1、BRITISH STANDARDBS EN ISO 17864:2008Corrosion of metals and alloys Determination of the critical pitting temperature under potientiostatic controlICS 77.060g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g48g44g55g
2、55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58BS EN ISO 17864:2008This British Standard was published under the authority of the Standards Policy and Strategy Committee on 17 January 2006 BSI 2008ISBN 978 0 580 60543 7National forewordThis British Standard is the UK implementation of EN IS
3、O 17864:2008. It is identical with ISO 17864:2005. It supersedes BS ISO 17864:2005, which is withdrawn.The UK participation in its preparation was entrusted to Technical Committee ISE/NFE/8, Corrosion of metals and alloys.A list of organizations represented on this committee can be obtained on reque
4、st 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 Standard cannot confer immunity from legal obligations.Amendments/corrigenda issued since publicationDate Comments
5、30 June 2008 This corrigendum renumbers BS ISO 17864:2005 as BS EN ISO 17864:2008EUROPEAN STANDARDNORME EUROPENNEEUROPISCHE NORMEN ISO 17864April 2008ICS 77.060English VersionCorrosion of metals and alloys - Determination of the criticalpitting temperature under potientiostatic control (ISO17864:200
6、5)Corrosion des mtaux et alliages - Determination de latemprature critique de piqration des aciers inoxydablessous contrle potentiostatique (ISO 17864:2005)Korrosion von Metallen und Legierungen - Bestimmung derkritischen Lochkorrosionstemperatur bei potentiostatischerBelastung (ISO 17864:2005)This
7、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 alteration. Up-to-date lists and bibliographical references c
8、oncerning 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 translationunder the responsibility of a CEN member into its o
9、wn 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, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuani
10、a, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMIT EUROPEN DE NORMALISATIONEUROPISCHES KOMITEE FR NORMUNGManagement Centre: rue de Stassart, 36 B-1050 Brussels 2008 CEN All
11、 rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN ISO 17864:2008: EForeword The text of ISO 17864:2005 has been prepared by Technical Committee ISO/TC 156 “Corrosion of metals and alloys” of the International Organization for Standardization
12、(ISO) and has been taken over as EN ISO 17864:2008 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 endorsement,
13、 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 identifying
14、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, Greece, Hun
15、gary, 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 17864:2005 has been approved by CEN as a EN ISO 17864:2008 without any modifi
16、cation. BS EN ISO 17864:2008iiiContents Page Introduction v 1 Scope . 1 2 Normative references . 1 3 Terms and definitions. 1 4 Principle. 1 5 Apparatus 2 6 Specimens . 3 7 Calibration of specimen temperature vs. solution temperature 4 8 Procedure 4 9 Assessment of results 5 10 Test report . 6 Annex
17、 A (informative) Guidelines for selecting the test parameters 7 Annex B (informative) Method of preventing a crevice attack. 9 Annex C (informative) Potential difference of selected reference electrodes at 25 C with respect to the standard hydrogen electrode (SHE) 13 BS EN ISO 17864:2008blankvIntrod
18、uction Stainless steel is susceptible to pitting corrosion, crevice corrosion, and stress-corrosion cracking, etc., although it is used as generally a corrosion-resistant material. Pitting phenomenon is generally of a random nature, therefore its measurement requires at least a couple of values. Cri
19、tical pitting temperature defines the lowest potential-independent temperature, below which pitting does not occur. The basic methodology was first standardized in ASTM G150, Standard test method for electrochemical critical pitting temperature testing of stainless steels. BS EN ISO 17864:2008blank1
20、Corrosion of metals and alloys Determination of the critical pitting temperature under potientiostatic control 1 Scope This International Standard describes the procedure for determining the critical pitting temperature for stainless steels (austenitic, ferritic/austenitic, ferritic stainless steel)
21、 under potentiostatic control. The principal advantage of the test is the rapidity with which the critical pitting temperature can be measured in a single test. The critical pitting temperature, as determined in this International Standard, can be used as a relative index of performance, for example
22、, to compare the relative performance of different grades of stainless steel. The test described in this International Standard is not intended to determine the temperature at which pitting will occur in service. 2 Normative references The following referenced documents are indispensable for the app
23、lication 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, Corrosion of metals and alloys Basic terms and definitions 3 Terms and definitions For the purpose
24、s of this document, the following terms and definitions apply. 3.1 critical pitting temperature CPT lowest temperature on the surface of the specimen at which stable propagating pitting occurs under specified test conditions 3.2 temperature ramp rate rate at which the temperature of the surface of t
25、he specimen is increased during the test NOTE The temperature ramp rate is expressed in degrees Celsius per second (C s1). 4 Principle 4.1 The test involves increasing the temperature of the surface of the specimen at a specified rate, whilst exposing the specimen to a specified environment and main
26、taining the potential of the specimen at a specified value. The temperature of the surface of the specimen is increased by heating the solution. BS EN ISO 17864:20082 4.2 The critical pitting temperature is defined as the temperature of the specimen at which the current density exceeds a specified v
27、alue for 60 s. A 60 s delay is used in order to ensure that the observed current increase originates from stable propagating pitting, and not short-lived current peaks originating from metastable pitting. 4.3 The specimen holder is designed to ensure that crevice corrosion does not occur at the seal
28、 between the specimen and the holder. 4.4 There may be a temperature gradient between the bulk of the solution and the surface of the specimen, the magnitude of which will depend on the geometry and dimensions of the specimen. Guidelines for calibrating the temperature of the surface of the specimen
29、 relative to the temperature of the solution are given in Clause 7. 4.5 The temperature ramp rate, environment and applied potential may be varied, depending on the material. Guidelines for selecting the test parameters for austenitic and duplex stainless steels are given in Annex A. 4.6 The critica
30、l pitting temperature is specific to the method of testing and should only be used as a comparative measure of performance. 5 Apparatus 5.1 Potentiostat The potentiostat shall be capable of controlling the electrode potential to within 1 mV of a preset value. 5.2 Electrode potential-measuring instru
31、ment The 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. 5.3 Current-measuring instruments The current in the ci
32、rcuit is evaluated from the potential drop measured across a known resistor. In many potentiostats, this measurement is made internally, but measurements can also be made externally by locating a resistor in the current line from the auxiliary electrode to the auxiliary connection on the potentiosta
33、t. The instrument shall be capable of measuring a current to within 2 % of the actual value. 5.4 Temperature controller The temperature controller shall be capable of increasing the temperature of the surface of the specimen from 0 C to 100 C at a controlled rate. This is achieved by heating or cool
34、ing the solution. Above 10 C, the average rate of temperature change of the specimen shall be controlled to within 30 % of the desired value, where the average is calculated over a temperature range of 10 C. Guidelines for calculating the temperature of the specimen relative to the temperature of th
35、e solution are given in Clause 7. 5.5 Temperature-measurement instrumentation The temperature-measurement instrumentation shall be capable of measuring the temperature of the test solution with an accuracy of 0,4 C. BS EN ISO 17864:200835.6 Specimen holder 5.6.1 Any part of the specimen holder comin
36、g into contact with the test solution shall be made of an inert material. 5.6.2 The specimen holder shall be designed to ensure that crevice corrosion does not occur at the contact area between the specimen holder and the specimen. A method of preventing such crevice attack, using a flushed-port cel
37、l or a flushed specimen holder, is outlined in Annex B. 5.7 Test cell 5.7.1 The test cell shall contain the test specimen, a Luggin capillary probe connected to an external reference electrode for measuring the electrode potential, an auxiliary electrode, a port for insertion of a temperature-measur
38、ing device and a facility for stirring the solution in a repeatable manner. This can be achieved using a mechanical stirring device or simply by bubbling gas through the solution at a controlled rate. 5.7.2 A double-walled cell is commonly used to enable the solution to be cooled or heated by recirc
39、ulating a liquid from an external heating bath to the outer chamber of the cell. 5.7.3 The tip of the Luggin capillary probe shall be positioned so that it is at a distance from the specimen of about, but not closer than, twice the diameter of the tip. 5.7.4 Any part of the test cell or specimen hol
40、der that comes into contact with the solution shall be constructed from an inert material. Polycarbonate, glass and polytetrafluoroethylene (PTFE) are suitable materials. 5.7.5 The ratio of the volume of solution in the test cell to the specimen area shall be at least 100 ml/cm2. 5.8 Auxiliary elect
41、rode The auxiliary electrode is commonly prepared from high-purity platinum. Other materials may be used provided they are inert. The auxiliary electrode may be constructed in the form of sheet or rod, or in the form of a gauze supported on a glass frame. The area of the auxiliary electrode should b
42、e at least the area of the specimen. NOTE Graphite may be used as a auxiliary electrode but care must be taken to avoid contamination; desorption of species retained in the graphite may be necessary prior to use. 5.9 Reference electrode 5.9.1 The reference electrode shall be maintained at ambient te
43、mperature external to the test cell and connected to the test cell via a Luggin capillary probe. 5.9.2 Commonly used electrodes include the silver/silver chloride electrode and the saturated calomel electrode. The potentials of these electrodes at 25 C relative to the standard hydrogen electrode at
44、25 C are given in Annex C. 6 Specimens 6.1 Any specimen geometry compatible with the specimen holder may be used. 6.2 A minimum test area of 1 cm2shall be used. 6.3 The surface finish shall be reproducible. BS EN ISO 17864:20084 7 Calibration of specimen temperature vs. solution temperature 7.1 Ther
45、e may be a temperature gradient between the bulk solution and the surface of the specimen. A test shall be conducted to calibrate the temperature of the specimen relative to the temperature of the solution. The calibration shall be performed using the procedure for the CPT test, given in Clause 8, e
46、xcept that no control or measurement of the electrode potential of the specimen is required. 7.2 The specimen size and geometry, solution volume, stirring rate and temperature ramp rate shall be the same for the calibration test as for the CPT test. 7.3 The specimen temperature shall be measured by
47、installing a suitable temperature-measuring device inside the specimen, as close as possible ( 40 C, the temperature ramp shall start at 30 C. 8.4.4 The specimen, counter electrode and salt bridge shall be placed in the test cell. The test cell shall then be filled with the solution. It is important
48、 to ensure that the salt bridge is filled with the test solution and is free of air bubbles, particularly in the restricted space at the tip. A wick, or equivalent device, may be placed in the salt bridge to ensure electric contact, even when small gas bubbles are formed during the test. 8.4.5 The s
49、olution shall be stirred continuously throughout the test. This can be achieved using a mechanical stirring device, or simply by bubbling an inert gas through the solution at a controlled rate. 8.4.6 The electrodes shall be connected to the potentiostat and data-recording device, and the connections for temperature measurement and control shall be made. The potential shall not be applied to the specimen until the temperature of the solution has been stable to within 1 C of the desired initial test temperature for a minimum of 600 s. 8.4.7 The open-c
