The ASTM B244-09 (2021) standard specifies a method for the nondestructive measurement of nonconductive Coating thickness on nonmagnetic base metals using an eddy current instrument. This method is particularly suitable for the measurement of the thickness of anode coatings on aluminum alloys, but not for chemical conversion coatings. The test requires that the conductivity of the substrate be consistent in the reference standard and the sample to be tested to ensure the accuracy of the measurement. This standard supplements the instrument operating instructions and does not replace the manufacturer's instructions for use.