1、BSI Standards PublicationBS ISO 17093:2015Corrosion of metals and alloys Guidelines for corrosiontest by electrochemical noisemeasurementsBS ISO 17093:2015 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of ISO 17093:2015. The UK participation in its preparation was e
2、ntrusted to TechnicalCommittee ISE/NFE/8, Corrosion 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 ap
3、plication. The British Standards Institution 2015.Published by BSI Standards Limited 2015ISBN 978 0 580 75558 3 ICS 77.060 Compliance with a British Standard cannot confer immunity from legal obligations.This British Standard was published under the authority of the Standards Policy and Strategy Com
4、mittee on 30 June 2015.Amendments/corrigenda issued since publicationDate T e x t a f f e c t e d ISO 2015Corrosion of metals and alloys Guidelines for corrosion test by electrochemical noise measurementsCorrosion des mtaux et alliages Lignes directrices pour essais de corrosion par mesures de bruit
5、 lectrochimiqueINTERNATIONAL STANDARDISO 17093First edition 2015-06-15Reference number ISO 17093:2015(E)BS ISO 17093:2015ISO 17093:2015(E)ii ISO 2015 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2015, Published in SwitzerlandAll rights reserved. Unless otherwise specified, no part of this pub
6、lication 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 permission. Permission can be requested from either ISO at the address below or ISOs member body in the cou
7、ntry 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.orgBS ISO 17093:2015ISO 17093:2015(E)Foreword iv1 Scope . 12 Normative references 13 Terms and definitions . 14 Principles . 25 App
8、aratus and measurement methods 36 Test cell . 57 Measurement procedure 58 Evaluation of instrument noise . 69 Test report . 8Annex A (informative) Analysis of data 9Annex B (informative) Example of simultaneous current and potential noise measurement on pitting corrosion of aluminium12Annex C (infor
9、mative) Example of simultaneous current and potential measurement on organically coated carbon steel .15Bibliography .19 ISO 2015 All rights reserved iiiContents PageBS ISO 17093:2015ISO 17093:2015(E)ForewordISO (the International Organization for Standardization) is a worldwide federation of nation
10、al 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 committee has been established has the right to be represented on that committee. Internatio
11、nal 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 electrotechnical standardization.The procedures used to develop this document and those intended
12、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 in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.
13、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. Details of any patent rights identified during the development of the document will
14、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 an endorsement.For an explanation on the meaning of ISO specific terms and expressio
15、ns 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 committee responsible for this document is ISO/TC 156, Corrosion of metals and alloys, in coo
16、peration with the ECG-COMON (European Cooperative Group on Corrosion Monitoring of Nuclear Materials, http:/www.ecg-comon.org).iv ISO 2015 All rights reservedBS ISO 17093:2015INTERNATIONAL STANDARD ISO 17093:2015(E)Corrosion of metals and alloys Guidelines for corrosion test by electrochemical noise
17、 measurements1 ScopeThis International Standard is intended to assist in corrosion testing by electrochemical noise measurement. It covers test procedures and analysis methods for reliable measurement of electrochemical noise for both uncoated and organically coated metal.2 Normative referencesThe f
18、ollowing 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. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 8044, Co
19、rrosion of metals and alloys Basic terms and definitionsISO 17475, Corrosion of metals and alloys Electrochemical test methods Guidelines for conducting potentiostatic and potentiodynamic polarization measurements3 Terms and definitionsFor the purposes of this document, the terms and definitions giv
20、en in ISO 8044 and the following apply.3.1electrochemical noiseENfluctuation typically at low frequencies (1 Hz) and low amplitude in current and potential generated by electrochemical reactions and other processes on the surface, for example, bubble evolution3.2electrochemical potential noisefluctu
21、ation in potential (typically in the range of V to mV) of an electrode relative to a reference electrode or fluctuation in potential between two similar electrodes3.3electrochemical current noisefluctuation in current (typically in the range of nA to A) of one electrode or between two electrodes3.4e
22、lectrochemical noise resistanceresistance obtained by dividing the standard deviation of potential noise by the standard deviation of current noise from the time record3.5power spectral density of potentialPSDEpower present in the potential noise as a function of frequency3.6power spectral density o
23、f currentPSDIpower present in the current noise as a function of frequency ISO 2015 All rights reserved 1BS ISO 17093:2015ISO 17093:2015(E)3.7electrochemical noise impedanceZnimpedance determined as ZPSD PSDnI=E/ where all terms are a function of frequencyNote 1 to entry: The noise impedance is real
24、 and positive.3.8working electrodeelectronic conductor in contact with the electrolyte, made out of the investigated materialNote 1 to entry: This definition differs from that of the same term given in ISO 8044:2015, 6.1.46, “test electrode in an electrochemical cell designed for polarization tests”
25、.3.9auxiliary electrodeelectrode commonly used in applied polarization to balance the current passing to the working electrodeNote 1 to entry: It is usually made from a non-corroding material.3.10Nyquist frequencyfrequency equal to one half of the sampling frequency (fs/2); maximum frequency about w
26、hich information can be obtained from the sampled data3.11thermal noisenoise resulting from thermal vibrations of electrons and charge carriersNote 1 to entry: Thermal noise is the absolute minimum of the noise that can be expected; also called Johnson noise.3.12shot noisenoise due to the quantized
27、nature of the charge carriers that move in very short times causing current peaks3.13dummy cellnon-electrochemical cell with a well-defined noise level that usually does not deliberately generate noise above normal thermal noise levels4 Principles4.1 The source of EN in corrosion might result from p
28、artial faradaic currents, adsorption/desorption processes, surface coverage, and, in the case of localized corrosion, the initiation of pits, crevice corrosion, and mechanical effects from cracking and several other processes. Special care has to be taken as a variety of other sources not related to
29、 corrosion might cause fluctuations in current and potential.4.2 Electrochemical noise can be measured potentiostatically, galvanostatically, or at the free corrosion potential (the various methods are described in Clause 5). Examples of two simple tests with EN measurements on aluminium during pitt
30、ing corrosion and on organically coated carbon steel can be found in Annexes B and C.4.3 Electrochemical noise data can be analysed in the time and/or frequency domains. Details of data analysis are described in Annex A.2 ISO 2015 All rights reservedBS ISO 17093:2015ISO 17093:2015(E)5 Apparatus and
31、measurement methods5.1 Instrumentation5.1.1 Accurate measurement of potential and current requires instruments that have appropriate input impedance (much higher than the system being measured in the case of potential and much lower in the case of current) and sensitivity (sufficient to minimize qua
32、ntization noise). Suggestions are given in the following Clauses but these will not be sufficient for some systems.5.1.2 Potential measuring instrumentsThe instrument should have an input impedance of at least 109ohm for bare metal and 1011ohm for coated metal to minimize current drawn from the syst
33、em during measurement. The higher input impedance might be necessary for very high impedance systems (e.g. for EN measurements with coated metals). The sensitivity and accuracy of the instrument should be sufficient to detect a change of 10 V or lower for the typical range of 1 V.5.1.3 Current measu
34、ring instrumentsThe instrument should be capable of measuring current to a resolution of 109A or better with a voltage burden (the voltage between the terminals, also known as a voltage drop or burden voltage) of less than 1 mV (the low voltage burden is only required when the current measurement is
35、 made between two corroding working electrodes). A low voltage burden ammeter is often termed a zero resistance ammeter (ZRA) in corrosion literature.5.1.4 PotentiostatSome measurement configurations use a potentiostat to control the potential of an electrode. The potentiostat shall have low noise c
36、haracteristics, which should be tested by using a dummy cell with comparable properties to the system under investigation (see Clause 8 or Reference 1).5.1.5 GalvanostatSome measurement configurations use a galvanostat to apply a current to an electrode. The galvanostat shall have low noise characte
37、ristics, which should be tested by using a dummy cell with comparable properties to the system under investigation (see Clause 8 or Reference 1).5.1.6 Grounding, shielding, and isolationIt is very important to ensure correct grounding and shielding of the measurement system. In particular, there sho
38、uld be a single well-defined connection to ground in order to avoid ground loops and to minimize induced interference. Isolated or differential measuring devices will commonly be required to avoid short-circuit connections to ground and ground loops, especially in plant monitoring conditions. ISO 20
39、15 All rights reserved 3BS ISO 17093:2015ISO 17093:2015(E)5.2 Measurement configurationsSchematics of the most important EN measurement configurations can be seen in Figure 1.a) Potentiostatic current noise b) Galvanostatic potential noisec) Open-circuit potential noised) Current noise at open-circu
40、it potentiale) Simultaneous current and potential noiseKey1 potentiostat (see 5.1.4)2 current measurement device (see 5.1.3, implies connection to PC or other device for recording or analysis)3 working electrode (WE)4 reference electrode (RE)5 auxiliary electrode (AE)6 galvanostat (see 5.1.5)7 poten
41、tial measurement device (see 5.1.2, implies connection to PC or other device for recording or analysis)Figure 1 Configurations for measurements5.2.1 Potentiostatic current noise measurementThe current to a potentiostatically controlled working electrode using an inert counter electrode is measured.
42、This is usually used to study individual current transients in localized corrosion, since the controlled potential minimizes fluctuation of current on the passive surface, and permits the potential to be held at a value at which the localized corrosion process occurs. The current can be measured in
43、the lead to the counter electrode, as shown in Figure 1a, or by using a current amplifier that is internal to the potentiostat.5.2.2 Galvanostatic potential noise measurementThe potential of one galvanostatically controlled working electrode relative to a low-noise reference is measured. This is als
44、o used to study individual potential transients in localized corrosion. If an AC current is used, this can also permit the simultaneous estimation of impedance.4 ISO 2015 All rights reservedBS ISO 17093:2015ISO 17093:2015(E)5.2.3 Open-circuit potential noise measurementThe potential of one working e
45、lectrode relative to a low-noise reference electrode or the potential difference between two identical working electrodes is measured in open-circuit conditions. The use of two working electrodes typically reduces the DC component of the measured noise and permits higher sensitivity to be obtained w
46、ithout using very high resolution analogue to digital convertors. It does, however, lose information about the DC potential, which might be useful. This can be used for online corrosion monitoring.5.2.4 Current noise measurement at open-circuit potentialThe current noise between two identical workin
47、g electrodes is monitored.5.2.5 Simultaneous current and potential noise measurementTwo identical working electrodes are connected by low voltage burden ammeter, which records the fluctuating current between two electrodes. The potential fluctuations of this coupled electrode pair are recorded with
48、a voltmeter. This is the most common method for measuring coated substrates.5.3 Signal processing and recording5.3.1 Digital techniques are used in most EN measurements because of limitations in the accuracy for recording time record and data analysis with analogue methods. Amplifiers are used to co
49、nvert the current to a voltage and to condition the measured potential. The current and/or potential outputs from amplifiers are filtered and converted to a digital form for recording or analysis.5.3.2 Filters are used to prevent aliasing that occurs in the conversion of continuous analogue data to discrete signals. To avoid aliasing, it is necessary to remove frequencies above the Nyquist frequency, which reappear as false indications at a low frequency. In most EN measurements, power line frequency noise is a typical example of alia
