ASTM D 4138 : 1994 : R1999

1.1 These test methods cover the measurement of dry film thickness of coating films by microscopical observation of precision angular cuts in the coating film. Use of these methods usually requires repair of the coating film.

1.2 Three test methods are provided for measuring dry film thickness of protective coating system:

1.2.1 Test Method A--Using groove cutting instruments.

1.2.2 Test Method B --Using grinding instruments.

1.2.3 Test Method C --Using drill bit instruments.

1.3 The substrate should be sufficiently rigid to prevent deformation of the coating during the cutting process. The surface may be flat or moderately curved (pipes as small as 1 in. (25 mm) in diameter may be measured in the axial direction).

1.4 The range of thickness measurement is 0 to 50 mils (0 to 1.3 mm).

1.5 The values stated in inch-pound units are to be regarded as the standard. The values given in parentheses are for information only.

1.6 This standard does not purport to address all of the safety problems, 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.