Why might lower frequencies be selected in Eddy Current Testing?

Lower frequencies in Eddy Current Testing may be selected because they penetrate deeper into materials. This depth of penetration is crucial when inspecting components that are thicker or when assessing subsurface flaws. The electromagnetic field generated by lower frequencies can reach deeper than higher frequencies, which are primarily sensitive to surface defects. Consequently, when deeper inspection is needed, such as for detecting flaws that may be located several millimeters below the surface, lower frequencies become the preferred choice.

Other factors, such as ease of handling, testing times, and effects of surface coatings, may influence the selection of frequency, but they do not have the same significant impact on penetration depth as frequency itself does.