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GB/T 1839: Evolution and historical versions
| Standard ID | Contents [version] | USD | STEP2 | [PDF] delivery | Name of Chinese Standard | Status |
| GB/T 1839-2025 | English | 260 |
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Test method for gravimetric determination of the mass per unit area of galvanized coatings on steel products
| Valid |
| GB/T 1839-2008 | English | 85 |
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Test method for gravimetric determination of the mass per unit area of galvanized coatings on steel products
| Valid |
| GB/T 1839-2003 | English | 279 |
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Test method for gravimetric determination of the mass per unit area of galvanized coatings on steel products
| Obsolete |
| GB/T 1839-1993 | English | 199 |
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Steel product. Zinc coating mass testing method
| Obsolete |
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GB/T 1839-2025: Test method for gravimetric determination of the mass per unit area of galvanized coatings on steel products
---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/GBT1839-2025
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.040.99
CCS H 21
Replacing GB/T 1839-2008
Test Method for Gravimetric Determination of the Mass per
Unit Area of Galvanized Coatings on Steel Products
Issued on: AUGUST 29, 2025
Implemented on: MARCH 1, 2026
Issued by. State Administration for Market Regulation;
Standardization Administration of the People’s Republic of China.
Table of Contents
Foreword... 3
1 Scope... 5
2 Normative References... 5
3 Terms and Definitions... 5
4 Specimen... 5
5 Gravimetric Method... 6
6 X-Ray Fluorescence Method... 8
7 Selection of Test Methods... 11
8 Reproducibility... 11
9 Test Report... 11
Appendix A (Normative) Method for Measuring the Specimen Area of Irregularly
Shaped Galvanized Steel Products or Articles... 12
Appendix B (Normative) Preparation Method of Standard Samples for X-ray
Fluorescence Standard Curve... 14
Appendix C (Normative) Test Methods for Coating mass of Aluminum-Silicon Alloy
Coatings... 16
Bibliography... 17
Test Method for Gravimetric Determination of the Mass per
Unit Area of Galvanized Coatings on Steel Products
1 Scope
This Document specifies the principles, test solutions, specimens, selection of test methods, test
procedures, result calculation, reproducibility, and test reports for the method of testing the
quality of galvanized coating per unit area on steel products.
This Document applies to coating products including pure zinc coatings, zinc-iron alloy
coatings, zinc-magnesium alloy coatings, zinc-aluminum-magnesium alloy coatings,
aluminum-zinc alloy coatings, and aluminum-zinc-magnesium alloy coatings.
Other coating products, such as aluminum-silicon alloy coatings, shall refer to this Document
for further details.
2 Normative References
The provisions in following documents become the essential provisions of this Document
through reference in this Document. For the dated documents, only the versions with the dates
indicated are applicable to this Document; for the undated documents, only the latest version
(including all the amendments) is applicable to this Document.
GB/T 8170 Rules of rounding off for numerical values & expression and judgement of
limiting values
3 Terms and Definitions
For the purposes of this Document, there are no terms and definitions apply.
4 Specimen
4.1 The sampling location, position, and quantity shall comply with the provisions of relevant
product standards or agreements.
4.2 The test area shall be selected according to the coating thickness to ensure meeting the
requirements for specimen weighing accuracy.
4.3 When cutting the specimen, care shall be taken to avoid surface scratches. Specimens with
obvious local damage shall not be used.
4.4 The specimens of steel sheet and strip may be circular or square. The single-sided area of
the arbitration test specimen shall be no less than 1500.0 mm².
4.5 The length of the steel wire specimen shall be cut according to the provisions of Table 1.
4.6 Other types of galvanized steel products or articles may be tested in round, square, or tubular
shapes, or irregular shapes; and the area of the test specimen shall be no less than 2000.0 mm².
4.7 The total test area of irregularly shaped galvanized steel products or articles shall be
measured or theoretically calculated according to Appendix A.
5 Gravimetric Method
5.1 Principle
The galvanized coating on a certain surface area is dissolved in a test solution with corrosion
inhibition properties. The masses of the specimen before and after dissolution are measured.
The mass of the galvanized coating per unit area is calculated based on the difference in mass
and the specimen area.
5.2 Test solutions
5.2.1 Cleaning solution. Chemically pure anhydrous ethanol or other solutions that do not
damage the coating.
5.2.2 Galvanized coating stripping solution. Dissolve 3.5 g of chemically pure
hexamethylenetetramine (C6H12N4) in 500 mL of concentrated hydrochloric acid (ρ ≥ 1.18
g/mL); and dilute to 1000 mL with distilled or deionized water.
5.2.3 The galvanize coating stripping solution can be reused repeatedly as long as it can dissolve
the galvanized coating.
5.3 Test procedure
5.3.1 Clean or wipe the specimen surface clean off oil, dust, water stains, etc. with the cleaning
solution, then dry thoroughly and cool to room temperature.
5.3.2 Weigh the specimen using a balance, with an accuracy better than 1% of the expected
mass of the coating. When the coating mass is no less than 0.1 g, the weighing accuracy shall
be accurate to 0.001 g.
5.3.3 Immerse the specimen in the galvanized coating stripping solution. The amount of the
used galvanized coating stripping solution is usually no less than 10 mL per square centimeter
of sample surface area.
5.3.4 At room temperature, completely immerse the specimen in the solution; turning it
occasionally, until the coating is completely dissolved. The dissolution process is considered
complete when the emission of hydrogen evolution reaction (violent bubbling) clearly stops.
Then take out the sample and rinse it under running water. If necessary, use a nylon brush to
remove any loose adhering substances that may be attached on the specimen surface. Finally,
wash with a cleaning solution, dry quickly; or use absorbent paper to remove moisture. After
rapid and thorough drying, cool to room temperature.
5.3.5 Weigh the specimen using a balance with the same accuracy as in 5.3.2.
5.3.6 After weighing, measure the exposed surface area after the galvanized coating of the
specimen dissolves, with the accuracy no less than 1%. The diameter or side length of the steel
sheet or strip specimen shall be measured, accurate to at least 0.1 mm. The diameter of the steel
wire shall be measured once at mutually perpendicular locations on the same circumference;
and the average value shall be taken. When the diameter of the steel wire is greater than 0.50
mm, the diameter measurement shall be accurate to at least 0.01 mm. When the diameter of the
steel wire is no greater than 0.50 mm, the diameter measurement shall be accurate to at least
0.001 mm.
5.3.7 When measuring the galvanized coating mass of a single side of a galvanized sheet, one
side shall be sealed in an appropriate manner before measurement; after that, the second side
shall be measured. If necessary, the thickness direction of the sample sheet can be sealed.
5.4 Calculation of results
5.4.1 The galvanized coating mass per unit area of steel products (excluding steel wire) or
products is calculated according to Formula (1).
Where.
M - mass of the galvanized coating per unit area, in g/m2;
m1 - mass of the specimen galvanized coating before dissolving, in g;
m2 - mass of the specimen galvanized coating after dissolving, in g;
A - exposed area of the specimen, such as steel sheet, strip, or product; or the sum of the inner
and outer surface areas of the steel pipe specimen, in mm2.
5.4.2 The mass of the galvanized coating per unit area of the galvanized steel wire is calculated
according to Formula (2).
Where.
M - mass of the galvanized coating per unit area, in g/m2;
m1 - mass of the specimen galvanized coating before dissolving, in g;
m2 - mass of the specimen galvanized coating after dissolving, in g;
D – diameter of the specimen galvanized coating after dissolving, in mm;
1962 – constant number.
5.4.3 When it is necessary to express the approximate thickness of the galvanized coating, it
shall be calculated according to Formula (3).
Where.
d – thickness of galvanized coating, in μm;
M - mass of the galvanized coating per unit area, in g/m2;
ρ - Galvanized coating density, in g/cm³. Typically, the density of pure galvanized coating and
zinc-iron alloy coating is 7.1 g/cm ³ ; the density of zinc-aluminum and zinc-aluminum-
magnesium alloy coating is 5.6 g/cm³; and the density of aluminum-zinc and aluminum-zinc-
magnesium alloy coating is 3.8 g/cm³. Special compositions will be specified separately.
5.4.4 The inspection results shall be performed in accordance with the provisions of GB/T 8170,
using the rounding-off comparison method. The retain number of digits shall meet the
requirements of the relevant product standards.
6 X-Ray Fluorescence Method
6.1 Principle
6.1.1 Absorption method. A steel sheet covered with a metallic coating is irradiated with
primary radiation generated by a radiographic source (X-ray tube or radioactive isotope). Under
certain conditions, iron-characterized fluorescent X-rays (secondary radiation) are excited
within the steel substrate. They experience varying degrees of intensity attenuation as they
penetrate metallic coatings of different thicknesses. The intensity of the fluorescent X-rays is
detected. When the generation of primary radiation and the detection of secondary radiation are
constant, the detected intensity of the fluorescent X-rays is a function of the coating thickness.
The mass of the coating is obtained by the quantitative relationship between intensity and
coating thickness.
6.1.2 Scattering method. A steel sheet with a metallic coating is irradiated with primary X-rays.
Under certain conditions, characteristic X-rays of the coating metal, i.e., fluorescent X-rays, are
excited within the metallic coating. The intensity of the fluorescent X-rays is detected. The
mass of the coating is obtained by the quantitative relationship between intensity and metallic
coating thickness.
6.2 Test apparatus
6.2.1 The test uses an X-ray thickness gauge or gamma-ray thickness gauge for the metal
coating. The instrument consists of a radiation source, a goniometer, a detector, and an
electronic system, etc. The radiation source is an X-ray tube or a radioactive isotope that
generates primary radiation. Primary radiation excites secondary radiation in the specimen; the
goniometer drives a spectroscopic crystal and detector matched to the analyte; the detector
receives the characteristic secondary radiation (fluorescent X-rays) from the specimen, converts
it into an electrical pulse signal, and measures it; the electronic system controls the test
apparatus, processes the data, and converts the measured signal intensity into coating mass.
6.2.2 When using the measurement method of characteristic fluorescent X-rays of the coating
(scattering method), the incident intensity of the primary radiation shall ensure that the
characteristic fluorescent X-rays of the element to be measured in the coating are excited and
detected across the entire thickness of the coating. If the measurement method using matrix
characteristic fluorescence X-rays (absorption method) is adopted, the incident intensity of the
primary radiation shall ensure that the characteristic fluorescence X-rays excited in the steel
matrix have sufficient exit intensity when passing through the coating.
6.2.3 The apparatus shall have sufficiently high radiation source intensity and detection
sensitivity, enabling accurate measurement of coatings of various thicknesses with a short data
acquisition time.
6.2.4 The radiation generated from radiation source shall provide sufficient irradiation area for
the specimen; the single-sided irradiation area shall be no less than 314.0 mm².
6.2.5 The goniometer shall have sufficient positioning accuracy and precision to ensure
accurate acquisition of the characteristic fluorescent X-rays generated by the coating or
substrate. The detector shall have sufficient detection efficiency to ensure accurate
7 Selection of Test Methods
Select the test method according to the sample type and the relevant agreement between the
supplier and the purchaser.
For steel sheet and strip specimens, the galvanized coating mass test can be performed using
the gravimetric method or X-ray fluorescence method. When conditions permit, the method
recommended in YB/T 4829 may also be used for testing. For steel wire specimen and
irregularly shaped galvanized steel products or articles, the galvanized coating mass test
generally uses the gravimetric method.
The galvanized coating mass test for aluminum-silicon alloy coated steel sheet and strip
specimens shall be performed according to Appendix C.
When the correlation between X-ray intensity and coating mass is poor (e.g., pure zinc coating
mass > 200 g/m²) or in arbitration, the gravimetric method shall be used for testing.
8 Reproducibility
When measured by different instruments, under different operating conditions, and by different
testers, the reproducibility of this method is approximately ±5% of the mean.
9 Test Report
If applicable, the test report shall include at least the following.
a) Product name;
b) Specimen identification;
c) This Document number and test method;
d) Specimen shape and dimensions;
e) Test results;
f) Test date and testers;
g) Other information.
......
Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al.
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