1、Designation: G 97 97 (Reapproved 2002)e1Standard 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 originalado
2、ption 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.e1NOTECautionary notes were moved into the section text editorially October 2002.1
3、. Scope1.1 This test method describes a laboratory procedure thatmeasures the two fundamental performance properties ofmagnesium sacrificial anode test specimens operating in asaturated calcium sulfate, saturated magnesium hydroxideenvironment. The two fundamental properties are electrode(oxidation
4、potential) and ampere hours (Ah) obtained per unitmass of specimen consumed. Magnesium 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 hyd
5、roxide test electrolyte simulates thelong term environment around an anode installed in 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 identi
6、cal toproperty measurements obtained using this laboratory test.NOTE 1Refer to Terminology G 15 for 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 establi
7、sh appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. For specificprecautions, See Section 7 and Paragraph 8.1.1.2. Referenced Documents2.1 ASTM Standards:D 1193 Specification for Reagent Water2G 3 Practice for Conventions Applicable to
8、ElectrochemicalMeasurements in Corrosion Testing3G 15 Terminology Relating to Corrosion and CorrosionTesting3G 16 Guide for Applying Statistics to Analysis of CorrosionData32.2 American National Standard:ANSI/NFPA 480 Storage, Handling, and Processing ofMagnesium, 1987 Edition43. Summary of Test Met
9、hod3.1 A known direct current is passed through test cellsconnected in series. Each test cell consists 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
10、after the current is turned off at the end of the test. The totalAh passed through the cells are 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 evaluati
11、ng magnesium anodes.The degree of correlation between this test and service perfor-mance has not 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
12、 Pot, as shown in Fig. 1.5.1.3 Copper Coulometer, as shown in Fig. 2, or ElectronicCoulometer.5.1.4 Saturated Calomel Reference Electrode.5.1.5 Electrometer, with an input impedance of 107orgreater ohms.5.1.6 Balance, 100-g capacity with 0.1 mg sensitivity.5.1.7 Drying Oven, with temperature capabil
13、ity of 110C orhigher.6. Reagents6.1 Test Electrolyte, Saturated Calcium Sulfate-MagnesiumHydroxide SolutionAdd 5.0 g of reagent grade CaSO42H2O,1This test method is under the jurisdiction of ASTM Committee G01 onCorrosion of Metals, and is the direct responsibility of Subcommittee G01.10 onCorrosion
14、 in Soils.Current edition approved Oct. 10, 1997. Published December 1997. Originallypublished as G 97 89. Last previous edition G 97 89 (1995)e1.2Annual Book of ASTM Standards, Vol 11.01.3Annual Book of ASTM Standards, Vol 03.02.4Available from National Fire Protection Association, Inc., Batterymar
15、ch Park,Quincy, MA 02269.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.0.1 g of reagent grade Mg(OH)2, to 1000 mL of Type IV orbetter reagent grade water (see Specification D 1193).6.2 Coulometer SolutionAdd 235 g of reagent gradeC
16、uSO45H2O, 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 grade water.7. Precautions7.1 Eye protection and skin protection are required whenhandling the
17、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 disposing of used cleaning solution.8. Specimen Preparation8.1 Fig. 3 shows typical test specimen selec
18、tion 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 andapproximately 13 mm from the edge. Machine each testspecimen from a sawed, 180-mm long, 16-mm square cros
19、ssection 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 rate of 0.5 mm per revolution, and a depthof cut of 1.9 mm or less. Cut the machined test specimen
20、 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 magnesium.8.1.2 Band saws and power hacksaws with the followingcharacteristics are recommended f
21、or use on magnesium:8.1.2.1 Blade pitch (teeth/cm)Band saw = 1.6 to 2.4,power hacksaw = 0.8 to 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.FIG. 1 Detai
22、l of Test PotFIG. 2 Copper CoulometerFIG. 3 Test Specimen Preparation from Cast AnodeG 97 97 (2002)e128.2 Rinse each machined test specimen with water, rinsewith acetone, dry in an oven at 105C for 30 min, cool, andweigh to the nearest 0.1 mg. (WarningThe specimensshould be handled with clean gloves
23、 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 13 mm from the non-faced end. The area exposed to theelectrolyte will be the faced end, plus
24、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 plastic brush. If the testpot internal surface becomes completely covered with a highlyresisti
25、ve 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-lometer is used, prepare the copper coulometer as shown inFig. 2. Buff the coulometer wire wit
26、h 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 mm. Clean the copper sheet anodes before their initialinstallation into the coulometer. The co
27、pper 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 each end of each wire. Use the calomelelectrode only when oxidation potential measurements areb
28、eing obtained.9. Procedure (See Practice G 3)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 stoppersand insert the sample stopper assemblies into the cathode testpots.9.3 Wire the circuit as
29、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,and 14 days using a saturated calomel electrode and anelectrometer. Obtain the potential me
30、asurement 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 6 5C duringthe test.9.7 Turn off the power supply after 14 days. One hour lateropen circuit
31、 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 and the rubber stoppers,and remove the tape from the specimens.9.9 Place an untested test sp
32、ecimen 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 than5 mg, discard the cleaning solution. If the untested testspecimen mass loss is less than 5
33、 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 isgreater than 5 mg, discard the cleaning solution and repeat thetest.9.9.1 An alternative cl
34、eaning 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 coulometer, rinse in tap water, and place in a drying ovenat 105C for 30 min.9.11 Remove the tes
35、t 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 weighingprocess to avoid contamination of the specimens and coulom-eter wires.)10. Calculation
36、 and Report (See Guide G 16)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 calculation 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 cou
37、lometer wire, g.FIG. 4 Experimental CellsG 97 97 (2002)e1310.1.2 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 report the Ah per mass loss for each testspecimen as follows:Ah/g 5 Ah!/MMg12 MMg2! (3)w
38、here: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 Bias511.1 The following criteria should be used to judge theacceptability of the results at the
39、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 obtained from a duplicate test on five specimens.Ah/g value 0.06 Ah/gFinal closed circuit p
40、otential 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 byone lab differs by more than the following from the mean fromfive specimens tested by th
41、e 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 methodof insuring that identical test specimens are being evaluated isto retest a test specim
42、en. 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 values of potential and Ah per unit mass consumedas measured by this test method, may not
43、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 to allow precise correlation of laboratory and fieldresults.12. Keywords12.1 coulometer
44、; 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 expressly advised that determination of the validity of any such patent rights, and the
45、 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 revised, either reapproved or withdrawn. Your comments are invited either for revision of
46、 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 may attend. If you feel that your comments have not received a fair hearing you shouldm
47、ake 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 States. Individual reprints (single or multiple copies) of this standard may be obtained
48、 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).5The precision data were derived from results of cooperative tests on magnesiumtest samples. Supporting data available from ASTM headquarters. Request RR:G01-1007.G 97 97 (2002)e14
