ASTM G82-1998(2014) Standard Guide for Development and Use of a Galvanic Series for Predicting Galvanic Corrosion Performance《预测电偶腐蚀性能用电偶系列的制定和使用标准指南》.pdf-资源下载-麦多课文库

ASTM G82-1998(2014) Standard Guide for Development and Use of a Galvanic Series for Predicting Galvanic Corrosion Performance《预测电偶腐蚀性能用电偶系列的制定和使用标准指南》.pdf

1、Designation: G82 98 (Reapproved 2014)Standard Guide forDevelopment and Use of a Galvanic Series for PredictingGalvanic Corrosion Performance1This standard is issued under the fixed designation G82; the number immediately following the designation indicates the year of originaladoption or, in the cas

2、e of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscriptepsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide covers the development of a galvanic seriesand its subsequent use as a method of pre

3、dicting the effect thatone metal can have upon another metal can when they are inelectrical contact while immersed in an electrolyte. Sugges-tions for avoiding known pitfalls are included.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in t

4、hisstandard.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 limitations prior to use. Sp

5、ecific precau-tionary statements are given in Section 5.2. Referenced Documents2.1 ASTM Standards:2G3 Practice for Conventions Applicable to ElectrochemicalMeasurements in Corrosion TestingG15 Terminology Relating to Corrosion and Corrosion Test-ing (Withdrawn 2010)3G16 Guide for Applying Statistics

6、 to Analysis of CorrosionDataG71 Guide for Conducting and Evaluating Galvanic Corro-sion Tests in Electrolytes3. Terminology3.1 Definitions of terms used in this guide are from Termi-nology G15.3.2 activethe negative (decreasingly oxidizing) directionof electrode potential.3.3 corrosion potentialthe

7、 potential of a corroding surfacein an electrolyte relative to a reference electrode measuredunder open-circuit conditions.3.4 galvanic corrosionaccelerated corrosion of a metalbecause of an electrical contact with a more noble metal ornonmetallic conductor in a corrosive electrolyte.3.5 galvanic se

8、riesa list of metals and alloys arrangedaccording to their relative corrosion potentials in a givenenvironment.3.6 noblethe positive (increasingly oxidizing) direction ofelectrode potential.3.7 passivethe state of the metal surface characterized bylow corrosion rates in a potential region that is st

9、ronglyoxidizing for the metal.3.8 polarizationthe change from the open-circuit elec-trode potential as the result of the passage of current.4. Significance and Use4.1 When two dissimilar metals in electrical contact areexposed to a common electrolyte, one of the metals canundergo increased corrosion

10、 while the other can show de-creased corrosion.This type of accelerated corrosion is referredto as galvanic corrosion. Because galvanic corrosion can occurat a high rate, it is important that a means be available to alertthe user of products or equipment that involve the use ofdissimilar metal combi

11、nations in an electrolyte of the possibleeffects of galvanic corrosion.4.2 One method that is used to predict the effects of galvaniccorrosion is to develop a galvanic series by arranging a list ofthe materials of interest in order of observed corrosion poten-tials in the environment and conditions

12、of interest. The metalthat will suffer increased corrosion in a galvanic couple in thatenvironment can then be predicted from the relative position ofthe two metals in the series.4.3 Types of Galvanic Series:4.3.1 One type of Galvanic Series lists the metals of interestin order of their corrosion po

13、tentials, starting with the mostactive (electronegative) and proceeding in order to the most1This guide is under the jurisdiction of ASTM Committee G01 on Corrosion ofMetalsand is the direct responsibility of Subcommittee G01.11 on ElectrochemicalMeasurements in Corrosion Testing.Current edition app

14、roved May 1, 2014. Published May 2014. Originallyapproved in 1983. Last previous edition approved in 2009 as G8298(2009). DOI:10.1520/G0082-98R14.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards

15、 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.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1noble (electropos

16、itive). The potentials themselves (versus anappropriate reference half-cell) are listed so that the potentialdifference between metals in the series can be determined. Thistype of Galvanic Series has been put in graphical form as aseries of bars displaying the range of potentials exhibited bythe met

17、al listed opposite each bar. Such a series is illustrated inFig. 1.NOTE 1Dark boxes indicate active behavior of active-passive alloys.FIG. 1 Galvanic Series of Various Metals in Flowing Seawater at 2.4 to 4.0 m/s for 5 to 15 Days at 5 to 30C (Redrawn from Original)(see Footnote 5)G82 98 (2014)24.3.2

18、 The second type of galvanic series is similar to the firstin that it lists the metals of interest in order of their corrosionpotentials. The actual potentials themselves are not specified,however. Thus, only the relative position of materials in theseries is known and not the magnitude of their pot

19、entialdifference. Such a series is shown in Fig. 2.4.4 Use of a Galvanic Series:4.4.1 Generally, upon coupling two metals in the GalvanicSeries, the more active (electronegative) metal will have atendency to undergo increased corrosion while the more noble(electropositive) metal will have a tendency

20、 to undergo re-duced corrosion.4.4.2 Usually, the further apart two metals are in the series,and thus the greater the potential difference between them, thegreater is the driving force for galvanic corrosion. All otherfactors being equal, and subject to the precautions in Section 5,this increased dr

21、iving force frequently, although not always,results in a greater degree of galvanic corrosion.5. Precautions in the Use of a Galvanic Series5.1 The galvanic series should not be confused with theelectromotive force series, which, although of a similar appear-ance to the galvanic series, is based on

22、standard electrodepo-tentials of elements and not on corrosion potentials of metals.The electromotive force series should not be used for galvaniccorrosion prediction.5.2 Each series is specific to the environment for which itwas compiled. For example, a series developed in a flowingambient temperat

23、ure seawater should not be used to predict theperformance of galvanic couples in fresh water or in heatedseawater.5.3 Corrosion potentials can change with time and theenvironment. These changes can affect the potential differencebetween the metals of interest and, in some cases, can reverserelative

24、positions. It is thus imperative that the series used forthe prediction be obtained under similar conditions of exposureduration and electrolyte composition as the situation beingpredicted.5.4 Galvanic corrosion can occur between two identicalmaterials in different environments. The galvanic series

25、gen-erated herein cannot be applied to this situation.5.5 Use of a galvanic series provides qualitative predictionof galvanic corrosion. It should not be used for quantitativepredictions of galvanic corrosion rate. A more precise deter-mination of the effect of galvanic coupling can be obtained byth

26、e measurement of the corrosion currents involved as outlinedin Guide G71.4,55.6 Some published Galvanic Series, such as those in Fig. 16and Fig. 2, consider the possibility of there being more thanone potential range for the same material, depending onwhether the material is in the active or the pas

27、sive state.Knowledge of conditions affecting passivity of these materialsis necessary to determine which potential range to use in aparticular application.5.7 Galvanic corrosion behavior is affected by many factorsbesides corrosion potentials. These factors must also be con-sidered in judging the pe

28、rformance of a galvanic couple. Theyinclude, but are not limited to, the following:5.7.1 Anode-to-cathode area ratio,5.7.2 Electrolyte conductivity,5.7.3 Distance between coupled metals,5.7.4 Shielding of metal surfaces by marine growth,sediments, and so forth,5.7.5 Localized electrolyte concentrati

29、on changes inshielded areas, and4Brasunas, A., Editor, NACE Basic Corrosion Course, Chapter 3, NACE,Houston, TX, 1970.5Baboian, R., “Electrochemical Techniques for Predicting Galvanic Corrosion,”Galvanic and Pitting Corrosion-Field and Laboratory Studies, ASTM STP 576,Am.Soc. Testing Mats., 1976, pp

33、nless Steel Type 316 (Passive)(+) SilverNOBLE or GraphitePASSIVE END GoldPlatinumFIG. 2 Galvanic Series of Various Metals Exposed to Seawater(see Footnote 3)G82 98 (2014)35.7.6 Polarization characteristics of the metals involved.5.8 Some materials that are subject to chemical attack inalkaline solut

34、ions may suffer increased attack when made thecathode in a galvanic couple due to generation of hydroxyl ionsby the cathodic reaction. Use of a galvanic series will notpredict this behavior.5.9 A more detailed discussion of the theory of galvaniccorrosion prediction is presented in Appendix X1 and i

35、nASTMSTP 576.56. Development of a Galvanic Series6.1 The development of a Galvanic Series may be dividedinto several steps. First is the selection of the environment andconditions of interest. During the exposures, the environmentand conditions should be as close as possible to serviceconditions. A

36、list of environmental factors and conditions thatcould affect open-circuit potentials follows. This is not in-tended to be a complete listing, but it should serve as a guideto the types of factors that require consideration:6.1.1 Temperature,6.1.2 Flow velocity, and6.1.3 Electrolyte composition:6.1.

37、3.1 Dissolved oxygen,6.1.3.2 Salinity,6.1.3.3 Heavy-metal ions,6.1.3.4 Organic matter, including bacteria and marinegrowth,6.1.3.5 Soluble corrosion products,6.1.3.6 pH,6.1.3.7 Conductivity,6.1.3.8 Corrodents not part of the original environment (forexample, de-icing salts, fertilizers, and industri

38、al effluents), and6.1.3.9 Waterline effects.6.2 The metals of interest are to be obtained and preparedfor exposure. The processing and surface condition of thesemetals should be as close as possible to the expected conditionof the metals used in service. A list of factors that could affectthe potent

39、ials of the metals follows. This is not intended to bea complete listing, but it should serve as a guide to the types offactors that require consideration:6.2.1 Bulk composition,6.2.2 Casting or wrought processing method,6.2.3 Heat treatment, and6.2.4 Surface condition:6.2.4.1 Mill finish,6.2.4.2 De

40、gree of cold-work from surface preparation,6.2.4.3 Corrosion product films,6.2.4.4 Prior electrochemical history-passive versus active,and6.2.4.5 Pits or shielded (crevice) areas.6.3 Panels of the materials of interest should have electricalwires attached, with the attachment points protected from t

41、heelectrolyte by coating of an appropriate nonconductive materialor by the panels being mounted such that the point of electricalconnection is not in contact with the electrolyte. A referencehalf-cell, which is stable in the environment of interest over theanticipated duration of exposure, should be

42、 selected. Duringexposure of the panels, their corrosion potential relative to thereference half-cell will be measured periodically, using avoltmeter.6.3.1 The size of the panels, wire connections, and voltme-ter input resistance should be selected to preclude errors causedby polarization of the pan

43、el material, any voltage drop in thewire, and polarization of the reference half-cell during thepotential measurement procedure.6.3.2 Exposure duration should be sufficiently long to beindicative of the anticipated service condition.6.3.3 Potentials should be measured frequently enough toprovide goo

44、d indications of potential variability duringexposure, as well as systematic potential shifts that may occur.6.3.4 If the intent is to simulate long-term service, thepotential readings should show no systematic variation over thelatter portion of the exposures which would preclude theaccurate extrap

45、olation of the data to the service times ofinterest.6.4 Information relevant to selecting environment andmaterials, as well as to the mounting of specimens and takingdata, may be found in Practice G71.7. Report7.1 The report concerning the development of the galvanicseries should include as much det

46、ailed information as possible,such as the following:7.1.1 The metallurgical history of the metals tested, includ-ing the factors listed in 6.2,7.1.2 The size, shape, and surface preparation of panelsbefore exposure, and the method used to hold the panels,7.1.3 The environment and conditions, includi

47、ng thoseitems listed in 6.1,7.1.4 The equipment and procedure used for potentialmeasurements,7.1.5 The exposure duration and potential measurementfrequency,7.1.6 The condition of panels after exposure, and type ofcorrosion, and7.1.7 A listing of the materials arranged in order of averageor steady-st

48、ate corrosion potential over the time of interest.This list should follow the guidelines set forth in Practice G3.7.1.7.1 The measured corrosion potential for each materialmay be listed beside that material in the form of an average orsteady-state value with or without a standard deviation or othere

49、rror band as calculated by procedures in Practice G16,orinthe form of a total range of potentials. This information may beplotted in bar graph form.7.1.7.2 The final listing or graph should contain an indica-tion of the noble and active directions, and sufficient informa-tion about the conditions under which the series was obtainedto prevent misuse of the series for other environments andconditions.8. Keywords8.1 active; corrosion potential; galvanic corrosion; GalvanicSeries; noble; passiveG82 98 (2014)4APPENDIX(Nonmandatory Information)X1. THEORY OF GALVANIC CORROS

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