Meaning and Purpose
4.1 this practice describes ensure accurate thickness measurement for three steps: coating thickness measurement instrument calibration, verification and adjustment, as well as on the black metal and non-ferrous metal base material to obtain the correct coating thickness measurement method.

4.2 commercial and industrial coating project of many specifications require a coating system in minimum and maximum dry film thickness of each layer. In addition, most high-performance coating manufacturers will guarantee the coating system partly based on achieving the proper thickness for each layer and the entire coating system. Recommendations published by paint manufacturers on product data sheets can become management documents even if project specifications are not provided. Equipment manufacturers produce nondestructive coating thickness testers that measure the cumulative or individual thickness of a coating after drying. The manufacturer usually provides information on the adjustment and use of these gauges in the form of operating instructions. Users of this equipment need to understand the proper operation of these equipment, including methods to verify the accuracy of the equipment before, during and after use, as well as measurement procedures.

ASTM D7091-2022 Standard Practice for Nondestructive Measurement of Dry Film Thickness of Nonmagnetic and Nonconductive Coatings Applied to Ferrous Metals and Nonmagnetic and Nonconductive Coatings Applied to Nonferrous Metals

Scope of
1.1 This practice describes the use of magnetic and eddy current meters for dry film thickness measurements. This practice is intended to complement the manufacturer’s instructions for the manual operation of the gauges, not to replace them. It includes definitions of key terms, reference documents, meaning and use in practice, advantages and limitations of coating thickness gauges, and a description of specimens. It describes the methods and recommended frequencies for verifying the accuracy of the gauges and adjusting the equipment, and lists the reporting recommendations.

1.2 the program does not apply to the meter/probe easy deformation under the load of the coating, because the measuring probe need to be placed directly on the coating surface to obtain readings. 5.7 describes the measurements on the soft coating or sticky coating.

1.3 Coating thickness can be measured using various measuring tools. These gauges are divided into “magnetic pull off” and “electronic”. They use a sensing probe or magnet to measure the gap (distance) between the base metal and the probe. This measuring distance is displayed by the measuring tool as the coating thickness.

ASTM D7091-2022 Standard Practice for Nondestructive Measurement of Dry Film Thickness of Nonmagnetic and Nonconductive Coatings Applied to Ferrous Metals and Nonmagnetic and Nonconductive Coatings Applied to Nonferrous Metals

1.4 The coating thickness varies greatly over the entire surface. Therefore, obtaining single-point measurements may not accurately represent the actual coating system thickness. SSPC-PA 2 specifies the frequency of coating thickness measurements based on the size of the coating area. The measurement frequencies of coated steel beams (beams) and coated test plates are also provided in the appendix of SSPC-PA 2. The management code is responsible for providing the user with the minimum and maximum coating thickness for each layer and the entire coating system.

1.5 value to SI units shall be deemed to be standard. The SI units given in parentheses value is for reference only, not be regarded as standard.

1.6 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.

1.7 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.