1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS EN ISO 28706-4:2011Vitreous and porcelain enamels Determination of resistanceto chemical corrosionPart 4: Determination of resistance tochemical corrosion by alkaline liquids
2、usinga cylindrical vessel (ISO 28706-4:2008)Licensed Copy: Wang Bin, ISO/EXCHANGE CHINA STANDARDS, 22/09/2011 07:33, Uncontrolled Copy, (c) BSIBS EN ISO 28706-4:2011 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of EN ISO28706-4:2011. It is identical to ISO 28706-4:
3、2008. It supersedes BS EN14483-4:2004 which is withdrawn.The UK participation in its preparation was entrusted to TechnicalCommittee STI/36, Vitreous enamel coatings.A list of organizations represented on this committee can beobtained on request to its secretary.This publication does not purport to
4、include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. BSI 2011ISBN 978 0 580 72280 6ICS 25.220.50Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the authority of theStandards Poli
5、cy and Strategy Committee on 30 June 2011.Amendments issued since publicationDate Text affectedLicensed Copy: Wang Bin, ISO/EXCHANGE CHINA STANDARDS, 22/09/2011 07:33, Uncontrolled Copy, (c) BSIEUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN ISO 28706-4 May 2011 ICS 25.220.50 Supersedes EN 1448
6、3-4:2004English Version Vitreous and porcelain enamels - Determination of resistance to chemical corrosion - Part 4: Determination of resistance to chemical corrosion by alkaline liquids using a cylindrical vessel (ISO 28706-4:2008) maux vitrifis - Dtermination de la rsistance la corrosion chimique
7、- Partie 4: Dtermination de la rsistance la corrosion chimique par des liquides alcalins dans un rcipient cylindrique (ISO 28706-4:2008) Emails und Emaillierungen - Bestimmung der Bestndigkeit gegen chemische Korrosion - Teil 4: Bestimmung der Bestndigkeit gegen chemische Korrosion durch alkalische
8、Flssigkeiten unter Verwendung eines Gertes mit zylindrischem Gef (ISO 28706-4:2008) This European Standard was approved by CEN on 15 April 2011. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a
9、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 Management Centre or to any CEN member. This European Standard exists in three official versions (English, French, German). A
10、 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 status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cypr
11、us, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION CO
12、MIT 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 reserved worldwide for CEN national Members. Ref. No. EN ISO 28706-4:2011: ELicensed Copy: Wang Bin, ISO/EXCHANGE CHINA ST
13、ANDARDS, 22/09/2011 07:33, Uncontrolled Copy, (c) BSIBS EN ISO 28706-4:2011EN ISO 28706-4:2011 (E) 3 Foreword The text of ISO 28706-4:2008 has been prepared by Technical Committee ISO/TC 107 “Metallic and other inorganic coatings” of the International Organization for Standardization (ISO) and has b
14、een taken over as EN ISO 28706-4:2011 by Technical Committee CEN/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 lates
15、t 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 document may be the subject of patent rights. CEN and/or CENELEC shall not be held responsible for identifying any or all
16、such patent rights. This document supersedes EN 14483-4:2004. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estoni
17、a, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. Endorsement notice The text of ISO 28706-4:2008 has been approved by CEN
18、 as a EN ISO 28706-4:2011 without any modification. Licensed Copy: Wang Bin, ISO/EXCHANGE CHINA STANDARDS, 22/09/2011 07:33, Uncontrolled Copy, (c) BSIBS EN ISO 28706-4:2011ISO 28706-4:2008(E) ISO 2008 All rights reserved iiiContents Page Foreword iv Introduction v 1 Scope . 1 2 Normative references
19、 . 1 3 Principle. 1 4 Reagents 2 5 Apparatus and material 2 6 Test specimens . 7 7 Procedure 7 8 Expression of results . 8 8.1 Total loss in mass per unit area 8 8.2 Corrosion rate . 8 9 Hot sodium hydroxide test 9 9.1 General. 9 9.2 Test solution, c(NaOH) = 0,1 mol/l. 9 9.3 Test temperature. 9 9.4
20、Duration of the test. 9 9.5 Test report . 9 10 Other test solutions 10 10.1 General. 10 10.2 Test solution 10 10.3 Test temperature. 10 10.4 Duration of the test. 10 10.5 Test report . 10 Bibliography . 11 Licensed Copy: Wang Bin, ISO/EXCHANGE CHINA STANDARDS, 22/09/2011 07:33, Uncontrolled Copy, (c
21、) BSIBS EN ISO 28706-4:2011ISO 28706-4:2008(E) iv ISO 2008 All rights 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 IS
22、O technical 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 c
23、losely with the International Electrotechnical Commission (IEC) on all 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. D
24、raft 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 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this do
25、cument may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 28706-4 was prepared by the European Committee for Standardization (CEN) (as EN 14483-4) and was adopted, under a special “fast-track procedure”, by Technical Committee IS
26、O/TC 107, Metallic and other inorganic coatings, in parallel with its approval by the ISO member bodies. It cancels and replaces ISO 2734:1997 and ISO 2745:1998, which have been technically revised. ISO 28706 consists of the following parts, under the general title Vitreous and porcelain enamels Det
27、ermination of resistance to chemical corrosion: 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 chemi
28、cal corrosion by alkaline liquids using 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, 22/09
29、/2011 07:33, Uncontrolled Copy, (c) BSIBS EN ISO 28706-4:2011ISO 28706-4:2008(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. Aft
30、er hydrolysis, it decomposes and forms silicic 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
31、 medium. The whole process results in a 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 s
32、eries of solutions can a scientifically 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 resulti
33、ng from the limited solubility of silica 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 atta
34、cked at 80 C. Silicates and most of the 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 (millimetr
35、es per year). b) At room temperature, in 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 ext
36、ent from the surface. Highly resistant enamels 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), the silica network of the enamel is being attacked, and silica as well as the other enam
37、el components are released into solution. 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 equi
38、pment also releases silica by acid 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 m
39、anner see 1) and linearly see 2) are: 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 influence
40、d by inhibition effects, and corrosion 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
41、 boiling acid, its concentration in 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, IS
42、O/EXCHANGE CHINA STANDARDS, 22/09/2011 07:33, Uncontrolled Copy, (c) BSIBS EN ISO 28706-4:2011ISO 28706-4:2008(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 tempe
43、ratures, with tests in the liquid phase 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 ch
44、emical reaction vessel). In addition, 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 (se
45、e Clause 10 of ISO 28706-5:2008) or 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 s
46、urface is leached and silica is dissolved 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
47、 raise pH-values to alkaline levels, 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 in
48、dicated. 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 the test report. h) For other acids (
49、see Clause 14 of ISO 28706-2:2008) and other alkaline solutions (see Clause 10 of ISO 28706-3:2008 and Clause 10 of ISO 28706-4:2008), it will also not be known if a linear corrosion rate will be reached during the test period. Calculation of the corrosion rate is therefore not included in the test reports of those parts of this International Standard. For vitreous enamels fired at temperatures below 700 C, the test parameters (media, temperatures and times) of this International Standard are not appropriate. For such enamels, fo
