The GB/T 1764-1979 standard specifies a method for measuring the thickness of a paint film using a bar micrometer or a magnetic thickness gauge. The bar micrometer has an accuracy of 2um and is suitable for unpainted substrates. Zero and correction are required for measurement, followed by measurement at multiple locations 1cm from the edge. The magnetic thickness gauge method also requires zero and correction first, then the probe is placed on the sample for measurement, and finally the average thickness of each point is taken as the thickness value of the paint film. These methods can be used to determine the Coating thickness to ensure compliance with product requirements.