to work with painted surfaces.