ASTM G69-20
(Test Method)Standard Test Method for Measurement of Corrosion Potentials of Aluminum Alloys
Standard Test Method for Measurement of Corrosion Potentials of Aluminum Alloys
SIGNIFICANCE AND USE
3.1 The corrosion potential of an aluminum alloy depends upon the amounts of certain alloying elements that the alloy contains in solid solution. Copper and zinc, which are two of the major alloying elements for aluminum, have the greatest effect with copper shifting the potential in the noble or positive direction, and zinc in the active or negative direction. For example, commercially unalloyed aluminum (1100 alloy) has a potential of –750 mV when measured in accordance with this method, 2024–T3 alloy with nearly all of its nominal 4.3 % copper in solid solution, a potential of –600 mV to –620 mV, depending upon the rate of quenching and 7072 alloy with nearly all of its nominal 1.0 % zinc in solid solution, a potential of –885 mV (SCE) (1-3).3
3.2 Because it reflects the amount of certain alloying elements in solid solution, the corrosion potential is a useful tool for characterizing the metallurgical condition of aluminum alloys, especially those of the 2XXX and 7XXX types, which contain copper and zinc as major alloying elements. Its uses include the determination of the effectiveness of solution heat treatment and annealing (1), of the extent of precipitation during artificial aging (4) and welding (5), and of the extent of diffusion of alloying elements from the core into the cladding of Alclad products (2).
SCOPE
1.1 This test method covers a procedure for measurement of the corrosion potential (see Note 1) of an aluminum alloy in an aqueous solution of sodium chloride with enough hydrogen peroxide added to provide an ample supply of cathodic reactant.
Note 1: The corrosion potential is sometimes referred to as the open-circuit solution or rest potential. See Terminology G193.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 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.
1.4 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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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: G69 − 20
Standard Test Method for
1
Measurement of Corrosion Potentials of Aluminum Alloys
ThisstandardisissuedunderthefixeddesignationG69;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Significance and Use
3.1 The corrosion potential of an aluminum alloy depends
1.1 Thistestmethodcoversaprocedureformeasurementof
upon the amounts of certain alloying elements that the alloy
thecorrosionpotential(seeNote1)ofanaluminumalloyinan
contains in solid solution. Copper and zinc, which are two of
aqueous solution of sodium chloride with enough hydrogen
the major alloying elements for aluminum, have the greatest
peroxide added to provide an ample supply of cathodic
effectwithcoppershiftingthepotentialinthenobleorpositive
reactant.
direction, and zinc in the active or negative direction. For
NOTE 1—The corrosion potential is sometimes referred to as the
example,commerciallyunalloyedaluminum(1100alloy)hasa
open-circuit solution or rest potential. See Terminology G193.
potential of –750 mV when measured in accordance with this
method, 2024–T3 alloy with nearly all of its nominal 4.3 %
1.2 The values stated in SI units are to be regarded as
copper in solid solution, a potential of –600mV to –620 mV,
standard. No other units of measurement are included in this
depending upon the rate of quenching and 7072 alloy with
standard.
nearlyallofitsnominal1.0%zincinsolidsolution,apotential
1.3 This standard does not purport to address all of the 3
of –885 mV (SCE) (1-3).
safety concerns, if any, associated with its use. It is the
3.2 Because it reflects the amount of certain alloying ele-
responsibility of the user of this standard to establish appro-
ments in solid solution, the corrosion potential is a useful tool
priate safety, health, and environmental practices and deter-
for characterizing the metallurgical condition of aluminum
mine the applicability of regulatory limitations prior to use.
alloys, especially those of the 2XXX and 7XXX types, which
1.4 This international standard was developed in accor-
contain copper and zinc as major alloying elements. Its uses
dance with internationally recognized principles on standard-
include the determination of the effectiveness of solution heat
ization established in the Decision on Principles for the
treatment and annealing (1), of the extent of precipitation
Development of International Standards, Guides and Recom-
during artificial aging (4) and welding (5), and of the extent of
mendations issued by the World Trade Organization Technical
diffusion of alloying elements from the core into the cladding
Barriers to Trade (TBT) Committee.
of Alclad products (2).
2. Referenced Documents
4. Apparatus
2
2.1 ASTM Standards: 4.1 The apparatus consists of an inert container for the test
D1193Specification for Reagent Water solution, a mechanical support for the test specimens that
E691Practice for Conducting an Interlaboratory Study to insulates them electrically from each other and from ground, a
Determine the Precision of a Test Method saturated calomel electrode (SCE), wires and other accessories
G3Practice for Conventions Applicable to Electrochemical for electrical connections, and equipment for the measurement
Measurements in Corrosion Testing of potential. See Note 2.
G193Terminology and Acronyms Relating to Corrosion
NOTE 2—Saturated calomel electrodes are available from several
manufacturers.Itisagoodpracticetoensuretheproperfunctioningofthe
reference electrode by measuring its potential against one or more
reference electrodes. The potential difference should not exceed 2 mV or
1
This test method is under the jurisdiction of ASTM Committee G01 on
3mV.
Corrosion of Metals and is the direct responsibility of Subcommittee G01.11 on
12
Electrochemical Measurements in Corrosion Testing. 4.2 High-impedance(>10 Ω)voltmeterissuitableformea-
Current edition approved May 1, 2020. Published June 2020. Originally
surementofthepotential.Measurementofthispotentialshould
approved in 1981. Last previous edition approved in 2012 as G69–12. DOI:
be carried out to within 61 mV. Automatic data recording
10.1520/G0069-20.
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
3
Standards volume information, refer to the standard’s Document Summary page on The boldface numbers in parentheses refer to the references at the end of this
the ASTM website. standard
...
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: G69 − 12 G69 − 20
Standard Test Method for
1
Measurement of Corrosion Potentials of Aluminum Alloys
This standard is issued under the fixed designation G69; 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 covers a procedure for measurement of the corrosion potential (see Note 1) of an aluminum alloy in an
aqueous solution of sodium chloride with enough hydrogen peroxide added to provide an ample supply of cathodic reactant.
NOTE 1—The corrosion potential is sometimes referred to as the open-circuit solution or rest potential. See PracticeTerminology G193.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 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.
1.4 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
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
G3 Practice for Conventions Applicable to Electrochemical Measurements in Corrosion Testing
G193 Terminology and Acronyms Relating to Corrosion
3. Significance and Use
3.1 The corrosion potential of an aluminum alloy depends upon the amounts of certain alloying elements that the alloy contains
in solid solution. Copper and zinc, which are two of the major alloying elements for aluminum, have the greatest effect with copper
shifting the potential in the noble or positive direction, and zinc in the active or negative direction. For example, commercially
unalloyed aluminum (1100 alloy) has a potential of –750 mV when measured in accordance with this method, 2024–T3 alloy with
nearly all of its nominal 4.3 % copper in solid solution, a potential of –600–600 mV to –620 mV, depending upon the rate of
3
quenching and 7072 alloy with nearly all of its nominal 1.0 % zinc in solid solution, a potential of —885–885 mV (SCE) (1-3).
3.2 Because it reflects the amount of certain alloying elements in solid solution, the corrosion potential is a useful tool for
characterizing the metallurgical condition of aluminum alloys, especially those of the 2XXX and 7XXX types, which contain
copper and zinc as major alloying elements. Its uses include the determination of the effectiveness of solution heat treatment and
annealing (1), of the extent of precipitation during artificial aging (4) and welding (5), and of the extent of diffusion of alloying
elements from the core into the cladding of Alclad products (2).
4. Apparatus
4.1 The apparatus consists of an inert container for the test solution, a mechanical support for the test specimens that insulates
them electrically from each other and from ground, a saturated calomel electrode (SCE), wires and other accessories for electrical
connections, and equipment for the measurement of potential. See Note 2.
1
This test method is under the jurisdiction of ASTM Committee G01 on Corrosion of Metals and is the direct responsibility of Subcommittee G01.11 on Electrochemical
Measurements in Corrosion Testing.
Current edition approved May 1, 2012May 1, 2020. Published October 2012June 2020. Originally approved in 1981. Last previous edition approved in 20092012 as
G69–97(2009).G69–12. DOI: 10.1520/G0069-12.10.1520/G0069-20.
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’sstandard’s Document Summary page on the ASTM website.
3
The boldface numbers in parentheses refer to the references at the end of this standard.
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