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GB/T 13448-2019: Test methods for prepainted steel sheet and strip Delivery: 9 seconds. True-PDF full-copy in English & invoice will be downloaded + auto-delivered via email. See step-by-step procedure Status: Valid GB/T 13448: Historical versions
Similar standardsGB/T 13448-2019: Test methods for prepainted steel sheet and strip---This is an excerpt. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.), auto-downloaded/delivered in 9 seconds, can be purchased online: https://www.ChineseStandard.net/PDF.aspx/GBT13448-2019NATIONAL STANDARD OF THE PEOPLE’S REPUBLIC OF CHINA ICS 77.060 H 25 Replacing GB/T 13448-2006 Test methods for prepainted steel sheet and strip Issued on. MARCH 25, 2019 Implemented on. FEBRUARY 01, 2020 Issued by. State Administration for Market Regulation; Standardization Administration of the People's Republic of China. Table of ContentsForeword... 4 1 Scope... 7 2 Normative references... 7 3 Terms and definitions... 7 4 Coating thickness determination... 9 5 Specular gloss determination... 15 6 Chromatic aberration determination... 17 7 Bending test... 19 8 Reverse impact test... 22 9 Pencil hardness test... 24 10 Organic solvent resistance test... 26 11 Abrasion resistance test... 29 12 Scratch resistance test... 31 13 Cross-cut test... 33 14 Cupping test... 35 15 Surface resistivity test... 37 16 Coating contact angle test... 38 17 Water immersion test... 40 18 Acid and alkali resistance test... 42 19 Contamination resistance test... 44 20 Carbon black contamination test... 47 21 Neutral salt spray test... 48 22 Dry heat resistance test... 51 23 Damp heat resistance test... 54 24 Cyclic corrosion test... 56 25 Xenon accelerated aging test... 59 26 UV lamp accelerated aging test... 62 27 Atmospheric exposure test... 65 Annex A (normative) Prepainted sheets’ coating peeling method and plating thickness measuring method... 69 Annex B (informative) Knoop hardness range of Zhonghua 505 coil steel coating hardness test pencils and its corresponding relationship with Knoop hardness of Zhonghua 101 drawing pencils... 701 ScopeThis Standard specifies terms and definitions of prepainted steel sheets and steel strips, as well as related test methods, test reports, etc. This Standard is applicable to the determination and evaluation of the coating properties of prepainted steel sheets and strips (hereinafter referred to as prepainted sheets).2 Normative referencesThe following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. GB/T 1410 Methods of test for volume resistivity and surface resistivity of solid electrical insulating materials GB/T 1766 Paints and varnishes - Rating schemes of degradation of coats GB/T 1839 Test method for gravimetric determination of the mass per unit area of galvanized coatings on steel products GB/T 10125 Corrosion tests in artificial atmospheres - Salt spray tests GB/T 12754 Prepainted steel sheet GB/T 30693 Measurement of water-contact angle of plastic films3 Terms and definitionsFor the purpose of this document, the terms and definitions defined in GB/T 12754 and the following apply. 3.1 specular gloss Relative luminous reflectance factor of the sample in the direction of specular reflection. 3.2 relative luminous reflectance factor Under the same geometric conditions, the ratio of the luminous flux value reflected by the sample to the luminous flux value reflected by the standard surface. 3.3 tristimulus values In a three-color system, the amount of three original stimuli required to achieve color matching with the light to be measured. 3.4 chromaticity coordinate Ratio of any tristimulus value to the sum of the tristimulus values. 3.5 T-bend Carry out the 180° reverse bending test with the radius of curvature of n (n = 0, 1, 2...) times the tested sample’s thickness in turn. The minimum n value at which the coating does not peel off or crack is the T-bend value.4 Coating thickness determination4.1 General 4.1.1 This method is applicable to the determination of the coating thickness of prepainted sheets. 4.1.2 The following methods can be used to determine the coating thickness of prepainted sheets. 4.2 Principle 4.2.1 Magnetic thickness gauge method Using the principle of electromagnetic field magnetoresistance, the coating thickness is measured by the amount of magnetic flux flowing into the prepainted steel substrate. 4.2.2 Micrometer method The coating thickness is determined by measuring the difference in thickness of the prepainted sheet before and after removal of coating. 4.3 Test equipment and materials 4.3.1 Magnetic thickness gauge 4.3.2 Micrometer 4.3.3 Metallographic microscope 4.4 Sample preparation and test environment 4.4.1 The sample size is not less than 75 mm × 150 mm. The surface of the sample shall be flat, no oil, no damage, and no burrs on the edges. 4.4.2 The test is carried out in a laboratory environment. In case of dispute, the sample to be tested shall be placed in an environment with a temperature of 23 °C ± 2 °C and a relative humidity of 50 % ± 5 % for at least 24 h before test. 4.5 Test procedure 4.5.1 Magnetic thickness gauge method 4.5.1.2 Determination 4.5.2 Micrometer method 4.5.2.1 SELECT 3 different parts in the area not less than 10 mm from the edge of the sample to mark. USE a micrometer to measure the thickness of the marks and record. Be careful not to make the coating have visible deformations during operation, otherwise it will affect the measurement results. 4.5.3 Metallographic microscope method 4.5.5 Magnetic-eddy current thickness gauge method 4.5.5.1 Instrument calibration and accuracy verification 4.5.5.2 Determination 4.6 Expression of results 4.6.1 Magnetic thickness gauge method The arithmetic mean of the coating thicknesses of the 5 different measurement positions is the coating thickness of the sample, expressed in micrometers (μm). 4.7 Test report The test report shall include the following.5 Specular gloss determination5.1 General The method is applicable to the determination of specular gloss of the coating of prepainted sheets. 5.2 Principle The specular gloss of the sample can be measured by determining the relative luminous reflectance factor of the coating. The unit of measurement is GU. 5.3 Test equipment and materials 5.5 Test procedure 5.5.1 Instrument calibration and accuracy verification The gloss meter shall be calibrated in accordance with the provisions of the equipment instructions. 5.5.2 Measurement 5.6 Expression of results The arithmetic mean of the coating’s specular gloss of the 3 different measurement positions, that is the gloss of the sample, in units of GU. 5.7 Test report The test report shall include the following.6 Chromatic aberration determination6.1 General The method is applicable to the determination of chromatic aberration of prepainted sheets. 6.2 Principle MEASURE the spectral data of the reference sample and the sample by the colorimeter under the International Lighting Association (CIE) standard light source and standard observation conditions, USE the CIE color system to calculate the tristimulus values of the reference sample and the sample, and USE the selected chromaticity coordinates to calculate the chromatic aberration results of the sample and the reference sample. 6.3 Test equipment and materials 6.3.1 Colorimeter 6.3.2 Colorimeter calibration sheet/sample Provided by the colorimeter supplier. 6.3.3 Reference sample A standard swatch approved by both the supply and demand parties. The reference sample shall be stored in a dark and laboratory environment to avoid large changes in color that may affect the determination results. 6.4 Sample preparation and test environment 6.4.1 The size of the sample shall meet the requirement that it is able to covering the measuring aperture of the colorimeter. The surface of the sample shall be flat, no oil, no damage, and no burrs on the edges. 6.4.2 The test is carried out in the laboratory environment. In case of dispute, the sample to be tested shall be placed in an environment with a temperature of 23 °C ± 2 °C and a relative humidity of 50 % ± 5 % for at least 24 h before test. 6.5 Test procedure 6.6 Expression of results The chromatic aberration between the sample and the reference sample can be calculated by formula (1). 6.7 Test report The test report shall include the following.7 Bending test7.1 General This method is applicable to the evaluation of the ability of the coating to resist peeling off or cracking when the prepainted sheet is bent. 7.2 Principle 180° bending. The sample is bent 180° around itself to determine whether the coating has peeled off or cracked, to determine the minimum thickness multiple value of the sample that does not cause the coating to peel off or crack. 7.3 Test equipment and materials 7.4 Sample preparation and test environment 7.4.1 The sample size is that the width is not less than 100 mm and the length is about twice the width. The sample shall be flat, no oil, no damage, and no burrs on the edges. 7.4.2 The test is carried out in a laboratory environment. In case of dispute, the sample to be tested shall be placed in an environment with a temperature of 23 °C ± 2 °C and a relative humidity of 50 % ± 5 % for at least 24 h before test. 7.5 Test procedure 7.5.1 180° bending 7.5.2 90° bending 7.5.2.1 INSERT one end of the sample into the bending test machine for about 10 mm, PRESS the sample tightly, TURN the handle to bend the sample by 90°. 7.5.3 Negotiation content It shall be agreed upon between the supply and demand parties on whether the 180° or 90° bending test is used, and whether the bending test result is determined by tape peeling or by observing the cracking visually or by magnifying glass. 7.6 Expression of results The 180° bending test does not cause the coating shedding. The minimum multiple of the sample thickness at which the cracking is observed visually or by magnifying glass is the T-bend value. The 90° bending test result is indicated as pass/fail. 7.7 Test report The test report shall include the following.8 Reverse impact test8.1 General This method is applicable to the evaluation of the ability of the coating to resist peeling off or cracking when the prepainted sheet is subjected to rapid deformation. 8.3 Test equipment and materials 8.4 Sample preparation and test environment 8.4.1 The sample size shall not be less than 75 mm × 150 mm. The sample shall be flat, no oil, no damage, and no burrs on the edges. 8.4.2 The test is carried out in the laboratory environment. In case of dispute, the sample to be tested shall be placed in an environment with a temperature of 23 °C ± 2 °C and a relative humidity of 50 % ± 5 % for at least 24 h before test. 8.5 Test procedure 8.5.1 Specified impact absorption energy test 8.5.2.1 TEST according to steps 8.5.1.1 to 8.5.1.4. 8.6 Expression of results 8.6.1 In the specified the impact energy absorption test, the result shall be expressed as whether the coating of the sample is peeled off or cracked under the specified impact absorption energy test. 8.7 Test report The test report shall include the following.9 Pencil hardness test9.1 General This method is applicable to determination of pencil hardness of the coating of prepainted sheets. 9.2 Principle Use a set of pencils of known hardness to determine the relative hardness of the coating surface of prepainted sheets. 9.3 Test equipment and materials 9.4 Sample preparation and test environment 9.4.1 The sample size is 75 mm × 150 mm. The surface shall be flat, no oil and no damage. 9.4.2 The test is carried out in the laboratory environment. In case of dispute, the sample to be tested shall be placed in an environment with a temperature of 23 °C ± 2 °C and a relative humidity of 50 % ± 5 % for at least 24 h before test. 9.5 Test procedure 9.5.1 Manual pencil method 9.5.2 Instrument pencil method 9.6 Expression of results The hardest pencil hardness by which the coating cannot be plowed at least 4 times out of 5 times is taken as the pencil hardness of the coating to be tested. 9.7 Test report The test report shall include the following. ......Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al. 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