Measurement of Thickness of Nickel-Layer on Steel Using Electromagnetic Method

There is a need to inspect the thickness of a nickel layer of nickel-coated steel, which is used to prevent rust, in the production process to guarantee the quality. Although an X-ray measurement is generally used, the protection wall of X-ray is necessary in the inspection equipment. Since the equipment of the electromagnetic inspection is cheap and simple compared with an X-ray equipment, the inspection of the thickness using the electromagnetic method is examined. In this paper, the electromagnetic method for measuring the thickness of a nickel layer using an alternating magnetic field is proposed. The detailed phenomenon of the measurement method is examined using the 3-D edge-based hexahedral nonlinear finite-element method (FEM). It is shown that the electromagnetic inspection of the thickness of nickel layer is possible by using the property that the flux density in nickel- coated steel is reduced when the thickness of nickel layer is increased. The FEM analysis is verified by experiment