Standard Eddy Current Testing is essentially a near surface technique. It is useful for detecting surface-breaking or near-surface cracking and variations in material composition. This technique also used to measure the thickness of non-electrically conductive coatings on electrically conductive substrates. Generally, this method are only used in plant inspection for non-ferritic materials or for special applications, such as in the inspection of heat exchanger tubing for cracking or corrosion thinning.