Meaning and Purpose
5.1 Many coating properties are significantly affected by dry film thickness, such as adhesion, flexibility, wear, durability, chemical resistance, and hardness. In order to be able to compare the results obtained by different operators, the film thickness needs to be carefully measured.

5.2 Most protective and high performance coatings are designed to meet the requirements or specifications for the dry film thickness of each coating or the whole system or both. Coatings need to be applied within certain minimum and maximum thickness tolerances so that they can perform their intended function. In addition to potential performance defects, it is uneconomical to use more material than necessary when coating large areas such as floors and walls.

5.3 Occasionally low readings may occur on coatings with rough surfaces. The instrument can allow the user to adjust to prevent this.

5.4 This test method may not be suitable for measuring the thickness of organic coatings on all substrates. The ability of the instrument to detect different interfaces between the coating and the substrate may be hampered if the composition, density, or attenuation of the coating and the substrate are similar, or if the coating is not uniform. If these conditions are considered, verify the operation on a coating/substrate combination of known thickness.

5.5 The multilayer coating has many interfaces, and the instrument will measure the interface separating the two materials with the greatest acoustic difference. Some instruments are able to detect and measure the thickness of individual layers in multi-layer systems.

5.6 The use of this test method is not necessarily limited by the type of substrate material.

ASTM D 6132-2020 “Measurement of Dry Film Thickness of Organic Coatings Applied to Concrete by a Non-destructive Method (i.e. Using an Ultrasonic Apparatus)”

Scope of
1.1 The test method describes the accurate and nondestructive measurement of dry film thickness of organic coatings applied to substrates of different materials using ultrasonic film thickness gauges. Measurements can be made on field structures, commercially manufactured products, or laboratory test samples. These types of gauges can accurately measure the dry film thickness of organic coatings on various substrates such as concrete, wood, wall panels, plastics, fiber composites, and metals.

1.2 The test method is not applicable to coatings that are prone to deform under the load of the measuring instrument because the instrument probe is placed directly on the surface of the coating for reading.

1.3 The effective range of instruments using ultrasonic principles is limited by the design of measuring tools. Thickness ranges from 8 μm to 7.60 mm (0.3 to 300 mils).

1.4 Values expressed in SI units should be considered standard values. Other units of measurement are not included in this standard.

1.5 This standard is not intended to address all safety issues, 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 to determine the applicability of regulatory restrictions prior to use.

1.6 This international Standard has been developed in accordance with the internationally recognized standardization principles established in the Decision on Principles for the Development of International Standards, Guidelines and Recommendations issued by the Committee on Technical Barriers to Trade of the World Trade Organization.