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.

1.2 This test method is applicable to the coatings covered by the following ASTM specifications: A 599/A 599M, A 623, A 623M, A 653/A 653M, A 792/A 792M, A 875/A 875M, A 879/A 879M, A 918, and A 924/A 924M. 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.

1.3 This test method includes the procedure for developing a single standard determination of coating weight (mass).

1.4 This test method includes procedures for both X-ray tube and isotope coating weight (mass) measuring instruments.

1.5 The values stated in either inch-pound units or SI units are to be regarded separately as standard. Within the text, the SI units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in nonconformance with the specification.

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.