ASTM D6208-2007 Standard Test Method for Repassivation Potential of Aluminum and Its Alloys by Galvanostatic Measurement《用恒电流测量铝及其合金的再钝化电位的标准试验方法》.pdf
《ASTM D6208-2007 Standard Test Method for Repassivation Potential of Aluminum and Its Alloys by Galvanostatic Measurement《用恒电流测量铝及其合金的再钝化电位的标准试验方法》.pdf》由会员分享,可在线阅读,更多相关《ASTM D6208-2007 Standard Test Method for Repassivation Potential of Aluminum and Its Alloys by Galvanostatic Measurement《用恒电流测量铝及其合金的再钝化电位的标准试验方法》.pdf(6页珍藏版)》请在麦多课文档分享上搜索。
1、Designation: D 6208 07Standard Test Method forRepassivation Potential of Aluminum and Its Alloys byGalvanostatic Measurement1This standard is issued under the fixed designation D 6208; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision
2、, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 A procedure to determine the repassivation potential ofaluminum alloy 3003-H14 (UNS A93003) (1)2as a me
3、asure ofrelative susceptibility to pitting corrosion by conducting agalvanostatic polarization is described.Aprocedure that can beused to check experimental technique and instrumentation isdescribed, as well.1.2 The test method serves as a guide for similar measure-ment on other aluminum alloys and
4、metals (2-5).1.3 The values stated in SI units are to be regarded as thestandard. Values given in parentheses are for information only.1.4 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 est
5、ablish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3D 1193 Specification for Reagent WaterD 3585 Specification for ASTM Reference Fluid for Cool-ant TestsG3 Practice for ConventionsApplicab
6、le to ElectrochemicalMeasurements in Corrosion TestingG15 Terminology Relating to Corrosion and CorrosionTestingG46 Guide for Examination and Evaluation of PittingCorrosionG 107 Guide for Formats for Collection and Compilation ofCorrosion Data for Metals for Computerized DatabaseInput3. Terminology3
7、.1 Definitions: Terms used in this test method can be foundin Practice G3and Terminology G15.3.2 Symbols:3.2.1 EBbreak potential, potential at which the passivealuminum oxide layer breaks down.3.2.2 EGprotection potential as measured in this galvano-static method, potential at which oxide layer repa
8、ssivates.3.2.3 Jcurrent density, in A/m24. Summary of Test Method4.1 The test method described is an adaptation of themethod described in FORD Motor Company standards (6).4.2 An aluminum alloy specimen is polarized at fixedcurrent density for 20 min. in a solution of coolant andcorrosive water conta
9、ining chloride. The potential as a functionof time is recorded.4.3 The maximum potential, EBreached upon polarizationis determined, as is the minimum potential following themaximum potential, EG.4.4 Visual examination of the specimen may be made usingGuide G46as a guide after disassembly and rinsing
10、.5. Significance and Use5.1 This test method is designed to measure the relativeeffectiveness of inhibitors to mitigate pitting corrosion ofaluminum and its alloys, in particular AA3003-H14, rapidlyand reproducibly. The measurements are not intended tocorrelate quantitatively with other test method
11、values or withsusceptibility to localized corrosion of aluminum observed inservice. Qualitative correlation of the measurements and sus-ceptibility in service has been established (1).5.2 The maximum potential reached upon initial polariza-tion, EB,is a measure of the resistance to breakdown of thea
12、luminum oxide film. Lower susceptibility to initiation of1This test method is under the jurisdiction of ASTM CommitteeD15 on EngineCoolants and is the direct responsibility of SubcommitteeD15.06 on GlasswarePerformance Tests.Current edition approved April 1, 2007. Published April 2007. Originallyapp
13、roved in 1997. Last previous edition approved in 2002 as D 6208 - 97(2002).2The boldface numbers in parentheses refer to the list of references at the end ofthis standard.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Ann
14、ual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.pitting corrosion is indicated by a more noble potential (SeePractice G3and
15、 Terminology G 15.) This potential, as mea-sured in this test method, is not very sensitive to the inhibitorspresent.5.3 The minimum potential, EG,following the maximumpotential is a measure of the protection against continuedpitting corrosion by the inhibitors. Again, a more noblepotential indicate
16、s better protection. This potential is sensitiveto the inhibitors present.5.4 Visual examination of the specimens can provide infor-mation about subleties of the pitting and inhibition mecha-nisms. Number of pits, pit depth, amount of deposit, andsurface discoloration are some examples of recordable
17、 obser-vations, which can assist evaluation of inhibitor effectiveness.5.5 The presence of chloride in the test solution is critical toobservation of pitting corrosion. Also, a coolant/corrosivewater solution in which gas bubbles evolve spontaneously onthe aluminum (indicating general corrosion) is
18、unlikely to havea significant amount of observable pitting corrosion.6. Apparatus6.1 General DescriptionThe apparatus for the electro-chemical test consists of a cell, current supply, recorder, andthree electrodes. Fig. 1 is a generalized schematic of thearrangement. More specific requirements for e
19、ach componentare given below.6.2 CellThe cell consists of a No.25 O-ring borosilicateglass joint held vertically using standard laboratory clamps andring stand. The working electrode will be clamped to thebottom using the matching O-ring clamp and viton or siliconerubber gasket.6.3 Current Supply an
20、d RecorderA constant current sup-ply capable of generating 872 Acontinuously is required. Therecorder must have a high input impedance ( 1012Ohms), becapable of recording potentials of 62 V with mV accuracy, andhave a low gain. These capabilities are typical of commercialpotentiostat/galvanostat ins
21、truments connected to either a stripchart recorder or computer, for experimental control and dataacquisition. The schematic in Fig. 1 shows connections using acurrent supply and mV strip chart recorder, and Fig. X2.1shows a schematic for using a computer and potentiostat/galvanostat.6.4 Electrodes:6
22、.4.1 Working Electrode (WE)The working electrode,aluminum test coupon, is cut as 51 3 51 mm (2 in. 3 2 in. )squares from aluminum sheet 2 to 6 mm (1/16 in. to 1/4 in.)thick. The standard material is AA3003-H14 (UNS A93003),used to develop the precision and bias statements. The couponis rinsed thorou
23、ghly (both sides) with methanol and placed ina low temperature drying oven. No additional surface prepa-ration is desirable. Prior to testing, a coupon is allowed to coolto room temperature. Then it is clamped to the bottom of theO-ring joint using the matching O-ring (viton or siliconerubber) and c
24、lamp. The clamping screw may be tightened tofinger tightness, if desired. Excessive tightening must beavoided. This gives an area of 8.72 cm2aluminum exposed tothe solution.6.4.2 Auxiliary Electrode (AE)Ultrafine grade graphiterod, 6-8 mm (1/4 in.) in diameter and at least 20 cm (8 in.)long. Avoid c
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