Manufacturing and Metrological Certification of Samples of Properties of Metal Coatings for Еddy Сurrent Thickness Gauges

Syasko, Vladimir; Constanta Ltd; Russian Federation

Golubev, S.S.; Federal Agency on Technical Regulating and Metrology; Russia
Smirnova, N.I.; D.I. Mendeleev Institute for Metrology (VNIIM); Russia
Syasko, V.A.; Constanta Ltd; Russia

ID: ECNDT-0086-2018
Session: Eddy Current-Application 1
Room: H2
Date: 2018-06-15
Time: 10:00 - 10:20

In today’s high-tech industries using large range of protective and functional metal coatings. The requirements for accuracy of measurement of the thickness Tc are constantly increasing. Manufacture and use of eddy current thickness gauges of metal coatings implies the use of coating standards for calibration and verification in production, and also for setting before measurements. At the same time, for reliable measurements, it is necessary to ensure that the electromagnetic parameters of coating materials and bases are kept constant within the sets of coating thickness measures. However existing calibration schemes assume only control the geometric parameters of the coating standards.

To evaluate the influence of the electromagnetic parameters of the coating thickness measures on the Tc measurement results, a model of an eddy current three-winding transformer primary measuring transducer with a ferrite core over a two-layer metal structure was developed. Based on the analysis of the influencing parameters: the electrical conductivity σc of the coating, the relative magnetic permeability μb, and the conductivity σb of the base, the requirements were formulated for the range of their variation, providing an error ΔTс ≤ ± (0.02Tс + 1) μm.
Based on the calculations performed, a reference complex was developed to measure the electromagnetic parameters of the samples of the properties of metal coatings (coating thickness measures), allowing σc, μb and σb in the frequency range from 50 kHz to 200 MHz in the Tc = 5 – 300 μm range. Details onsidered complex structure, measurement algorithms and key metrological characteristics