1、BSI Standards PublicationBS ISO 15158:2014Corrosion of metals and alloys Method of measuring thepitting potential for stainlesssteels by potentiodynamiccontrol in sodium chloridesolutionBS ISO 15158:2014 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of ISO 15158:201
2、4.The UK participation 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 contr
3、act. Users are responsible for its correctapplication. The British Standards Institution 2014. Published by BSI StandardsLimited 2014ISBN 978 0 580 70245 7ICS 77.060Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the authority
4、 of theStandards Policy and Strategy Committee on 28 February 2014.Amendments issued since publicationDate Text affectedBS ISO 15158:2014 ISO 2014Corrosion of metals and alloys Method of measuring the pitting potential for stainless steels by potentiodynamic control in sodium chloride solutionCorros
5、ion des mtaux et alliages Mthode de mesure du potentiel de piqre des aciers inoxydables par contrle potentiodynamique en solution de chlorure de sodiumINTERNATIONAL STANDARDISO15158First edition2014-02-15Reference numberISO 15158:2014(E)BS ISO 15158:2014ISO 15158:2014(E)ii ISO 2014 All rights reserv
6、edCOPYRIGHT PROTECTED DOCUMENT ISO 2014All 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, without prior written
7、permission. Permission can be requested from either ISO at the address below or ISOs member body in the country of the requester.ISO copyright officeCase postale 56 CH-1211 Geneva 20Tel. + 41 22 749 01 11Fax + 41 22 749 09 47E-mail copyrightiso.orgWeb www.iso.orgPublished in SwitzerlandBS ISO 15158:
8、2014ISO 15158:2014(E) ISO 2014 All rights reserved iiiContents PageForeword ivIntroduction v1 Scope . 12 Principle 13 Apparatus . 13.1 Potentiostat 13.2 Electrode potential-measuring instrument . 13.3 Current-measuring instruments 13.4 Specimen holder 23.5 Test cell 23.6 Auxiliary electrode 23.7 Ref
9、erence electrode 24 Specimens 35 Procedure. 35.1 Preparation of reference electrodes . 35.2 Preparation of specimen. 35.3 Preparation of solution 35.4 Setting up test 45.5 Recording . 45.6 Ending test 56 Statistical analysis of pitting potential data . 57 Test report . 5Annex A (informative) Specime
10、n holder 7Annex B (informative) An example of statistical analysis of pitting potential data .11Bibliography .13BS ISO 15158:2014ISO 15158:2014(E)ForewordISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of p
11、reparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental,
12、in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.The procedures used to develop this document and those intended for its further maintenance are described in the ISO/I
13、EC Directives, Part 1. In particular the different approval criteria needed for the different types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).Attention is drawn to the possibility
14、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. 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
15、 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 an endorsement.For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment, as well as informat
16、ion about ISOs adherence to the WTO principles in the Technical Barriers to Trade (TBT) see the following URL: Foreword - Supplementary informationThe committee responsible for this document is ISO/TC 156, Corrosion of metals and alloys.iv ISO 2014 All rights reservedBS ISO 15158:2014ISO 15158:2014(
17、E)IntroductionAlthough stainless steel is generally used as a corrosion-resistant material, it is susceptible to pitting corrosion, crevice corrosion, stress corrosion cracking, etc. Among those, pitting corrosion is one of the most common phenomena that occur on stainless steels. A commonly used pa
18、rameter to evaluate the pitting corrosion resistance of stainless steel, is so-called pitting potential that defines the lowest potential below which stables pits are not considered to grow. Since pitting corrosion generally shows a stochastic nature dependent upon inhomogeneity in terms of size, or
19、ientation, alloying components, impurity, inclusions, segregation, surface treatment, history, elapsed time, fluctuation of environment, etc., its measurement requires at least a couple of values. ISO 2014 All rights reserved vBS ISO 15158:2014BS ISO 15158:2014Corrosion of metals and alloys Method o
20、f measuring the pitting potential for stainless steels by potentiodynamic control in sodium chloride solution1 ScopeThis International Standard describes the procedure for determining the pitting potential for stainless steels (austenitic, ferritic/austenitic, ferritic, martensitic stainless steel)
21、under potentiodynamic control.The principal advantage compared with other potentiostatic test methods12is the rapidity of this test method, with which the pitting potential can be measured in a single potential scan.The pitting potential as determined by this International Standard can be used as a
22、relative index of performance. For example, one can compare the relative performances for different lots of stainless-steel grades and products. The test described in this International Standard is not intended to determine the pitting potential at which actual pitting can occur under real service c
23、onditions, or not.2 PrincipleThe test involves increasing the anodic potential of the specimen at a specified scan rate while exposing the specimen to a normalized sodium chloride solution at a constant temperature.The pitting potential (Vc10or Vc100) (see JIS G 05773) is defined as the potential at
24、 which the current density exceeds 10 A/cm2or 100 A/cm2for more than 60 s. A 60 s delay is used in order to ensure that the observed current increase originates from stably propagating pitting, since short-lived current peaks originate from metastable pitting.The specimen holder and the specimen its
25、elf are designed to ensure that crevice corrosion does not occur.3 Apparatus3.1 PotentiostatThe potentiostat shall be capable of controlling the electrode potential to within 1 mV of a preset value.3.2 Electrode potential-measuring instrumentThe instrument shall have high input impedance sufficient
26、to eliminate potential read error due to current drawn by the instrument during measurement; impedance of the order of 1011 to 1014 is typical. The sensitivity and accuracy of the instrument should be sufficient to detect a change of 1,0 mV.3.3 Current-measuring instrumentsThe current in the circuit
27、 is evaluated from the potential drop measured across a known resistor. In many potentiostats, this measurement is made internally. But measurements may also be made externally by locating a resistor in the current line from the auxiliary electrode to the auxiliary connection of the potentiostat. Th
28、e instrument shall be capable of measuring a current within 2 % error around the actual value.INTERNATIONAL STANDARD ISO 15158:2014(E) ISO 2014 All rights reserved 1BS ISO 15158:2014ISO 15158:2014(E)3.4 Specimen holder3.4.1 Any part of the specimen holder coming into contact with the test solution s
29、hall be made of an inert material.3.4.2 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. Some methods to prevent such crevice attack, using a flushed port cell, or using a flushed specimen holder,
30、are outlined in A.1 and A.2.3.4.3 If the specimen holder avoiding crevice corrosion cannot be used, the specimen electrode could be treated by the special method as outlined in A.3.3.5 Test cell3.5.1 The test cell shall contain the test specimen, a Luggin capillary probe connected to an external ref
31、erence electrode for measuring the electrode potential, an auxiliary electrode, a port for insertion of a temperature measuring device, a bubbler for de-aeration by inert gas such as N2or Ar, and/or a facility for stirring the solution in a repeatable manner.NOTE This can be achieved by using a mech
32、anical stirring device, or simply by bubbling inert gas through the solution at a controlled rate.An accuracy of the temperature measuring instrument shall be 0,4 C.3.5.2 A double-walled cell is commonly used to enable the solution to be cooled or to be heated by recirculating a liquid from an exter
33、nal cooling or heating bath to the outer chamber of the cell.3.5.3 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.3.5.4 Any part of the test cell or specimen holder that comes into c
34、ontact with the solution shall be constructed from an inert material. Polycarbonate, glass and polytetrafluoroethylene (PTFE) are suitable materials.3.5.5 The ratio of the volume of solution in the test cell to the specimen area shall be at least 100 ml/cm2.3.6 Auxiliary electrodeThe auxiliary elect
35、rode 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, rod, wire, or in the form of gauze supported on a glass frame. The area of the auxiliary electrode shall be at least the area of
36、the specimen.Graphite may be used as an auxiliary electrode, but care shall be taken to avoid contamination; desorption of species retained in the graphite may be necessary prior to usage.3.7 Reference electrode3.7.1 The reference electrode shall be maintained at ambient temperature external to the
37、test cell, and shall be connected to the test cell via a Luggin capillary probe.2 ISO 2014 All rights reservedBS ISO 15158:2014ISO 15158:2014(E)3.7.2 Commonly used electrode is the saturated silver/silver chloride electrode (sat.SSCE). The potentials of these electrodes relative to the standard hydr
38、ogen electrode at 25 C are given in ISO 17474.4If the saturated calomel electrode (SCE) is used, strict control to handle mercury and mercury containing substances in terms of health and environmental issues shall be taken. The use of saturated calomel electrode shall follow nations rules and regula
39、tions.4 Specimens4.1 The specimen shall be taken from a test material such that the test area is minimum 1,0 cm2. Different surfaces are permitted, if they are used in actual application: e.g. different heat treatments, and different surface finish.4.2 The specimen may be taken by sawing, cutting, g
40、rinding, etc. The depth affected by machining shall be removed by progressive grinding so that the traces of machining may not affect the test results.NOTE If relevant parties agree, any surface finishes different from the above recommendation may apply as far as they are reproducible.5 Procedure5.1
41、 Preparation of reference electrodes5.1.1 The difference in potential among the reference electrode and two other validation electrodes shall be measured. The latter electrodes shall be traceable to the standard hydrogen electrode, and shall be maintained solely for the purpose of validation. If the
42、 potential is different by greater than 3 mV, the electrode shall be rejected.5.1.2 The validation electrodes shall be stored in optimum conditions and regularly compared. If the potential difference between these varies by more than 1 mV, replacement shall be undertaken.5.2 Preparation of specimen5
43、.2.1 The final grinding of the specimen may be dry or wet. Before measurement, the specimen is recommended to be ground with 600 grit paper, and shall then be thoroughly cleaned.NOTE 1 After grinding, it takes time for the air formed film to achieve a quasi-steady condition. The most rapid change in
44、 filming occurs in the first period with progressive stabilization at longer periods.NOTE 2 A minimum time period of 24 h is recommended. However, a shorter period may be adopted depending on the purpose of the test. Nevertheless, the time period in a set of tests should be consistent.NOTE 3 If rele
45、vant parties agree, surface finishes different from the above recommendation may apply as far as they are reproducible.5.2.2 The specimen shall be cleaned prior to immersion into the test solution, by degreasing, rinsing in high purity water (with a conductivity less than 1 S/cm), followed by ethano
46、l or a similar solvent, and then air drying. After degreasing, care shall be taken not to contaminate the test surface of the specimen.5.3 Preparation of solution5.3.1 The solution shall be prepared using reagent-grade chemicals and high purity water. ISO 2014 All rights reserved 3BS ISO 15158:2014I
47、SO 15158:2014(E)5.3.2 The test solution should reflect the intended application; otherwise 1 M (k mol m3) sodium chloride aqueous solution may be used.NOTE The recommended test solution of 1 M sodium chloride aqueous solution can be prepared by dissolving 58,44 g of reagent-grade sodium chloride int
48、o 1 000 mL of distilled or ion-exchange water.5.4 Setting up test5.4.1 The exposed surface area of the test specimen shall be measured.5.4.2 The standard temperature of the test solution shall be (30 1) C.The tests may be performed at a different temperature depending on the purpose, but the same te
49、mperature for a particular set of tests shall be applied.5.4.3 For anodic polarization, completely immerse the test surface area in the de-aerated test solution; leave it to stand there to stabilize temperature and corrosion potential for at least 1 min. Then, start potential sweeping at the rate of 10 mV/min from corrosion potential until the anodic current density reaches more than 500 A/cm2and less than 1 000 A/cm2. In case statistical analysis of the potential data was intended, the sweep rate of 20 mV/min may be used. If
