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
GB/T 13448-2019 The following standards are cited：
