Codeofchina.com is in charge of this English translation. In case of any doubt about the English translation, the Chinese original shall be considered authoritative.
This standard is developed 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 and strip, and the following main technical changes have been made with respect to GB/T 13448-2006:
——Measuring 3 different positions is changed into measuring 5 different positions in the magnetic thickness gauge method (see 4.5.1.2; 4.5.1 in Edition 2006);
——The magnetic-eddy current thickness gauge method is added (see 4.5.5);
——The unit description of specular gloss is added, the requirements for gloss meter accuracy verification are added, and the description of measuring angle of gloss meter is revised (see Clause 5; Clause 5 in Edition 2006);
——The theory for measuring color difference with a colorimeter, the requirements for the colorimeter, the description of the calibration plate/specimen of the colorimeter and the calculation formula for color difference value are modified (see Clause 6; Clause 6 in Edition 2006);
——In the bend test, the requirements for magnification factor of the magnifying glass are canceled, the 90° bend test is added, and the description of cracking observation with the magnifying glass is added (see Clause 7; Clause 7 in Edition 2006);
——In the reverse impact test, the description of the diameter of 12.7 mm puncher pin is added, the requirements for magnification factor of the magnifying glass is canceled, the description for observing the cracking with a magnifying glass is added, the description for checking the cracking with copper sulfate is deleted, and the contents of the result expression and the negotiable contents of the test report are added (see Clause 8; Clause 8 in Edition 2006);
——In the clauses about organic solvent resistance test, the description of hygroscopicity of cotton cloth or absorbent cotton is added, and the description of the test process such as "the test process shall be continuous, if reagents need to be supplemented, the interruption time of the test process shall not exceed 10 s" is added (see Clause 10; Clause 10 in Edition 2006);
——In the clauses about scratch resistance test, the test theory is revised, the diameter range of the test needle is modified, and the requirements of weight loading interval is added, and the requirement “repeat the test by gradually increasing the weight of the load weight” in 12.5.2.1 is modified as "repeat the test by gradually decreasing or increasing the weight of the load weight” (see Clause 12; Clause 12 in Edition 2006);
——The test method for surface resistivity is added (see Clause 15);
——The test method for coating contact angle is added (see Clause 16);
——The "boiling water resistance test” is renamed as "water immersion resistance test", and the application scope and specific test details of this method are modified (see Clause 17; Clause 15 in Edition 2006);
——In the clauses about acid and alkali resistance test, the test device, materials, test procedures and other contents are modified (see Clause 18; Clause 16 in Edition 2006);
——In the clauses about pollution resistance test, the disinfectant solution is added as an test material, test procedures are modified, and the detailed procedures for removing residual pollutants after the completion of the pollution resistance test are added (see Clause 19; Clause 17 in Edition 2006);
——The method for carbon black pollution resistance test is added (see Clause 20);
——The test method for verifying salt spray chamber corrosion resistance is added, and the requirements for the exposure time of specimens are modified (see Clause 21);
——The application scope of dry heat resistance test is extended, the "forced ventilation oven" in the previous standard is changed to "oven” which is common in the laboratory, and two test temperatures commonly used in the dry heat resistance test on prepainted steel sheet are recommended (see Clause 22);
——The contents of damp heat resistance test procedures and result expression are modified (see Clause 23; Clause 20 in Edition 2006);
——The sulfur dioxide damp heat resistance test method is deleted (Clause 21 in Edition 2006);
——The method for cyclic corrosion test is added (see Clause 24);
——The spectral energy distribution diagram of the ultraviolet light source is modified, the previous continuous illumination test method is deleted, and the irradiation intensity of the four test methods in Table 7 "Test methods for ultraviolet lamps within four different periods" is modified (see Clause 26; Clause 23 in Edition 2006);
——The method for measuring the plating mass and plating thickness of prepainted steel sheets is added (see Annex A).
This standard was proposed by the China Iron and Steel Association.
This standard is under the jurisdiction of the SAC/TC 183 National Technical Committee on Iron and Steel of Standardization Administration of China.
This standard was issued in 1992 as first edition, and revised for the first time in 2006 and for the second time in 2019.
Test methods for prepainted steel sheet and strip
1 Scope
This standard specifies the terms and definitions as well as related test methods, test reports, etc. of tests on the prepainted steel sheet and strip.
This standard is applicable to the determination and evaluation of the performance of the coating of prepainted steel sheet and strip (hereinafter referred to as prepainted steel sheet).
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 and strip
GB/T 30693 Measurement of water-contact angle of plastic films
3 Terms and definitions
For the purposes of this document, the terms and definitions given in GB/T 12754 and the following apply.
3.1
specular gloss
relative luminous reflectance factor of the specimen in the specular reflection direction
3.2
relative luminous reflectance factor
ratio of the luminous flux reflected by the specimen to that by standard surface under the same geometric conditions
3.3
tristimulus values
amount of three reference stimuluses required to achieve color matching with the light to be measured in a three-color system
3.4
chromaticity coordinate
proportion of any single tristimulus value accounting for the sum of tristimulus values
3.5
T-bend
minimum n value at which the coating does not fall off or crack in the 180° reverse bend test with n (n=0, 1, 2 ...) times of the thickness of the specimen under test as the curvature radius
3.6
pencil hardness
judging the anti-plowing ability of the coating by scratching the surface of the coating with a set of pencils of specified pencil lead size, shape and hardness
3.7
cupping height
height of the cup deformed by stamping at the end of the test
3.8
blank plate
flat plate with the same size as the specimen, which is used to cover the gap of the specimen holder to prevent light leakage when the specimen holder is not full of specimens
4 Coating thickness determination
4.1 General
4.1.1 This method is applicable to the determination of coating thickness of the prepainted steel sheet.
4.1.2 The following methods may be used to determine the coating thickness of the prepainted steel sheet:
a) magnetic thickness gauge method: it is applicable to the determination of coating thickness of prepainted steel sheet with cold-rolled sheet and galvanized sheet as substrate. This method is not applicable if the coating thickness is less than 3μm. This method is not applicable if the coating has a special uneven surface effect.
b) micrometer method: it is applicable to the determination of coating thickness of prepainted steel sheet with various materials as substrate. This method is not applicable to coatings that easily deform under the load of micrometer measuring devices. This method is not applicable if the coating has a special uneven surface effect.
c) metallographic microscopic method: it is applicable to the determination of coating thickness of prepainted steel sheet with various materials as substrate.
d) DJH method: it is applicable to the determination of coating thickness of prepainted steel sheet with various materials as substrate. It is also applicable to the separate determination of coating (including primary and fine coatings) thickness if the interface of each coating may be clearly distinguished
e) magnetic-eddy current thickness gauge method: it is applicable to the determination of coating thickness of prepainted steel sheet with various materials as substrate. This method is not applicable if the coating has a special uneven surface effect.
Foreword i
1 Scope
2 Normative references
3 Terms and definitions
4 Coating thickness determination
5 Determination of specular gloss
6 Determination of color difference
7 Bending test
8 Reverse impact test
9 Pencil hardness test
10 Organic solvent resistance test
11 Wear resistance test
12 Scratch resistance test
13 Cross cut test
14 Cupping test
15 Surface resistivity test
16 Coating contact angle test
17 Water immersion resistance test
18 Acid and alkali resistance test
19 Pollution resistance test
20 Carbon black pollution resistance test
21 Neutral salt mist resistance test
22 Dry heat resistance test
23 Damp heat resistance test
24 Cyclic corrosion test
25 Accelerated aging test by using xenon lamp
26 Accelerated aging test by using ultraviolet lamp
27 Atmospheric exposure test
Annex A (Normative) Methods for shedding the coating of prepainted steel sheets and measuring the plating thickness
Annex B (Informative) Range of Knoop hardness of Zhonghua Brand special pencil with 505 rolled steel coating for hardness test and its corresponding relationship with the range of Knoop hardness of Zhonghua Brand 101 drawing pencil
