GB/T 7998-2023 PDF English
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| Standard ID | Contents [version] | USD | STEP2 | [PDF] delivery | Name of Chinese Standard | Status |
| GB/T 7998-2023 | English | 350 |
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Method for evaluating the susceptibility to intergranular corrosion of aluminum alloys
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| GB/T 7998-2005 | English | 90 |
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Test method for intergranular corrosion of aluminium alloy
| Obsolete |
| GB/T 7998-1987 | English | 199 |
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The method for determining the intergranular corrosion of aluminium alloy
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Excerpted PDFs (Download full copy in 9 seconds upon purchase)PDF Preview: GB/T 7998-2023
GB/T 7998-2023: Method for evaluating the susceptibility to intergranular corrosion of aluminum alloys
---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/GBT7998-2023
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.040.30
CCS H 25
Replacing GB/T 7998-2005, GB/T 26491-2011
Method for evaluating the susceptibility to intergranular
corrosion of aluminum alloys
Issued on. MAY 23, 2023
Implemented on. DECEMBER 01, 2023
Issued by. State Administration for Market Regulation;
National Standardization Administration.
Table of Contents
Foreword... 3
1 Scope... 5
2 Normative references... 5
3 Terms and definitions... 5
4 Principle... 6
5 Test conditions... 6
6 Reagents... 6
7 Instruments and materials... 7
8 Specimens... 8
9 Test procedure... 19
10 Result processing and result expression... 23
11 Test report... 25
1 Scope
This document describes the evaluation method of intergranular corrosion sensitivity
of aluminum alloy products.
This document is applicable to the determination of intergranular corrosion sensitivity
of 2××× series, 5××× series, 6××× series, 7××× series aluminum alloy products.
2 Normative references
The contents of the following documents constitute essential clauses of this document
through normative references in the text. Among them, for dated references, only the
version corresponding to that date is applicable to this document; for undated references,
the latest version (including all amendments) is applicable to this document.
GB/T 3246.1 Inspection method for structure of wrought aluminum and aluminum
alloy products - Part 1.Inspection method for microstructure
GB/T 6682 Water for analytical laboratory use - Specification and test methods
GB/T 6684-2002 Chemical reagent - Hydrogen peroxide 30%
GB/T 8170 Rules of rounding off for numerical values and expression and
judgement of limiting values
JJG (Education committee) 012 Calibration procedures for metallographic
microscopes
3 Terms and definitions
The following terms and definitions apply to this document.
3.1
Intergranular corrosion
Corrosion that develops along the grain boundary of a metal or alloy or its adjacent
area.
4 Principle
According to the principle of cathode depolarization, the aluminum alloy specimen is
placed in a specific test solution for a certain period of time, to accelerate the corrosion
of the alloy grain boundary or near the grain boundary; the corrosion depth or mass loss
is measured to evaluate the intergranular corrosion sensitivity of the aluminum alloy.
5 Test conditions
The test environment temperature shall not be higher than the test temperature;
ventilation facilities shall be configured.
6 Reagents
Warning - The inorganic acids used in the analysis are corrosive to the human
body. The test personnel shall wear personal protective equipment to reduce the
danger caused by direct contact.
6.1 Nitric acid (ρ = 1.40 g/mL).
6.2 Nitric acid (1 + 4).
6.3 Sodium hydroxide solution A. 100 g/L.
6.4 Sodium hydroxide solution B. 50 g/L.
6.5 Sodium chloride-hydrogen peroxide solution. Dissolve 57 g of sodium chloride in
a small amount of water; stir evenly; dilute to 990 mL with water. During the test, first
heat the test solution to the test temperature; add 10 mL of hydrogen peroxide (mass
fraction 30%).
6.6 Sodium chloride-hydrochloric acid solution. Dissolve 30 g of sodium chloride in a
small amount of water; stir evenly; dilute to 990 mL with water; add 10 mL of
hydrochloric acid (ρ = 1.19 g/mL); stir evenly.
6.7 Etching agent. Mix hydrofluoric acid (ρ = 1.15 g/mL), hydrochloric acid (ρ = 1.19
g/mL), nitric acid (ρ = 1.40 g/mL), water in a volume of (2 + 3 + 5 + 190); mix evenly.
7 Instruments and materials
7.1 Conduction constant temperature device. The temperature control accuracy shall
comply with the provisions of Table 1.
7.2 Test liquid container (with lid). Beaker or other container with lid.
7.3 Specimen holder. Made of glass, plastic or other inert materials.
7.4 Sandpaper. Particle size is 35 μm.
7.5 Optical (metallographic) microscope. In accordance with JJG (Education
Committee) 012, it shall be equipped with an eyepiece micrometer 0.1 mm scale plate
(or integrated with the eyepiece); the magnification should be 100X ~ 500X.
7.6 Metallographic grinding and polishing machine.
7.7 Ultrasonic cleaning machine. Working frequency 30 kHz ~ 60 kHz.
7.10 Micrometer. The graduation value shall not be greater than 0.01 mm; the
maximum allowable deviation is ±4.0 μm.
8 Specimens
8.1 The samples shall be cut from the products and retain the original surface. The
number of samples shall comply with the requirements of the relevant product standards
or the agreement between the supplier and the buyer.
8.2 The specimens shall be cut from the samples; at least one surface of the cut
specimens shall be the original surface of the product. The original surface shall be
clean and shall not have defects such as bumps and scratches that affect the test results.
The length direction of the specimen is the main deformation direction of the product.
8.3 The specimen shall not be cut at the flange or rib of the product, or the weld of the
seamed extruded material.
8.4 The type, shape, size, quantity of the specimen shall comply with the requirements
of Table 2.
8.6 Corrosion depth method specimens can be directly marked; the marking shall be
carried out on the non-test surface. Mass loss method specimens should be marked with
hanging tags.
8.7 If there are a large number of specimens, through-holes with a diameter not greater
than 4 mm may be drilled on the surface of the specimens shown in Figures 5 ~ 7 for
ease of cleaning.
9 Test procedure
9.1 Pretreatment of specimens
Before pretreatment of the mass loss method specimen, use a fine file or sandpaper (7.4)
to grind all edges to remove burrs, scratches and other defects that may affect the test
results; then measure the length, width, thickness of the specimen, accurate to 0.02 mm.
9.2 Calculation and weighing
The total surface area (S) of the mass loss method specimen shall be calculated; the
additional surface of the hole wall of the perforated specimen shall be ignored. Then it
shall be placed on an electronic balance and weighed (m1), accurate to 0.1 mg.
9.3 Corrosion
9.4 Measurement
9.4.1 Corrosion depth method
9.4.2 Mass loss method
9.4.2.1 Take out the mass loss method specimen; rinse it with water to remove the acid.
9.4.2.2 Immerse the specimen (see Figure 18) or hang it (see Figure 19) in an ultrasonic
cleaning machine for 1 min ~ 2 min; rinse with water; air dry or blow dry with clean
compressed air.
10 Result processing and result expression
10.1 Corrosion depth method
The test results are divided into two types. no intergranular corrosion (see Figures 20
and 21) and intergranular corrosion (see Figures 22 and 23). Intergranular corrosion
shall be graded according to the maximum corrosion depth D as specified in Table 8.
11 Test report
The test report shall include at least the following contents.
......
Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al.
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