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1、BRITISH STANDARD BS ISO 15724:2001 Metallic and other inorganic coatings Electrochemical measurement of diffusible hydrogen in steels Barnacle electrode method ICS 25.220.40; 25.220.99 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW Licensed Copy: sheffieldun sheffieldun, na,
2、Sun Nov 26 11:39:42 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 15724:2001 This British Standard, having been prepared under the direction of the Sector Policy and Strategy Committee for Materials and Chemicals, was published under the authority of the Standards Policy and Strategy Committee o
3、n 21 December 2001 BSI 21 December 2001 ISBN 0 580 38800 X National foreword This British Standard reproduces verbatim ISO 15724:2001 and implements it as the UK national standard. The UK participation in its preparation was entrusted to Technical Committee STI/37, Methods of test for metallic and r
4、elated inorganic coatings including corrosion tests, which has the responsibility to: A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards which implement international or European publications referred to in this d
5、ocument may be found in the BSI Standards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility of the BSI Standards Electronic Catalogue. A British Standard does not purport to include all the necessary provisions of a contract. Users o
6、f British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or p
7、roposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. Summary of pages This document comprises a front cover, an inside front cover, the ISO title page, pages ii to v, a blank page, pages 1 to 10, an inside bac
8、k cover and a back cover. The BSI copyright date displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. DateComments Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 11:39:42 GMT+00:00 2006, Uncontrolled Copy, (c) BSI INTERNATIONAL
9、STANDARD ISO 15724 First edition 2001-12-01 Reference number ISO 15724:2001(E) Metallic and other inorganic coatings Electrochemical measurement of diffusible hydrogen in steels Barnacle electrode method Revtements mtalliques et autres revtements inorganiques Mesurage lectrochimique de lhydrogne dif
10、fusible dans les aciers Mthode par lectrode anatife Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 11:39:42 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ISO 15724:2001(E) ii Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 11:39:42 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ISO 15724:200
11、1(E) iii ContentsPage 1Scope .1 2Normative references .1 3Principle 2 4Reagents 2 5Apparatus .3 6Test specimens .5 7Calibration 5 8Procedure .5 9Results 8 10Interpretation of results .8 11Test report 8 Bibliography.10 Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 11:39:42 GMT+00:00 2006, Un
12、controlled Copy, (c) BSI ISO 15724:2001(E) iv Foreword ISO (the 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 mem
13、ber 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, in liaison with ISO, also take part in the work. ISO collaborates closely with the International El
14、ectrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3. Draft International Standards adopted by the technical committees are circulated to the member bodies for voti
15、ng. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this International Standard may be the subject of patent rights. ISO shall not be held responsible for identifying a
16、ny or all such patent rights. International Standard ISO 15724 was prepared by Technical Committee ISO/TC 107,Metallic and other inorganic coatings, Subcommittee SC 2,Test methods. Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 11:39:42 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ISO 15724:20
17、01(E) v Introduction When atomic hydrogen enters steels and certain other alloys, it can cause loss of ductility or of load-carrying ability, cracking (usually submicroscopic cracks) or catastrophic brittle failure at applied stresses well below the yield strength or even the normal design strength
18、of the alloys. This phenomenon often occurs in alloys that show no significant loss in ductility when measured by conventional tensile tests and is frequently referred to as “hydrogen- induced delayed brittle failure”, “hydrogen stress cracking” or “hydrogen embrittlement”. The hydrogen can be intro
19、duced during fabrication, cleaning, pickling, phosphating, electroplating, autocatalytic processes and in the service environment as a result of cathodic protection reactions or corrosion reactions. Parts that have been machined, ground, cold-formed or cold-straightened subsequent to any heat treatm
20、ent are especially susceptible to hydrogen embrittlement damage. Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 11:39:42 GMT+00:00 2006, Uncontrolled Copy, (c) BSI Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 11:39:42 GMT+00:00 2006, Uncontrolled Copy, (c) BSI INTERNATIONAL STANDAR
21、DISO 15724:2001(E) 1 Metallic and other inorganic coatings Electrochemical measurement of diffusible hydrogen in steels Barnacle electrode method WARNING This International Standard does not address any health hazards and safety matters associated with its use. It is the responsibility of the user o
22、f this International Standard to establish appropriate health and safety practices and take suitable actions for any national regulations. 1Scope This International Standard describes a method that uses an electronic hydrogen detection instrument for measuring relative, diffusible hydrogen concentra
23、tions in bare steels or in plated steels after the coating has been removed. It is assumed that the hydrogen is uniformly distributed throughout a part. The method does not measure actual hydrogen concentration. However, oxidation current densities measured against time provide a useful indication o
24、f relative hydrogen concentrations and, therefore, the measurements can be used for comparison purposes. The method may be used as a quality control procedure as it does provide a quick means of measuring the effectiveness of pre- and/or post-plating heat treatments or of monitoring hydrogen uptake
25、during plating or due to corrosion. It is important to note that the absence of failure in a particular test does not provide confirmation of complete elimination of hydrogen embrittlement because no one test method can provide all the data necessary to evaluate the degree of hydrogen degradation. F
26、or unplated parts the method is non-destructive; however, for plated parts the coating has to be removed prior to measurement by a means proven not to damage the steel or to introduce hydrogen. This test method is limited to: carbon and alloy steels, excluding austenitic stainless steels (see note 1
27、); flat specimens to which the cell can be attached (see note 2); measurements at room temperature (). NOTE 1If this method is used for austenitic stainless steels and other face centred cubic (FCC) alloys, measurement times and interpretation of results will have to be determined because of the dif
28、ferent kinetics involved. NOTE 2For slightly curved surfaces it is essential to define an area that is reproducible. The area calculation will be different from that described in this International Standard. NOTE 3The method can be applied to small parts, however, this necessitates some modification
29、 of the technique, procedure and interpretation of results. 2Normative references The following normative documents contain provisions which, through reference in this text, constitute provisions of this International Standard. For dated references, subsequent amendments to, or revisions of, any of
30、these publications do not apply. However, parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For 25 C 1 C Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 11:3
31、9:42 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ISO 15724:2001(E) 2 undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain registers of currently valid International Standards. ISO 9587,Metallic and other inorganic coatings Pretreatments
32、 of iron or steel to reduce the risk of hydrogen embrittlement ISO 9588,Metallic and other inorganic coatings Post-coating treatments of iron or steel to reduce the risk of hydrogen embrittlement 3Principle This method is an adaptation of the electrochemical permeation method for hydrogen diffusion.
33、 A hydrogen-containing steel part is made the anode in an electrochemical cell containing an alkaline solution as the electrolyte, with a nickel-nickel oxide (Ni/NiO) electrode forming the cathode. The cell maintains zero hydrogen concentration at the surface of the steel by oxidizing the hydrogen a
34、toms to water. As there is no corrosion reaction taking place at the steel surface, the anodic current measured as a function of time is attributed to the concentration of mobile hydrogen. In this method, the actual hydrogen concentration is not determined. This is because the calculation of hydroge
35、n concentration requires knowledge of the hydrogen diffusion coefficient in the alloy and knowledge of the decay curve, both of which are not always known, especially at very low hydrogen concentrations. However, comparative current densities can be used to indicate relative hydrogen concentrations.
36、 In this method, it is assumed that the hydrogen is uniformly distributed throughout the steel part and that hydrogen is not appreciably lost due to diffusion during the course of the measurement. Furthermore, as the measurement is relatively rapid, it is probable that trapped hydrogen that is not e
37、asily released without stress but that could contribute to delayed failure, will not be detected. This method is based on measurement of current that decays over a fixed period, in this case for. The current density will depend on the material as well as on the hydrogen concentration. Each material
38、will have a background current density (see 7.4). A measurement higher than background indicates the presence of hydrogen. Higher current densities indicate higher hydrogen concentrations; the higher the current densities the higher the likelihood of hydrogen embrittlement. A background correction o
39、f the actual measurement, however, is not made (see note to 7.4). 4Reagents Reagent grade chemicals of sufficiently high purity to ensure the accuracy of the determination shall be used in all tests. 4.1Electrolyte (sodium hydroxide solution), dissolveof sodium hydroxide (NaOH) pellets in distilled
40、or de-ionized water and dilute to. 4.2Methyl alcohol (CH3OH). 4.3Ethyl alcohol (C2H5OH). 30 min 0,2 M8 g 1 l Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 11:39:42 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ISO 15724:2001(E) 3 5Apparatus See Figures 1 and 2. 5.1The barnacle electrode system
41、. This consists of 5.1.1cell, left open to the atmosphere without any purging (see Figure 2), and made of a non-metallic inert material that will not react with or contaminate the electrolyte, and the side opening of which has a recess to accommodate a silicon rubber gasket. 5.1.2gasket, made of sil
42、icon rubber, that shall provide a reproducible contact area between the solution and the specimen, preferably. 5.1.3cell holder, a cradle-like C-clamp. Key 1Strip chart recorder 2Electrometer 3Known resistance 4Driving electrode, Ni/NiO 5NaOH 6Gasket 7Hydrogen-containing part Figure 1 Schematic diag
43、ram of a barnacle electrode system 0,2 M 1 cm2 Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 11:39:42 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ISO 15724:2001(E) 4 5.1.4anode (i.e. the specimen to be tested). 5.1.5cathode, a Ni/NiO electrode (e.g. from a nickel-cadmium battery), the area o
44、f which shall be approximately five times that of the anode. 5.1.6a current measuring device. NOTEThe current can be measured by any method that will not adversely affect the system; e.g., in this International Standard, the device consists of: a)a standard resistance connected across the two electr
45、odes via a switch; b)an electrometer to determine the current by measuring the voltage drop across the resistance (aresistor with an electrometer having an input impedance ofhas been found to be satisfactory); c)a strip chart recorder to monitor the electrometer measurements (an input resistance ofh
46、as been found to be satisfactory); d)a timer accurate to withinin arun. Dimensions in millimetres Key 1Gasket seat Figure 2 Barnacle electrode cell 10 k 1012 100 k 10 s30 min Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 11:39:42 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ISO 15724:2001(E)
47、5 5.2Microscope. 5.3Nylon cleaning pad, impregnated with aluminium oxide. 6Test specimens The specimen can be an actual part or a coupontothick. If a coupon is used, it shall be of the same material and form, and have the same heat treatment and surface finish as the part, in order to depict the sam
48、e hydrogen parameters, such as hydrogen uptake during processing, mobile versus trapped hydrogen and surface finish. The specimen shall be sufficiently large to accommodate the cell and for a duplicate measurement to be made (see 8.3.6). It shall also be sufficiently flat and smooth to prevent leaka
49、ge of the electrolyte under the gasket. 7Calibration 7.1Calibrate the Ni/NiO electrode (5.1.5) against a saturated calomel electrode (SCE) inNaOH solution (4.1). A freshly charged Ni/NiO electrode will be at leastmore noble (i.e. positive) than the SCE. It shall be recharged when its potential drops to less thanmore noble (i.e. positive) than SCE. 7.2Charge the Ni/NiO electrode using a platinum, or similar, inert electrode as the cathode and the Ni/NiO electrode as the anode inNaOH solution forat a current density ofto. NOTETo prevent a tempor
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