GB/T 4334-2020 English PDF (GBT4334-2020)

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GB/T 4334-2020: Corrosion of metals and alloys -- Test methods for intergranular corrosion of austenitic and ferritic-austenitic (duplex) stainless steels
GB/T 4334-2020
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.060
H 25
Replacing GB/T 4334-2008
Corrosion of metals and alloys - Test methods for
intergranular corrosion of austenitic and ferritic-
austenitic (duplex) stainless steels
[ISO 3651-1:1998, Determination of resistance to intergranular corrosion of
stainless steels - Part 1: Austenitic and ferritic-austenitic (duplex) stainless steels
- Corrosion test in nitric acid medium by measurement of loss in mass (Huey
test); ISO 3651-2:1998, Determination of resistance to intergranular corrosion of
stainless steels - Part 2: Ferritic, austenitic and ferritic-austenitic (duplex)
stainless steels - Corrosion test in media containing sulfuric acid, MOD]
ISSUED ON: APRIL 28, 2020
IMPLEMENTED ON: NOVEMBER 01, 2020
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 ... 6 
3 Method summary ... 7 
4 Method A 10% oxalic acid corrosion test method ... 16 
5 Method B 50% sulfuric acid-ferric sulfate corrosion test method ... 24 
6 Method C 65% nitric acid corrosion test method ... 26 
7 Method E copper-copper sulfate-16% sulfuric acid corrosion test method . 27 
8 Method F copper-copper sulfate-35% sulfuric acid corrosion test method . 30 
9 Method G 40% sulfuric acid-ferric sulfate corrosion test method ... 32 
Appendix A (Informative) Structural changes of this Standard compared with
ISO 3651-1:1998 and ISO 3651-2:1998 ... 33 
Appendix B (Informative) Technical differences between this Standard and ISO
3651-1:1998 and ISO 3651-2:1998 and their reasons ... 35 
Appendix C (Informative) Test methods and characteristics of this Standard 36 
Appendix D (Informative) Scope of application of Method E, Method F and
Method G ... 37 
Corrosion of metals and alloys - Test methods for
intergranular corrosion of austenitic and ferritic-
austenitic (duplex) stainless steels
1 Scope
This Standard specifies the samples, test solutions, test instruments and
equipment, test conditions and procedures, test result evaluation and test report
of test methods for intergranular corrosion of austenitic and ferritic-austenitic
(duplex) stainless steels.
This Standard applies to the inspection of intergranular corrosion tendency of
austenitic stainless steels and ferritic-austenitic (duplex) stainless steels
(hereinafter referred to as duplex stainless steels). It includes the following test
methods:
a) Method A: 10% oxalic acid corrosion test method
It is a screening test to check the intergranular corrosion of austenitic
stainless steels. After the sample is electrolytically etched in 10% oxalic
acid solution, observe the metallographic structure of the etched surface
under a microscope, so as to determine whether Method B, Method C,
Method E and other long-time hot acid tests are required. In the case of
not allowing damage to the tested structural parts and equipment, it can
also be used as an independent intergranular corrosion inspection method.
b) Method B: 50% sulfuric acid-ferric sulfate corrosion test method
Place the austenitic stainless steels in the 50% sulfuric acid-ferric sulfate
solution for a boiling test; then, use the corrosion rate to evaluate the
intergranular corrosion tendency.
c) Method C: 65% nitric acid corrosion test method
Place the austenitic stainless steels in the 65% nitric acid solution for a
boiling test; then, use the corrosion rate to evaluate the intergranular
corrosion tendency.
d) Method E: copper-copper sulfate-16% sulfuric acid corrosion test method
Place the austenitic stainless steels and duplex stainless steels in the
copper-copper sulfate-16% sulfuric acid solution for a boiling test; then,
use the bending method or the metallographic method to determine the
intergranular corrosion tendency.
e) Method F: copper-copper sulfate-35% sulfuric acid corrosion test method
Place the austenitic stainless steels and duplex stainless steels in the
copper-copper sulfate-35% sulfuric acid solution for a boiling test; then,
use the bending method or the metallographic method to determine the
intergranular corrosion tendency.
f) Method G: 40% sulfuric acid-ferric sulfate corrosion test method
Place the austenitic stainless steels and duplex stainless steels in the 40%
sulfuric acid-ferric sulfate solution for a boiling test; then, use the bending
method or the metallographic method to determine the intergranular
corrosion tendency.
Appendix C of this Standard gives the characteristics of each test method in the
form of a table; Appendix D gives the application examples of method E, method
F, and method G.
The test methods in this Standard are not applicable to predicting the
intergranular corrosion resistance of stainless steels under other media, nor to
predicting the corrosion resistance of stainless steels to other forms of corrosion
(such as pitting corrosion, uniform corrosion, stress corrosion).
2 Normative references
The following documents are indispensable for the application of this document.
For dated references, only the dated version applies to this document. For
undated references, the latest edition (including all amendments) applies to this
document.
GB/T 625, Chemical reagent - Sulfuric acid (GB/T 625-2007, ISO 6353-
2:1983, NEQ)
GB/T 626, Chemical reagent - Nitric acid (GB/T 626-2006, ISO 6353-2:1983,
NEQ)
GB/T 655, Chemical reagent - Ammonium persulfate
GB/T 665, Chemical reagent - Copper (II) sulfate pentahydrate (GB/T 665-
2007, ISO 6353-2:1983, NEQ)
GB/T 2100, Corrosion-resistant steel castings for general applications (GB/T
2100-2017, ISO 11972:2015, MOD)
cannot be ground or pickled, the surface cannot be oxidized during heat
treatment.
3.1.9 During the cutting and surface grinding process of samples for Method B,
Method C, Method E, Method F, Method G , the surface shall be prevented from
overheating; the surface roughness Ra value of the processed sample shall
generally be no more than 0.8 μm. For samples that cannot be ground, other
surface roughness can also be used according to the agreement between the
two parties.
Table 1 -- Sample size and preparation requirements of Method B and
Method C
Classification
Thickness or
diameter a
mm
Sample size
mm
Number of
samples
pcs
Note
Length Width Thickness
Steel plate,
strip (flat
steel)
≤3 30±10 20±10 - 2 Take samples along the rolling direction
>3 30±10 20±10 3~4 2
Take samples along the
rolling direction; process one
sample from one side to the
thickness of the sample;
process the other sample
from the other side to the
thickness of the sample
Section
steel,
forging
- 30±10 20±10 3~4 2
Take samples longitudinally
from the middle of the cross
section
Steel rod
(steel wire)
≤10 30±10 - - 2 -
>10 30±10 ≤20 ≤5 2
Take samples longitudinally
from the middle of the cross
section
Seamless
steel tube
< 5 30±10 - - 2 Take a full-tubular sample
5~15 30±10 - - 2 Take a semi-tubular or boat-shaped sample
>15 30±10 ≤20 -
Wall
thickness <
4 mm
2 -
Wall
thickness ≥
4 mm
Process one group (2
samples) from the outer wall
to the thickness of the
sample; process the other
group (2 samples) ...