MPI : Magnetic Particle Inspection is a method that is used for the detection of surface and near-surface flaws in ferromagnetic materials and is primarily used for crack detection.
LPI : Liquid penetrant inspection is a low-cost inspection method used to locate surface-breaking defects in nonporous materials. Penetrant inspection is used to detect casting, forging and welding surface defects such as hairline cracks, porosity, leaks in new products and fatigue cracks on in-service components.