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1、BRITISH STANDARD BS ISO 11846:1995 Implementation of ISO 11846:1995 Corrosion of metals and alloys Determination of resistance to intergranular corrosion of solution heat-treatable aluminium alloys ICS 77.060 Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 08:48:11 GMT+00:00 2006, Uncontrolle
2、d Copy, (c) BSI BS ISO 11846:1995 This British Standard, having been prepared under the direction of the Engineering Sector Board, was published under the authority of the Standards Board and comes into effect on 15 October 1996 BSI 11-1998 The following BSI references relate to the work on this sta
3、ndard: Committee reference ISE/NFE/8 Draft for comment 93/312931 DC ISBN 0 580 26046 1 Committees responsible for this British Standard The preparation of this British Standard was entrusted to Technical Committee ISE/NFE/8, Corrosion of metals and alloys, upon which the following bodies were repres
4、ented: AEA Technology Aluminium Federation British Gas plc British Non-Ferrous Metals Federation British Iron and Steel Producers Association Department of Trade and Industry (National Physical Laboratory) Department of Transport (Transport Research Laboratory) Electricity Association Institute of C
5、orrosion Ministry of Defence Society of Chemical Industry The Welding Institute Zinc Development Association Amendments issued since publication Amd. No.DateComments Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 08:48:11 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 11846:1995 BSI 11-19
6、98i Contents Page Committees responsible Inside front cover National forewordi Foreword iii Text of ISO 118461 Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 08:48:11 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 11846:1995 ii BSI 11-1998 National foreword This British Standard reproduce
7、s verbatim ISO 11846:1995 and implements it as the UK national standard. This British Standard is published under the direction of the Engineering Sector Board whose Technical Committee ISE/NFE/8 has the responsibility to: aid enquirers to understand the text; present to the responsible internationa
8、l committee any enquiries on interpretation, or proposals for change, and keep UK interests informed; monitor related international and European developments and promulgate them in the UK. NOTEInternational and European Standards, as well as overseas standards, are available from Customer Services,
9、BSI, 389 Chiswick High Road, London W4 4AL. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligation
10、s. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii the ISO title page, pages ii to iv, pages 1 to 4 and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment ta
11、ble on the inside front cover. Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 08:48:11 GMT+00:00 2006, Uncontrolled Copy, (c) BSI Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 08:48:11 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 11846:1995 ii Contents Forewordiii 1Scope1 2Norm
12、ative references 1 3Definitions1 4Test specimens1 5Surface preparation2 6Tests2 7Metallographic examination3 8Interpretation of the results3 9Test report3 Annex A (informative) Bibliography4 Figure 1 Typical anodic polarization curve3 Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 08:48:11 G
13、MT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 11846:1995 BSI 11-1998iii 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 t
14、echnical 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, in liaison with ISO, also take part in the work. ISO collaborates clos
15、ely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75
16、 % of the member bodies casting a vote. International Standard ISO 11846 was prepared by Technical Committee ISO/TC 156, Corrosion of metals and alloys. Annex A of this International Standard is for information only. Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 08:48:11 GMT+00:00 2006, Unc
17、ontrolled Copy, (c) BSI iv blank Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 08:48:11 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 11846:1995 BSI 11-19981 1 Scope 1.1 This International Standard specifies the methods of integranular corrosion testing for solution heat-treatable alumi
18、nium 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 heat treatment, quench treatment and artificial precipitation hardening (ageing) treatmen
19、t. 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 temperature range. 1.2 This International Standard is applicable to cast and wrought heat-treatab
20、le 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 depending on their chemical composition and other factors, and also to check the thermal pro
21、cessing 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 cannot be regarded as absolute, because they are not applicable to all environments that can
22、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 standards contain provisions which, through reference in this text, constitute provisions o
23、f 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 to investigate the possibility of applying the most recent editions of the standards indi
24、cated below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO 3696:1987, Water for analytical laboratory use Specification and test methods. ISO 8044:1989, Corrosion of metals and alloys Vocabulary. ISO 8407:1991, Corrosion of metals and alloys Removal of cor
25、rosion products from corrosion test specimens. 3 Definitions For the purposes of this International Standard, the definitions given in ISO 8044 apply. 4 Test specimens 4.1 Sampling Sampling should be carried out in such a manner as to provide specimens from the most typical areas of the material or
26、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 are quenched in baskets, the samples are taken from the central part of the basket. If
27、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 the lower and upper ends. If there are no differences in the cooling conditions, the sa
28、mples 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 and surface requirements Specimens can have arbitrary configuration and dimensions, bu
29、t they should be similar for repetitive tests. The specimen surface area should be between 4 cm2 and 20 cm2. Flat specimens should be cut in such a way that the longer dimension is parallel to the metal working direction. The specimen surface should maintain the initial condition of the material or
30、finished part, or it should be machined in such a way that the surface roughness Ra is 2,5 m. Specimens with surface defects (metallurgical or mechanical) should not be tested. Specimens from clad materials are tested without cladding. The cladding layer is removed from both sides by machining or ch
31、emical etching. Etching is carried out in the solutions for dimensional chemical etching or according to 5.2.1. To be certain that all cladding has been removed, it is necessary to remove 0,1 mm more than the thickness of the cladding. NOTE 1Specimen heating to above 60 C during machining is not per
32、mitted. Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 08:48:11 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 11846:1995 2 BSI 11-1998 Tests should be carried out on not less than three specimens having the same configuration, dimensions and surface preparation. 5 Surface preparation 5.1
33、 Before testing, 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 in 5.2.1 or 5.2.2. 5.2.1 Specimens are immersed for 2 min to 5 min in sodium hydroxide solution 5 % (m/m) to 10 % (m/m) at a t
34、emperature of 50 C to 60 C, washed in running water, immersed for 2 min in concentrated nitric acid (r = 1,4 g/ml) for desmutting, rinsed in running water and then in distilled water, and dried. 5.2.2 Specimens are immersed for 1 min in a solution containing 50 ml of nitric acid (r = 1,4 g/ml) and 5
35、 ml of hydrofluoric acid (r = 1,15 g/ml) per litre, at a solution temperature of 95 C 2 C. They are then rinsed in running water, immersed for 2 minutes in concentrated nitric acid (r = 1,4 g/ml) for desmutting at room temperature, rinsed in running water and then in distilled water, and dried. 6 Te
36、sts 6.1 Naturally aged alloys are tested not earlier than 24 h 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 in 6.2.1 to 6.2.3. 6.2.1 Method A, used to determine quenching quality. Specimens are
37、 immersed for 6 h in a solution containing 57 g/l 1 g/l of sodium chloride and 10 ml 1 ml of hydrogen peroxide 30 % (V/V) at a temperature of 30 C 3 C. 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
38、rinsing and/or preferrably dipping in concentrated nitric acid 70 % (m/m) HNO3, p = 1,4 g/ml for only a few minutes just sufficient to dissolve corrosion products, followed by rinsing thoroughly with tap water. (See ISO 8407.) 6.2.2 Method B, used to compare the intergranular corrosion resistance of
39、 various solution heat-treatable aluminium alloys, depending on chemical composition and heat treatment. Specimens are immersed for 24 h in a solution containing 30 g/l sodium chloride and 10 ml 1 ml of concentrated hydrochloric acid (r = 1,19 g/ml) at room temperature. After testing, the specimens
40、are rinsed in running water and then in distilled water and 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) HNO3, r = 1,4 g/ml for only a few minutes just sufficient to dissolve corrosion
41、 products, followed by rinsing thoroughly with tap water. (See ISO 8407.) 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 allo
42、y shows intergranular corrosion susceptibility and to the exposure at this potential (Eicc). (See Figure 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)
43、. The test solution is 0,01 % (m/m) sodium chloride. A potentiostat is used to polarize the test electrode at controlled scan rates and at the Eicc potential. The test electrode is a specimen with a mechanically or electrochemically polished surface area of 1 cm2. The auxiliary electrode is a platin
44、um electrode, and the reference electrode is either calomel 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, Epf. (The pitting potential is a p
45、otential at which the density of current is increased by at least one order in the process of anodic polarization.) Another specimen is then immersed in the same cell, allowed to rest for 5 min, and the potential moved to Eicc = Epf + 20 mV Exposure at this potential is continued as follows: for cop
46、per-containing alloys: 15 min 1 min; for copper-free alloys: 90 min 5 min. 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
47、S/cm (see ISO 3696) just before testing. To prepare the solutions, analytical grades of chemicals are used. Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 08:48:11 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 11846:1995 BSI 11-19983 6.4 The ratio of the solution volume to the total spec
48、imen area should be not less than 5 cm3/cm2. 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 level above the specimens should be not less than 20 mm above the upper edge, and it should be the same for all the specimens.
49、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 materials. 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 tested specimen and should be taken far enough from th
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