DIN EN ISO 17475-2008 Corrosion of metals and alloys - Electrochemical test methods - Guidelines for conducting potentiostatic and potentiodynamic polarization measurements (ISO 17.pdf

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1、July 2008DEUTSCHE NORM English price group 11No part of this standard may be reproduced without prior permission ofDIN Deutsches Institut fr Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany,has the exclusive right of sale for German Standards (DIN-Normen).ICS 77.060!$Pdm“1456574www.di

2、n.deDDIN EN ISO 17475Corrosion of metals and alloys Electrochemical test methods Guidelines for conducting potentiostatic and potentiodynamicpolarization measurements (ISO 17475:2005+Cor. 1:2006)English version of DIN EN ISO 17475:2008-07Korrosion von Metallen und Legierungen Elektrochemische Prfver

3、fahren Leitfaden fr die Durchfhrung potentiostatischer und potentiodynamischerPolarisationsmessungen (ISO 17475:2005+Cor. 1:2006)Englische Fassung DIN EN ISO 17475:2008-07www.beuth.deDocument comprises 19 pagesDIN EN ISO 17475:2008-07 2 National foreword This standard has been prepared by Technical

4、Committee ISO/TC 156 “Corrosion of metals and alloys” (Sec-retariat: SAC, China). Based on the results of the unique acceptance procedure, ISO 17475:2005/Cor. 1:2006 has been adopted by Technical Committee CEN/TC 262 “Metallic and other inorganic coatings” (Secretariat: BSI, United Kingdom) as a Eur

5、opean Standard. The responsible German body involved in its preparation was the Normenausschuss Materialprfung (Materials Testing Standards Committee), Technical Committee NA 062-01-71 AA Korrosion und Korrosions-schutz. The DIN Standards corresponding to the International Standards referred to in c

6、lause 2 of the EN is as follows: ISO 8044:1999 DIN EN ISO 8044:1999-11 ISO 9400:1990 DIN EN ISO 9400:1995-12 National Annex NA (informative) Bibliography DIN EN ISO 8044:1999-11, Corrosion of metals and alloys Basic terms and definitions (ISO 8044:1999) Trilingual version EN ISO 8044:1999 DIN EN ISO

7、 9400:1995-12, Nickel-based alloys Determination of resistance to intergranular corrosion (ISO 9400:1990) EUROPEAN STANDARDNORME EUROPENNEEUROPISCHE NORMEN ISO 17475April 2008ICS 77.060English VersionCorrosion of metals and alloys - Electrochemical test methods -Guidelines for conducting potentiosta

8、tic and potentiodynamicpolarization measurements (ISO 17475:2005/Cor 1:2006)Corrosion des mtaux et alliages - Mthodes dessaislectrochimiques - Lignes directrices pour la ralisation demesures de polarisations potentiostatique etpotentiodynamique (ISO 17475:2005/Cor 1:2006)Korrosion von Metallen und L

9、egierungen -Elektrochemische Prfverfahren - Leitfaden fr dieDurchfhrung potentiostatischer und potentiodynamischerPolarisationsmessungen (ISO 17475:2005/Cor 1:2006)This European Standard was approved by CEN on 21 March 2008.CEN members are bound to comply with the CEN/CENELEC Internal Regulations wh

10、ich stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the CEN Management Centre or to any CEN member.This European Sta

11、ndard exists in three official versions (English, French, German). A version in any other language made by translationunder the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as theofficial versions.CEN members are the national stan

12、dards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United King

13、dom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMIT EUROPEN DE NORMALISATIONEUROPISCHES KOMITEE FR NORMUNGManagement Centre: rue de Stassart, 36 B-1050 Brussels 2008 CEN All rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN ISO 17475:2008: EConten

14、ts Page 1 2 3 4 5 6 Annex B (informative) Potential of selected reference electrodes at 25 C with respect to the 2 DIN EN ISO 17475:2008-07 Procedure 11 Test report . 13 Annex A (informative) Method of preventing a crevice attack for certain applications 14 standard hydrogen electrode (SHE) . 16 Bib

15、liography . 17 Normative references . 5 Introduction 4 Principle. 5 Scope . 5 Foreword 3 EN ISO 17475:2008 (E) Apparatus 8 Foreword The text of ISO 17475:2005/Cor 1:2006 has been prepared by Technical Committee ISO/TC 156 “Corrosion of metals and alloys” of the International Organization for Standar

16、dization (ISO) and has been taken over as EN ISO 17475:2008 by Technical Committee CEN/TC 262 “Metallic and other inorganic coatings” the secretariat of which is held by BSI. This European Standard shall be given the status of a national standard, either by publication of an identical text or by end

17、orsement, at the latest by October 2008, and conflicting national standards shall be withdrawn at the latest by October 2008. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN and/or CENELEC shall not be held responsible for ide

18、ntifying any or all such patent rights. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Gr

19、eece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. Endorsement notice The text of ISO 17475:2005/Cor 1:2006 has been approved by CEN as a EN ISO 17475:200

20、8 without any modification. 3 DIN EN ISO 17475:2008-07 EN ISO 17475:2008 (E) Introduction Corrosion of metals and alloys in aqueous solutions is generally caused by an electrochemical mechanism. Therefore, one can measure or analyse corrosion phenomena, utilizing a variety of electrochemical techniq

21、ues. This International Standard, based on ASTM G51and ASTM G1502, defines basic guidelines for potentiostatic potentiodynamic polarization measurements to characterize an electrochemical kinetics of anodic and cathodic reactions. 4 DIN EN ISO 17475:2008-07 EN ISO 17475:2008 (E) 1 Scope This Interna

22、tional Standard applies to corrosion of metals and alloys, and describes the procedure for conducting potentiostatic and potentiodynamic polarization measurements. The test method can be used to characterise the electrochemical kinetics of anodic and cathodic reactions, the onset of localised corros

23、ion and the repassivation behaviour of a metal. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any

24、 amendments) applies. ISO 8044:1999, Corrosion of metals and alloys Basic terms and definitions ISO 8407:1991, Corrosion of metals and alloys Removal of corrosion products from corrosion test specimens ISO 9400:1990, Nickel-based alloys Determination of resistance to intergranular corrosion ISO 1146

25、3:1995, Corrosion of metals and alloys Evaluation of pitting corrosion ISO 11846:1995, Corrosion of metals and alloys Determination of resistance to intergranular corrosion of solution heat-treatable aluminium alloys 3 Principle 3.1 When a metal is immersed in a solution, the rate of the anodic reac

26、tion and that of the cathodic reaction will be in balance at the open-circuit potential (free corrosion potential, Ecor). If the electrode potential is displaced from the open-circuit value, the applied current measured will represent the difference between the anodic-reaction current and the cathod

27、ic-reaction current. If the displacement of potential is sufficiently large, the net current will be essentially equal to the anodic or cathodic-reaction kinetics, depending on whether the potential is made respectively more positive or more negative with respect to the open-circuit value as shown f

28、or a metal in the active state in acid solutions Figure 1 a) and in neutral aerated solutions Figure 1 b). 3.2 In certain metal-environment combinations, the metal may be in the passive state (Figure 2). If an aggressive anion is present and the potential is increased (made more positive) with respe

29、ct to the open-circuit potential, localised breakdown of passivity (e.g. pitting, crevice corrosion, intergranular attack) can result with an attendant increase in the applied current (Figure 2). The potential corresponding to the increase in current can be used as a measure of the resistance of a m

30、etal to localised corrosion. 5 DIN EN ISO 17475:2008-07 EN ISO 17475:2008 (E) a) Corrosion rate is under diffusion control b) Example by diffusion of oxygen in water Key X potential Y log current density 1 cathodic 2 anodic Ecorcorrosion potential icorcorrosion current density Erreversible electrode

31、 potential ioexchange current density idlimiting diffusion current density, which corresponds to the maximum diffusion rate of oxygen in the solution Figure 1 Schematic anotic and cathodic polarization curves for metals corroding in a system where the cathodic reaction is reduction of protons 6 DIN

32、EN ISO 17475:2008-07 EN ISO 17475:2008 (E) a) Metals with active-passive transition b) Metals without active-passive transition Key X potential Y log current density Ecorcorrosion potential icorcorrosion current density Epppassivation potential icritcritical current density for passivation ippassive

33、 current density Efflade potential Ebbreakdown potential Espsecondary passivation potential aActive. bPassive. cTranspassive. Figure 2 Schematic anodic polarization curves 7 DIN EN ISO 17475:2008-07 EN ISO 17475:2008 (E) 3.3 If the potential is subsequently decreased after the onset of localised cor

34、rosion, the potential at which repassivation occurs (when the applied current returns to approximately the same value as the passive current) can be considered to be indicative of the resistance of the metal to propagation of localised corrosion; the more noble the potential, the greater the resista

35、nce. 3.4 The displacement in potential can be stepwise, with the magnitude of the potential step and the time at a specific potential selected according to the application and purpose of the experiment. This type of testing is known as potentiostatic. 3.5 When the potential is displaced in a continu

36、ous mode at a controlled scan (displacement) rate, the test is described as potentiodynamic. 3.6 The kinetics of the electrochemical processes occurring on the surface can be time dependent, for example due to film formation, and hence the time that the potential is held at a specific potential in p

37、otentiostatic testing or the potential scan rate in potentiodynamic testing can be critical. For example, too high a rate of change may lead to overestimation of the breakdown potential for localised attack. For this reason, the interpretation of polarization data shall be considered carefully, part

38、icularly when applied to service conditions. 3.7 The measurement of the electrode potential can be influenced by ohmic drop in the solution. For solutions of low conductivity, a correction shall be made. 4 Apparatus 4.1 Potentiostat The potentiostat should be capable of controlling the electrode pot

39、ential to within 1 mV of a preset value. A scanning potentiostat is used for potentiodynamic measurements. For such measurements, the potentiostat shall be capable of automatically scanning the potential at a constant rate between preset potentials. 4.2 Electrode potential-measuring instruments The

40、instrument should have a high input impedance of the order of 1011 to 1014, to minimize current drawn from the system during measurement. The sensitivity and accuracy of the instrument should be sufficient to detect a change of 1,0 mV. 4.3 Current-measuring instruments Use appropriate current-measur

41、ing instruments with maximum error 0,5 %. 4.4 Test cell 4.4.1 The test cell should contain the working electrode (the metal to be polarized), a reference electrode for measuring the electrode potential, and one or two auxiliary electrodes. The test cell should incorporate inlet and outlet gas ports

42、and a port for insertion of a temperature-measuring device. NOTE The term auxiliary electrode is synonymous with counter electrode. 4.4.2 The detailed construction of the test cell depends on the application. Examples commonly used are shown in Figure 3. The important distinction of Figure 3 b) is t

43、hat the auxiliary electrodes are separated from the main cell of the working electrode by a fritted disc, in order to limit contamination of the main cell by reaction products generated at the auxiliary electrodes. 4.4.3 The auxiliary electrodes should be positioned so that the current distribution

44、about the specimen is symmetrical. 8 DIN EN ISO 17475:2008-07 EN ISO 17475:2008 (E) a) Auxiliary electrode included in the main cell b) Auxiliary electrode separated from the main cell Key 1 specimen 6 fritted disc 2 reference electrode 7 thermometer 3 auxiliary electrodes 8 probe here corresponds t

45、o Luggin capillary 4 reference electrode 9 salt-bridge connection to the reference electrode (not shown) 5 gas inlet Figure 3 Schematic diagram of electrochemical polarization cells with auxiliary electrode 9 DIN EN ISO 17475:2008-07 EN ISO 17475:2008 (E) 4.4.4 The reference electrode may be inserte

46、d directly into the main cell. Precautions should be taken to ensure that it is maintained in the proper condition. To avoid mutual contamination, a double-junction reference electrode may be used or the reference electrode located in a separate chamber and linked to the main cell by a salt bridge.

47、To minimise the potential drop between the reference electrode and the working electrode, a Luggin capillary should be used as shown in Figure 3 a) and Figure 3 b). The tip of the capillary probe shall be positioned so that it is at a distance from the working electrode of about, but not closer than

48、, 2 times the diameter of the tip. 4.4.5 The test cell should be constructed of a material which is inert in the environment at the temperature of testing. 4.4.6 The volume of solution in the test cell shall be such as to reduce to insignificance any change in the solution chemistry as a consequence

49、 of the reaction processes. NOTE In most cases, a solution volume greater than 100 ml/cm2 of specimen surface is considered to be adequate. 4.4.7 To assess the effect of flow on the electrode kinetics, a magnetic stirrer may be used but, where more defined control is required, the use of a rotating disc or rotating-cylinder assembly is recommended. 4.5 Electrode holder The auxiliary and working electrodes shall be mounted in such a way that the holder and mounting material have no influence on the measurement. An ex