Simultaneous electromagnetic evaluation method for surface thickness of nickel layer and lift-off on nickel coating steel by alternating magnetic field

Nickel plating is used on the surface of rolling rolls in paper mills, and it is important to monitor the thickness of the nickel plating. In this research, the electromagnetic inspection method for the thickness of the nickel plating using the difference in electromagnetic properties between the nickel and the base material of S25C steel is proposed. On the other hand, the detection signal is also affected by the changing distance (lift-off: Lo) between the proposed electromagnetic sensor and the nickel plating. In this paper, by measuring the magnetic field in two directions of the electromagnetic sensor, it is shown that both the thickness of the nickel plating and the lift-off (Lo) are evaluated.