1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS EN ISO 28706-2:2011Vitreous and porcelain enamels Determination of resistance to chemical corrosionPart 2: Determination of resistance to chemical corrosion by boiling acids,
2、boiling neutral liquids and/or their vapours (ISO 28706-2:2008)Licensed Copy: Wang Bin, ISO/EXCHANGE CHINA STANDARDS, 21/09/2011 09:18, Uncontrolled Copy, (c) BSIBS EN ISO 28706-2:2011 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of EN ISO 28706-2:2011. It is ident
3、ical to ISO 28706-2:2008. It supersedes BS EN 14483-2:2004, which is withdrawn.The UK participation in its preparation was entrusted to T e c h n i c a l C o m m i t t e e S T I / 3 6 , V i t r e o u s e n a m e l c o a t i n g s . A list of organizations represented on this committee can be obtaine
4、d 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. BSI 2011 ISBN 978 0 580 72278 3 ICS 25.220.50 Compliance with a British Standard cannot confer immunity from legal obligations.Thi
5、s British Standard was published under the authority of the Standards Policy and Strategy Committee on 30 June 2011.Amendments issued since publicationDate T e x t a f f e c t e dLicensed Copy: Wang Bin, ISO/EXCHANGE CHINA STANDARDS, 21/09/2011 09:18, Uncontrolled Copy, (c) BSIEUROPEAN STANDARD NORM
6、E EUROPENNE EUROPISCHE NORM EN ISO 28706-2 May 2011 ICS 25.220.50 Supersedes EN 14483-2:2004English Version Vitreous and porcelain enamels - Determination of resistance to chemical corrosion - Part 2: Determination of resistance to chemical corrosion by boiling acids, boiling neutral liquids and/or
7、their vapours (ISO 28706-2:2008) maux vitrifis - Dtermination de la rsistance la corrosion chimique - Partie 2: Dtermination de la rsistance la corrosion chimique par des acides bouillantsou des liquides neutres bouillants, et/ou leurs vapeurs (ISO 28706-2:2008) Emails und Emaillierungen - Bestimmun
8、g der Bestndigkeit gegen chemische Korrosion - Teil 2: Bestimmung der Bestndigkeit gegen chemische Korrosion durch kochende Suren, kochende neutrale Flssigkeiten und/oder deren Dmpfe (ISO 28706-2:2008) This European Standard was approved by CEN on 15 April 2011. CEN members are bound to comply with
9、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-CENELEC Managem
10、ent Centre 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-CENELEC Management Centre has the same statu
11、s as the official versions. CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
12、 Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG Management Centre: Avenue Marnix 17, B-1000 Brussels 2011 CEN All rights of exploitation in any form and by any means rese
13、rved worldwide for CEN national Members. Ref. No. EN ISO 28706-2:2011: ELicensed Copy: Wang Bin, ISO/EXCHANGE CHINA STANDARDS, 21/09/2011 09:18, Uncontrolled Copy, (c) BSIBS EN ISO 28706-2:2011 EN ISO 28706-2:2011 (E) 3 Foreword The text of ISO 28706-2:2008 has been prepared by Technical Committee I
14、SO/TC 107 “Metallic and other inorganic coatings” of the International Organization for Standardization (ISO) and has been taken over as EN ISO 28706-2:2011 by Technical Committee CEN/TC 262 “Metallic and other inorganic coatings” the secretariat of which is held by BSI. This European Standard shall
15、 be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by November 2011, and conflicting national standards shall be withdrawn at the latest by November 2011. Attention is drawn to the possibility that some of the elements of this doc
16、ument may be the subject of patent rights. CEN and/or CENELEC shall not be held responsible for identifying any or all such patent rights. This document supersedes EN 14483-2:2004. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are
17、bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spai
18、n, Sweden, Switzerland and the United Kingdom. Endorsement notice The text of ISO 28706-2:2008 has been approved by CEN as a EN ISO 28706-2:2011 without any modification. Licensed Copy: Wang Bin, ISO/EXCHANGE CHINA STANDARDS, 21/09/2011 09:18, Uncontrolled Copy, (c) BSIBS EN ISO 28706-2:2011ISO 2870
19、6-2:2008(E) ISO 2008 All rights reserved iiiContents Page Foreword iv Introduction v 1 Scope . 1 2 Normative references . 1 3 Principle. 1 4 Reagents 2 5 Apparatus and materials 2 6 Packing rings 7 6.1 General. 7 6.2 Packing A. 7 6.3 Packing B. 8 7 Test specimens . 8 8 Procedure 8 9 Expression of re
20、sults . 9 9.1 Total loss in mass per unit area 9 9.2 Corrosion rate . 9 10 Boiling citric acid 9 10.1 General. 9 10.2 Citric acid test solution 10 10.3 Duration of the test. 10 10.4 Test report . 10 11 Boiling sulfuric acid 10 11.1 General. 10 11.2 Test solution 10 11.3 Duration of the test. 10 11.4
21、 Test report . 11 12 Boiling hydrochloric acid. 11 12.1 General. 11 12.2 Test solution 11 12.3 Duration of the test. 11 12.4 Test report . 12 13 Boiling distilled or demineralized water. 12 13.1 General. 12 13.2 Test solution 12 13.3 Duration of the test. 12 13.4 Test report . 13 14 Other test solut
22、ions and/or conditions. 13 14.1 General. 13 14.2 Test solution 13 14.3 Duration of the test. 13 14.4 Test report . 14 Bibliography . 15 Licensed Copy: Wang Bin, ISO/EXCHANGE CHINA STANDARDS, 21/09/2011 09:18, Uncontrolled Copy, (c) BSIBS EN ISO 28706-2:2011ISO 28706-2:2008(E) iv ISO 2008 All rights
23、reservedForeword 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 member body interested in a subject for w
24、hich 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 Electrotechnical Commission (IEC) on all
25、 matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are c
26、irculated to the member bodies for voting. 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 document may be the subject of patent rights. ISO shall not be held resp
27、onsible for identifying any or all such patent rights. ISO 28706-2 was prepared by the European Committee for Standardization (CEN) (as EN 14483-2) and was adopted, under a special “fast-track procedure”, by Technical Committee ISO/TC 107, Metallic and other inorganic coatings, in parallel with its
28、approval by the ISO member bodies. It cancels and replaces ISO 2733:1983, ISO 2742:1998, ISO 2743:1986 and ISO 2744:1998, which have been technically revised. ISO 28706 consists of the following parts, under the general title Vitreous and porcelain enamels Determination of resistance to chemical cor
29、rosion: Part 1: Determination of resistance to chemical corrosion by acids at room temperature Part 2: Determination of resistance to chemical corrosion by boiling acids, boiling neutral liquids and/or their vapours Part 3: Determination of resistance to chemical corrosion by alkaline liquids using
30、a hexagonal vessel Part 4: Determination of resistance to chemical corrosion by alkaline liquids using a cylindrical vessel Part 5: Determination of resistance to chemical corrosion in closed systems Licensed Copy: Wang Bin, ISO/EXCHANGE CHINA STANDARDS, 21/09/2011 09:18, Uncontrolled Copy, (c) BSIB
31、S EN ISO 28706-2:2011ISO 28706-2:2008(E) ISO 2008 All rights reserved vIntroduction Corrosion of vitreous and porcelain enamels by aqueous solutions is a dissolution process. The main component of the enamel, SiO2, forms a three-dimensional silica network. After hydrolysis, it decomposes and forms s
32、ilicic acid or silicates. These are released into the attacking medium. Other components, mainly metal oxides, are hydrolysed as well and form the corresponding hydrated metal ions or hydroxides. All corrosion products are more or less soluble in the attacking medium. The whole process results in a
33、loss in mass per unit area. For some aqueous solutions, the attack on the enamel proceeds linearly during the corrosion time; for other aqueous solutions, the attack on the enamel proceeds in a logarithmic manner during the corrosion time. Only for the first series of solutions can a scientifically
34、exact rate of loss in mass per unit area (g/m2h) be calculated as well as a corrosion rate (mm/year). The most important parameters influencing aqueous corrosion of the enamel are the enamel quality, the temperature and the pH-value. Inhibition effects resulting from the limited solubility of silica
35、 can also contribute. The following list describes different types of enamel attack for different corrosion conditions: a) In aqueous alkali solutions like 0,1 mol/l NaOH (see Clause 9 of ISO 28706-4:2008), the silica network of the enamel is considerably attacked at 80 C. Silicates and most of the
36、other hydrolysed components are soluble in the alkali. Attack proceeds linearly during regular test times. Therefore, test results are expressed in terms of a rate of loss in mass per unit area (mass loss per unit area and time) and a corrosion rate (millimetres per year). b) At room temperature, in
37、 weak aqueous acids like citric acid (see Clause 9 of ISO 28706-1:2008) or also in stronger acids like sulfuric acid (see Clause 10 of ISO 28706-1:2008), there is only minor attack on the silica network of the enamel. Other constituents are leached to some extent from the surface. Highly resistant e
38、namels will show no visual change after exposure. On less resistant enamels, some staining or surface roughening will occur. c) In boiling aqueous acids (see ISO 28706-2:2008), the silica network of the enamel is being attacked, and silica as well as the other enamel components are released into sol
39、ution. However, the solubility of silica in acids is low. Soon, the attacking solutions will become saturated with dissolved silica and will then only leach the surface. The acid attack is inhibited and the rate of corrosion drops markedly. NOTE The glass test equipment also releases silica by acid
40、attack and contributes to the inhibition of the corrosion. Inhibition is effectively prevented in vapour phase tests. The condensate formed on the test specimen is free of any dissolved enamel constituents. Examples of enamel corrosion proceeding in a logarithmic manner see 1) and linearly see 2) ar
41、e: 1) Boiling citric acid (see Clause 10 of ISO 28706-2:2008) and boiling 30 % sulfuric acid (see Clause 11 of ISO 28706-2:2008) Since only minute amounts of these acids are found in their vapours, the test is restricted to the liquid phase. The attack is influenced by inhibition effects, and corros
42、ion depends on the time of exposure. Therefore, test results are expressed in terms of loss in mass per unit area; no rate of loss in mass per unit area is calculated. 2) Boiling 20 % hydrochloric acid (see Clause 12 of ISO 28706-2:2008) Since this is an azeotropic boiling acid, its concentration in
43、 the liquid and the vapour phase are identical, and liquid phase testing need not be performed. Vigorous boiling supplies an uninhibited condensate, and the attack proceeds linearly with time of exposure. Therefore, test results are only Licensed Copy: Wang Bin, ISO/EXCHANGE CHINA STANDARDS, 21/09/2
44、011 09:18, Uncontrolled Copy, (c) BSIBS EN ISO 28706-2:2011ISO 28706-2:2008(E) vi ISO 2008 All rights reservedexpressed in terms of rate of loss in mass per unit area (mass loss per unit area and time) and the corrosion rate (millimetres per year). d) At high temperatures, with tests in the liquid p
45、hase under autoclave conditions (see ISO 28706-5), aqueous acid attack is severe. To avoid inhibition, the test time is restricted to 24 h and the ratio of attacking acid to attacked enamel surface is chosen so that it is comparatively high (similar to that in a chemical reaction vessel). In additio
46、n, only low-silica water is used for the preparation of test solutions. Under these conditions, attack will proceed linearly with time of exposure. Therefore, test results with 20 % hydrochloric acid (see Clause 8 of ISO 28706-5:2008), artificial test solutions (see Clause 10 of ISO 28706-5:2008) or
47、 process fluids (see Clause 11 of ISO 28706-5:2008) are also expressed in terms of a rate of loss in mass per unit area (loss in mass per unit area and time). e) In boiling water (see Clause 13 of ISO 28706-2:2008), the silica network is fairly stable. The enamel surface is leached and silica is dis
48、solved only to a small extent. This type of attack is clearly represented by the vapour phase attack. In the liquid phase, some inhibition can be observed with highly resistant enamels. However, if the enamel being tested is weak, leached alkali from the enamel can raise pH-values to alkaline levels
49、, thus increasing the attack by the liquid phase. Both liquid and vapour phase testing can give valuable information. f) Since the attack may or may not be linear, the results are expressed only in terms of loss in mass per unit area, and the test time should be indicated. g) For standard detergent solution (see Clause 9 of ISO 28706-3:2008), it will not be certain whether the linear part of the corrosion curve will be reached during testing for 24 h or 168 h. Calculation of the corrosion rate is therefore not included in
