Measuring Thickness and Conductivity of Metallic Layers with Eddy Currents

Coated metals are used increasingly for a variety of technological purposes; the coatings provide wear resistance, good electrical contact, corrosion protection, and thermal isolation. Consequently the ability to determine the thickness, conductivity, and structural integrity of such coatings is important for both process control and in-service inspection of parts. Presently ultrasonic, thermal, and eddy current inspection methods are used, depending on the circumstances. Current inspection practices using these methods are often limited in their ability to provide quantitative estimates of the important parameters. In this paper we present a robust method that uses eddy current measurements to determine the thickness and conductivity of uniform conductive layers