Quantitative Approach for Thickness and Conductivity Measurement of Monolayer Coating by Dual-Frequency Eddy Current Technique

A new approach is proposed to measure the coating material's thickness and its conductivity simultaneously by using the eddy current technique. The proposed approach can be used for a coating material with unknown or inhomogeneous conductivity. This is achieved by exploring an inverse algorithm to investigate the relationship between the thickness and the perpendicular component of the magnetic flux density for different coating conductivities. The measured average relative error is less than 10%, which makes the monitoring of the coating thickness possible under variation of the conductivity due to the applied loads and the manufacturing process.