How does frequency influence the Eddy Current Testing method?

In Eddy Current Testing, frequency plays a crucial role in determining the sensitivity of the technique to surface and subsurface defects. Higher frequencies are particularly effective in providing better sensitivity to surface defects. This is due to the skin effect, which causes eddy currents to be concentrated near the surface of the conductive material. As frequency increases, the eddy currents are restricted to even shallower depths, enhancing the ability to detect smaller and shallower surface-breaking defects.

Additionally, while higher frequencies improve the sensitivity to surface anomalies, they can also reduce the penetration depth of the eddy currents. This reduction means that higher frequencies can identify small surface defects effectively but may overlook defects that lie deeper within the material because the eddy currents do not penetrate as far.

In contrast, lower frequencies might be better for detecting deeper faults within the material, but they generally have reduced sensitivity to minor surface defects. Therefore, the use of high frequencies is advantageous when the goal is to identify surface imperfections, confirming that option related to higher frequencies providing better sensitivity to surface defects is indeed the correct choice.