ASTM G67-04
(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to Intergranular Corrosion of 5XXX Series Aluminum Alloys by Mass Loss After Exposure to Nitric Acid (NAMLT Test) (Withdrawn 2013)
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to Intergranular Corrosion of 5XXX Series Aluminum Alloys by Mass Loss After Exposure to Nitric Acid (NAMLT Test) (Withdrawn 2013)
SIGNIFICANCE AND USE
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/in2), whereas, samples of intergranular-resistant materials lose only about 1 to 15 mg/cm2 (10 to 100 mg/in2). 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.
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 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.
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 and health practices and determine the applicability of regulatory limitations prior to use.
WITHDRAWN RATIONALE
This test method describes a procedure for constant immersion intergranular corrosion testing of 5XXX series aluminum alloys.
Formerly under the jurisdiction of Committee G01 on Corrosion of Metals, this test method was withdrawn in January 2013 in accordance with section 10.5.3.1 of the Regulations Governing ASTM Technical Committees, which requires that standards shall be updated by the end of the eighth year since the last approval date.
General Information
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: G67 − 04
StandardTest 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.Anumber in parentheses indicates the year of last reapproval.Asuperscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 4. Significance and Use
4.1 This test method provides a quantitative measure of the
1.1 This test method describes a procedure for constant
susceptibility to intergranular corrosion of Al-Mg and Al-
immersion intergranular corrosion testing of 5XXX series
Mg-Mn alloys. The nitric acid dissolves a second phase, an
aluminum alloys.
aluminum-magnesium intermetallic compound (βAl-Mg), in
1.2 This test method is applicable only to wrought products.
preference to the solid solution of magnesium in the aluminum
matrix. When this compound is precipitated in a relatively
1.3 This test method covers type of specimen, specimen
continuous network along grain boundaries, the effect of the
preparation, test environment, and method of exposure.
preferential attack is to corrode around the grains, causing
1.4 The values stated in SI units are to be regarded as the
themtofallawayfromthespecimens.Suchdroppingoutofthe
standard. The values given in parentheses are for information
grains causes relatively large mass losses of the order of 25 to
only.
2 2
75 mg/cm (160 to 480 mg/in ), whereas, samples of
1.5 This standard does not purport to address all of the
intergranular-resistant materials lose only about 1 to 15 mg/
2 2
safety concerns, if any, associated with its use. It is the
cm (10 to 100 mg/in ). When the βAl-Mg compound is
responsibility of the user of this standard to establish appro-
randomly distributed, the preferential attack can result in
priate safety and health practices and determine the applica-
intermediate mass losses. Metallographic examination is re-
bility of regulatory limitations prior to use.
quiredinsuchcasestoestablishwhetherornotthelossinmass
is the result of intergranular attack.
2. Referenced Documents
4.2 The precipitation of the second phase in the grain
2
boundaries also gives rise to intergranular corrosion when the
2.1 ASTM Standards:
material is exposed to chloride-containing natural
D1193 Specification for Reagent Water
environments, such as seacoast atmospheres or sea water. The
G1 Practice for Preparing, Cleaning, and Evaluating Corro-
extent to which the alloy will be susceptible to intergranular
sion Test Specimens
corrosion depends upon the degree of precipitate continuity in
the grain boundaries. Visible manifestations of the attack may
3. Summary of Test Method
be in various forms such as pitting, exfoliation, or stress-
3.1 This test method consists of immersing test specimens
corrosion cracking, depending upon the morphology of the
in concentrated nitric acid at 30°C (86°F) for 24 h and 3
grain structure and the presence of sustained tensile stress.
determining the mass loss per unit area as a measure of
susceptibility to intergranular corrosion. 5. Interferences
5.1 If all loose particles are not removed during cleaning
after exposure, the mass loss will be low relative to the amount
1
This test method is under the jurisdiction of ASTM Committee G01 on of corrosion that actually occurred.
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
6. Apparatus
The Aluminum Association, Inc.
6.1 Nonmetallic Container—A suitable inert, nonmetallic
Current edition approved May 1, 2004. Published May 2004. Originally
approved in 1980. Last previous edition approved in 1999 as G67 – 99. DOI:
container should be used to contain the nitric acid and
10.1520/G0067-04.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
3
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Craig, H. L. Jr., “NitricAcid Weight Loss Test for the H116 and H117 Tempers
Standards volume information, refer to the standard’s Document Summary page on of 5086 and 5456 Aluminum Alloys,” Localized Corrosion—Cause of Metal
the ASTM website. Failure, ASTM STP 516, ASTM, pp. 17–37, 1972.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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G67−04
specimens during the period of the test. The use of individual 11.4 Immerse the specimens in 5 % NaOH solution at 80°C
beakers for each specimen is recommended; however, the (176°F) for 1 min followed by a wat
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