The ISO 21968:2019 "Phase-sensitive eddy current method for the measurement of the thickness of nonmagnetic metallic coatings on metals and Non-metallic substrates" standard specifies a method for nondestructive measurement of the thickness of nonmagnetic metallic coatings, suitable for metals and Non-metallic substrates. This method uses a phase-sensitive eddy current instrument for measurement. Compared with the amplitude-sensitive eddy current method, it can be effectively applied on surfaces with smaller surface area and stronger curvature, and has less magnetic effect on the substrate. However, the phase-sensitive eddy current method is more sensitive to the electrical performance of the coating material. The standard applies to a variety of coating types, including paints, Eletroplating coatings, enamel coatings, etc., and is particularly suitable for measuring the thickness of metallic coatings.