When the surface of the gold is rusted, the rust products (mainly metal oxides) have different physical properties from the base metal. Their physical properties, especially the conductivity, the difference between the magnetic permeability, will affect the reflection resistance of the eddy current probe coil and reflect the inductance so that the eddy current method can be used to detect the corrosion of the metal surface. In order to detect the rusted state of the metal surface, we make The double-coil eddy current sensor that can detect the corrosion condition of the metal surface by using the experimentally determined optimal detection rate excitation and the corresponding detection circuit. According to our experiments, the lift-off effect curve of the rust test block at a fixed frequency is approximately a straight line. The change of the slope of the line can be used to determine the degree of corrosion of the metal surface. For carbon steel parts, the more serious the surface rust is the slope of the line The smaller. After the microcomputer data acquisition system is adopted, the collection, conversion and processing of the detection signals can be conveniently performed.
As long as the detection probe moves up and down over the sample, the lift-off effect curve of the sample can be displayed on the screen, and then the fitted straight line is drawn by linear regression processing, and then the fitting is drawn by linear regression processing. Straight line, calculate the slope of the line. Then, the slope is compared with the detection result of the standard sample, and the rust is more serious when the slope value is smaller. As a new type of non-destructive testing method, eddy current testing technology and theoretical research are progressing rapidly. With the development of electronic technology, especially computer and information processing technology, eddy current testing equipment has been developing in the direction of computerization and intelligence, and the quantitative evaluation and display technology for defects have been continuously improved. It is foreseeable that the application of eddy current testing technology will become wider and wider.