ASTM G67-24
(Test Method)Standard Test Method for Determining the Susceptibility to Intergranular Corrosion of 5XXX Series Aluminum Alloys by Mass Loss After Exposure to Nitric Acid (NAMLT Test)
Standard Test Method for Determining the Susceptibility to Intergranular Corrosion of 5XXX Series Aluminum Alloys by Mass Loss After Exposure to Nitric Acid (NAMLT Test)
SIGNIFICANCE AND USE
4.1 This test method provides a quantitative measure of the susceptibility to intergranular corrosion of Al-Mg and Al-Mg-Mn alloys. The nitric acid dissolves a second phase, an aluminum-magnesium intermetallic compound (βAl-Mg), in preference to the solid solution of magnesium in the aluminum matrix. When this compound is precipitated in a relatively continuous network along grain boundaries, the effect of the preferential attack is to corrode around the grains, causing them to fall away from the specimens. Such dropping out of the grains causes relatively large mass losses of the order of 25 mg/cm2 to 75 mg/cm2 (160 mg/in.2 to 480 mg/in.2), whereas, samples of intergranular-resistant materials lose only about 1 mg/cm2 to 15 mg/cm2 (10 mg/in.2 to 100 mg/in.2). When the βAl-Mg compound is randomly distributed, the preferential attack can result in intermediate mass losses. Metallographic examination is required in such cases to establish whether or not the loss in mass is the result of intergranular attack.
4.2 The precipitation of the second phase in the grain boundaries also gives rise to intergranular corrosion when the material is exposed to chloride-containing natural environments, such as seacoast atmospheres or sea water. The extent to which the alloy will be susceptible to intergranular corrosion depends upon the degree of precipitate continuity in the grain boundaries. Visible manifestations of the attack may be in various forms such as pitting, exfoliation, or stress-corrosion cracking, depending upon the morphology of the grain structure and the presence of sustained tensile stress.3
SCOPE
1.1 This test method, also known as the Nitric Acid Mass Loss Test (NAMLT), covers a procedure for constant immersion intergranular corrosion testing of 5XXX series aluminum alloys.
1.2 This test method is applicable only to wrought products.
1.3 This test method covers type of specimen, specimen preparation, test environment, and method of exposure.
1.4 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
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Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: G67 − 24
Standard Test Method for
Determining the Susceptibility to Intergranular Corrosion of
5XXX Series Aluminum Alloys by Mass Loss After Exposure
1
to Nitric Acid (NAMLT Test)
This standard is issued under the fixed designation G67; the number immediately following the designation indicates the year of original
adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope E691 Practice for Conducting an Interlaboratory Study to
Determine the Precision of a Test Method
1.1 This test method, also known as the Nitric Acid Mass
G1 Practice for Preparing, Cleaning, and Evaluating Corro-
Loss Test (NAMLT), covers a procedure for constant immer-
sion Test Specimens
sion intergranular corrosion testing of 5XXX series aluminum
G16 Guide for Applying Statistics to Analysis of Corrosion
alloys.
Data
1.2 This test method is applicable only to wrought products.
3. Summary of Test Method
1.3 This test method covers type of specimen, specimen
preparation, test environment, and method of exposure.
3.1 This test method consists of immersing test specimens
in concentrated nitric acid at 30 °C (86 °F) for 24 h and
1.4 The values stated in SI units are to be regarded as the
determining the mass loss per unit area as a measure of
standard. The values given in parentheses are for information
susceptibility to intergranular corrosion.
only.
1.5 This standard does not purport to address all of the
4. Significance and Use
safety concerns, if any, associated with its use. It is the
4.1 This test method provides a quantitative measure of the
responsibility of the user of this standard to establish appro-
susceptibility to intergranular corrosion of Al-Mg and Al-
priate safety, health, and environmental practices and deter-
Mg-Mn alloys. The nitric acid dissolves a second phase, an
mine the applicability of regulatory limitations prior to use.
aluminum-magnesium intermetallic compound (βAl-Mg), in
1.6 This international standard was developed in accor-
preference to the solid solution of magnesium in the aluminum
dance with internationally recognized principles on standard-
matrix. When this compound is precipitated in a relatively
ization established in the Decision on Principles for the
continuous network along grain boundaries, the effect of the
Development of International Standards, Guides and Recom-
preferential attack is to corrode around the grains, causing
mendations issued by the World Trade Organization Technical
them to fall away from the specimens. Such dropping out of the
Barriers to Trade (TBT) Committee.
grains causes relatively large mass losses of the order of
2
2 2 2
2. Referenced Documents
25 mg ⁄cm to 75 mg ⁄cm (160 mg ⁄in. to 480 mg ⁄in. ),
2
whereas, samples of intergranular-resistant materials lose only
2.1 ASTM Standards:
2 2 2 2
about 1 mg ⁄cm to 15 mg ⁄cm (10 mg ⁄in. to 100 mg/in. ).
D1193 Specification for Reagent Water
When the βAl-Mg compound is randomly distributed, the
E29 Practice for Using Significant Digits in Test Data to
preferential attack can result in intermediate mass losses.
Determine Conformance with Specifications
Metallographic examination is required in such cases to
establish whether or not the loss in mass is the result of
1
This test method is under the jurisdiction of ASTM Committee G01 on
intergranular attack.
Corrosion of Metals and is the direct responsibility of Subcommittee G01.05 on
Laboratory Corrosion Tests. This method was developed by a joint task group with
4.2 The precipitation of the second phase in the grain
The Aluminum Association, Inc.
boundaries also gives rise to intergranular corrosion when the
Current edition approved Jan. 15, 2024. Published January 2024. Originally
material is exposed to chloride-containing natural
approved in 1980. Last previous edition approved in 2018 as G67 – 18. DOI:
10.1520/G0067-24.
environments, such as seacoast atmospheres or sea water. The
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
extent to which the alloy will be susceptible to intergranular
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
corrosion depends upon the degree of precipitate continuity in
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. the grain boundaries. Visible manifestations of the attack may
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
---------------------- Page: 1 ----------------------
G67
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: G67 − 18 G67 − 24
Standard Test Method for
Determining the Susceptibility to Intergranular Corrosion of
5XXX Series Aluminum Alloys by Mass Loss After Exposure
1
to Nitric Acid (NAMLT Test)
This standard is issued under the fixed designation G67; the number immediately following the designation indicates the year of original
adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This test method, also known as the Nitric Acid Mass Loss Test (NAMLT) describes(NAMLT), covers a procedure for constant
immersion intergranular corrosion testing of 5XXX series aluminum alloys.
1.2 This test method is applicable only to wrought products.
1.3 This test method covers type of specimen, specimen preparation, test environment, and method of exposure.
1.4 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2
2.1 ASTM Standards:
D1193 Specification for Reagent Water
E29 Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
G1 Practice for Preparing, Cleaning, and Evaluating Corrosion Test Specimens
G16 Guide for Applying Statistics to Analysis of Corrosion Data
3. Summary of Test Method
3.1 This test method consists of immersing test specimens in concentrated nitric acid at 30°C (86°F) for 24 h 30 °C (86 °F) for
24 h and determining the mass loss per unit area as a measure of susceptibility to intergranular corrosion.
1
This test method is under the jurisdiction of ASTM Committee G01 on Corrosion of Metals and is the direct responsibility of Subcommittee G01.05 on Laboratory
Corrosion Tests. This method was developed by a joint task group with The Aluminum Association, Inc.
Current edition approved Oct. 1, 2018Jan. 15, 2024. Published January 2019January 2024. Originally approved in 1980. Last previous edition approved in 20132018 as
G67 – 13.G67 – 18. DOI: 10.1520/G0067-18.10.1520/G0067-24.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
---------------------- Page: 1 ----------------------
G67 − 24
4. Significance and Use
4.1 This test method provides a quantitative measure of the susceptibility to intergranular corrosion of Al-Mg and Al-Mg-Mn
alloys. The nitric acid dissolves a second phase, an aluminum-magnesium intermetallic compound (βAl-Mg), in preference to the
solid solution of magnesium in the aluminum matrix. When this compound is precipitated in a relatively continuous network along
grain boundaries, the effect of the preferential attack is to corrode around the grains, causing them to fall away from the specimens.
2 2
Such dropping out of the grains causes relatively large mass losses of the order of 2525 mg ⁄cm to 75 75 mg mg/cm⁄cm
2 2 2
(160(160 mg ⁄in. to 480 480 mg mg/in.⁄in. ), whereas, samples of intergranular-resistant materials lose only about 11 mg ⁄cm to
2 2 2
15 15 mg mg/cm⁄cm (10(10 mg ⁄in. to 100 mg/in. ). When the βAl-Mg compound is randomly distributed, the preferential attack
can result in intermediate mass losses. Metallographic examination is required in such cases to establish whether or not the loss
in mass is the result of intergranular attack.
4.2 The precipitation of the second phase in the grain boundaries also gives rise to intergranular corrosion when the material is
exposed to chloride-containing natural e
...
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