EN ISO 17475-2008 en Corrosion of metals and alloys - Electrochemical test methods - Guidelines for conducting potentiostatic and potentiodynamic polarization measurements《金属和合金的腐蚀.pdf

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1、BRITISH STANDARDBS EN ISO 17475:2008Incorporating corrigendum May 2006Corrosion of metals and alloys Electrochemical test methods Guidelines for conducting potentiostatic and potentiodynamic polarization measurements ICS 77.060g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g5

2、3g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g48g44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58BS EN ISO 17475:2008This British Standard was published under the authority of the Standards Policy and Strategy Committee on 10 January 2006 BSI 2008ISBN 978 0 580 60542 0N

3、ational forewordThis British Standard is the UK implementation of EN ISO 17475:2008. It is identical with ISO 17475:2005, incorporating corrigendum May 2006. It supersedes BS ISO 17475:2005, which is withdrawn.The UK participation in its preparation was entrusted to Technical Committee ISE/NFE/8, Co

4、rrosion of metals and alloys.A list of organizations represented on this committee can be obtained on request to its secretary.This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standar

5、d cannot confer immunity from legal obligations.Amendments/corrigenda issued since publicationAmd. No. Date Comments16464 30 June 2006 Implementation of ISO corrigendum May 2006. Addition of missing labels in Figure 131 July 2008 This corrigendum renumbers BS ISO 17475:2005 as BS EN ISO 17475:2008 E

6、UROPEAN STANDARDNORME EUROPENNEEUROPISCHE NORMEN ISO 17475April 2008ICS 77.060English VersionCorrosion of metals and alloys - Electrochemical test methods -Guidelines for conducting potentiostatic and potentiodynamicpolarization measurements (ISO 17475:2005/Cor 1:2006)Corrosion des mtaux et alliages

7、 - Mthodes dessaislectrochimiques - Lignes directrices pour la ralisation demesures de polarisations potentiostatique etpotentiodynamique (ISO 17475:2005/Cor 1:2006)Korrosion von Metallen und Legierungen -Elektrochemische Prfverfahren - Leitfaden fr dieDurchfhrung potentiostatischer und potentiodyna

8、mischerPolarisationsmessungen (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 which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any

9、 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 Standard exists in three official versions (English, French, German). A version in any other language made by

10、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 standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,France, Germa

11、ny, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMIT EUROPEN DE NORMALISATIONEUROPISCHES KOMITEE FR NORMUNGManag

12、ement 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: EForeword The text of ISO 17475:2005/Cor 1:2006 has been prepared by Technical Committee ISO/TC 156 “Corrosion of

13、metals and alloys” of the International Organization for Standardization (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 nationa

14、l standard, either by publication of an identical text or by endorsement, 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

15、rights. CEN and/or CENELEC shall not be held responsible for identifying 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

16、, 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 the United Kingdom. Endorsement notice The text of ISO 1747

17、5:2005/Cor 1:2006 has been approved by CEN as a EN ISO 17475:2008 without any modification. BS EN ISO 17475:2008iiiContents Page Introduction v 1 Scope . 1 2 Normative references . 1 3 Principle. 1 4 Apparatus 4 5 Procedure 7 6 Test report . 9 Annex A (informative) Method of preventing a crevice att

18、ack for certain applications 10 Annex B (informative) Potential of selected reference electrodes at 25 C with respect to the standard hydrogen electrode (SHE) . 12 Bibliography . 13 BS EN ISO 17475:2008blankIntroduction Corrosion of metals and alloys in aqueous solutions is generally caused by an el

19、ectrochemical mechanism. Therefore, one can measure or analyse corrosion phenomena, utilizing a variety of electrochemical techniques. This International Standard, based on ASTM G51and ASTM G1502, defines basic guidelines for potentiostatic potentiodynamic polarization measurements to characterize a

20、n electrochemical kinetics of anodic and cathodic reactions. v BS EN ISO 17475:2008blank1Corrosion of metals and alloys Electrochemical test methods Guidelines for conducting potentiostatic and potentiodynamic polarization measurements 1 Scope This International Standard applies to corrosion of meta

21、ls 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 corrosion and the repassivation behaviour of a met

22、al. 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 amendments) applies. ISO 8044:1999, Corrosi

23、on 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 11463:1995, Corrosion of metals and alloys Evalu

24、ation 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 reaction and that of the cathodic reaction will

25、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 cathodic-reaction current. If the displacement of

26、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 for a metal in the active state in acid solut

27、ions 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 respect to the open-circuit potential, localised

28、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 metal to localised corrosion. BS EN ISO 17475

29、:20082 BS EN ISO 17475:2008a) 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 potential ioexchange current density idlimiting di

30、ffusion 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 3a) Metals with active-passive transition b) Metals witho

31、ut active-passive transition Key X potential Y log current density Ecorcorrosion potential icorcorrosion current density Epppassivation potential icritcritical current density for passivation ippassive current density Efflade potential Ebbreakdown potential Espsecondary passivation potential aActive

32、. bPassive. cTranspassive. Figure 2 Schematic anodic polarization curves BS EN ISO 17475:20084 3.3 If the potential is subsequently decreased after the onset of localised corrosion, the potential at which repassivation occurs (when the applied current returns to approximately the same value as the p

33、assive 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 resistance. 3.4 The displacement in potential can be stepwise, with the magnitude of the potential step and the time at a specific po

34、tential 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 continuous mode at a controlled scan (displacement) rate, the test is described as potentiodynamic. 3.6 The kinetics of the electroch

35、emical 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 potentiostatic testing or the potential scan rate in potentiodynamic testing can be critical. For example, too high a rate of c

36、hange may lead to overestimation of the breakdown potential for localised attack. For this reason, the interpretation of polarization data shall be considered carefully, particularly when applied to service conditions. 3.7 The measurement of the electrode potential can be influenced by ohmic drop in

37、 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 potential to within 1 mV of a preset value. A scanning potentiostat is used for potentiodynamic measurements. For such measuremen

38、ts, the potentiostat shall be capable of automatically scanning the potential at a constant rate between preset potentials. 4.2 Electrode potential-measuring instruments The instrument should have a high input impedance of the order of 1011 to 1014, to minimize current drawn from the system during m

39、easurement. 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-measuring instruments with maximum error 0,5 %. 4.4 Test cell 4.4.1 The test cell should contain the working electrode (the metal to

40、 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 and a port for insertion of a temperature-measuring device. NOTE The term auxiliary electrode is synonymous with counter elect

41、rode. 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 that the auxiliary electrodes are separated from the main cell of the working electrode by a fritted disc, in order to limit co

42、ntamination 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 about the specimen is symmetrical. BS EN ISO 17475:20085a) Auxiliary electrode included in the main cell b) Auxiliary electrod

43、e separated from the main cell Key 1 specimen 6 fritted disc 2 reference electrode 7 thermometer 3 auxiliary electrodes 8 probe here corresponds to Luggin capillary 4 reference electrode 9 salt-bridge connection to the reference electrode (not shown) 5 gas inlet Figure 3 Schematic diagram of electro

44、chemical polarization cells with auxiliary electrode BS EN ISO 17475:20086 4.4.4 The reference electrode may be inserted 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 electr

45、ode may be used or the reference electrode located in a separate chamber and linked to the main cell by a salt bridge. 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 c

46、apillary probe shall be positioned so that it is at a distance from the working electrode of about, but not closer than, 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 solut

47、ion in the test cell shall be such as to reduce to insignificance any change in the solution chemistry as a consequence 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

48、 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 hav

49、e no influence on the measurement. An example of an electrode-mounting assembly is shown in Figure 4. For steels with a protective oxide film, the seal of the test specimen to the holder can sometimes lead to undesired crevice attack of the steel at the interface. A method of preventing such crevice attack for certain applications, using a flushed port cell or a flushed specimen holder, is outlined in Annex A, although the method is not suitable for studies of rotating electrodes. 4.6 Electrode material The working electrode is pre