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GB/T 13448-2019 PDF English


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GB/T 13448-2019English605 Add to Cart 0-9 seconds. Auto-delivery. Test methods for prepainted steel sheet and strip Valid
GB/T 13448-2006English150 Add to Cart 0-9 seconds. Auto-delivery. Test methods for prepainted steel sheet Obsolete
GB/T 13448-1992English599 Add to Cart 4 days Test methods for colour-coated steel plates and strips Obsolete
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GB/T 13448-2019: PDF in English (GBT 13448-2019)

GB/T 13448-2019 NATIONAL 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 Contents Foreword ... 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 ... 70 Foreword This Standard is drafted in accordance with the rules given in GB/T 1.1-2009. This Standard replaces GB/T 13448-2006 “Test methods for prepainted steel sheet”. Compared with GB/T 13448-2006, main technical changes are as follows: - MODIFY 3 different measurement positions in the magnetic thickness gauge method to 5 different measurement positions (see 4.5.1.2 of this Standard, 4.5.1 of the 2006 edition); - ADD the magnetic-eddy current thickness gauge method (see 4.5.5 of this Standard); - ADD the unit expression of specular gloss; ADD the provisions for the accuracy verification of gloss meters; MODIFY the description of the measurement angle of gloss meters (see Clause 5 of this Standard, Clause 5 of the 2006 edition); - MODIFY the principle for determining the chromatic aberration by colorimeter and the equipment requirements for colorimeter, and the description of the colorimeter calibration sheet/sample; MODIFY the chromatic aberration calculation formula (see Clause 6 of this Standard, Clause 6 of the 2006 edition); - In the bending test, CANCEL the provisions for the magnification factor of magnifying glass; ADD the 90° bending test; ADD the description of observing the cracking by magnifying glass (see Clause 7 of this Standard, Clause 7 of the 2006 edition); - In the reverse impact test, ADD the description of 12.7 mm punch diameter; CANCEL the provisions for the magnification factor of magnifying glass; ADD the description of observing the cracking by magnifying glass; CANCEL the description of observing the cracking by copper sulfate; ADD the content of result expression and the negotiated content in the test report (see Clause 8, Clause 8 of the 2006 edition); - In the clause of organic solvent resistance test, ADD the description of the hygroscopicity of cotton cloth or cotton wool; ADD the description of the test procedure such as “The test process shall be continuous. If the reagent needs to be replenished, the interruption of the test process shall not exceed 10 s”. (See Clause 10 of this Standard, Clause 10 of the 2006 edition); Test methods for prepainted steel sheet and strip 1 Scope This 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 references The 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 films 3 Terms and definitions For 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 When the sample holder is not full of samples, a plate of the same size as the sample used to cover the sample holder space in order to prevent light leakage. 4 Coating thickness determination 4.1 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: a) Magnetic thickness gauge method: It is applicable to the determination of the coating thickness of the prepainted sheets with cold rolled plate and galvanized plate as the steel substrate. This method is not applicable if the coating thickness is less than 3 μm. This method is not applicable if the coating is a special uneven surface effect. b) Micrometer method: It is applicable to the determination of the coating thickness of the prepainted sheets with various materials as the steel substrate. This method is not applicable for coatings that are easily deformed under the load of the micrometer measuring device. This method is not applicable if the coating is a special uneven surface effect. c) Metallographic microscope method: It is applicable to the determination of the coating thickness of the prepainted sheets with various materials as the steel substrate. d) Drilling damage microscopic observation method: It is applicable to the determination of the coating thickness of the prepainted sheets with various materials as the steel substrate. When the interface of each coating can be clearly distinguished, it can also be applied to the determination of the thickness of each coating (primary coating, fine coating). e) Magnetic-eddy current thickness gauge method: It is applicable to the determination of the coating thickness of the prepainted sheets with various materials as the steel substrate. This method is not applicable if the coating is a special uneven surface effect. 4.2 Principle 4.2.1 Magnetic thickness gauge method Using the principle of electromagnetic field magnetoresistance, the coating 4.3.3.1 The measurement accuracy of the instrument shall be better than 2 μm. 4.3.3.2 Metallic sandpaper of the appropriate grade. 4.3.3.3 The material used for fixing the sample (such as resin) shall have no damage to the coating and its color is clearly different from the coating. 4.3.4 Drilling destructive micrometer thickness gauge 4.3.4.1 The measurement accuracy of the instrument shall be better than 10 % of the coating thickness. 4.3.4.2 Micrometer thickness gauge, which consists mainly of an automatic drilling device and a microscopic video imaging system. 4.3.5 Magnetic-eddy current thickness gauge 4.3.5.1 The instrument’s maximum indication error is ± (1 + 3 % standard thickness) μm. 4.3.5.2 Standard sheets of known thickness (non-magnetic films), which shall be of similar thickness to the coating to be tested. 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 4.5.1.1 Instrument calibration 4.5.1.1.1 USE the uncoated steel substrate of which the chemical composition and thickness are the same as those of the sample to be tested AS the zero- adjusting plate. ZERO the instrument at several different positions on the surface. When the steel substrate is a galvanized plate, it shall be zeroed on the steel substrate on which the zinc layer is removed, and the zero error shall not be greater than 1 μm. 4.5.1.1.2 SELECT the standard sheet of which the thickness is close to that of the measured coating to calibrate the instrument, to make it accurately indicate the thickness of the standard sheet. REPEAT the zeroing and calibration 4.5.4.1 PLACE the sample on the drilling table; ADJUST the drilling depth control wheel of the automatic drilling device so that the drill bit just penetrates the steel substrate and a circular shallow angle shrinkage hole is drilled in 2 different parts of the sample. 4.5.4.2 PLACE the sample on the measuring table; ADJUST the micro video image system so that the interface of the coating at the shrinkage hole can be clearly imaged on the video. The thickness of each coating can be read directly using the scale of the micro video system. 4.5.5 Magnetic-eddy current thickness gauge method 4.5.5.1 Instrument calibration and accuracy verification 4.5.5.1.1 The equipment may be calibrated by the equipment supplier using the thickness standard sheet before leaving the factory; or it may be calibrated by the equipment user using the thickness standard sheet according to the specifications of equipment instructions. 4.5.5.1.2 USE a thickness standard sheet or a self-made standard sheet of known coating thickness to verify the accuracy of the calibrated instrument. The accuracy of the verification test and the frequency of the test can be determined according to actual needs. When developing the accuracy requirements for verification tests, the accuracy of the equipment and standard sheets shall be considered. The unit of the thickness standard sheets for equipment calibration using this method is micrometer (μm). It may use the plating thickness standard sheets prepared by the method of Annex A, and the plating mass (g/m2) is into thickness (μm). 4.5.5.2 Determination 4.5.5.2.1 MEASURE at least 5 different positions with a distance greater than 25 mm from the edge of the sample. In order to improve the representativeness of the measurement results, the number of measurements can be appropriately increased. 4.5.5.2.2 The accuracy of this method for determining the coating thickness of prepainted sheets is affected by the following factors: a) Bending of the sample: It shall ensure that the sample to be tested is flat without bending. b) Foreign particles: It shall ensure that the surface of the sample and the surface of the probe are clean. It shall prevent foreign particles from affecting the test results. c) External magnetic field: The measurement result of the magnetic probe is measured surface is the coating thickness of the sample, expressed in micrometers (μm). 4.7 Test report The test report shall include the following: a) the test standard and negotiation terms adopted; b) instrument model; c) sample information; d) test results; e) test date and test personnel. 5 Specular gloss determination 5.1 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 5.3.1 60° gloss meter or multi-angle gloss meter. The equipment’s measurement indication error is not more than 1.0 GU. 5.3.2 Calibration plate: It is usually the polished glass plate or ceramic plate that comes with the instrument for instrument calibration. 5.4 Sample preparation and test environment 5.4.1 The sample size is not less than 75 mm × 150 mm. The sample shall be flat, no oil, no damage, and no burrs on the edges. 5.4.2 The test is carried out in a laboratory environment. In case of dispute, the test sample 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. 5.5 Test procedure 6 Chromatic aberration determination 6.1 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 6.3.1.1 The geometry of colorimeter is usually divided into two types: directional type and integrating sphere type. The geometry of directional type is usually divided into 45°/0°, 0°/45° and multi-angle colorimeters. The geometry of integrating sphere type is usually divided into d/8° and 8°/d. 6.3.1.2 The colorimeter shall be capable of measuring the spectral data of the sample in the range of 400 nm to 700 nm under the CIE standard light source and standard observation conditions. Due to different geometric mechanisms, standard light sources, standard chromatic observers, color systems, chromaticity coordinates for calculation, and detection areas of the colorimeter, the measured chromatic aberration values are different. The geometry of the colorimeter is related to the equipment selection. Once the geometry of the colorimeter is selected, it cannot be changed. The test parameters such as standard light source, standard chromatic observer, color system, and chromaticity coordinates for calculation can be switched by the data processing system of the 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. 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. 90° bending: The sample is bent 90° around itself to determine whether the coating has peeled off or cracked. 7.3 Test equipment and materials 7.3.1 Bending test machine: It is able to bend the sample at an acute angle. 7.3.2 Flattening machine or vise: It is used to flatten the sample. 7.3.3 Scotch tape: The width is approximately 25 mm and the bond strength is (10 ± 1) N/25 mm wide. Tapes agreed upon between the supply and demand parties can also be used. 7.3.4 Magnifying glass: The magnification factor is determined by negotiation between the supply and demand parties. It is generally 5 times to 10 times magnifying glass. 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 7.5.1.1 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 to an acute angle. Then TAKE OUT the sample and INSERT it into the flattening machine, PRESS the bent portion of the sample, that is the “0T” bent (see Figure 1). 7.5.1.2 APPLY scotch tape along the bent surface, REMOVE the air bubbles while flattening the tape, and then quickly PEEL OFF the tape in a 60° direction along the bent surface, CHECK for any peeling coating on the tape. It may also check whether the coating of the bent portion is cracked by visual inspection or magnifying glass. a) the test standard and negotiation terms adopted; b) instrument model; c) sample information; d) description of whether it is 180° bending or 90° bending, and whether the determination method is tape peeling or observing cracking; e) test results; f) test date and test personnel. 8 Reverse impact test 8.1 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. 8.2 Principle ALLOW the free-falling weight to impact the sample, to deform the sample quickly and form a convex area. CHECK whether the coating in the convex area is peeled off or cracked, thereby evaluating the ability of the coating to resist peeling off or cracking. 8.3 Test equipment and materials 8.3.1 Impact tester: It usually consists of a pedestal, a vertical duct, a weight and a hemispherical punch at the end. The diameter of the punch is 12.7 mm or 15.9 mm or other diameters. It usually uses the punch of which the dimeter is 15.9 mm. 8.3.2 Scotch tape: The width is approximately 25 mm and the bond strength is (10 ± 1) N/25 mm wide. Tapes agreed upon between the supply and demand parties can also be used. 8.3.3 Magnifying glass: The magnification is determined by negotiation between the supply and demand parties. It is generally 5 times to 10 times magnifying glass. 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. expressed as whether the coating of the sample is peeled off or cracked under the specified impact absorption energy test. 8.6.2 In the determination of the maximum impact absorption energy at which the coating does not peel off or crack, the result shall be expressed as the product of height and mass of the weight (J). 8.6.3 Specified impact energy absorption test or the maximum impact energy absorption test, the test condition parameters (punch diameter, amount of impact absorption energy, evaluation result of coating peeling or cracking). 8.7 Test report The test report shall include the following: a) the test standard adopted and the agreed test condition parameters; b) instrument model, punch diameter (mm); c) sample information; d) test results; e) impact absorption energy; f) test date and test personnel. 9 Pencil hardness test 9.1 General This method is applicable to determination of pencil hardness of the coating of prepainted sheets. This method specifies two test methods: manual pencil method and instrument pencil method. 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 9.3.1 A set of verified wooden pencils or moving pencils, labeled 6H, 5H, 4H, 3H, 2H, H, F, HB, B, 2B, 3B, 4B, 5B, 6B, among which 6H is the hardest, 6B is the softest, with a decreasing hardness from 6H to 6B. In general, 9.5.1.3 Starting with the hardest pencil, use each grade of pencil to draw 5 times. If the coating can be plowed twice in 5 times, use a softer pencil until it finds a pencil that cannot plow the coating at least 4 times out of 5 times. The hardness of the pencil is the pencil hardness of the coating to be tested. 9.5.2 Instrument pencil method 9.5.2.1 PLACE the sample horizontally on the operating table. PLACE the mechanical trolley for pencil marking on the sample. 9.5.2.2 FIX the pencil that has been processed in accordance with the procedure of 9.5.1.1 into the mechanical trolley so that the tip of the pencil can be freely contacted with the surface of the sample. PUSH the mechanical trolley so that the stroke on the sample is 6.5 mm. 9.5.2.3 CARRY OUT the mechanical trolley test with pencils of different hardness according to the procedure of 9.5.1.3 until the hardest pencil that cannot plow the coating at least 4 times out of 5 times is found. The hardness of the pencil is the pencil hardness of the coating to be tested. 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: a) the test standard and negotiation terms adopted; b) grade and manufacturer of the test pencil; c) sample information; d) test results (indicate whether the manual pencil method or the instrument pencil method is used); e) test date and test personnel. 10 Organic solvent resistance test 10.1 General This method is applicable to the evaluation of organic solvent resistance of the coating of prepainted sheets. the edge of the sample to avoid wetting the edges. 10.5.1.3 KEEP the cotton cloth moist during the test. 10.5.1.4 WIPE continuously until the coating is damaged and record the number of wiping times or WIPE continuously to the specified number of times to observe if the coating is damaged. The coating damage at both ends of the wiping area is not counted. The test area in the middle with a length of 125 mm is used as the evaluation area. The test process shall be continuous. If the reagent needs to be replenished, the interruption of the test process shall not exceed 10 s. 10.5.1.5 USE a new cotton cloth every time when test a new sample. 10.5.2 Instrument method 10.5.2.1 WRAP the entire contact area of the artificial finger with a certain thickness of cotton cloth or cotton wool. Completely SOAK the cotton cloth or cotton wool with the specified solvent by immersion or dropping. PLACE the artificial fingertip on the surface of the sample, leaving the edge of the sample well to avoid wetting the edges. 10.5.2.2 MOVE the fingertip by the specified number of wiping times at a speed of one back and forth per second. The motion shall be continuous. 10.5.2.3 The absorbent cotton shall be kept moist during the test. 10.5.2.4 After the test of the specified number of wiping times, observe whether the coating is damaged. The coating damage at both ends of the wiping area is not counted. The test process shall be continuous. If the reagent needs to be replenished, the interruption of the test process shall not exceed 10 s. 10.6 Expression of results 10.6.1 Manual method: It is indicated by-pass or fail under the specified number of wiping times, or record the number of wiping times when the coating is damaged. 10.6.2 Instrument method: It is indicated by-pass or fail under the specified number of wiping times. 10.7 Test report The test report shall include the following: a) the test standard and negotiation terms adopted; b) instrument model, solvent used; ± 5 % for at least 24 h before test. 11.5 Test procedure 11.5.1 USE the analytical balance to accurately determine the mass of each sample, weigh to the nearest 0.1 mg. 11.5.2 PLACE the sample on the sample sheet holder with the surface to be tested facing up; FIX it with screws. MOUNT a pair of ground abrasion wheels on the two arms of the abrasion tester. The additional mass is such that the total load of the arms is typically 500 g or 1000 g. PLACE the arms on the sample; TURN ON the abrasion tester. The abrasion wheel speed is generally 60 r/min and the maximum is 100 r/min. 11.5.3 Test to the specified number of abrasion revolutions or until the steel substrate is exposed. The vacuum cleaner shall continuously absorb the debris from the surface of the sample during the operation of the abrasion tester. 11.5.4 REMOVE the sample, CLEAN it and USE the analytical balance to accurately determine the mass of the sample after the abrasion resistance test. 11.5.5 After the abrasion wheel has been rotated 500 times to 1000 times or before the new abrasion wheel is used, the abrasion wheel is ground with 25 to 50 revolutions using S-11 grinding disc sandpaper. 11.6 Expression of results The result is expressed by the mass loss of the sample after the specified number of abrasion revolutions (the difference in mass before and after the test), in milligrams (mg), or by the number of abrasion revolutions after which the steel substrate is exposed. The arithmetic mean of the test results of two parallel samples is taken as the test result. 11.7 Test report The test report shall include the following: a) the test standard and negotiation terms adopted; b) instrument model; c) total load and abrasion revolutions; d) sample information; e) test results; f) test date and test personnel. scratches the topcoat, it indicates that the sample has failed the scratch resistance test under the load; if the steel needle does not scratch the coating to the steel substrate or scratch the topcoat, it indicates that the sample passed the scratch resistance test under the load. 12.5.1.3 DETERMINE on three different parts of the sample surface; RECORD the test results separately. 12.5.2 Test for determining the maximum load under which the coating is scratched 12.5.2.1 According to the procedure of 12.5.1, repeat the test by gradually reducing or increasing the mass of the weight until it finds the maximum mass of the weight under which the coating is not scratched to the steel substrate or the topcoat is not scratched. According to the load, the interval of reducing or increasing the weight each time may be 100 g, 200 g or 300 g. Both the supply and demand parties shall negotiate whether to reduce the weight or increase the weight for test before the test. 12.5.2.2 DETERMINE on three different parts of the sample surface. 12.6 Expression of results 12.6.1 Judge whether the test is passed/failed under fixed load If the sample passes at least two of the three tests, it is determined passing the scratch resistance test under the fixed load. 12.6.2 Test for determining the maximum l...... ......
 
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