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!$Pdo“1456576www.di
2、n.deDDIN EN ISO 17864Corrosion of metals and alloys Determination of the critical pitting temperature under potentiostaticcontrol (ISO 17864:2005)English version of DIN EN ISO 17864:2008-07Korrosion von Metallen und Legierungen Bestimmung der kritischen Lochkorrosionstemperatur unter potentiostatisc
3、her Kontrolle(ISO 17864:2005)Englische Fassung DIN EN ISO 17864:2008-07www.beuth.deDocument comprises 19 pagesDIN EN ISO 17864:2008-07 2 National foreword This standard has been prepared by Technical Committee ISO/TC 156 “Corrosion of metals and alloys” (Secretariat: SAC, China). Based on the result
4、s of the unique acceptance procedure, ISO 17864:2005 has been adopted by Technical Committee CEN/TC 262 “Metallic and other inorganic coatings” (Secretariat: BSI, United Kingdom) as a European Standard. The responsible German body involved in its preparation was the Normenausschuss Materialprfung (M
5、aterials Testing Standards Committee), Technical Committee NA 062-01-71 AA Korrosion und Korrosions-schutz. The DIN Standard corresponding to the International Standard referred to in clause 2 of the EN is as follows: ISO 8044:1999 DIN EN ISO 8044 National Annex NA (informative) Bibliography DIN EN
6、ISO 8044, Corrosion of metals and alloys Basic terms and definitions EUROPEAN STANDARDNORME EUROPENNEEUROPISCHE NORMEN ISO 17864April 2008ICS 77.060English VersionCorrosion of metals and alloys - Determination of the criticalCorrosion des mtaux et alliages - Determination de latemprature critique de
7、 piqration des aciers inoxydablessous contrle potentiostatique (ISO 17864:2005)Korrosion von Metallen und Legierungen - Bestimmung derkritischen Lochkorrosionstemperatur unter potentiostatischerThis European Standard was approved by CEN on 21 March 2008.CEN members are bound to comply with the CEN/C
8、ENELEC 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 concerning such nationalstandards may be obtained on application to the CEN Management Centre or to an
9、y 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 own language and notified to the CEN Management Centre has the same status as theofficial versions.CEN
10、 members are the national standards 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, Swede
11、n, 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 rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref.
12、No. EN ISO 17864:2008: E(ISO 17864:2005)Kontrolle (ISO 17864:2005)pitting temperature under potentiostatic controlContents Page 1 2 3 4 5 6 7 8 9 10 Annex C (informative) Potential difference of selected reference electrodes at 25 C with respect 2 DIN EN ISO 17864:2008-07 Test report . 10 Annex A (i
13、nformative) Guidelines for selecting the test parameters 11 Annex B (informative) Method of preventing a crevice attack. 13 to the standard hydrogen electrode (SHE) 17 Assessment of results 9 Procedure 8 Specimens . 7 Principle. 5 Normative references . 5 Introduction 4 Calibration of specimen tempe
14、rature vs. solution temperature 8 Apparatus 6 Terms and definitions. 5 Scope . 5 Foreword 3 EN ISO 17864:2008 (E)Foreword 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 (ISO) and ha
15、s 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, at the late
16、st 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 any or all s
17、uch 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, Hungary, Icelan
18、d, 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 modification. 3 DI
19、N EN ISO 17864:2008-07 EN ISO 17864:2008 (E)Introduction 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 mea
20、surement requires at least a couple of values. Critical 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 testi
21、ng of stainless steels. 4 DIN EN ISO 17864:2008-07 EN ISO 17864:2008 (E)1 Scope This International Standard describes the procedure for determining the critical pitting temperature for stainless steels (austenitic, ferritic/austenitic, ferritic stainless steel) under potentiostatic control. The prin
22、cipal 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, to compare the relative performance o
23、f 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 application of this document. For dated re
24、ferences, 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 purposes of this document, the following terms
25、 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 the specimen is increased during the tes
26、t 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 maintaining the potential of the specimen a
27、t a specified value. The temperature of the surface of the specimen is increased by heating the solution. 5 DIN EN ISO 17864:2008-07 EN ISO 17864:2008 (E)4.2 The critical pitting temperature is defined as the temperature of the specimen at which the current density exceeds a specified value for 60 s
28、. 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 between the
29、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 relative to
30、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 critical pitting tem
31、perature 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 instrument The inst
32、rument 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 circuit is eval
33、uated 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 potentiostat. The instru
34、ment 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 cooling the solut
35、ion. 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 the solution ar
36、e 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. 6 DIN EN ISO 17864:2008-07 EN ISO 17864:2008 (E)5.6 Specimen holder 5.6.1 Any part of the specime
37、n holder coming 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 fl
38、ushed-port cell 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 temp
39、erature-measuring 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 he
40、ated by recirculating 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 o
41、r specimen holder 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 A
42、uxiliary electrode 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 elec
43、trode should be 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
44、 at ambient temperature 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
45、 electrode at 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. 7 DIN EN ISO 17864:2008-07 EN ISO 17864:2008 (E)7 Calibration of specimen tempe
46、rature vs. solution temperature 7.1 There 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 procedur
47、e for the CPT test, given in Clause 8, except 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 sp
48、ecimen temperature shall be measured by 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 f
49、illed with the solution. It is important 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 solution 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
