In magnetic particle inspection, what is the impact of using alternating current (AC) magnetization?

Using alternating current (AC) magnetization in magnetic particle inspection primarily reveals surface defects. AC magnetization induces a magnetic field that alternates in polarity, which is effective for detecting discontinuities that are open to the surface. The alternating nature of the current can make the magnetic field less effective for penetrating deeper into the material compared to direct current (DC) magnetization, which can magnetize deeper and is more sensitive for detecting internal defects.

AC magnetization is particularly suited for inspections where the focus is on surface breaking defects, as the magnetic particles tend to gather at the surface imperfection when exposed to the AC field. The efficiency of this method for surface defects makes it a commonly used technique in various applications where surface integrity is critical. This characteristic is why the answer indicates that AC magnetization is mainly for surface defects.