Technique for measuring the thickness of a non-conductive coatings on a non-magnetic electrically conductive base metals with automatic take account of the influence of the specific electrical conductivity of the base metal

Abstract

The results of measurements of the thickness of a non-conductive coating on an electrically conductive non-magnetic base metal using the existing amplitude technique of eddy current non-destructive testing are strongly influenced by the specific electrical conductivity of the base metal. To eliminate this problem, it is proposed to use an eddy current probe with amplitude-phase signal processing. Its graduation is carried out using several base metals with different specific electrical conductivity using a coating thickness simulator, the number of graduation points is comparable to the resolution of the thickness gauge. To calculate the thickness of the coating, taking into account the specific electrical conductivity of the base, an algorithm is used to determine the involvement of a point in a polygon.