1、BSI Standards PublicationBS EN ISO 28706-4:2016Vitreous and porcelain enamels Determination of resistanceto chemical corrosionPart 4: Determination of resistance tochemical corrosion by alkaline liquids usinga cylindrical vesselBS EN ISO 28706-4:2016 BRITISH STANDARDNational forewordThis British Sta
2、ndard is the UK implementation of EN ISO 28706-4:2016.It supersedes BS EN ISO 28706-4:2011 which is withdrawn.The UK participation in its preparation was entrusted to TechnicalCommittee STI/36, Vitreous enamel coatings.A list of organizations represented on this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 t
3、o its secretary.This publication does not purport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. The British Standards Institution 2016.Published by BSI Standards Limited 2016ISBN 978 0 580 86615 9ICS 25.220.50Compliance with a British Standar
4、d cannot confer immunity fromlegal obligations.This British Standard was published under the authority of theStandards Policy and Strategy Committee on 31 January 2016.Amendments/corrigenda issued since publicationDate T e x t a f f e c t e dEUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN ISO 2
5、8706-4 January 2016 ICS 25.220.50 Supersedes EN ISO 28706-4:2011English 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 28706-4:2016) maux vitrif
6、is - Dtermination de la rsistance la corrosion chimique - Partie 4: Dtermination de la rsistance la corrosion chimique par des liquides alcalins dans un rcipient cylindrique (ISO 28706-4:2016) Emails und Emaillierungen - Bestimmung der Bestndigkeit gegen chemische Korrosion - Teil 4: Bestimmung der
7、Bestndigkeit gegen chemische Korrosion durch alkalische Flssigkeiten unter Verwendung eines Gertes mit zylindrischem Gef (ISO 28706-4:2016) This European Standard was approved by CEN on 7 November 2015. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the con
8、ditions 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 Management Centre or to any CEN member. This European Standard exis
9、ts 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 status as the official versions. CEN members are the national sta
10、ndards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, S
11、lovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels 2016 CEN All rights of exploitation in any form and by any means reser
12、ved worldwide for CEN national Members. Ref. No. EN ISO 28706-4:2016 EBS EN ISO 28706-4:2016EN ISO 28706-4:2016 (E) 3 European foreword This document (EN ISO 28706-4:2016) has been prepared by Technical Committee ISO/TC 107 “Metallic and other inorganic coatings” in collaboration with Technical Comm
13、ittee 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 latest by July 2016, and conflicting national standards shal
14、l be withdrawn at the latest by July 2016. 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. This document supersedes EN ISO 28706-4:201
15、1. 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, Estonia, Finland, Former Yugoslav Republic of Macedonia, France,
16、Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom. Endorsement notice The text of ISO 28706-4:2016 has been approved by CEN as EN ISO 2
17、8706-4:2016 without any modification. BS EN ISO 28706-4:2016ISO 28706-4:2016(E)Foreword ivIntroduction v1 Scope . 12 Normative references 13 Principle 14 Reagents 25 Apparatus and material 26 Test specimens 77 Procedure. 78 Expression of results 88.1 Total loss in mass per unit area 88.2 Corrosion r
18、ate 89 Hot 0,1 mol/l sodium hydroxide test . 99.1 General . 99.2 Test solution, c(NaOH) = 0,1 mol/l 99.3 Test temperature . 99.4 Duration of the test . 99.5 Test report . 910 Hot 1,0 mol/l sodium hydroxide test 1010.1 General 1010.2 Test solution, c(NaOH) = 1,0 mol/l . 1010.3 Test temperature 1010.4
19、 Duration of the test 1010.5 Test report 1011 Other test solutions 1111.1 General 1111.2 Test solution . 1111.3 Test temperature 1111.4 Duration of the test 1111.5 Test report 11Bibliography .12 ISO 2016 All rights reserved iiiContents PageBS EN ISO 28706-4:2016ISO 28706-4:2016(E)ForewordISO (the In
20、ternational 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 which a technical committee h
21、as 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 matters of electrotechnical
22、 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 different types of ISO documents should be noted. This document was drafted in ac
23、cordance 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 shall not be held responsible for identifying any or all such patent rights. Deta
24、ils 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 is information given for the convenience of users and does not constitute an e
25、ndorsement.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) see the following URL: Foreword - Supplementary information.The committee re
26、sponsible for this document is ISO/TC 107, Metallic and other inorganic coatings.This third edition cancels and replaces the second edition (ISO 28706-4:2008), of which it constitutes a minor revision.ISO 28706 consists of the following parts, under the general title Vitreous and porcelain enamels D
27、etermination 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 che
28、mical 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 systemsiv ISO 2016 All rights reservedBS EN ISO 28706-4:2016ISO 28
29、706-4:2016(E)IntroductionCorrosion 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 silicic acid or silicates. These are released into the attac
30、king 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 loss in mass per unit area.For some aqueous solutions, the
31、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 exact rate of loss in mass per unit area (g/m2h) be calculat
32、ed 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 can also contribute. The following list describes different
33、types of enamel attack for different corrosion conditions:a) In aqueous alkali solutions like 0,1 mol/l NaOH (see Clause 9 of this part of ISO 28706), the silicanetwork of the enamel is considerably attacked at 80 C. Silicates and most of the other hydrolysedcomponents are soluble in the alkali. Att
34、ack 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 areaand time) and a corrosion rate (millimetres per year).b) At room temperature, in weak aqueous acids like citric acid (see ISO 28706-1:2008, C
35、lause 9) or alsoin stronger acids like sulfuric acid (see ISO 28706-1:2008, Clause 10), there is only minor attack onthe silica network of the enamel. Other constituents are leached to some extent from the surface.Highly resistant enamels will show no visual change after exposure. On less resistant
36、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, andsilica as well as the other enamel components are released into solution. However, the solubility ofsilica in acids is low. Soon, the attacking
37、 solutions will become saturated with dissolved silica andwill 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 attack and contributes to the inhibition of the corrosion.Inhibition is effecti
38、vely prevented in vapour phase tests. The condensate formed on the testspecimen is free of any dissolved enamel constituents.Examples of enamel corrosion proceeding in a logarithmic manner see 1) and linearly see 2) are:1) Boiling citric acid (see of ISO 28706-2:2008, Clause 10) and boiling 30 % sul
39、furic acid (seeISO 28706-2:2008, Clause 11)Since only minor amounts of these acids are found in their vapours, the test is restricted to theliquid phase. The attack is influenced by inhibition effects, and corrosion depends on the timeof exposure. Therefore, test results are expressed in terms of lo
40、ss in mass per unit area; no rateof loss in mass per unit area is calculated.2) Boiling 20 % hydrochloric acid (see ISO 28706-2:2008, Clause 12)Since this is an azeotropic boiling acid, its concentration in the liquid and the vapour phaseare identical, and liquid phase testing need not be performed.
41、 Vigorous boiling supplies anuninhibited condensate, and the attack proceeds linearly with time of exposure. Therefore, ISO 2016 All rights reserved vBS EN ISO 28706-4:2016ISO 28706-4:2016(E)test results are only expressed in terms of rate of loss in mass per unit area (mass loss per unit area and t
42、ime) and the corrosion rate (millimetres per year).d) At high temperatures, 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 ofattacking acid to attacked enamel surface is
43、 chosen so that it is comparatively high (similar to thatin a chemical reaction vessel). In addition, only low-silica water is used for the preparation of testsolutions. Under these conditions, attack will proceed linearly with time of exposure. Therefore,test results with 20 % hydrochloric acid (se
44、e ISO 28706-5:2010, Clause 8), artificial test solutions(see ISO 28706-5:2010, Clause 10) or process fluids (see ISO 28706-5:2010, Clause 11) are alsoexpressed 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 ISO 28706-2:2008, Clause 13)
45、, the silica network is fairly stable. The enamelsurface is leached and silica is dissolved only to a small extent. This type of attack is clearlyrepresented by the vapour phase attack. In the liquid phase, some inhibition can be observed withhighly resistant enamels. However, if the enamel being te
46、sted is weak, leached alkali from theenamel can raise pH-values to alkaline levels, thus increasing the attack by the liquid phase. Bothliquid 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 massp
47、er unit area, and the test time should be indicated.g) For standard detergent solution (see ISO 28706-3:2008, Clause 9), it will not be certain whether thelinear part of the corrosion curve will be reached during testing for 24 h or 168 h. Calculation of thecorrosion rate is therefore not included i
48、n the test report.h) For other acids (see ISO 28706-2:2008, Clause 14) and other alkaline solutions (see ISO 28706-3:2008, Clause 10 and Clause 11 of this part of ISO 28706), it will also not be known if a linear corrosion ratewill be reached during the test period. Calculation of the corrosion rate
49、 is therefore not included inthe 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 part of ISO 28706 are not appropriate. For such enamels, for example aluminium enamels, other media, temperatures and/or times should be used. This can be done following the procedures described in the clauses for “Other test solutions” in Parts 1, 2, 3 and 4 of this International Standard.vi ISO 2016 All rights reservedBS EN ISO 28
