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1.1 This test method covers the measurement of dry film thickness (DFT) of coating films by microscopic observation of a precision-cut, shallow-angle crater bored into the coating film. This crater reveals cross sectional layers appearing as rings, whose width is proportional to the depth of the coating layer(s) and allows for direct calculation of dry film thickness.

1.2 The substrate may be any rigid, metallic material, such as cold-rolled steel, hot-dipped galvanized steel, aluminum, etc. The substrate must be planar with the exception of substrates exhibiting “coil set,” which may be held level by the use of the clamping tool on the drilling device.

1.3 The range of thickness measurement is 0 μm to 89 μm (0 mils to 3.5 mils).

1.4 Measurements may be made on coil-coated sheet, certain formed products, or on test panels.

1.5 The values stated in SI 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 concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

3.1 Measurement of dry film thickness of organic coatings by physically cutting through the film and optically observing and measuring the thickness offers the advantage of direct measurement as compared with nondestructive means.

3.2 Constituent coating layers can usually be measured individually by this test method, provided adhesion between each layer is sufficient. However, this can be difficult in cases where the primer, topcoat, or multiple coating layers have the same, or very similar, appearance.