ASTM G97-18(2022)
(Test Method)Standard Test Method for Laboratory Evaluation of Magnesium Sacrificial Anode Test Specimens for Underground Applications
Standard Test Method for Laboratory Evaluation of Magnesium Sacrificial Anode Test Specimens for Underground Applications
SIGNIFICANCE AND USE
5.1 This test is a guide for evaluating magnesium anodes. The degree of correlation between this test and service performance has not been fully determined.
5.2 Test specimens from the same casting may not be identical because of inhomogeneities in the casting. A method of ensuring that identical test specimens are being evaluated is to retest a test specimen. The surface of the test specimen should be smoothed by machining before retesting. The new diameter should be measured and the test current adjusted so that the retest current density is 0.039 mA/cm2 (0.25 mA/in.2).
5.3 The values of potential and Ah per unit mass consumed as measured by this test method, may not agree with those found in field applications. It is unlikely that field results of Ah per unit mass consumed would ever be greater than those measured in this test. However, actual test comparisons are not sufficient to allow precise correlation of laboratory and field results.
SCOPE
1.1 This test method covers a laboratory procedure that measures the two fundamental performance properties of magnesium sacrificial anode test specimens operating in a saturated calcium sulfate, saturated magnesium hydroxide environment. The two fundamental properties are electrode (oxidation) potential and ampere hours (Ah) obtained per unit mass of specimen consumed. Magnesium anodes installed underground are usually surrounded by a backfill material that typically consists of 75 % gypsum (CaSO4·2H2O), 20 % bentonite clay, and 5 % sodium sulfate (Na2SO4). The calcium sulfate, magnesium hydroxide test electrolyte simulates the long term environment around an anode installed in the gypsum-bentonite-sodium sulfate backfill.
1.2 This test method is intended to be used for quality assurance by anode manufacturers or anode users. However, long term field performance properties may not be identical to property measurements obtained using this laboratory test.
Note 1: Refer to Terminology G193 for terms used in this test method.
1.3 The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for information only and are not considered standard.
1.4 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. For specific precautions, See Section 8 and Paragraph 9.1.1.
1.5 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
Relations
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:G97 −18 (Reapproved 2022)
Standard Test Method for
Laboratory Evaluation of Magnesium Sacrificial Anode Test
Specimens for Underground Applications
ThisstandardisissuedunderthefixeddesignationG97;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 2. Referenced Documents
1.1 This test method covers a laboratory procedure that 2.1 ASTM Standards:
measures the two fundamental performance properties of D1193 Specification for Reagent Water
magnesium sacrificial anode test specimens operating in a E691 Practice for Conducting an Interlaboratory Study to
saturated calcium sulfate, saturated magnesium hydroxide Determine the Precision of a Test Method
environment. The two fundamental properties are electrode G3 Practice for Conventions Applicable to Electrochemical
(oxidation) potential and ampere hours (Ah) obtained per unit Measurements in Corrosion Testing
mass of specimen consumed. Magnesium anodes installed G16 Guide for Applying Statistics to Analysis of Corrosion
underground are usually surrounded by a backfill material that Data
typically consists of 75 % gypsum (CaSO ·2H O), 20 % ben- G193 Terminology and Acronyms Relating to Corrosion
4 2
tonite clay, and 5 % sodium sulfate (Na SO ). The calcium G215 Guide for Electrode Potential Measurement
2 4
sulfate, magnesium hydroxide test electrolyte simulates the
2.2 American National Standard:
long term environment around an anode installed in the
ANSI/NFPA 480 Storage,Handling,andProcessingofMag-
gypsum-bentonite-sodium sulfate backfill. 3
nesium Solids and Powders, 1998 Edition
1.2 This test method is intended to be used for quality
assurance by anode manufacturers or anode users. However, 3. Terminology
long term field performance properties may not be identical to
3.1 Definitions—The terminology used herein shall be in
property measurements obtained using this laboratory test.
accordance with Terminology G193.
NOTE1—RefertoTerminologyG193fortermsusedinthistestmethod.
4. Summary of Test Method
1.3 The values stated in SI units are to be regarded as
standard. The values given in parentheses after SI units are 4.1 A known direct current is passed through test cells
provided for information only and are not considered standard. connected in series. Each test cell consists of a pre-weighed
test magnesium alloy anode specimen, a steel pot container
1.4 This standard does not purport to address all of the
cathode, and a known electrolyte. Test specimen oxidation
safety concerns, if any, associated with its use. It is the
potential is measured several times during the 14-day test and
responsibility of the user of this standard to establish appro-
1 h after the current is turned off at the end of the test.The total
priate safety, health, and environmental practices and deter-
Ah passed through the cells are measured.At the conclusion of
mine the applicability of regulatory limitations prior to use.
the test, each test specimen is cleaned and weighed. The Ah
For specific precautions, See Section 8 and Paragraph 9.1.1.
obtained per unit mass of specimen lost is calculated.
1.5 This international standard was developed in accor-
dance with internationally recognized principles on standard-
5. Significance and Use
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
5.1 This test is a guide for evaluating magnesium anodes.
mendations issued by the World Trade Organization Technical
The degree of correlation between this test and service perfor-
Barriers to Trade (TBT) Committee. mance has not been fully determined.
1 2
This test method is under the jurisdiction of ASTM Committee G01 on For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Corrosion of Metals and is the direct responsibility of Subcommittee G01.10 on contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Corrosion in Soils. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Oct. 1, 2022. Published October 2022. Originally the ASTM website.
approved in 1989. Last previous edition approved in 2018 as G97 – 18. DOI: Available from National Fire Protection Association (NFPA), 1 Batterymarch
10.1520/G0097-18R22. Park, Quincy, MA 02169-7471, http://www.nfpa.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
G97−18 (2022)
5.2 Test specimens from the same casting may not be
identical because of inhomogeneities in the casting. A method
of ensuring that identical test specimens are being evaluated is
to retest a test specimen. The surface of the test specimen
should be smoothed by machining before retesting. The new
diameter should be measured and the test current adjusted so
2 2
that the retest current density is 0.039 mA/cm (0.25 mA/in. ).
5.3 The values of potential andAh per unit mass consumed
as measured by this test method, may not agree with those
found in field applications. It is unlikely that field results ofAh
per unit mass consumed would ever be greater than those
measured in this test. However, actual test comparisons are not
sufficient to allow precise correlation of laboratory and field
results.
FIG. 2Copper Coulometer
6. Apparatus
6.1 The basic test equipment consists of the following:
7. Reagents
6.1.1 Direct Current Power Source, (optional), capable of
7.1 Test Electrolyte, Saturated Calcium Sulfate-Magnesium
delivering at least 2 mA and 12 V.
Hydroxide Solution—Add 5.0 g of reagent grade CaSO ·2H O,
4 2
6.1.2 Steel Cathode Test Pot, as shown in Fig. 1.
0.1 g of reagent grade Mg(OH) , to 1000 mL of Type IV or
6.1.3 Copper Coulometer, as shown in Fig. 2,or Electronic
better reagent grade water (see Specification D1193).
Coulometer.
7.2 Coulometer Solution—Add 235 g of reagent grade
6.1.4 Saturated Calomel Reference Electrode.
CuSO ·5H O, 27 mL 98 % H SO,50cm undenatured ethyl
6.1.5 Electrometer, with an input impedance of 10 or
4 2 2 4
alcohol to 900 mL of Type IV or better reagent grade water.
greater ohms.
6.1.6 Balance, 100 g capacity with 0.1 mg sensitivity.
7.3 Anode Cleaning Solution—Add 250 g of reagent grade
6.1.7 Drying Oven, with temperature capability of 110 °C
CrO to 1000 mL of Type IV or better reagent grade water.
(230 °F) or higher.
8. Precautions
8.1 Eye protection and skin protection are required when
handling the coulometer solution and when handling the
cleaning solution. Test specimen cleaning should be done in a
ventilated laboratory hood.
8.2 Local, state, and federal regulations should be complied
with in disposing of used cleaning solution.
9. Specimen Preparation
9.1 Fig. 3 shows typical test specimen selection and prepa-
ration from a cast anode. Since all sizes and shapes of cast
anodes are not shown, the sampling is only illustrative. Test
specimens are obtained across the width of a cast anode and
approximately 13 mm (0.51 in.) from the edge. Machine each
test specimen from a sawed, 180 mm (7.1 in.) long, 16 mm
(0.63 in.) square cross section portion of the cast anode. Dry
machinethesquarecrosssection,whichshouldbemarkedwith
a stamped identification number, down to 12.7 mm (0.50 in.)
diameter using a machining speed of 800 r/min, a feed rate of
0.5 mm (0.02 in.) per revolution, and a depth of cut of 1.9 mm
(0.07 in.) or less. Cut the machined test specimen to a 152 mm
(6 in.) length and machine-face one end.
9.1.1 Magnesium fines produced during cutting and ma-
chining operations can present a fire hazard. ANSI/NFPA 480
should be consulted for procedures for handling magnesium.
9.1.2 Band saws and power hacksaws with the following
characteristics are recommended for use on magnesium:
9.1.2.1 Blade pitch (teeth/cm)—Band saw = 1.6 to 2.4,
FIG. 1Detail of Test Pot power hacksaw = 0.8 to 2.4.
G97−18 (2022)
obtained, sandblast, wire brush, or scrape some of the hard
adherent deposits off the surface.
9.5 If a copper coulometer rather than an electronic cou-
lometer is used, prepare the copper coulometer as shown in
Fig. 2. Buff the coulometer wire with fine (00 gr
...
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