ASTM G69-20

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.

General Information

• Status: Published
• Publication Date: 30-Apr-2020
• ICS: 77.120.10 - Aluminium and aluminium alloys
• Technical Committee: G01 - Corrosion of Metals
• Drafting Committee: G01.11 - Electrochemical Measurements in Corrosion Testing

Relations

• Replaces: ASTM G69-12 - Standard Test Method for Measurement of Corrosion Potentials of Aluminum Alloys
• Effective Date: 01-May-2020
• Refers: ASTM G3-14(2019) - Standard Practice for Conventions Applicable to Electrochemical Measurements in Corrosion Testing
• Effective Date: 01-May-2019
• Refers: ASTM G3-14 - Standard Practice for Conventions Applicable to Electrochemical Measurements in Corrosion Testing
• Effective Date: 15-Dec-2014
• Refers: ASTM G3-13 - Standard Practice for Conventions Applicable to Electrochemical Measurements in Corrosion Testing
• 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 E691-11 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-Nov-2011
• Refers: ASTM G3-89(2010) - Standard Practice for Conventions Applicable to Electrochemical Measurements in Corrosion Testing
• Effective Date: 01-May-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 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 G3-89(2004) - Standard Practice for Conventions Applicable to Electrochemical Measurements in Corrosion Testing
• Effective Date: 01-Nov-2004
• Refers: ASTM G3-89(1999) - Standard Practice for Conventions Applicable to Electrochemical Measurements in Corrosion Testing
• Effective Date: 10-Aug-1999
• Refers: ASTM E691-99 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 10-May-1999
• Refers: ASTM D1193-99 - Standard Specification for Reagent Water
• Effective Date: 10-Feb-1999
• Refers: ASTM D1193-99e1 - Standard Specification for Reagent Water
• Effective Date: 10-Feb-1999

Overview

ASTM G69-20: Standard Test Method for Measurement of Corrosion Potentials of Aluminum Alloys outlines procedures for evaluating the corrosion potential, also known as open-circuit or rest potential, of aluminum alloys in an aqueous sodium chloride solution with hydrogen peroxide. Measuring corrosion potentials is critical for understanding the metallurgical state and corrosion behavior, especially in aluminum alloys containing copper and zinc. This standard provides an important quantitative tool for characterizing alloys, assessing heat treatment, aging, and evaluating the effectiveness of surface processing operations.

Key Topics

• Corrosion Potential Measurement: Defines a systematic procedure for measuring the corrosion potential of aluminum alloys using a sodium chloride solution with hydrogen peroxide to maintain cathodic reactant supply. High-impedance voltmeters and saturated calomel electrodes are used for precise readings.

• Metallurgical Characterization: Corrosion potential is highly dependent on the type and amount of alloying elements in solid solution, particularly copper and zinc, which significantly influence the measured potential. This test method is especially relevant for 2XXX (copper-rich) and 7XXX (zinc-rich) aluminum alloys.

• Sample Preparation: Details both mechanical (e.g., abrasion with aluminum oxide or silicon carbide cloth) and chemical preparation (e.g., etching with various acid and alkali solutions) methods to ensure accurate and repeatable measurements. Special procedures for Alclad materials ensure representative assessment of core and cladding alloys.

• Test Conditions:

  • Standardized solution preparation with precisely defined concentrations of sodium chloride and hydrogen peroxide.
  • Strict temperature control (25°C ± 2°C) during testing.
  • Measurement of multiple time points, with results averaged as specified by the method for repeatability and reproducibility.

Applications

• Quality Control: Used to verify the metallurgical state of aluminum alloys during production, post-treatment, and prior to application, ensuring desired properties and corrosion resistance.

• Process Validation: Assesses the effectiveness of solution heat treatments, annealing, artificial aging, and welding processes, providing quality assurance for aerospace, automotive, and other industries relying on high-performance aluminum alloys.

• Product Development: Supports research into new alloy compositions and surface treatments by quantifying the influence of copper, zinc, and other elements on corrosion behavior.

• Inspection of Cladded Materials: Evaluates the diffusion and integrity of core and cladding in Alclad products, ensuring proper manufacturing and long-term durability.

Related Standards

• ASTM G3 - Practice for Conventions Applicable to Electrochemical Measurements in Corrosion Testing
• ASTM G193 - Terminology and Acronyms Relating to Corrosion
• ASTM D1193 - Specification for Reagent Water
• ASTM E691 - Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method

Summary

ASTM G69-20 provides a standardized, reliable method for measuring corrosion potentials of aluminum alloys, using precise chemical and electrochemical procedures designed to capture alloy-specific corrosion behavior. This guidance is essential for producers, researchers, and engineers focused on aluminum alloy performance, enabling informed decisions on material selection, processing, and quality control. Adherence to this standard supports consistent assessment of critical corrosion-related properties in line with international best practices.

Keywords: aluminum alloy, corrosion potential, ASTM G69, sodium chloride, hydrogen peroxide, copper, zinc, electrochemical measurement, metallurgical condition, solution heat treatment, quality control, Alclad, solid solution.

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: G69 − 20
Standard Test Method for
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
2.1 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
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
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.
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 boldface numbers in parentheses refer to the references at the end of this
the ASTM website. standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
G69−20
systems may be used to permit the simultaneous measurement an electrical connection outside the test solution.Aspecimen a
of many specimens and the continuous recording of corrosion few millimetres thick by about 15 mm wide and 100 mm long
potentials. is a convenient size.
5. Reagents
8. Specimen Preparation
5.1 Purity of Reagents—Reagent grade chemicals shall be
8.1 Any convenient means, such as sawing or stamping,
used in all tests. Unless otherwise indicated, it is intended that
maybeusedtoprepareaspecimentosizeprovidedthatitdoes
all reagents shall conform to the specifications of the Commit-
not heat the specimen enough to change its metallurgical
tee onAnalytical Reagents of theAmerican Chemical Society,
structure.
where such specifications are available.
8.2 Irregular-shaped specimens shall be machined or pre-
5.2 Purity of Water—Purifiedwaterconformingtothepurity
paredwithacoarsefiletoprovideareasonablyflatsurfaceand
requirements of Specification D1193, Type IV reagent water
to remove nonrepresentative metal (for example, affected by
shall be used.
sawingorstamping,orincaseofcladproductwherecoreisto
5.3 Sodium Chloride (NaCl) Analytical Reagent (AR). bemeasured).Furtherpreparationconsistsoffilingwithalong
lathe file. Original flat surface specimens are also filed with
5.4 Hydrogen Peroxide(H O )(30%)—Reagentcontaining
2 2
long lathe file to remove the original mill scale oxide layer.
no less than 20% hydrogen peroxide shall be used.
8.3 No filing or machining is needed to prepare specimens
NOTE 3—Hydrogen peroxide reagent concentration can degrade over
that have original flat surface, representative of its metallurgi-
time.Useofacontrolsamplecanprovideanindicationwhentheperoxide
calstructure,ortopreparespecimensthataretoothintopermit
has degraded. The concentration of hydrogen peroxide in the reagent can
be confirmed by chemical analysis as described in Annex A1.
more than minimal removal of metal; these include clad
products with thin claddings which are to be measured.
5.5 Nitric Acid—70% (conc).
8.4 Specimen Surface Preparation—The surfaces of all
5.6 Hydrochloric Acid—12 N (conc).
products selected for measurement shall be prepared by either
5.7 Sulfuric Acid—36 N (conc).
the mechanical preparation procedure in 8.5 or the chemical
5.8 Sodium Hydroxide.
preparation procedure in 8.6.
8.5 Mechanical Preparation—The surfaces of all products
6. Solution Conditions
selected for measurement, including those with no previous
6.1 Thetestsolutionshallconsistof58.5g 60.1gofNaCl
preparation, are abraded dry with No. 320 grade aluminum
and9mL 6 1 mLof 30% hydrogen peroxide reagent per 1 L
oxide or silicon carbide cloth and then with either No. 00 steel
of aqueous solution. (This solution is 1 M with respect to
wool or 400 to 600 grade aluminum oxide. (Warning—Clad
concentration of sodium chloride.)
products with thin claddings should only be abraded lightly,
6.2 The hydrogen peroxide reagent shall be added just
except to remove the cladding for measurement of the core.)
before measurements are made, because it decomposes upon
8.5.1 Following mechanical preparation, the specimen is
standing.
cleaned or degreased in an inert solvent (for example, acetone,
MEK, EtOH).
6.3 Freshly prepared solution shall be used for each set of
measurements.
8.6 Chemical Preparation—Anyone of the following five
procedures may be used. The etch treatment is followed by a
6.4 Not less than 500 mLof solution shall be used for each
rinse in Specification D1193 Type IV water, desmut for one
set of measurements.
minute in conc. nitric acid, and final rinse in Specification
6.5 The total exposed area of all the specimens of the same
D1193 water and air dry.
composition in each set of measurements shall not exceed 100
8.6.1 One minute immersion in HF/HNO at 93°C 62°C
2 3
mm per 100 mL of solution.
containing 5 mL/L of 48% HF and 50 mL/L of concentrated
6.6 The temperature of the test solution shall be maintained
nitricacid.DonotlettheHFsolutionremainintheborosilicate
at 25°C 6 2°C.
glass vessels used in this method, because the HF solution will
attack the glass.
7. Test Specimen
8.6.2 One minute in 10% NaOH solution at 71°C 6 2°C.
7.1 For measurement alone, specimen size is unimportant
8.6.3 Thirty seconds immersion in 12 N HCL at room
provided that the area for measurement is at least 25 mm , but temperature (22°C 6 2°C).
for convenience the specimen, wherever possible, should be
8.6.4 Sixty seconds immersion in 5N HCl at room tempera-
largeenoughtopermiteaseofhandlingduringpreparationand ture (22°C 6 2°C).
8.6.5 Fiveminuteimmersionin1NH SO at60°C 62°C.
2 4
8.7 Measurement of the core alloy inAlclad alloys requires
Reagent Chemicals, American Chemical Society Specifications, American
Chemical Society, Washington, DC. For Suggestions on the testing of reagents not
removalofthecladdingsurfaces.Thiscanbeaccomplishedby
listed by the American Chemical Society, see Annual Standards for Laboratory
either mechanical or chemical means.
...

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
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
2.1 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
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.
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.
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’sstandard’s Document Summary page on the ASTM website.
The boldface numbers in parentheses refer to the references at the end of this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
G69 − 20
NOTE 2—Saturated calomel electrodes are available from several manufacturers. It is a good practice to ensure the proper functioning of the reference
electrode by measuring its potential against one or more reference electrodes. The potential difference should not exceed 2 mV or 3 mV.
4.2 High-impedance (>10 Ω) voltmeter is suitable for measurement of the potential. Measurement of this potential should be
carried out to within 6 1 61 mV. Automatic data recording systems may be used to permit the simultaneous measurement of many
specimens and the continuous recording of corrosion potentials.
5. Reagents
5.1 Purity of Reagents—Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all
reagents shall conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society, where
such specifications are available.
5.2 Purity of Water—The water shall be distilled or deionized Purified water conforming to the purity requirements of
Specification D1193, Type IV reagent water.water shall be used.
5.3 Sodium Chloride (NaCl) Analytical Reagent (AR).
5.4 Hydrogen Peroxide (H O ) (30 %)—In case of uncertainty (for example, whenever freshly opened reagent is not used), the
2 2
concentration of hydrogen peroxide in the reagent shall be confirmed by chemical analysis as described in Reagent containing
Annex A1. In no case shall reagent containing no less than 20 % hydrogen peroxide shall be used.
NOTE 3—Hydrogen peroxide reagent concentration can degrade over time. Use of a control sample can provide an indication when the peroxide has
degraded. The concentration of hydrogen peroxide in the reagent can be confirmed by chemical analysis as described in Annex A1.
5.5 Nitric Acid—70 % (conc).
5.6 Hydrochloric Acid—12 N (conc).
5.7 Sulfuric Acid—36 N (conc).
5.8 Sodium Hydroxide. Sodium Hydroxide.
6. Solution Conditions
6.1 The test solution shall consist of 58.5 g 6 0.1 g of NaCl and 9 mL 6 1 mL of 30 % hydrogen peroxide reagent per 1 L
of aqueous solution. (This solution is 1 M with respect to concentration of sodium chloride.)
6.2 The hydrogen peroxide reagent shall be added just before measurements are made, because it decomposes upon standing.
6.3 Freshly prepared solution shall be used for each set of measurements.
6.4 Not less than 500 mL of solution shall be used for each set of measurements.
6.5 The total exposed area of all the specimens of the same composition in each set of measurements shall not exceed 100 mm
per 100 mL of solution.
6.6 The temperature of the test solution shall be maintained at 2525 °C 6 2°C.2 °C.
7. Test Specimen
7.1 For measurement alone, specimen size is unimportant provided that the area for measurement is at least 25 mm , but for
convenience the specimen, wherever possible, should be large enough to permit ease of handling during preparation and an
electrical connection outside the test solution. A specimen a few millimetres thick by about 15 mm wide and 100 mm long is a
convenient size.
8. Specimen Preparation
8.1 Any convenient means, such as sawing or stamping, may be used to prepare a specimen to size provided that it does not
heat the specimen enough to change its metallurgical structure.
8.2 Irregular-shaped specimens shall be machined or prepared with a coarse file to provide a reasonably flat surface and to
remove nonrepresentative metal (for example, affected by sawing or stamping, or in case of clad product where core is to be
measured). Further preparation consists of filing with a long lathe file. Original flat surface specimens are also filed with long lathe
file to remove the original mill scale oxide layer.
8.3 No filing or machining is needed to prepare specimens that have original flat surface, representative of its metallurgical
structure, or to prepare specimens that are too thin to permit more than minimal removal of metal; these include clad products with
thin claddings which are to be measured.
Reagent Chemicals, American Chemical Society Specifications, American Chemical Society, Washington, DC. For Suggestions on the testing of reagents not listed by
the American Chemical Society, see Annual Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and National
Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.
G69 − 20
8.4 Specimen Surface Preparation—The surfaces of all products selected for measurement shall be prepared by either the
mechanical preparation procedure in 8.5 or the chemical preparation procedure in 8.6.
8.5 Mechanical Preparation—The surfaces of all products selected for measurement, including those with no previous
preparation, are abraded dry with No. 320 grade aluminum oxide or silicon carbide cloth and then with either No. 00 steel
wool.wool or 400 to 600 grade aluminum oxide. (Warning—Clad products with thin claddings should only be abraded lightly,
except to remove the cladding for measurement of the core.)
NOTE 3—Caution: Clad products with thin claddings should only be abraded lightly except to remove the cladding for measurement of the core.
8.5.1 Following mechanical preparation, the specimen is cleaned or degreased in an inert solvent (for example, acetone, MEK,
EtOH).
8.6 Chemical Preparation—Anyone of the following five procedures may be used. The etch treatment is followed by a rinse
in Specification D1193 Type IV water, desmut for one minute in conc. nitric acid, and final rinse in Specification D1193 water and
air dry.
8.6.1 One minute immersion in HF/HNO at 9393 °C 6 2°C2 °C containing 5 mL/L of 48%48 % HF and 50 mL/L of
concentrated nitric acid. Do not let the HF solution remain in the borosilicate glass vessels used in this method, because the HF
solution will atta
...