ASTM G67-18

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 to 75 mg/cm2  (160 to 480 mg/in.2), whereas, samples of intergranular-resistant materials lose only about 1 to 15 mg/cm2 (10 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) describes 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.

General Information

• Status: Historical
• Publication Date: 30-Sep-2018
• ICS: 77.120.10 - Aluminium and aluminium alloys
• Technical Committee: G01 - Corrosion of Metals
• Drafting Committee: G01.05 - Laboratory Corrosion Tests

Relations

• Replaces: ASTM G67-13 - 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)
• Effective Date: 01-Oct-2018
• Refers: ASTM G16-13(2019) - Standard Guide for Applying Statistics to Analysis of Corrosion Data
• Effective Date: 15-Feb-2019
• Refers: ASTM G16-13 - Standard Guide for Applying Statistics to Analysis of Corrosion Data
• Effective Date: 01-Dec-2013
• Refers: ASTM E691-13 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-May-2013
• Refers: ASTM G1-03(2011) - Standard Practice for Preparing, Cleaning, and Evaluating Corrosion Test Specimens
• Effective Date: 01-Dec-2011
• Refers: ASTM E691-11 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-Nov-2011
• Refers: ASTM G16-95(2010) - Standard Guide for Applying Statistics to Analysis of Corrosion Data
• Effective Date: 01-Feb-2010
• Refers: ASTM E691-08 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-Oct-2008
• Refers: ASTM E29-08 - Standard Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications
• Effective Date: 01-Oct-2008
• Refers: ASTM E29-06b - Standard Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications
• Effective Date: 15-Nov-2006
• Refers: ASTM E29-06a - Standard Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications
• Effective Date: 15-Sep-2006
• Refers: ASTM E29-06 - Standard Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications
• Effective Date: 01-May-2006
• Refers: ASTM D1193-06 - Standard Specification for Reagent Water
• Effective Date: 01-Mar-2006
• Refers: ASTM E691-05 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-Nov-2005
• Refers: ASTM E29-04 - Standard Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications
• Effective Date: 01-Dec-2004

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 −18
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)
ThisstandardisissuedunderthefixeddesignationG67;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope Determine Conformance with Specifications
E691 Practice for Conducting an Interlaboratory Study to
1.1 This test method, also known as the Nitric Acid Mass
Determine the Precision of a Test Method
LossTest (NAMLT) describes a procedure for constant immer-
G1 Practice for Preparing, Cleaning, and Evaluating Corro-
sion intergranular corrosion testing of 5XXX series aluminum
sion Test Specimens
alloys.
G16 Guide for Applying Statistics to Analysis of Corrosion
1.2 This test method is applicable only to wrought products.
Data
1.3 This test method covers type of specimen, specimen
3. Summary of Test Method
preparation, test environment, and method of exposure.
3.1 This test method consists of immersing test specimens
1.4 The values stated in SI units are to be regarded as the
in concentrated nitric acid at 30°C (86°F) for 24 h and
standard. The values given in parentheses are for information
determining the mass loss per unit area as a measure of
only.
susceptibility to intergranular corrosion.
1.5 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
4. Significance and Use
responsibility of the user of this standard to establish appro-
4.1 This test method provides a quantitative measure of the
priate safety, health, and environmental practices and deter-
susceptibility to intergranular corrosion of Al-Mg and Al-
mine the applicability of regulatory limitations prior to use.
Mg-Mn alloys. The nitric acid dissolves a second phase, an
1.6 This international standard was developed in accor-
aluminum-magnesium intermetallic compound (βAl-Mg), in
dance with internationally recognized principles on standard-
preference to the solid solution of magnesium in the aluminum
ization established in the Decision on Principles for the
matrix. When this compound is precipitated in a relatively
Development of International Standards, Guides and Recom-
continuous network along grain boundaries, the effect of the
mendations issued by the World Trade Organization Technical
preferential attack is to corrode around the grains, causing
Barriers to Trade (TBT) Committee.
themtofallawayfromthespecimens.Suchdroppingoutofthe
grains causes relatively large mass losses of the order of 25 to
2. Referenced Documents
2 2
75 mg/cm (160 to 480 mg/in. ), whereas, samples of
2
2.1 ASTM Standards:
intergranular-resistant materials lose only about 1 to 15 mg/
2 2
D1193 Specification for Reagent Water
cm (10 to 100 mg/in. ). When the βAl-Mg compound is
E29 Practice for Using Significant Digits in Test Data to
randomly distributed, the preferential attack can result in
intermediate mass losses. Metallographic examination is re-
quiredinsuchcasestoestablishwhetherornotthelossinmass
1
This test method is under the jurisdiction of ASTM Committee G01 on
is the result of 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 Oct. 1, 2018. Published January 2019. Originally
material is exposed to chloride-containing natural
approved in 1980. Last previous edition approved in 2013 as G67 – 13. DOI:
10.1520/G0067-18.
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 [e-mail]. 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 ----------------------
G67−18
be in various forms such as pitting, exfoliation, or stress- grade water bath be used
...

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 − 13 G67 − 18
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 method, also known as the Nitric Acid Mass Loss Test (NAMLT) describes 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 safety, health, and healthenvironmental 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 and determining
the mass loss per unit area as a measure of susceptibility to intergranular corrosion.
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 25 to 75 mg/cm (160 to 480 mg/inmg/in. ),
2 2
whereas, samples of intergranular-resistant materials lose only about 1 to 15 mg/cm (10 to 100 mg/inmg/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.
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 May 1, 2013Oct. 1, 2018. Published May 2013January 2019. Originally approved in 1980. Last previous edition approved in 20042013 as
G67 – 04G67 – 13., which was withdrawn January 2013 and reinstated May 2013. DOI: 10.1520/G0067-13. DOI: 10.1520/G0067-18.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. 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 − 18
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 seacoa
...