1、Designation: G 97 97 (Reapproved 2007)Standard Test Method forLaboratory Evaluation of Magnesium Sacrificial Anode TestSpecimens for Underground Applications1This standard is issued under the fixed designation G 97; the number immediately following the designation indicates the year of originaladopt
2、ion or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscriptepsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers a laboratory procedure thatmeasures the two fund
3、amental performance properties ofmagnesium sacrificial anode test specimens operating in asaturated calcium sulfate, saturated magnesium hydroxideenvironment. The two fundamental properties are electrode(oxidation potential) and ampere hours (Ah) obtained per unitmass of specimen consumed. Magnesium
4、 anodes installedunderground are usually surrounded by a backfill material thattypically consists of 75 % gypsum (CaSO42H2O), 20 % ben-tonite clay, and 5 % sodium sulfate (Na2SO4). The calciumsulfate, magnesium hydroxide test electrolyte simulates thelong term environment around an anode installed i
5、n thegypsum-bentonite-sodium sulfate backfill.1.2 This test method is intended to be used for qualityassurance by anode manufacturers or anode users. However,long term field performance properties may not be identical toproperty measurements obtained using this laboratory test.NOTE 1Refer to Termino
6、logy G15for terms used in this test method.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulato
7、ry limitations prior to use. For specificprecautions, See Section 7 and Paragraph 8.1.1.2. Referenced Documents2.1 ASTM Standards:2D 1193 Specification for Reagent WaterG3 Practice for ConventionsApplicable to ElectrochemicalMeasurements in Corrosion TestingG15 Terminology Relating to Corrosion and
8、CorrosionTestingG16 Guide for Applying Statistics to Analysis of CorrosionData2.2 American National Standard:ANSI/NFPA 480 Storage, Handling, and Processing ofMagnesium, 1987 Edition33. Summary of Test Method3.1 A known direct current is passed through test cellsconnected in series. Each test cell c
9、onsists of a pre-weighedtest magnesium alloy anode specimen, a steel pot containercathode, and a known electrolyte. Test specimen oxidationpotential is measured several times during the 14-day test and1 h after the current is turned off at the end of the test. The totalAh passed through the cells ar
10、e measured. At the conclusion ofthe test, each test specimen is cleaned and weighed. The Ahobtained per unit mass of specimen lost is calculated.4. Significance and Use4.1 This test is a guide for evaluating magnesium anodes.The degree of correlation between this test and service perfor-mance has no
11、t been fully determined.5. Apparatus5.1 The basic test equipment consists of the following:5.1.1 Direct Current Power Source,(optional), capable ofdelivering at least 2 mA and 12 V.5.1.2 Steel Cathode Test Pot, as shown in Fig. 1.5.1.3 Copper Coulometer, as shown in Fig. 2,orElectronicCoulometer.5.1
12、.4 Saturated Calomel Reference Electrode.5.1.5 Electrometer, with an input impedance of 107orgreater ohms.1This test method is under the jurisdiction of ASTM Committee G01 onCorrosion of Metals and is the direct responsibility of Subcommittee G01.10 onCorrosion in Soils.Current edition approved Nov.
13、 1, 2007. Published January 2008. Originallyapproved in 1989. Last previous edition approved in 2002 as G 97(2002)e1.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to
14、 the standards Document Summary page onthe ASTM website.3Available from National Fire Protection Association (NFPA), 1 BatterymarchPark, Quincy, MA 02169-7471, http:/www.nfpa.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.1.6
15、Balance, 100-g capacity with 0.1 mg sensitivity.5.1.7 Drying Oven, with temperature capability of 110C orhigher.6. Reagents6.1 Test Electrolyte, Saturated Calcium Sulfate-MagnesiumHydroxide SolutionAdd 5.0 g of reagent grade CaSO42H2O,0.1 g of reagent grade Mg(OH)2, to 1000 mL of Type IV orbetter re
16、agent grade water (see Specification D 1193).6.2 Coulometer SolutionAdd 235 g of reagent gradeCuSO45H2O, 27 mL 98 % H2SO4,50cm3undenatured ethylalcohol to 900 mL of Type IV or better reagent grade water.6.3 Anode Cleaning SolutionAdd 250 g of reagent gradeCrO3to 1000 mL of Type IV or better reagent
17、grade water.7. Precautions7.1 Eye protection and skin protection are required whenhandling the coulometer solution and when handling thecleaning solution. Test specimen cleaning should be done in aventilated laboratory hood.7.2 Local, state, and federal regulations should be compliedwith in disposin
18、g of used cleaning solution.8. Specimen Preparation8.1 Fig. 3 shows typical test specimen selection and prepa-ration from a cast anode. Since all sizes and shapes of castanodes are not shown, the sampling is only illustrative. Testspecimens are obtained across the width of a cast anode andapproximat
19、ely 13 mm from the edge. Machine each testspecimen from a sawed, 180-mm long, 16-mm square crosssection portion of the cast anode. Dry machine the square crosssection, which should be marked with a stamped identificationnumber, down to 12.7-mm diameter using a machining speedof 800 r/min, a feed rat
20、e of 0.5 mm per revolution, and a depthof cut of 1.9 mm or less. Cut the machined test specimen to a152-mm length and machine-face one end.8.1.1 Magnesium fines produced during cutting and ma-chining operations can present a fire hazard. ANSI/NFPA 480should be consulted for procedures for handling m
21、agnesium.FIG. 1 Detail of Test PotFIG. 2 Copper CoulometerFIG. 3 Test Specimen Preparation from Cast AnodeG 97 97 (2007)28.1.2 Band saws and power hacksaws with the followingcharacteristics are recommended for use on magnesium:8.1.2.1 Blade pitch (teeth/cm)Band saw = 1.6 to 2.4,power hacksaw = 0.8 t
22、o 2.4.8.1.2.2 Tooth set (cm)Band saw = 0.05 to 0.13, powerhacksaw = 0.038 to 0.076.8.1.2.3 End relief angleBand saw = 10 to 12.8.1.2.4 Clearance angleBand saw = 20 to 30, powerhacksaw = 20 to 30.8.2 Rinse each machined test specimen with water, rinsewith acetone, dry in an oven at 105C for 30 min, c
23、ool, andweigh to the nearest 0.1 mg. (WarningThe specimensshould be handled with clean gloves at all times after theacetone rinsing step to avoid contamination of the specimens.)8.3 Mask each weighed test specimen with electroplaterstape. Start 100 mm from the faced end and extend to approxi-mately
24、13 mm from the non-faced end. The area exposed to theelectrolyte will be the faced end, plus the side area for a lengthof 100 mm. This exposed area is 41.2 cm2. A current flowthrough the test circuit of 1.60 mA results in an anode currentdensity of 0.039 mA/cm2.8.4 Brush the test pots using a soft p
25、lastic brush. If the testpot internal surface becomes completely covered with a highlyresistive coating that prevents the required current from beingobtained, sandblast, wire brush, or scrape some of the hardadherent deposits off the surface.8.5 If a copper coulometer rather than an electronic cou-l
26、ometer is used, prepare the copper coulometer as shown inFig. 2. Buff the coulometer wire with fine (00 grit or finer)abrasive, dry in an oven at 105C for 15 min, cool and weighbefore assembling into the coulometer. The length of thecopper wire in the coulometer solution should be between 10and 50 m
27、m. Clean the copper sheet anodes before their initialinstallation into the coulometer. The copper wire and sheetshould have a purity of 99.9 % or higher.8.6 Fig. 4 is a schematic diagram of the complete testcircuit. Circuit wiring is No. 18 insulated stranded copper withalligator clips or lugs at ea
28、ch end of each wire. Use the calomelelectrode only when oxidation potential measurements arebeing obtained.9. Procedure (See Practice G3)9.1 Fill the cathode test pots to within approximately 15 mmof the top with the anode test electrolyte.9.2 Insert the test specimens into the No. 14 rubber stopper
29、sand insert the sample stopper assemblies into the cathode testpots.9.3 Wire the circuit as shown in Fig. 4.9.4 Turn on the power supply, adjust the current to 1.60 mAand check periodically to ensure the current remains constant atthat level.9.5 Obtain closed circuit test specimen potentials at 1, 7
30、,and 14 days using a saturated calomel electrode and anelectrometer. Obtain the potential measurement of each testspecimen as shown in Fig. 4. The tip of the calomel referenceshould be within 10 mm of the test specimen surface when thismeasurement is made.9.6 The electrolyte temperature should be 22
31、 6 5C duringthe test.9.7 Turn off the power supply after 14 days. One hour lateropen circuit potentials of the test specimens are obtained. Thetechnique is identical to the closed circuit measurements (9.5).9.8 Remove the wiring from the test specimens, remove thetest specimens from the electrolyte
32、and the rubber stoppers,and remove the tape from the specimens.9.9 Place an untested test specimen in the cleaning solutionwhich has been previously heated to 6080C. Leave thespecimen in the solution for 10 min, rinse in tap water, and dryin an oven at 105C for 30 min. If its mass loss is greater th
33、an5 mg, discard the cleaning solution. If the untested testspecimen mass loss is less than 5 mg, place the test specimensalong with an untested test specimen in the 6080C cleaningsolution for 10 min. Then rinse in tap water and dry in an ovenat 105C for 3 h. If the untested test specimen mass loss i
34、sgreater than 5 mg, discard the cleaning solution and repeat thetest.9.9.1 An alternative cleaning procedure is to replace the 10min immersion in 6080C cleaning solution with a 30 minimmersion in ambient temperature cleaning solution.9.10 If copper coulometers are used, remove the wires fromthe coul
35、ometer, rinse in tap water, and place in a drying ovenat 105C for 30 min.9.11 Remove the test specimens, the untested specimen andthe copper coulometer wires from the heating oven and allowto cool to room temperature, then weigh to the nearest 0.1 mg.(WarningClean gloves should be worn during the we
36、ighingprocess to avoid contamination of the specimens and coulom-eter wires.)FIG. 4 Experimental CellsG 97 97 (2007)310. Calculation and Report (See Guide G16)10.1 Calculate and report the Ah passed through the testcells during the 14-day test.10.1.1 If a copper coulometer is used, the Ah calculatio
37、n isas follows:Ah 5 0.8433 Ah/g Cu! M22 M1! (1)where:M2= final mass of copper coulometer wire, g, andM1= initial mass of copper coulometer wire, g.10.1.2 If an electronic coulometer is used, the Ah calcula-tion is as follows:Ah 5 ampere second measurement from coulometer!/3600! (2)10.2 Calculate and
38、 report the Ah per mass loss for each testspecimen as follows:Ah/g 5 Ah!/MMg12 MMg2! (3)where:MMg1= initial mass of magnesium test specimen, g, andMMg2= final mass of magnesium test specimen, g.10.3 Report closed and open circuit potential measurementsfor each test specimen.11. Precision and Bias411
39、.1 The following criteria should be used to judge theacceptability of the results at the 5 % significance level.11.1.1 RepeatabilityResults (on identical test specimens)by the same operator should be considered suspect if the meanfrom five specimens differs by more than the following fromthe mean ob
40、tained from a duplicate test on five specimens.Ah/g value 0.06 Ah/gFinal closed circuit potential 0.01 VOpen circuit potential 0.02 V11.1.2 ReproducibilityResults (on identical test speci-mens) submitted by each of two laboratories should beconsidered suspect if the mean from five specimens tested b
41、yone lab differs by more than the following from the mean fromfive specimens tested by the other lab.Ah/g value 0.15 Ah/gFinal closed circuit potential 0.05 VOpen circuit potential 0.08 V11.1.3 Test specimens from the same casting may not beidentical because of inhomogeneities in the casting. A meth
42、odof insuring that identical test specimens are being evaluated isto retest a test specimen. The surface of the test specimenshould be smoothed by machining before retesting. The newdiameter should be measured and the test current adjusted sothat the retest current density is 0.039 mA/cm2.11.2 The v
43、alues of potential andAh per unit mass consumedas measured by this test method, may not agree with thosefound in field applications. It is unlikely that field results of Ahper unit mass consumed would ever be greater than thosemeasured in this test. However, actual test comparisons are notsufficient
44、 to allow precise correlation of laboratory and fieldresults.12. Keywords12.1 coulometer; electroplaters tape; sacrificial anodeASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are
45、 expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not r
46、evised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you
47、 may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United
48、States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).4Supporting data (derived from results of cooperative tests on magnesium testsamples) have been filed at ASTM International Headquarters and may be obtainedby requesting Research Report RR:G01-1007.G 97 97 (2007)4
