Magnetic Particle Examination (MT) is a popular, relatively low-cost method to perform nondestructive examination on ferromagnetic materials. As defined by ASME V, ferromagnetics are simply “magnetic” materials that can be magnetized and are strongly attracted by a magnetic field. MT is defined as a method that verifies the presence of defects on the surface of a component (or just below the surface).
MT was first introduced during early 1920s, after workers noticed that metallic grindings appeared to be arranged in patterns around cracks on components under machining. The technique was the result of exploiting the principles of magnetism. The ferromagnetic powder-to-steel parts allowed a more visible indication of discontinuities and defects. MT was first introduced in the railroad industry and quickly replaced other rudimental surface NDEs like “oil and whiting.”