1、Designation: G97 97 (Reapproved 2013)G97 18Standard Test Method forLaboratory Evaluation of Magnesium Sacrificial Anode TestSpecimens for Underground Applications1This standard is issued under the fixed designation G97; the number immediately following the designation indicates the year of originala
2、doption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscriptepsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers a laboratory procedure that measures the two fund
3、amental performance properties of magnesiumsacrificial anode test specimens operating in a saturated calcium sulfate, saturated magnesium hydroxide environment. The twofundamental properties are electrode (oxidation potential)(oxidation) potential and ampere hours (Ah) obtained per unit mass ofspeci
4、men consumed. Magnesium anodes installed underground are usually surrounded by a backfill material that typically consistsof 75 % gypsum (CaSO42H2O), 20 % bentonite clay, and 5 % sodium sulfate (Na2SO4). The calcium sulfate, magnesiumhydroxide test electrolyte simulates the long term environment aro
5、und an anode installed in the gypsum-bentonite-sodium sulfatebackfill.1.2 This test method is intended to be used for quality assurance by anode manufacturers or anode users. However, long termfield performance properties may not be identical to property measurements obtained using this laboratory t
6、est.NOTE 1Refer to Terminology G15G193 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 forinformation only and are not considered standard.1.4 This standard does not purport to address al
7、l of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine theapplicability of regulatory limitations prior to use. For specific precautions, See Secti
8、on 78 and Paragraph 8.1.19.1.1.1.5 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organi
9、zation Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent WaterE691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test MethodG3 Practice for Conventions Applicable to Electrochemical Measurements i
10、n Corrosion TestingG15 Terminology Relating to Corrosion and Corrosion Testing (Withdrawn 2010)3G16 Guide for Applying Statistics to Analysis of Corrosion DataG193 Terminology and Acronyms Relating to CorrosionG215 Guide for Electrode Potential Measurement2.2 American National Standard:ANSI/NFPA 480
11、 Storage, Handling, and Processing of Magnesium, 1987 Magnesium Solids and Powders, 1998 Edition33. Terminology3.1 DefinitionsThe terminology used herein shall be in accordance with Terminology G193.1 This test method is under the jurisdiction of ASTM Committee G01 on Corrosion of Metals and is the
12、direct responsibility of Subcommittee G01.10 on Corrosion inSoils.Current edition approved May 1, 2013Nov. 1, 2018. Published July 2013December 2018. Originally approved in 1989. Last previous edition approved in 20072013 asG97G97 97 (2013).97 (2007). DOI: 10.1520/G0097-97R13.10.1520/G0097-18.2 For
13、referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 Available from National Fire Protection Association (NFPA), 1 Bat
14、terymarch Park, Quincy, MA 02169-7471, http:/www.nfpa.org.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. Becauseit may not be technically possible to adequately depict all change
15、s accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. Unit
16、ed States14. Summary of Test Method4.1 A known direct current is passed through test cells connected in series. Each test cell consists of a pre-weighed testmagnesium alloy anode specimen, a steel pot container cathode, and a known electrolyte. Test specimen oxidation potential ismeasured several ti
17、mes during the 14-day test and 1 h after the current is turned off at the end of the test. The total Ah passedthrough the cells are measured.At the conclusion of the test, each test specimen is cleaned and weighed. TheAh obtained per unitmass of specimen lost is calculated.5. Significance and Use5.1
18、 This test is a guide for evaluating magnesium anodes. The degree of correlation between this test and service performancehas not been fully determined.5.2 Test specimens from the same casting may not be identical because of inhomogeneities in the casting.Amethod of ensuringthat identical test speci
19、mens are being evaluated is to retest a test specimen. The surface of the test specimen should be smoothedby machining before retesting. The new diameter should be measured and the test current adjusted so that the retest current densityis 0.039 mA/cm2 (0.25 mA/in.2).5.3 The values of potential and
20、Ah per unit mass consumed as measured by this test method, may not agree with those foundin field applications. It is unlikely that field results of Ah per unit mass consumed would ever be greater than those measured inthis test. However, actual test comparisons are not sufficient to allow precise c
21、orrelation of laboratory and field results.6. Apparatus6.1 The basic test equipment consists of the following:6.1.1 Direct Current Power Source, (optional), capable of delivering at least 2 mA and 12 V.6.1.2 Steel Cathode Test Pot, as shown in Fig. 1.6.1.3 Copper Coulometer, as shown in Fig. 2, or E
22、lectronic Coulometer.6.1.4 Saturated Calomel Reference Electrode.6.1.5 Electrometer, with an input impedance of 107 or greater ohms.6.1.6 Balance, 100-g capacity with 0.1 mg sensitivity.6.1.7 Drying Oven, with temperature capability of 110C (230F) or higher.FIG. 1 Detail of Test PotG97 1827. Reagent
23、s7.1 Test Electrolyte, Saturated Calcium Sulfate-Magnesium Hydroxide SolutionAdd 5.0 g of reagent grade CaSO42H2O, 0.1g of reagent grade Mg(OH)2, to 1000 mL of Type IV or better reagent grade water (see Specification D1193).7.2 Coulometer SolutionAdd 235 g of reagent grade CuSO45H2O, 27 mL 98 % H2SO
24、4, 50 cm3 undenatured ethyl alcoholto 900 mL of Type IV or better reagent grade water.7.3 Anode Cleaning SolutionAdd 250 g of reagent grade CrO3 to 1000 mL of Type IV or better reagent grade water.8. Precautions8.1 Eye protection and skin protection are required when handling the coulometer solution
25、 and when handling the cleaningsolution. 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 Preparation9.1 Fig. 3 shows typical test specimen selection and preparat
26、ion from a cast anode. Since all sizes and shapes of cast anodesare not shown, the sampling is only illustrative. Test specimens are obtained across the width of a cast anode and approximately13 mm (0.51 in.) from the edge. Machine each test specimen from a sawed, 180-mm long, 16-mm 180 mm (7.1 in.)
27、 long, 16 mm(0.63 in.) square cross section portion of the cast anode. Dry machine the square cross section, which should be marked with astamped identification number, down to 12.7-mm 12.7 mm (0.50 in.) diameter using a machining speed of 800 r/min, a feed rateof 0.5 mm (0.02 in.) per revolution, a
28、nd a depth of cut of 1.9 mm (0.07 in.) or less. Cut the machined test specimen to a 152-mm152 mm (6 in.) length and machine-face one end.9.1.1 Magnesium fines produced during cutting and machining operations can present a fire hazard.ANSI/NFPA 480 should beconsulted for procedures for handling magne
29、sium.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, power hacksaw = 0.8 to 2.4.9.1.2.2 Tooth set (cm)Band saw = 0.05 to 0.13, power hacksaw = 0.038 to 0.076.9.1.2.3 End relief angleBand s
30、aw = 10 to 12.9.1.2.4 Clearance angleBand saw = 20 to 30, power hacksaw = 20 to 30.9.2 Rinse each machined test specimen with water, rinse with acetone, dry in an oven at 105C (221F) for 30 min, cool, andweigh to the nearest 0.1 mg. (WarningThe specimens should be handled with clean gloves at all ti
31、mes after the acetone rinsingstep to avoid contamination of the specimens.)9.3 Mask each weighed test specimen with electroplaters tape. Start 100 mm (3.9 in.) from the faced end and extend toapproximately 13 mm (0.51 in.) from the non-faced end. The area exposed to the electrolyte will be the faced
32、 end, plus the sidearea for a length of 100 mm. mm (3.9 in.). This exposed area is 41.2 cm2. (6.4 in.2). A current flow through the test circuit of 1.60mA results in an anode current density of 0.039 mA/cm2. (0.25 mA/in.2).9.4 Brush the test pots using a soft plastic brush. If the test pot internal
33、surface becomes completely covered with a highlyresistive coating that prevents the required current from being obtained, sandblast, wire brush, or scrape some of the hard adherentdeposits off the surface.9.5 If a copper coulometer rather than an electronic coulometer is used, prepare the copper cou
34、lometer as shown in Fig. 2. Buffthe coulometer wire with fine (00 grit or finer) abrasive, dry in an oven at 105C (221F) for 15 min, cool and weigh beforeFIG. 2 Copper CoulometerG97 183assembling into the coulometer. The length of the copper wire in the coulometer solution should be between 10 and 5
35、0 mm. mm(0.4 and 2.0 in.). Clean the copper sheet anodes before their initial installation into the coulometer. The copper wire and sheetshould have a purity of 99.9 % or higher.9.6 Fig. 4 is a schematic diagram of the complete test circuit. Circuit wiring is No. 18 insulated stranded copper with al
36、ligatorclips or lugs at each end of each wire. Use the calomel electrode only when oxidation potential measurements are being obtained.10. Procedure (See Practice G3)10.1 Fill the cathode test pots to within approximately 15 mm (0.6 in.) of the top with the anode test electrolyte.10.2 Insert the tes
37、t specimens into the No. 14 rubber stoppers and insert the sample stopper assemblies into the cathode test pots.10.3 Wire the circuit as shown in Fig. 4.10.4 Turn on the power supply, adjust the current to 1.60 mA and check periodically to ensure the current remains constant atthat level.10.5 Obtain
38、 closed circuit test specimen potentials at 1, 7, and 14 days using a saturated calomel electrode and an electrometer.Obtain the potential measurement of each test specimen as shown in Fig. 4. The tip of the calomel reference should be within 10mm (0.4 in.) of the test specimen surface when this mea
39、surement is made.10.6 The electrolyte temperature should be 22 6 5C (72 6 9F) during the test.10.7 Turn off the power supply after 14 days. One hour later open circuit potentials of the test specimens are obtained. Thetechnique is identical to the closed circuit measurements (9.510.5).10.8 Remove th
40、e wiring from the test specimens, remove the test specimens from the electrolyte and the rubber stoppers, andremove the tape from the specimens.10.9 Place an untested test specimen in the cleaning solution which has been previously heated to 6080C. 6080C(140176F). Leave the specimen in the solution
41、for 10 min, rinse in tap water, and dry in an oven at 105C (221F) for 30 min.FIG. 3 Test Specimen Preparation from Cast AnodeG97 184If its mass loss is greater than 5 mg, discard the cleaning solution. If the untested test specimen mass loss is less than 5 mg, placethe test specimens along with an u
42、ntested test specimen in the 6080C (140176F) cleaning solution for 10 min. Then rinse intap water and dry in an oven at 105C (221F) for 3 h. If the untested test specimen mass loss is greater than 5 mg, discard thecleaning solution and repeat the test.10.9.1 An alternative cleaning procedure is to r
43、eplace the 10 min immersion in 6080C (140176F) cleaning solution witha 30 min immersion in ambient temperature cleaning solution.10.10 If copper coulometers are used, remove the wires from the coulometer, rinse in tap water, and place in a drying oven at105C (221F) for 30 min.10.11 Remove the test s
44、pecimens, the untested specimen and the copper coulometer wires from the heating oven and allow tocool to room temperature, then weigh to the nearest 0.1 mg. (WarningClean gloves should be worn during the weighing processto avoid contamination of the specimens and coulometer wires.)11. Calculation a
45、nd Report (See Guide G16)11.1 Calculate and report the Ah passed through the test cells during the 14-day test.11.1.1 If a copper coulometer is used, the Ah calculation is as follows:Ah50.8433 Ah/gCu!M22M1! (1)where:M 2 = final mass of copper coulometer wire, g, andM1 = initial mass of copper coulom
46、eter wire, g.11.1.2 If an electronic coulometer is used, the Ah calculation is as follows:Ah5ampere second measurement from coulometer!/3600! (2)11.2 Calculate and report the Ah per mass loss for each test specimen as follows:Ah/g5Ah!/MMg12MMg2! (3)where:MMg1 = initial mass of magnesium test specime
47、n, g, andMMg2 = final mass of magnesium test specimen, g.11.3 Report closed and open circuit potential measurements for each test specimen.FIG. 4 Experimental CellsG97 18512. Precision and Bias412.1 PrecisionThe following criteria should be used to judge the acceptabilityprecision of this test metho
48、d was determinedby analysis of the results at from an interlaboratory test program in which seven laboratories participated using two samples ofmagnesium alloys. Practice E691the 5 % significance level. was used to analyze the results.12.1.1 RepeatabilityResults (on identical test specimens) by The
49、repeatability standard deviations and repeatability statisticsare shown in Table 1the same operator should be considered suspect if the mean from five specimens differs by more than thefollowing from the mean obtained from a duplicate test on five specimens. for the current capacity per unit mass and the opencircuit, OC, and closed circuit, CC, potentials.Ah/g value 0.06 Ah/gFinal closed circuit potential 0.01 VOpen circuit potential 0.02 V12.1.2 ReproducibilityResults (on identical test specimens) submitted by each of
