1、Designation: G97 97 (Reapproved 2013)Standard 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 originaladoptio
2、n or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscriptepsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers a laboratory procedure thatmeasures the two fundame
3、ntal 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 an
4、odes 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 in t
5、hegypsum-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 Terminolog
6、y G15 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 establish appro-priate safety and health practices and determine the applica-bility of regulatory
7、 limitations prior to use. For specificprecautions, See Section 7 and Paragraph 8.1.1.2. Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent WaterG3 Practice for Conventions Applicable to ElectrochemicalMeasurements in Corrosion TestingG15 Terminology Relating to Corrosion and Co
8、rrosion Test-ing (Withdrawn 2010)3G16 Guide for Applying Statistics to Analysis of CorrosionData2.2 American National Standard:ANSI/NFPA 480 Storage, Handling, and Processing ofMagnesium, 1987 Edition43. Summary of Test Method3.1 A known direct current is passed through test cellsconnected in series
9、. 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 after the current is turned off at the end of the test. The totalAh passed th
10、rough 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 evaluating magnesium anodes.The degree of correlation between this test and service p
11、erfor-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 Pot, as shown in Fig. 1.5.1.3 Copper Coulometer, as shown in Fig. 2,orElect
12、ronicCoulometer.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 capability of 110C orhigher.1This test method is under the jurisdiction of ASTM Commi
13、ttee G01 onCorrosion of Metals and is the direct responsibility of Subcommittee G01.10 onCorrosion in Soils.Current edition approved May 1, 2013. Published July 2013. Originally approvedin 1989. Last previous edition approved in 2007 as G9797 (2007). DOI:10.1520/G0097-97R13.2For referenced ASTM stan
14、dards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.4A
15、vailable from National Fire Protection Association (NFPA), 1 BatterymarchPark, Quincy, MA 02169-7471, http:/www.nfpa.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States16. Reagents6.1 Test Electrolyte, Saturated Calcium Sulfate-Magnes
16、iumHydroxide SolutionAdd 5.0 g of reagent grade CaSO42H2O,0.1 g of reagent grade Mg(OH)2, to 1000 mL of Type IV orbetter reagent grade water (see Specification D1193).6.2 Coulometer SolutionAdd 235 g of reagent gradeCuSO45H2O, 27 mL 98 % H2SO4,50cm3undenatured ethylalcohol to 900 mL of Type IV or be
17、tter 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 coulometer solution and when handling thecleaning solution. Test specimen cleaning
18、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 selection and prepa-ration from a cast anode. Since all sizes and shapes of castanodes a
19、re 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 crosssection portion of the cast anode. Dry machine the square crosssection, which shou
20、ld 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 to a152-mm length and machine-face one end.8.1.1 Magnesium fines produced during c
21、utting 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 for use on magnesium:8.1.2.1 Blade pitch (teeth/cm)Band saw = 1.6 to 2.4,power hacks
22、aw = 0.8 to 2.4.FIG. 1 Detail of Test PotFIG. 2 Copper CoulometerFIG. 3 Test Specimen Preparation from Cast AnodeG97 97 (2013)28.1.2.2 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, powerhac
23、ksaw = 20 to 30.8.2 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 at all times after theacetone rinsing step to avoid contamination of the specimens.)8
24、.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 the side area for a lengthof 100 mm. This exposed area is 41.2 cm2. A current flowthro
25、ugh 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 highlyresistive coating that prevents the required current from beingobtained, sandblast, wire brus
26、h, 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 with fine (00 grit or finer)abrasive, dry in an oven at 105C for 15 min, cool and weighbe
27、fore 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 copper wire and sheetshould have a purity of 99.9 % or higher.8.6 Fig. 4 is a schematic
28、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 arebeing obtained.9. Procedure (See Practice G3)9.1 Fill the cathode test pots to within a
29、pproximately 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 shown in Fig. 4.9.4 Turn on the power supply, adjust the current to 1.60 mAand check pe
30、riodically 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 measurement of each testspecimen as shown in Fig. 4. The tip of the calomel referenceshou
31、ld 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 potentials of the test specimens are obtained. Thetechnique is identical to the closed
32、 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 specimen in the cleaning solutionwhich has been previously heated to 6080C. Leave thespec
33、imen 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 mg, place the test specimensalong with an untested test specimen in the 6080C cleaning
34、solution 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 cleaning procedure is to replace the 10min immersion in 6080C cleaning solution with a 30
35、 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 test specimens, the untested specimen andthe copper coulometer wires from the heating oven
36、 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.)FIG. 4 Experimental CellsG97 97 (2013)310. Calculation and Report (See Guide G16)10.1 Calculate and re
37、port 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 coulometer wire, g.10.1.2 If an electronic coulometer
38、 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)where:MMg1= initial mass of magnesium test specimen, g, andMMg2= final mass of magnesium test
39、 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 5 % significance level.11.1.1 RepeatabilityResults (on identical test specimens)by the same
40、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 potential 0.01 VOpen circuit potential 0.02 V11.1.2 ReproducibilityResults (on identical test
41、 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 the other lab.Ah/g value 0.15 Ah/gFinal closed circuit potential 0.05 VOpen circuit potential
42、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 specimen. The surface of the test specimenshould be smoothed by machining before retesting. The ne
43、wdiameter should be measured and the test current adjusted sothat the retest current density is 0.039 mA/cm2.11.2 The values 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
44、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; electroplaters tape; sacrificial anodeASTM International takes no position respecting the v
45、alidity 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 riskof infringement of such rights, are entirely their own responsibility.This standard is s
46、ubject 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 this standard or for additional standardsand should be addressed to ASTM International Headq
47、uarters. 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 shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This stan
48、dard 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 by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or se
49、rviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).5Supporting 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.G97 97 (2013)4
