ASTM D6208-2007(2014) 2004 Standard Test Method for Repassivation Potential of Aluminum and Its Alloys by Galvanostatic Measurement《采用恒电流测量的铝及其合金再钝化电位的标准试验方法》.pdf
《ASTM D6208-2007(2014) 2004 Standard Test Method for Repassivation Potential of Aluminum and Its Alloys by Galvanostatic Measurement《采用恒电流测量的铝及其合金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(2014) 2004 Standard Test Method for Repassivation Potential of Aluminum and Its Alloys by Galvanostatic Measurement《采用恒电流测量的铝及其合金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: D6208 07 (Reapproved 2014)Standard Test Method forRepassivation Potential of Aluminum and Its Alloys byGalvanostatic Measurement1This standard is issued under the fixed designation D6208; the number immediately following the designation indicates the year oforiginal adoption or, in the
2、case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 A procedure to determine the repassivation potential ofaluminum alloy 3003-H14 (UNSA9300
3、3) (1)2as a measure 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 alumin
4、um alloys and 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 s
5、tandard 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:3D1193 Specification for Reagent WaterD3585 Specification for ASTM Reference Fluid for CoolantTestsG3 Practice for Conventio
6、ns Applicable to ElectrochemicalMeasurements in Corrosion TestingG15 Terminology Relating to Corrosion and Corrosion Test-ing (Withdrawn 2010)4G46 Guide for Examination and Evaluation of Pitting Cor-rosionG107 Guide for Formats for Collection and Compilation ofCorrosion Data for Metals for Computeri
7、zed DatabaseInput3. Terminology3.1 Definitions: Terms used in this test method can be foundin Practice G3 and 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, po
8、tential at which oxide layer repassivates.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
9、 coolant andcorrosive water containing 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 G46 as a g
10、uide after disassembly and rinsing.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 quan
11、titatively with other test method 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 initialpolarization, EB,is a measure of the
12、 resistance to breakdown ofthe aluminum oxide film. Lower susceptibility to initiation ofpitting corrosion is indicated by a more noble potential (See1This test method is under the jurisdiction of ASTM CommitteeD15 on EngineCoolants and Related Fluids and is the direct responsibility of Subcommittee
13、D15.06on Glassware Performance Tests.Current edition approved Feb. 1, 2014. Published March 2014. Originallyapproved in 1997. Last previous edition approved in 2007 as D6208 - 07. DOI:10.1520/D6208-07R14.2The boldface numbers in parentheses refer to the list of references at the end ofthis standard.
14、3For 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 the standards Document Summary page onthe ASTM website.4The last approved version of this historical standard is ref
15、erenced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1Practice G3 and Terminology G15.) This potential, as mea-sured in this test method, is not very sensitive to the inhibitorspresent.5.3 The minimum potential, EG,fo
16、llowing the maximumpotential is a measure of the protection against continuedpitting corrosion by the inhibitors. Again, a more noblepotential indicates better protection. This potential is sensitiveto the inhibitors present.5.4 Visual examination of the specimens can provide infor-mation about subl
17、eties of the pitting and inhibition mecha-nisms. Number of pits, pit depth, amount of deposit, andsurface discoloration are some examples of recordableobservations, which can assist evaluation of inhibitor effective-ness.5.5 The presence of chloride in the test solution is critical toobservation of
18、pitting corrosion. Also, a coolant/corrosivewater solution in which gas bubbles evolve spontaneously onthe aluminum (indicating general corrosion) is unlikely to havea significant amount of observable pitting corrosion.6. Apparatus6.1 General DescriptionThe apparatus for the electro-chemical test co
19、nsists of a cell, current supply, recorder, andthree electrodes. Fig. 1 is a generalized schematic of thearrangement. More specific requirements for each componentare given below.6.2 CellThe cell consists of a No.25 O-ring borosilicateglass joint held vertically using standard laboratory clamps andr
20、ing stand. The working electrode will be clamped to thebottom using the matching O-ring clamp and viton or siliconerubber gasket.6.3 Current Supply and RecorderA constant current sup-ply capable of generating 872 Acontinuously is required. Therecorder must have a high input impedance ( 1012Ohms), be
21、capable of recording potentials of 62 V with mV accuracy, andhave a low gain. These capabilities are typical of commercialpotentiostat/galvanostat instruments connected to either a stripchart recorder or computer, for experimental control and dataacquisition. The schematic in Fig. 1 shows connection
22、s using acurrent supply and mV strip chart recorder, and Fig. X2.1shows a schematic for using a computer and potentiostat/galvanostat.6.4 Electrodes:6.4.1 Working Electrode (WE)The working electrode, alu-minum test coupon, is cut as 51 51 mm (2 in. 2 in. ) squaresfrom aluminum sheet 2 to 6 mm (1/16
23、in. to 1/4 in.) thick. Thestandard material is AA3003-H14 (UNS A93003), used todevelop the precision and bias statements.The coupon is rinsedthoroughly (both sides) with methanol and placed in a lowtemperature drying oven. No additional surface preparation isdesirable. Prior to testing, a coupon is
24、allowed to cool to roomtemperature. Then it is clamped to the bottom of the O-ringjoint using the matching O-ring (viton or silicone rubber) andclamp. The clamping screw may be tightened to fingertightness, if desired. Excessive tightening must be avoided.This gives an area of 8.72 cm2aluminum expos
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