Material identification for composite metal layer based on pulsed eddy current

Aiming at the problem of nondestructive in-situ identification of double clad metal tube in oil industry, a method based on pulsed eddy current for composite metal layer materials identification is proposed. The method takes advantages of pulsed eddy current, such as its wide frequency band and large detection depth, to realize the detection and identification of cladding metal layer by eliminating its shielding effect. In the experiment, pulse eddy current signals of three specimens of copper, iron, and aluminum cladded by stainless steel were acquisited and four characteristics of peak amplitude, peak area, zero-crossing time and decay time were extracted. The result shows that the four characteristics can effectively distinguish magnetic materials (iron) from non-ferromagnetic materials (copper, aluminum), and zero-crossing time can further realize the distinction between copper and aluminum. This research demonstrates that pulsed eddy current is effective for the material identification of composite metal layers, it provides reference for the in-situ identification of double clad metal tube.