ASTM B588-88(2010)

The thickness of a coating is often critical to its performance.

For some coating-substrate combinations, the interference microscope method is a reliable method for measuring coating thickness.

This test method is suitable for specification acceptance.

1.1 This test method covers the measurement of the thickness of transparent metal oxide and metallic coatings by utilizing a double-beam interference microscope.

1.2 The test method requires that the specimen surface or surfaces be sufficiently mirrorlike to form recognizable fringes.

1.3 This test method can be used nondestructively to measure 1 to 10μ m thick transparent coatings, such as anodic coatings on aluminum. The test method is used destructively for 0.1 to 10 μm thick opaque coatings by stripping a portion of the coating and measuring the step height between the coating and the exposed substrate. The stripping method can also be used to measure 0.2 to 10 μm thick anodic coatings on aluminum.

1.4 The test method is usable as a reference method for the measurement of the thickness of the anodic film on aluminum or of metallic coatings when the technique includes complete stripping of a portion of the coating without attack of the substrate. For anodic films on aluminum, the thickness must be greater than 0.4 μm; the uncertainty can be as great as 0.2 μm. For metallic coatings, the thickness must be greater than 0.25 μm; the uncertainty can be as great as 0.1 μm.

1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.6 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.