1、Designation: G 69 97 (Reapproved 2003)Standard Test Method forMeasurement of Corrosion Potentials of Aluminum Alloys1This standard is issued under the fixed designation G 69; the number immediately following the designation indicates the year of originaladoption or, in the case of revision, the year
2、 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 is a procedure for measurement of thecorrosion potential (see Note 1) of an aluminum alloy in an
3、aqueous solution of sodium chloride with enough hydrogenperoxide added to provide an ample supply of cathodicreactant.NOTE 1The corrosion potential is sometimes referred to as theopen-circuit solution or rest potential.1.2 This standard does not purport to address all of thesafety concerns, if any,
4、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 limitations prior to use.2. Referenced Documents2.1 ASTM Standards:D 1193 Specification for Reagent Water23. Significance
5、 and Use3.1 The corrosion potential of an aluminum alloy dependsupon the amounts of certain alloying elements that the alloycontains in solid solution. Copper and zinc, which are two ofthe major alloying elements for aluminum, have the greatesteffect with copper shifting the potential in the noble o
6、r positivedirection, and zinc in the active or negative direction. Forexample, commercially unalloyed aluminum (1100 alloy)3hasa potential of 750 mV when measured in accordance with thispractice, 2024T3 alloy with nearly all of its nominal 4.3 %copper in solid solution, a potential of 600 to 620 mV
7、(Note2), and 7072 alloy with nearly all of its nominal 1.0 % zinc insolid solution, a potential of 885 mV (SCE) (1-3).4NOTE 2The potential depends upon the rate of quenching.3.2 Because it reflects the amount of certain alloying ele-ments in solid solution, the corrosion potential is a useful toolfo
8、r characterizing the metallurgical condition of aluminumalloys, especially those of the 2XXX and 7XXX types, whichcontain copper and zinc as major alloying elements. Its usesinclude the determination of the effectiveness of solution heattreatment and annealing (1), of the extent of precipitationduri
9、ng artificial aging (4) and welding (5), and of the extent ofdiffusion of alloying elements from the core into the claddingof alclad products (2).4. Apparatus4.1 The apparatus consists of an inert container for the testsolution, a mechanical support for the test specimens thatinsulates them electric
10、ally from each other and from ground,saturated calomel electrode (SCE) (see Note 3), wires andaccessories for electrical connections, and equipment for themeasurement of potential.NOTE 3Saturated calomel electrodes are available from severalmanufacturers. It is a good practice to ensure the proper f
11、unctioning of thereference electrode by measuring its potential against one or morereference electrodes. The potential difference should not exceed 2 or 3mV.54.2 A high-impedence (1012V) voltmeter is suitable formeasurement of the potential. Measurement of this potentialshould be carried out to with
12、in 6 1 mV. Automatic datarecording systems may be used to permit the simultaneousmeasurement of many specimens and the continuous recordingof corrosion potentials.5. Reagents5.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall re
13、agents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.6Other grades may beused, provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening t
14、heaccuracy of the determination.1This practice is under the jurisdiction of Committee G01 on Corrosion ofMetals and is the direct responsibility of Subcommittee G01.11 on ElectrochemicalMeasurements in Corrosion Testing.Current edition approved Oct. 10, 1997. Published December 1997. Originallyappro
15、ved in 1981. Last previous edition approved in 1994 as G 69 81 (1994)e1.2Annual Book of ASTM Standards, Vol 11.01.3All alloy designations are those of the Aluminum Association.4The boldface numbers in parentheses refer to the references at the end of thisstandard.5Round-robin test conducted by G01.1
16、1 (unpublished results).6Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the
17、United States Pharmacopeiaand National Formulary, U.S. Pharmaceutical Convention, Inc. (USPC), Rockville,MD.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.2 Purity of WaterThe water shall be distilled or deion-ized conforming to t
18、he purity requirements of SpecificationD 1193, Type IV reagent water.5.3 Sodium Chloride (NaCl).5.4 Hydrogen Peroxide (H2O2) (30 %)In case of uncer-tainty (for example, whenever freshly opened reagent is notused), the concentration of hydrogen peroxide in the reagentshall be confirmed by chemical an
19、alysis as described in AnnexA1. In no case shall reagent containing less than 20 %hydrogen peroxide be used.6. Solution Conditions6.1 The test solution shall consist of 58.5 6 0.1 g of NaCland 9 6 1 mL of 30 % hydrogen peroxide reagent per 1 L ofaqueous solution. (This solution is 1 M with respect t
20、oconcentration of sodium chloride.)6.2 The hydrogen peroxide reagent shall be added justbefore measurements are made because it decomposes uponstanding.6.3 Freshly prepared solution shall be used for each set ofmeasurements.6.4 Not less than 500 mL of solution shall be used for eachset of measuremen
21、ts.6.5 The total exposed area of all the specimens of the samecomposition in each set of measurements shall not exceed 100mm2per 100 mL of solution.6.6 The temperature of the test solution shall be maintainedat 25 6 2C.7. Test Specimen7.1 For measurement alone, specimen size is unimportantprovided t
22、hat the area for measurement is at least 25 mm2, butfor convenience the specimen, wherever possible, should belarge enough to permit ease of handling during preparation andan electrical connection outside the test solution. A specimen afew millimetres thick by about 15 mm wide and 100 mm longis a co
23、nvenient size.8. Specimen Preparation8.1 Any convenient means such as sawing or stamping maybe used to prepare a specimen to size provided that it does notheat the specimen enough to change its metallurgical structure.8.2 Irregular-shaped specimens shall be machined or pre-pared with a coarse file t
24、o provide a reasonably flat surface andto remove nonrepresentative metal (for example, affected bysawing or stamping, or in case of clad product where core is tobe measured). Further preparation consists of filing with a longlathe file. Original flat surface specimens are also filed withlong lathe f
25、ile to remove the original mill scale oxide layer.8.3 No filing or machining is needed to prepare specimensthat have original flat surface, representative of its metallurgi-cal structure, or to prepare specimens that are too thin to permitmore than minimal removal of metal; these include cladproduct
26、s with thin claddings which are to be measured.8.4 The surfaces of all products selected for measurement,including those with no previous preparation, are abraded drywith No. 320 grade aluminum oxide or silicon carbide clothand then with No. 00 steel wool.NOTE 4Caution: Clad products with thin cladd
27、ings should only beabraded lightly except to remove the cladding for measurement of thecore.8.5 Following mechanical preparation, the specimen iscleaned, or degreased, in an inert solvent (for example, acetoneor perchloroethylene).8.6 All parts of a specimen and its electrical connection tobe expose
28、d in the test solution, except for the area of thespecimen prepared for measurement, are masked off. Anymaterial that masks a surface physically and electrically andthat is inert in the test solution may be used (see Annex A2).9. Procedure9.1 For corrosion potential measurements, the test speci-mens
29、 and the reference electrode are immersed in the appro-priate quantity of test solution; the test specimens are con-nected to the positive terminal of the equipment for measuringpotential, and the reference electrode to the negative terminal.9.2 Care should be taken to ensure that all the unmaskedar
30、ea of each test specimen prepared for measurement isexposed to the test solution and that any other unmasked areais not exposed. Care should also be taken to ensure that anyunmasked portion of the electrical connection is outside the testsolution.9.3 The potential of each specimen shall be measured
31、at5-min intervals for a period of1horrecorded continuouslyusing the output of a high-impedance voltmeter.9.4 The potential of each specimen shall be reported as theaverage of the values for the last 30 min of measurement (thatis, for the last 7 measurements).9.5 Duplicate specimens shall be measured
32、.9.6 The average of the values for duplicate specimens shallbe used if the values agree within 5 mV. If they do not agreewithin 5 mV at least one additional specimen shall be mea-sured. The values for the three or more specimens shall beaveraged if they agree within 10 mV but they shall be reportedi
33、ndividually if they do not agree.10. Standardization of Test Procedure10.1 The test procedure shall be standardized by measure-ment of the free corrosion potential of a sample of commer-cially produced 3003 alloy sheet. Sheet of any temper issuitable because the potential of this product is not affe
34、ctedsignificantly by temper.10.2 The procedure shall be considered acceptable if thevalue obtained is 748 6 11 mV (SCE).11. Report11.1 The following information shall be recorded:11.1.1 Identification of product, alloy, and temper includingreference to applicable specifications.11.1.2 The results of
35、 all measurements with an indication ofwhether they represent individual values or averages; and ifaverages, also the number of values averaged.G 69 97 (2003)212. Precision and Bias12.1 PrecisionThe precision of this test method wasdetermined by the statistical examination of the interlaboratorytest
36、 results.712.1.1 RepeatabilityThe repeatability (within laboratoryvariability) standard deviation (Srand the 95 % limit (r = 2.8Sr) was determined for two alloys as follows:Alloy Average Srr(95 %)1100-H18 758 mV 0.0018 65.1 mV3003-H18 748 mV 0.0017 64.7 mV12.1.2 ReproducibilityThe reproducibility (b
37、etween labo-ratory variability) standard deviation (SR) and the 95 % limit(R = 2.8 SR) was determined for two alloys as follows:Alloy Average SRR(95 %)1100-H18 758 mV 0.0018 612 mV3003-H18 748 mV 0.0017 611 mV12.2 BiasNo information can be presented on the bias ofthe procedure in this test method be
38、cause no accepted externalreference value is available. The values for corrosion potentialof aluminum alloys as measured by this test method are definedonly in terms of this method.13. Keywords13.1 aluminum alloy; aqueous; copper; corrosion potential;sodium chloride; solid solution; zincANNEXES(Mand
39、atory Information)A1. ANALYSIS OF HYDROGEN PEROXIDE REAGENTA1.1 Dilute a sample of the hydrogen peroxide reagent tocontain approximately6gH2O2/L. Then pipet a 10-mL aliquotof this solution into a beaker to which has already been added400 mL of water and 15 mL of 50 % sulfuric acid. Titrate thissolut
40、ion with standard 0.1 N potassium permanganate solution.A1.2 To obtain the grams of hydrogen peroxide per litre ofreagent, multiply the millilitres of potassium permanganatesolution used by 0.1 times 0.017 times the aliquot factor. Tablesin chemical handbooks provide the data required to convertgram
41、s per litre of hydrogen peroxide to percent.A1.3 Some stabilizers used with hydrogen peroxide reactwith permanganate, but this interference can be ignored when-ever the analysis given by the manufacturer was also deter-mined by permanganate analysis.A2. MASKING MATERIALSA2.1 Materials suitable for m
42、asking are made by severalmanufacturers.A2.2 A satisfactory masking material can be prepared byadding powdered rosin gradually to melted beeswax untilsaturation is obtained. Several hours may be required becauseof the slow rate of dissolution of the rosin.APPENDIX(Nonmandatory Information)X1. CONVER
43、SION FACTORS FOR POTENTIALSX1.1 Many corrosion potentials of aluminum alloys in theliterature were measured in an aqueous solution at 25Ccontaining 53 g of NaCl and 9 mL of 30 % H2O2/L. Thepotentials were measured with a 0.1 N calomel electrode withits tip immersed directly into the solution without
44、 bridging.X1.2 To a good approximation, values measured underX1.1 may be converted to those measured by this practicebythe addition of 92 mV (for example, 830 mV convertsto 738 mV).X1.3 Alternatively, values measured by this practice maybe converted to those measured under X1.1 by the subtractionof
45、92 mV (for example, 738 mV converts to 830 mV).7Supporting data are available from ASTM Headquarters. Request ResearchReport RR:G01.1015.G 69 97 (2003)3REFERENCES(1) Brown, R. H., Fink, W. L., and Hunter, M. S., “Measurement ofIrreversible Potentials as a Metallurgical Research Tool,” Transactionsof
46、 the American Institute of Mining and Metallurgical Engineers,Institute of Metals Division, Vol 143, 1941, pp. 115123.(2) Brown, R. H., “Aluminum Alloy Laminates: Alclad and Clad Alumi-num Alloy Products,” Chapter 11 in Composite Engineering Lami-nates, G. H. Dietz (editor), MIT Press, Cambridge, Ma
47、ss., 1969.(3) Anderson, W. A., and Stupf, H. C., Corrosion Magazine, Vol 6, 1980,p. 212.(4) Lifka, B. W., and Sprowls, D. O., “Significance of IntergranularCorrosion in High Strength Aluminum Alloys,” Symposium on Local-ized CorrosionCause of Metal Failure, ASTM STP 516, Am. Soc.Testing Mats., 1972,
48、 pp. 12044.(5) Shumaker, M. B., Kelsey, R. A., Sprowls, D. O., and Williamson, J. G.,“Evaluation of Various Techniques for Stress Corrosion TestingWelded Aluminum Alloys,” Symposium on Stress Corrosion Testing,ASTM STP 425, Am. Soc. Testing Mats., 1967, pp. 31741.ASTM International takes no position
49、 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 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 this standard or for additional s
