The eddy current inspection method is applied to the detection of cracks at or near the surface. An electrically charged coil carrying an alternate current causes an eddy current to flow in any nearby metal. The eddy current may react on the coil to produce substantial changes in its reactivity and resistance, and that reaction is used to pinpoint small cracks or defects.
Eddy current inspection is accurate for the detection of small flaws or material changes that may not be detected with other inspection methods, and the discontinuities in the casting will give an immediate response on the monitoring equipment. However, it requires a vast amount of knowledge and experience to properly interpret the results, which will affect the added cost to the part. The test only can be used with electrically conductive materials.