5.1 This test method provides a standard method, by the use of X-ray fluorescence (XRF) or isotope measuring instruments, for “on-line” determination of the weight [mass] of coatings on steel sheet produced on continuous production lines, for comparison with specification requirements, and for evaluating conformance of such products to a material specification under the jurisdiction of ASTM Committee A05 and its subcommittees as designated by a purchaser in a purchase order or contract. It may be applicable to other coatings, providing that the elemental nature of the coating and substrate are compatible with the technical aspects of XRF such as the absorption coefficient of the system, primary radiation, fluorescent radiation, type of detection.

5.1.1 This test method determines the coating thickness by repeatedly detecting fluorescent radiation from multiple, defined single spot data points, from which a weight [mass] can be determined, and may be used by other ASTM Committees and other standards writing bodies for the purpose of conformance testing.

5.1.2 The material condition at the time of testing, sampling frequency, specimen location and orientation, reporting requirements, and other test parameters are contained in the pertinent material specification or in a general requirement specification for the particular product form.

5.1.3 A coating of zinc on steel sheet provides protection against corrosion. As the protection is provided by sacrificial loss of zinc, the degree of protection is proportional to the weight [mass] of zinc coating. Specifications for zinc coated steel sheet frequently provide for different designations of coating so that the purchaser can select the coating weight [mass] most suitable for the intended application.

5.2 A reference is provided to the pertinent material specification for the procedures to be used to characterize the coating weight [mass] on production line coils of coated sheet.

This test method covers the use of X-ray fluorescence (XRF) for determining the coating weight (mass) of metallic coatings on steel sheets. This test method is intended to be used for “on-line” measurements of coatings on continuous production and is applicable to coatings such as tin mill products, zinc or zinc iron coatings, aluminum zinc-coating, zinc-aluminum coating, and zinc-nickel coating. This test method may be applicable to other coatings, provided that the elemental nature of the coating and substrate are compatible with the technical aspects of XRF such as the absorption coefficient of the system, primary radiation, fluorescent radiation, and type of detection. The test method includes the procedure for developing a single standard determination of coating weight (mass) and the procedures for both X-ray tube and isotope coating weight (mass) measuring instruments. The basic principle of the measurement by XRF method and the factors affecting accuracy and precision including equipment, data collection, and calibration of the instrument are detailed. The instrument shall be operated in a manner that meets the requirements specified for single data point definition, area of fluorescence, transverse scan speed, dwell time, and coating weight (mass) sampling width and location. The standard test condition and test locations across the strip width are illustrated.

1.1 This test method covers the use of X-ray fluorescence (XRF) for determining the coating weight [mass] of metallic coatings on steel sheet. The test method is intended to be used for “on-line” measurements of coating on continuous production lines and includes procedures for both X-ray tube and isotope coating weight [mass] equipment. In the body of this test method, reference to zinc coating shall be interpreted to also include zinc alloy coating except where specifically stated otherwise.

1.2 This test method is applicable to the coatings covered by the following ASTM Specifications: A463/A463M, A599/A599M, A623, A623M, A653/A653M, A792/A792M, A875/A875M, A879/A879M, A918, A924/A924M, A1046/A1046M, A1063/A1063M, and A1079.

1.3 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other, and values from the two systems shall not be combined.

1.4 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.

1.5 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.