Eddy Current Thickness Measurement Of The Thin Metal Cladding On Metal Base

The surface cladding of metal components, improving service characteristics of materials, such as corrosion resistance and wear resistance obviously, has been applied widely in various industry fields. Thickness measurement of the metal cladding is not only the basis of optimizing the cladding technology but also a key parameter of evaluating the coating quality. Though many non destructive methods for thickness measurement exist, such as radial method, ultrasonic method, magnetic induced current method and eddy current method , the eddy current technique, no doubt, is the most effective method for evaluating the thickness of the thinner metal cladding.In this paper, the influence of the properties of thin metal cladding and metal base on impedance curve was systematically discussed, and the relationship between thickness of a cladding and impedance (voltage) was given, furthermore a mathematical model was set up. On this basis, through an experimental research of the depth of penetration in various frequencies, it is proved that the negative influences of the thick metal base can be effectively controlled by means of higher frequency, and the frequency located in 500KHZ to 600KHZ, can meet the need of measurement thickness range of iM-m to 30Mm. In addition, in order to enhance the accuracy of measurement, it is necessary to decrease a tested area and to develop anew shielding transducer. Through designing of transducer, hardware and software, a system for thickness measurement of thin metal cladding has been realized finally. The experimental results on measuring thickness of reference by means of the developed system show that the system is feasible for measuring the thickness of thin cladding with good accuracy (lum?3%H) and stability. An available method of the thickness measurement of thin metal cladding on metal base has been obtained.