1、BSI Standards PublicationBS ISO 18089:2015Corrosion of metals and alloys Determination of the criticalcrevice temperature (CCT)for stainless steels underpotentiostatic controlBS ISO 18089:2015 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of ISO 18089:2015.The UK pa
2、rticipation in its preparation was entrusted to TechnicalCommittee ISE/NFE/8, Corrosion of metals and alloys.A list of organizations represented on this committee can beobtained on request to its secretary.This publication does not purport to include all the necessaryprovisions of a contract. Users
3、are responsible for its correctapplication. The British Standards Institution 2015.Published by BSI Standards Limited 2015ISBN 978 0 580 79070 6ICS 77.060Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the authority of theStan
4、dards Policy and Strategy Committee on 30 November 2015.Amendments/corrigenda issued since publicationDate T e x t a f f e c t e dBS ISO 18089:2015 ISO 2015Corrosion of metals and alloys Determination of the critical crevice temperature (CCT) for stainless steels under potentiostatic controlCorrosio
5、n des mtaux et alliages Dtermination de la temprature critique de corrosion caverneuse (TCCC) des aciers inoxydables sous contrle potentiostatiqueINTERNATIONAL STANDARDISO18089First edition2015-11-01Reference numberISO 18089:2015(E)BS ISO 18089:2015ISO 18089:2015(E)ii ISO 2015 All rights reservedCOP
6、YRIGHT PROTECTED DOCUMENT ISO 2015, Published in SwitzerlandAll rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, w
7、ithout prior written permission. Permission can be requested from either ISO at the address below or ISOs member body in the country of the requester.ISO copyright officeCh. de Blandonnet 8 CP 401CH-1214 Vernier, Geneva, SwitzerlandTel. +41 22 749 01 11Fax +41 22 749 09 47copyrightiso.orgwww.iso.org
8、BS ISO 18089:2015ISO 18089:2015(E)Foreword ivIntroduction v1 Scope . 12 Normative references 13 Terms and definitions . 14 Principle 25 Equipment . 26 Procedure. 36.1 Preparation of reference electrodes . 36.2 Preparation of specimen. 36.3 Preparation of solution 46.4 Setting up the test . 46.5 Endi
9、ng test 57 Assessment of results 58 Test report . 5Annex A (informative) Examples of how the connections of the electrode can be made 7Annex B (normative) Schematic representation of different crevice formers used for CCT-measurements . 8Annex C (normative) Calibration of specimen temperature vs. so
10、lution temperature if a specimen holder is used 11Annex D (informative) Potential difference of selected reference electrodes at 25 C with respect to the standard hydrogen electrode (SHE)12Bibliography .13 ISO 2015 All rights reserved iiiContents PageBS ISO 18089:2015ISO 18089:2015(E)ForewordISO (th
11、e International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committ
12、ee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechn
13、ical standardization.The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the different types of ISO documents should be noted. This document was drafted i
14、n accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives). Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
15、 Details of any patent rights identified during the development of the document will be in the Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents). Any trade name used in this document is information given for the convenience of users and does not constitute
16、 an endorsement.For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISOs adherence to the WTO principles in the Technical Barriers to Trade (TBT) see the following URL: Foreword - Supplementary informationThe committe
17、e responsible for this document is ISO/TC 156, Corrosion of metals and alloys.iv ISO 2015 All rights reservedBS ISO 18089:2015ISO 18089:2015(E)IntroductionStainless steel is susceptible to pitting corrosion, crevice corrosion, and stress-corrosion cracking, etc., although it is used as generally cor
18、rosion-resistant material. The basic methodology for testing localized corrosion was first standardized in ASTM G 150. This method describes the susceptible to pitting corrosion and it is also standardized in ISO 17864. In this International Standard, the susceptible to crevice corrosion is examined
19、. This is performed by recording the electrochemical critical crevice corrosion temperature for a material using a specific crevice former. Crevice corrosion phenomenon is generally of a random nature and therefore these measurements require at least a couple of values. ISO 2015 All rights reserved
20、vBS ISO 18089:2015BS ISO 18089:2015Corrosion of metals and alloys Determination of the critical crevice temperature (CCT) for stainless steels under potentiostatic control1 ScopeThis International Standard describes the procedure for determining the critical crevice temperature (CCT) for stainless s
21、teels under potentiostatic control.The principal advantage of the test is the rapidity with which the CCT can be measured in a single test procedure. The CCT, as determined in this International Standard, can be used as a relative index of performance, for example, to compare the relative performanc
22、e of different grades of stainless steel.The test described in this International Standard is not intended to determine the temperature at which crevice corrosion will occur in service.This method is not intended for materials with critical pitting temperature (CPT) values below 20 C measured in acc
23、ordance with ISO 17864, when measured in the same test solution and at the same potential2 Normative referencesThe following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. Fo
24、r undated references, the latest edition of the referenced document (including any amendments) applies.ISO 3696, Water for analytical laboratory use Specification and test methodsISO 8044, Corrosion of metals and alloys Basic terms and definitionsISO 17864, Corrosion of metals and alloys Determinati
25、on of the critical pitting temperature under potientiostatic controlISO 18070, Corrosion of metals and alloys Crevice corrosion formers with disc springs for flat specimens or tubes of stainless steels in corrosive solutions3 Terms and definitionsFor the purposes of this document, the terms and defi
26、nitions given in ISO 8044, ISO 17864 and the following apply.3.1critical crevice temperatureCCTlowest temperature on the surface of the specimen at which stable propagating crevice corrosion occurs under specified test conditionsNote 1 to entry: The critical crevice corrosion temperature is defined
27、as the temperature of the specimen at which the current density exceeds a specified value. A recommended value is 10 A cm-2, referring to area exposes in the measurement to make sure that it is above the passive current, for 60 s. A 60 s delay is used in order to ensure that the observed current inc
28、rease originates from stable propagating crevice corrosion, and not a short-lived current peak.4INTERNATIONAL STANDARD ISO 18089:2015(E) ISO 2015 All rights reserved 1BS ISO 18089:2015ISO 18089:2015(E)3.2temperature ramp raterate at which the temperature of the surface of the specimen is increased d
29、uring the test4 Principle4.1 The test involves increasing the temperature of the surface of the specimen at a specified rate, while exposing the specimen to a solution and maintaining the potential of the specimen at a specified value. The temperature of the surface of the specimen is increased by h
30、eating the solution.4.2 The temperature ramp rate, environment and applied potential may be varied, depending on the material.5 Equipment5.1 Experimental set-up is a vessel with immersion heater or a thermostatic bath.5.1.1 The test specimen, a reference electrode connected appropriately for measuri
31、ng the electrode potential, see 5.10, an auxiliary electrode, a port for insertion of a temperature-measuring device and a facility for stirring the solution in a repeatable manner.NOTE This can be achieved using a mechanical stirring device, using a peristaltic pump or by bubbling inert gas through
32、 the solution at a controlled rate.5.1.2 Any part of the test cell or specimen holder that comes into contact with the solution shall be constructed from an inert material. The connection of the electrode shall be design so no corrosion occurs in the connection point.NOTE 1 Examples of how the conne
33、ctions can be made are given in Annex A.NOTE 2 Polycarbonates, glass, polytetrafluoroethylene (PTFE), polypropylene (PP), polyethylene (HD-PE) are suitable materials but styrolic plastics are not allowed.5.1.3 The ratio of the volume of solution in the test cell to the specimen area shall be at leas
34、t 100 ml/cm2specimen area.5.2 Potentiostat shall be capable of controlling the electrode potential to within 1 mV of a preset value.5.3 Electrode potential-measuring instrument with a high input impedance of the order of 1011 to 1014, to minimize current drawn from the system during measurement. The
35、 sensitivity and accuracy of the instrument shall be sufficient to detect a change of 1,0 mV.5.4 Current-measuring instruments capable of measuring a current to within 2 % of the actual value. The current in the circuit is evaluated from the potential drop measured across a known resistor.NOTE In ma
36、ny 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.5.5 Temperature controller capable of increasing the temperature of the surface
37、of the specimen from 2 C to 100 C at a controlled rate. This is achieved by heating or cooling 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.NO
38、TE At temperatures above 85 C, avoid evaporation by suitable equipment.2 ISO 2015 All rights reservedBS ISO 18089:2015ISO 18089:2015(E)5.6 Temperature measurement instrumentation capable of measuring the temperature of the test solution with an accuracy of 1 C.5.7 Crevice formers or specimen holders
39、 of different types can be used in this International Standard.NOTE Annex B describes examples of different crevice formers and relevant aspects concerning these. Other different types of crevice formers can be used if relevant parties agree.5.8 Test solution, commonly containing of chlorides.5.9 Au
40、xiliary electrode of high-purity platinum or other materials inert to the test solution. The auxiliary electrode may be constructed in the form of thin foil, a sheet, a rod, or in the form of a gauze. It can also be supported on a glass frame. The area of the auxiliary electrode shall be at least th
41、e area of the specimen.5.10 Reference electrode shall be maintained at ambient temperature external to the test cell and connected to the test cell via a Luggin capillary probe.NOTE The silver/silver chloride electrode is preferred but there are other alternatives. The potentials of these Ag/AgCl el
42、ectrodes at 25 C relative to the standard hydrogen electrode at 25 C are given in Annex D.6 Procedure6.1 Preparation of reference electrodes6.1.1 The difference in potential between the reference electrode and two validation electrodes shall be measured. These electrodes shall be traceable to the st
43、andard hydrogen electrode and used and maintained solely for the purpose of validation. If the potential difference is greater than 3 mV, the test electrode shall be rejected.6.1.2 The validation electrodes shall be stored in optimum conditions and regularly compared. Replacement shall be undertaken
44、 if the potential difference between these varies by more than 1 mV.6.2 Preparation of specimen6.2.1 The minimum specimen area of 1 cm2shall be used but the dimensions shall be compatible with the crevice former or the crevice holder used for the test. Examples of specimens are given in Annex A.6.2.
45、2 The surface finish shall be as reproducible as possible. Any test surface may be tested but it is recommendable that all surfaces exposed to the test solution, including cut edges and drilled holes, shall be abraded down to a surface finish of at least P 80grit paper. Care shall be taken to avoid
46、overheating the surface.NOTE Ultrasonic cleaning can be used after the preparation.6.2.3 The specimens shall be left in air, at a temperature higher than the dew point temperature for at least 24 h before testing, to be able to form a stable oxide.The time elapsed between grinding and immersion can
47、have an influence on the subsequent crevice corrosion behaviour. The elapsed time selected will depend on the purpose of the test, but should be standardized for a particular set of tests. Little variation in surface film thickness occurs after 24 h, and hence a minimum elapsed time of 24 h is often
48、 useful.6.2.4 The specimen shall be cleaned immediately prior to immersion in the solution by degreasing, rinsing in high-purity water with a conductivity less than 1 S cm-1(according to ISO 3696, grade 2), ISO 2015 All rights reserved 3BS ISO 18089:2015ISO 18089:2015(E)followed by ethanol or a simi
49、lar solvent, and air drying. After degreasing, care shall be taken not to contaminate the test surface of the specimen.6.3 Preparation of solution6.3.1 In principle, the test solution is prepared using reagent grade chemicals and high purity water. Other type of solution may be used if relevant parties agree.6.3.2 Guidelines on the selection of the solution for stainless steels are given in ISO 17864.6.4 Setting up the test6.4.1 All parts shall be mounted together, for example, according to Annex B. The exposed surface area
