Measurements of film thickness are an essential part of most ASTM test methods related to coatings on steel pipe. Adequate thickness is important for a coating to fulfill its function of preventing or mitigating corrosion of steel pipelines.

The accuracy of the thickness measurements may be influenced by the deformability of the coating. This test method is not applicable to coatings that would be readily deformable under the force exerted by the probe of the measuring instrument.

1.1 This test method describes the nondestructive measurement of the thickness of a dry, nonmagnetic coating applied to the external surface of steel pipe. The method is recommended for coating thicknesses up to 6 mm (0.240 in.) and for any diameter pipe, but not smaller than 10 mm (0.5 in.). It does not apply to excessively soft films.

1.2 The values stated in SI units to three significant decimals are to be regarded as the standard. The values given in parentheses are for information only.

This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.