GB/T 13448-2019 English PDF (GB/T13448-2019)

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GB/T 13448-2019: Test methods for prepainted steel sheet and strip
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
da...