Glossary

Magnetic Particle Testing (MT) is a non-destructive testing (NDT) technique designed to detect surface and near-surface defects in ferromagnetic materials like iron, nickel, cobalt, and their alloys. The process begins by magnetizing the part either through direct current or by placing it in a magnetic field. When the material contains a discontinuity—such as a crack, seam, lap, or void—it interrupts the flow of the magnetic field. This disruption causes magnetic flux leakage at the defect site, which provides the basis for detection. Finely milled ferromagnetic particles, applied as either a dry powder or a suspension in liquid, are then spread across the surface. These particles are drawn toward the leakage fields and cluster along the defect, forming a visible indication of its presence.

This method is widely applied across industries like aerospace, automotive, construction, and energy, especially for inspecting welds, castings, and forgings. MT offers several advantages: it is highly effective for finding surface-breaking flaws and shallow subsurface defects, produces immediate and easily visible results, and is relatively quick and inexpensive to perform. However, it does have limitations—it only works on ferromagnetic materials, requires clean surfaces for accurate detection, and may miss deeper flaws that methods like ultrasonic or radiographic testing could identify. Despite these constraints, MT remains a practical, versatile, and widely used inspection tool for ensuring the integrity of critical components.