1、BRITISH STANDARD BS EN ISO 11846:2008 Corrosion of metals and alloys Determination of resistance to intergranular corrosion of solution heat-treatable aluminium alloys ICS 77.060 BS EN ISO 11846:2008 This British Standard was published under the authority of the Standards Board and comes into effect
2、 on 15 October 1996 BSI 2008 ISBN 978 0 580 60537 6 National foreword This British Standard is the UK implementation of EN ISO 11846:2008. It is identical with ISO 11846:1995. It supersedes BS ISO 11846:1995 which is withdrawn. The UK participation in its preparation was entrusted to Technical Commi
3、ttee 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 application. Compliance wi
4、th a British Standard cannot confer immunity from legal obligations. Amendments/corrigenda issued since publication Date Comments 31 July 2008 This corrigendum renumbers BS ISO 11846:1995 as BS EN ISO 11846:2008EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN ISO 11846 April 2008 ICS 77.060 Engl
5、ish Version Corrosion of metals and alloys - Determination of resistance to intergranular corrosion of solution heat-treatable aluminium alloys (ISO 11846:1995) Corrosion des mtaux et alliages - Dtermination de la rsistance la corrosion intergranulaire des alliages daluminium aptes au traitement the
6、rmique de mise en solution (ISO 11846:1995) Korrosion von Metallen und Legierungen - Bestimmung der Bestndigkeit von lsungsgeglhten Aluminiumlegierungen gegen interkristalline Korrosion (ISO 11846:1995) This European Standard was approved by CEN on 21 March 2008. CEN members are bound to comply with
7、 the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN Management Cen
8、tre or to any CEN member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as the offici
9、al versions. CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slov
10、enia, Spain, Sweden, Switzerland and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG Management Centre: rue de Stassart, 36 B-1050 Brussels 2008 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN
11、 national Members. Ref. No. EN ISO 11846:2008: EForeword The text of ISO 11846:1995 has been prepared by Technical Committee ISO/TC 156 “Corrosion of metals and alloys” of the International Organization for Standardization (ISO) and has been taken over as EN ISO 11846:2008 by Technical Committee CEN
12、/TC 262 “Metallic and other inorganic coatings” the secretariat of which is held by BSI. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by October 2008, and conflicting national standards shall be w
13、ithdrawn at the latest by October 2008. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN and/or CENELEC shall not be held responsible for identifying any or all such patent rights. According to the CEN/CENELEC Internal Regulati
14、ons, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherla
15、nds, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. Endorsement notice The text of ISO 11846:1995 has been approved by CEN as a EN ISO 11846:2008 without any modification. BSEN ISO11846:2008BS EN ISO11846:2008 iii Contents 1 Scope 1 2 Normat
16、ive references 1 3 Definitions 1 4 Test specimens 1 5 Surface preparation 2 6 Tests 2 7 Metallographic examination 3 8 Interpretation of the results 3 9 Test report 3 Annex A (informative) Bibliography 4 Figure 1 Typical anodic polarization curve 3 Pageblank1 1 Scope 1.1 This International Standard
17、specifies the methods of integranular corrosion testing for solution heat-treatable aluminium alloys without protective coatings. The sensitivity of solution heat-treatable aluminium alloys to intergranular corrosion is a function of the alloy chemical composition, method of manufacturing, solution
18、heat treatment, quench treatment and artificial precipitation hardening (ageing) treatment. In the naturally aged condition, the sensitivity of solution heat-treatable aluminium alloys to intergranular corrosion is a function primarily of the rate of cooling during quenching over a critical temperat
19、ure range. 1.2 This International Standard is applicable to cast and wrought heat-treatable aluminium alloys in the form of castings, forgings, plates, sheets, extrusions and semi-finished or finished parts, in order to carry out comparative assessment of alloys of different grades and thickness dep
20、ending on their chemical composition and other factors, and also to check the thermal processing quality of the tested materials. The test results provide information to determine the intergranular corrosion resistance and thermal processing quality of the tested materials. 1.3 The test results cann
21、ot be regarded as absolute, because they are not applicable to all environments that can be met in service. They are best used in a relative manner, to compare the intergranular corrosion resistance of various heats of solution heat-treatable aluminium alloys. 2 Normative references The following st
22、andards contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged
23、to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO3696:1987, Water for analytical laboratory use Specification and test methods. ISO8044:1989, Corrosion of met
24、als and alloys Vocabulary. ISO8407:1991, Corrosion of metals and alloys Removal of corrosion products from corrosion test specimens. 3 Definitions For the purposes of this International Standard, the definitions given in ISO8044 apply. 4 Test specimens 4.1 Sampling Sampling should be carried out in
25、such a manner as to provide specimens from the most typical areas of the material or the part being tested. When controlling solution heat treatment, samples are taken from that part of the semi-finished product where cooling rates during quenching are the lowest. In the case of small parts which ar
26、e quenched in baskets, the samples are taken from the central part of the basket. If quenching is performed on racks, samples are taken from the upper and lower parts of the rack. If semifinished products, such as tubes, sheets, plates or panels, are vertically quenched the samples are taken from th
27、e lower and upper ends. If there are no differences in the cooling conditions, the samples are taken at random. Samples shall be taken from each solution heat treatment charge. The location of sampling should be agreed upon between the user and supplier. 4.2 Dimensions, shapes, number of specimens a
28、nd surface requirements Specimens can have arbitrary configuration and dimensions, but they should be similar for repetitive tests. The specimen surface area should be between4 cm 2and 20 cm 2 . Flat specimens should be cut in such a way that the longer dimension is parallel to the metal working dir
29、ection. The specimen surface should maintain the initial condition of the material or finished part, or it should be machined in such a way that the surface roughness R ais 2,5 m. Specimens with surface defects (metallurgical or mechanical) should not be tested. Specimens from clad materials are tes
30、ted without cladding. The cladding layer is removed from both sides by machining or chemical etching. Etching is carried out in the solutions for dimensional chemical etching or according to5.2.1. To be certain that all cladding has been removed, it is necessary to remove 0,1mm more than the thickne
31、ss of the cladding. NOTE 1Specimen heating to above 60C during machining is not permitted. BS EN ISO11846:2008BSEN ISO 11846:2008 2 Tests should be carried out on not less than three specimens having the same configuration, dimensions and surface preparation. 5 Surface preparation 5.1 Before testing
32、, specimens are degreased with organic solvent (such as petrol or acetone). 5.2 The specimens are then treated in accordance with one of the methods described in5.2.1 or5.2.2. 5.2.1 Specimens are immersed for 2min to 5min in sodium hydroxide solution 5% (m/m) to 10% (m/m) at a temperature of 50C to
33、60C, washed in running water, immersed for 2min in concentrated nitric acid (r = 1,4g/ml) for desmutting, rinsed in running water and then in distilled water, and dried. 5.2.2 Specimens are immersed for 1min in a solution containing 50ml of nitric acid (r = 1,4g/ml) and 5ml of hydrofluoric acid (r =
34、 1,15g/ml) per litre, at a solution temperature of 95C 2C. They are then rinsed in running water, immersed for2minutes in concentrated nitric acid (r = 1,4g/ml) for desmutting at room temperature, rinsed in running water and then in distilled water, and dried. 6 Tests 6.1 Naturally aged alloys are t
35、ested not earlier than24h after quenching. Artificially aged alloys may be tested by this method at any time. 6.2 Tests are carried out according to one of the methods described in6.2.1 to6.2.3. 6.2.1 Method A, used to determine quenching quality. Specimens are immersed for 6h in a solution containi
36、ng 57g/l1g/l of sodium chloride and10ml1ml of hydrogen peroxide 30% (V/V) at a temperature of 30C 3C. After testing, the specimens are rinsed in running water and are allowed to dry. Corrosion products may be removed with a non-metallic brush during rinsing and/or preferrably dipping in concentrated
37、 nitric acid 70% (m/m) HNO 3 , p = 1,4g/ml for only a few minutes just sufficient to dissolve corrosion products, followed by rinsing thoroughly with tap water. (See ISO8407.) 6.2.2 Method B, used to compare the intergranular corrosion resistance of various solution heat-treatable aluminium alloys,
38、depending on chemical composition and heat treatment. Specimens are immersed for 24h in a solution containing 30g/l sodium chloride and 10ml1ml of concentrated hydrochloric acid (r = 1,19g/ml) at room temperature. After testing, the specimens are rinsed in running water and then in distilled water a
39、nd are allowed to dry. Corrosion products may be removed with a non-metallic brush during rinsing and/or preferrably dipping in concentrated nitric acid 70% (m/m) HNO 3 , r = 1,4g/ml for only a few minutes just sufficient to dissolve corrosion products, followed by rinsing thoroughly with tap water.
40、 (SeeISO8407.) 6.2.3 Method C, used to estimate the sensitivity of aluminium-lithium alloys to intergranular corrosion. The principle involves anodic polarization of specimens in sodium chloride solution up to the potential at which the alloy shows intergranular corrosion susceptibility and to the e
41、xposure at this potential (E icc ). (SeeFigure 1.) NOTE 2Method C can also be used for other alloy systems. Tests are carried out in a thermostatically controlled electrochemical cell (which includes test, auxiliary, and reference electrodes). The test solution is 0,01 % (m/m) sodium chloride. A pot
42、entiostat is used to polarize the test electrode at controlled scan rates and at the E iccpotential. The test electrode is a specimen with a mechanically or electrochemically polished surface area of 1 cm 2 . The auxiliary electrode is a platinum electrode, and the reference electrode is either calo
43、mel or silver/silver chloride. First, the anodic polarization curve is plotted for one specimen by scanning the potential from a cathodic value of E = 1,16 V at a scan rate of 0,6 V/h to the pitting potential, E pf . (The pitting potential is a potential at which the density of current is increased
44、by at least one order in the process of anodic polarization.) Another specimen is then immersed in the same cell, allowed to rest for 5min, and the potential moved to E icc= E pf+ 20 mV Exposure at this potential is continued as follows: for copper-containing alloys: 15min 1min; for copper-free allo
45、ys: 90min5min. After the tests the specimens are taken out of the cell, washed in distilled water, dried and metallographically examined. 6.3 Solutions are prepared using distilled or deionized water with a conductivity not greater than 10 S/cm (seeISO3696) just before testing. To prepare the soluti
46、ons, analytical grades of chemicals are used.BSEN ISO11846:2008 3 6.4 The ratio of the solution volume to the total specimen area should be not less than 5 cm 3 /cm 2 . 6.5 The specimens are placed in the solution in such a way that they do not touch each other and the vessel walls. The solution lev
47、el above the specimens should be not less than 20mm above the upper edge, and it should be the same for all the specimens. It is not permissible to test specimens of different alloy systems in the same solution. 6.6 Tests are carried out in glass vessels or in vessels made from inert organic materia
48、ls. 7 Metallographic examination Each tested specimen is examined at 5 magnification, and the two zones with the most serious corrosion attack are marked. The sections are cut from these zones and are prepared for microscopic examination. The sections are taken normal to the largest surface of the t
49、ested specimen and should be taken far enough from the edges of the test specimen to avoid areas of edge corrosion attack. Cross-sections are examined by microscope in the unetched condition with magnifications of 100 to 500. If there is any uncertainty that the corrosion is truly intergranular, a light metallographic etch may be used to identify actual grain boundaries. 8 Interpretation of the results Interpretation o
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