1、BSI Standards PublicationBS ISO 18070:2015Corrosion of metals and alloys Crevice corrosion formerswith disc springs for flatspecimens or tubes made fromstainless steelBS ISO 18070:2015 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of ISO 18070:2015.The UK participat
2、ion 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 are resp
3、onsible for its correctapplication. The British Standards Institution 2015.Published by BSI Standards Limited 2015ISBN 978 0 580 79069 0ICS 77.060Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the authority of theStandards Po
4、licy 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 18070:2015 ISO 2015Corrosion of metals and alloys Crevice corrosion formers with disc springs for flat specimens or tubes made from stainless steelCorrosion des mtaux et a
5、lliages Dispositif dessai de corrosion par crevasse avec rondelles ressort pour chantillons plats ou tubulaires en acier inoxydableINTERNATIONAL STANDARDISO18070First edition2015-11-01Reference numberISO 18070:2015(E)BS ISO 18070:2015ISO 18070:2015(E)ii ISO 2015 All rights reservedCOPYRIGHT PROTECTE
6、D 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, without prior wr
7、itten 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.orgBS ISO 18070:20
8、15ISO 18070:2015(E)Foreword ivIntroduction v1 Scope . 12 Normative references 13 Terms and definitions . 14 Symbols 15 Test specimen 25.1 Specimen specifications 25.1.1 Flat specimens . 25.1.2 Tubes 25.2 Surface preparation of the specimens 26 Crevice former and assembly 26.1 General . 26.2 Disc spr
9、ings 26.3 Crevice former . 36.4 Crevice formers for tubes 46.5 Preparation of the crevice formers surfaces . 56.6 Crevice assembly . 66.7 Ending test 76.8 Cleaning . 77 Documentation . 7Annex A (informative) Example of test report format of deflection measurements 8Bibliography 9 ISO 2015 All rights
10、 reserved iiiContents PageBS ISO 18070:2015ISO 18070:2015(E)ForewordISO (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 committ
11、ees. 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, in liaison with ISO, also take part in the work. ISO collaborates closely with the Int
12、ernational 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/IEC Directives, Part 1. In particular the different approval criteria needed for the di
13、fferent 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 that some of the elements of this document may be the subject of patent rights. ISO sh
14、all 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 declarations received (see www.iso.org/patents).Any trade name used in this document
15、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 information about ISOs adherence to the WTO principles in the Technical Barriers to Trade (TBT
16、) see the following URL: Foreword - Supplementary information.The committee responsible for this document is ISO/TC 156, Corrosion of metals and alloys.iv ISO 2015 All rights reservedBS ISO 18070:2015ISO 18070:2015(E)IntroductionThe working party on Marine Corrosion in the European Federation of Cor
17、rosion (EFC) has found that there is an industrial need for crevice corrosion testing for seawater applications that can estimate the maximum service temperature in natural seawater for stainless steels. Several aspects of crevice corrosion testing were elucidated by a research project.1It was found
18、 that an important factor is the crevice forming technique, and in order to have controlled crevices, the disc spring loaded crevice former was introduced. The general idea is that the disc springs shall keep the clamping force as constant as possible. In addition to the crevice forming technique fo
19、r plate specimens, a technique for a crevice former for tubular specimens was developed, which has given reproducible results.Round robin testing for the crevice forming technique was performed for both laboratory testing and in natural seawater and it showed improvement compared to traditional crev
20、ice formers. Good correlation was found between the laboratory testing and natural seawater. ISO 2015 All rights reserved vBS ISO 18070:2015BS ISO 18070:2015Corrosion of metals and alloys Crevice corrosion formers with disc springs for flat specimens or tubes made from stainless steel1 ScopeThis Int
21、ernational Standard specifies a crevice forming technique and crevice former which are intended to be used for crevice corrosion testing of flat specimens or tubes of stainless steels, in corrosive solutions. This International Standard specifies no information concerning how the crevice corrosion t
22、esting shall be performed and how the attack shall be evaluated. The crevice former specified in this International Standard can be used for electrochemical measurements, if the specimens are designed for electrical connections.2 Normative referencesThe following documents, in whole or in part, are
23、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 3696, Water for analytical laboratory use Specificatio
24、n and test methodsISO 8044, Corrosion of metals and alloys Basic terms and definitionsISO 6344-3, Coated abrasives Grain size analysis Part 3: Determination of grain size distribution of microgrits P240 to P2500DIN 2093, Disc springs Quality specifications Dimensions3 Terms and definitionsFor the pu
25、rposes of this document, the terms and definitions given in ISO 8044 apply.4 SymbolsLBL Length Before LoadingLAL1Length After LoadingLAL2Length After Loading and exposureL1Deflection before exposureL2Deflection after exposureINTERNATIONAL STANDARD ISO 18070:2015(E) ISO 2015 All rights reserved 1BS I
26、SO 18070:2015ISO 18070:2015(E)5 Test specimen5.1 Specimen specificationsBoth flat specimens and tubes made from stainless steels can be used as specimens in the crevice corrosion formers specified in this International Standard. The specimen outer surface area shall be at least 100 cm2.NOTE 1 A squa
27、red specimen with a centre hole is preferred since the distance between the anode and cathode area might be critical in solutions with low conductivity.NOTE 2 If an electrode potential is applied, a smaller specimen can be used.5.1.1 Flat specimensA hole, 7 mm in diameter, shall be drilled in the mi
28、ddle of each specimen.NOTE To hang up of specimen and for electrical connection, a small hole can be drilled at one end of the specimen.5.1.2 TubesA hole, 7 mm in diameter, shall be drilled in the middle of the tubes in radial dimension. The hole shall be drilled at both sides of the tube allowing a
29、 bolt to be inserted in the hole without alignment. The length of the tubes shall be at least 30 mm.NOTE To hang up of specimen and for electrical connection, a small hole can be drilled at one end of the specimen.5.2 Surface preparation of the specimens5.2.1 The surface finish shall be as reproduci
30、ble as possible. Any test surface may be tested but it is recommended that all surfaces, including cut edges and drilled holes, shall be abraded down to at least P120 grit paper, according to ISO 6344-3. Care shall be taken to avoid overheating the surface.NOTE Ultra sonic cleaning after abrading ca
31、n be used.5.2.2 After abrading and cleaning, 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.5.2.3 The specimens shall be cleaned immediately prior to immersion in the solution by degreasing
32、, rinsing in high-purity water with a conductivity less than 1 S/cm, (ISO 3696, grade 2) followed by ethanol or a similar solvent and air drying. After degreasing, care shall be taken not to contaminate the test surface of the specimens.6 Crevice former and assembly6.1 GeneralBoth flat specimens and
33、 tubular stainless steels can be used as specimens in the crevice corrosion formers specified in this International Standard, see Figure 1 and Figure 2.6.2 Disc springsDisc springs with a linear force versus deflection relationship shall be used. The relation between the force and deflection of the
34、setup of the disc springs shall be known. For disc springs according to 2 ISO 2015 All rights reservedBS ISO 18070:2015ISO 18070:2015(E)DIN 2093, the deflection that corresponds to 0,9 kN is 0,9 mm; for other disc springs, the deflection that corresponds to a force of 0,9 kN shall be measured with a
35、 tensile machine.NOTE In the USA, disc springs are called Belleville washers.6.3 Crevice formerThe crevice assembly is of the spring loaded type. Nut, bolt, and washers (rings) are made from titanium. The thickness of the washers is between 2 mm and 4 mm. Outer diameter of the washers shall be at le
36、ast 20 mm and the inner diameter at least 5,2 mm. Bolt diameter shall be 5 mm (M5 threads) and the length is about 75 mm. A PVC (polyvinyl chloride) or PE (polyethylene) hose is mounted around the bolt, from the head of the bolt to the crevice former at the nut side, to prevent electrical contact be
37、tween specimen and the assembly and to centre the rings, disc springs, and specimen. A schematic drawing of the assembly for flat specimens is shown in Figure 1 and for tubes is shown in Figure 2. A ring of inert polymeric material, like PTFE (polytetrafluoroethylene) is mounted to centre the disc s
38、prings, as shown in Figure 1 and Figure 2. The disc springs are made of titanium or nylon coated steel. The disc spring shall be according to DIN 2093 or with a calibrated deflection-force relationship. A set of four springs is used to obtain a load of 0,9 kN (this corresponds approximately to a tor
39、que of 3 Nm, with the crevice assembly applied using DIN 2093 disc springs). The crevice formers are made of PVDF (polyvinylidene fluoride) and can be used up to 95 C. The outside diameter is 20 mm and the inside diameter is 7 mm and height is 15 mm.12233874356Key1 nut 5 insulation hose (split only
40、for imaging purpose)2 crevice former 6 bolt3 washer 7 disc springs4 centralizing ring 8 test specimenFigure 1 Sketch of spring loaded crevice former for flat specimens ISO 2015 All rights reserved 3BS ISO 18070:2015ISO 18070:2015(E)21234356783Key1 nut 5 insulation hose (split only for imaging purpos
41、e)2 crevice former 6 bolt3 washer 7 disc springs4 centralizing ring 8 test specimenFigure 2 Sketch of the crevice assembly for tubes6.4 Crevice formers for tubesThe specifications for crevice formers for tubes are given in 6.3. In addition, on one side, a curvature shall be machined with same radius
42、 as the outer diameter of the tube. The crevice former shall not be thinner than 5 mm. Examples of the calibration curves for the force and torque that shall be used for tubular specimens are shown in Figure 3 and Figure 4, respectively. The force from Figure 3 shall be used for calculating the corr
43、esponding deflection using the linear relationship between the force and deflection for the spring assembly. The tube shall be thick enough to ensure no deflection of the tube during the test.4 ISO 2015 All rights reservedBS ISO 18070:2015ISO 18070:2015(E)y = 251,51 Ln (x) - 216,39R2 = 0,994 3400450
44、50055060065070075080015 20 25 30 35 40 45 50 55XYKeyX outer tube diameter (mm)Y force (N)Figure 3 Calibration curve for the force that shall be used for tubular specimensy = 0,838 4Ln(x) - 0,721 31,51,7522,252,52,75315 20 25 30 35 40 45 50 55R2 = 0,994 3YXKeyX outer tube diameter (mm)Y torque (Nm)Fi
45、gure 4 Calibration curve for the torque that shall be used for tubular specimens6.5 Preparation of the crevice formers surfacesThe crevice formers shall be wet ground with at least P1200 grit paper, according to ISO 6344-3, starting with lower grit paper. Make sure that all grooves from machining ar
46、e completely removed. When reusing the crevice formers, grinding with P1200 grit paper is sufficient. Make sure that there are no visible corrosion products on the crevice former. ISO 2015 All rights reserved 5BS ISO 18070:2015ISO 18070:2015(E)6.6 Crevice assembly6.6.1 The parts are mounted on the b
47、olt in the following order, relative to the bolt head: washer, 4-disc springs in position, washer, crevice former, specimen, crevice former, washer, nut. A schematic drawing of the assembly for flat specimens is shown in Figure 5.1262791005720237844635Key1 centralizing ring 5 washer2 hose 6 disc spr
48、ings3 test specimen 7 bolt4 crevice former 8 nutFigure 5 Sketch of spring loaded crevice former for flat specimens6.6.2 The bolt shall be insulated, as mentioned above, to avoid electrical contact with the specimen (see Figure 1 and Figure 2). This shall be checked with an Ohm-meter.6.6.3 In order t
49、o make sure that the torque on the specimens is constant during the exposure, the distance between washers shall be measured before and after exposure. An example of a test report is given in Annex A. The nut is turned on the thread by use of a torque wrench to 0,2 Nm. In this position, the distance between the washers mounted towards the springs is measured (e.g. with a vernier calliper measurement gauge) in four positions around the circumference (3 oclock, 6 oclock, 9 oclock and 12 oclock). The average value i
