EN ISO 28706-2-2017 en Vitreous and porcelain enamels - Determination of resistance to chemical corrosion - Part 2 Determination of resistance to chemical corrosion by boiling acid.pdf

1、BS EN ISO 28706-2:2017Vitreous and porcelain enamels Determination of resistanceto chemical corrosionPart 2: Determination of resistance tochemical corrosion by boiling acids, boilingneutral liquids, alkaline liquids and/or theirvapours (ISO 28706-2:2017)BSI Standards PublicationWB11885_BSI_Standard

2、Covs_2013_AW.indd 1 15/05/2013 15:06BS EN ISO 28706-2:2017 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of EN ISO28706-2:2017. It supersedes BS EN ISO 28706-2:2011 which is withdrawn.The UK participation in its preparation was entrusted to TechnicalCommittee STI/36

3、, Vitreous enamel coatings.A list of organizations represented on this committee can beobtained on request to 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 2017

4、. Published by BSI Standards Limited 2017ISBN 978 0 580 85101 8ICS 25.220.50Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the authority of theStandards Policy and Strategy Committee on 31 March 2017.Amendments/corrigenda iss

5、ued since publicationDate Text affectedEUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN ISO 28706-2 March 2017 ICS 25.220.50 Supersedes EN ISO 28706-2:2011English Version Vitreous and porcelain enamels - Determination of resistance to chemical corrosion - Part 2: Determination of resistance to c

6、hemical corrosion by boiling acids, boiling neutral liquids, alkaline liquids and/or their vapours (ISO 28706-2:2017) maux vitrifis - Dtermination de la rsistance la corrosion chimique - Partie 2: Dtermination de la rsistance la corrosion chimique par des acides bouillants, des liquides neutres boui

7、llants, ou des liquides alcalins et/ou leurs vapeurs (ISO 28706-2:2017) Emails und Emaillierungen - Bestimmung der Bestndigkeit gegen chemische Korrosion - Teil 2: Bestimmung der Bestndigkeit gegen chemische Korrosion durch kochende Suren, kochende neutrale Flssigkeiten, alkalische Flssigkeiten und/

8、oder deren Dmpfe (ISO 28706-2:2017) This European Standard was approved by CEN on 28 February 2017. 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 national standard without any alteration. Up-

9、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 version in any other language made by transl

10、ation 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, Cyprus, Czech Republic, Denmark, Estonia, Finland

11、, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom. EUROPEAN COMMITTEE FOR STANDARD

12、IZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels 2017 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN ISO 28706-2:2017 EBS EN ISO 28706-2:2017EN

13、ISO 28706-2:2017 (E) 3 European foreword This document (EN ISO 28706-2:2017) has been prepared by Technical Committee ISO/TC 107 “Metallic and other inorganic coatings“ in collaboration with Technical Committee CEN/TC 262 “Metallic and other inorganic coatings” the secretariat of which is held by BS

14、I. 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 September 2017 and conflicting national standards shall be withdrawn at the latest by September 2017. Attention is drawn to the possibility that

15、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 28706-2:2011. According to the CEN-CENELEC Internal Regulations, the national standards organizat

16、ions 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, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malt

17、a, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom. Endorsement notice The text of ISO 28706-2:2017 has been approved by CEN as EN ISO 28706-2:2017 without any modification. BS EN ISO 28706-2:2017ISO 28706-2:2017(E

18、)Foreword vIntroduction vi1 Scope . 12 Normative references 13 Terms and definitions . 14 Principle 25 Reagents 26 Apparatus and materials 36.1 Test apparatus . 36.2 Test materials . 87 Packing rings 87.1 General . 87.2 Packing A 87.3 Packing B 98 Test specimens 99 Procedure. 910 Expression of resul

19、ts .1010.1 Total loss in mass per unit area . 1010.2 Corrosion rate . 1011 Boiling citric acid 1111.1 General 1111.2 Test solution . 1111.3 Duration of the test 1111.4 Test report 1112 Boiling sulfuric acid .1112.1 General 1112.2 Test solution . 1112.3 Duration of the test 1212.4 Test report 1213 Bo

20、iling hydrochloric acid 1213.1 General 1213.2 Test solution . 1213.3 Duration of the test 1213.4 Test report 1314 Boiling distilled or demineralized water .1314.1 General 1314.2 Test solution . 1314.3 Duration of the test 1314.4 Test report 1415 Standard detergent solution .1415.1 General 1415.2 Tes

21、t solution . 1415.3 Test temperature 1515.4 Duration of the test 1515.5 Test report 1516 Other test solutions and/or conditions .1516.1 General 15 ISO 2017 All rights reserved iiiContents PageBS EN ISO 28706-2:2017ISO 28706-2:2017(E)16.2 Test solution . 1516.3 Duration of the test 1516.4 Test report

22、 16Bibliography .17iv ISO 2017 All rights reservedBS EN ISO 28706-2:2017ISO 28706-2:2017(E)ForewordISO (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 ou

23、t through ISO 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 co

24、llaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical 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 appr

25、oval criteria needed for the different types of ISO documents should be noted. This document was drafted in accordance 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 th

26、e subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details 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).

27、Any trade name used in this document is information given for the convenience of users and does not constitute an endorsement.For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISOs

28、 adherence to the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following URL: www .iso .org/ iso/ foreword .html.This document was prepared by Technical Committee ISO/TC 107, Metallic and other inorganic coatings.This second edition cancels and replaces

29、the first edition (ISO 28706-2:2008), which has been technically revised with changes as follows. This document can also be used to determine resistance to chemical corrosion using alkaline liquids. The title of this document has therefore been amended and a section on standard detergent solutions h

30、as been included. Additional reagents can be used for testing purposes and these have been included.A list of all parts in the ISO 28706 series can be found on the ISO website. ISO 2017 All rights reserved vBS EN ISO 28706-2:2017ISO 28706-2:2017(E)IntroductionCorrosion of vitreous and porcelain enam

31、els 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 attacking medium. Other components, mainly metal oxides, are hydrolyse

32、d 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 attack on the enamel proceeds linearly during the corrosion time;

33、 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 calculated as well as a corrosion rate (millimetres per year).The most im

34、portant 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 types of enamel attack for different corrosion condi

35、tions.a) In aqueous alkali solutions such as 0,1 mol/l NaOH (see ISO 28706-4:2016, Clause 9), the silicanetwork of the enamel is considerably attacked at 80 C. Silicates and most of the other hydrolysedcomponents are soluble in the alkali. Attack proceeds linearly during regular test times. Therefor

36、e,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 such as citric acid (see ISO 28706-1:2008, Clause 9) oralso in stronger acids such as sulfuric aci

37、d (see ISO 28706-1:2008, Clause 10), there is only minorattack on the silica network of the enamel. Other constituents are leached to some extent fromthe surface. Highly resistant enamels will show no visual change after exposure. On less resistantenamels, some staining or surface roughening will oc

38、cur.c) In boiling aqueous acids (as described in this document), the silica network of the enamel is beingattacked, and silica as well as the other enamel components are released into solution. However,the solubility of silica in acids is low. Soon, the attacking solutions will become saturated with

39、dissolved silica and will then only leach the surface. The acid attack is inhibited and the rate ofcorrosion drops markedly.NOTE The glass test equipment also releases silica by acid attack and contributes to the inhibition of the corrosion.Inhibition is effectively prevented in vapour phase tests.

40、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) areas follows:1) Boiling citric acid (see Clause 11) and boiling 30 % sulfuric acid (see Clause 12).Since only minute amou

41、nts of these acids are found in their vapours, the test is restricted tothe liquid phase. The attack is influenced by inhibition effects and corrosion depends on thetime 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

42、 calculated.2) Boiling 20 % hydrochloric acid (see Clause 13).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. Vigorous boiling supplies anuninhibited condensate, and the attack proceeds linea

43、rly with time of exposure. Therefore,vi ISO 2017 All rights reservedBS EN ISO 28706-2:2017ISO 28706-2:2017(E)test results are only expressed 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 t

44、ests 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 chosen so that it is comparatively high (similar to thatin a chemical reaction ve

45、ssel). 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 (see ISO 28706-5:2010, Clause 8), artificial test solutions(see ISO 28706-5:2010, Cla

46、use 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 Clause 14), the silica network is fairly stable. The enamel surface is leachedand silica is dissolved only to

47、a small extent. This type of attack is clearly represented by the vapourphase 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 toalkaline levels, thus increasing

48、the attack by the liquid phase. Both liquid and vapour phase testingcan give valuable information.f) Since the attack may or may not be linear, the results are expressed only in terms of loss in massper unit area and the test time should be indicated.g) For standard detergent solution (see ISO 28706

49、-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 in the test report.h) For other acids (see Clause 15) and other alkaline solutions (see ISO 28706-3:2008, Clause 10 andISO 28706-4:2016, Clause 10), it will also not be known if a linear corrosion rate will be reachedduring the test period. Calculation of the corrosion rate is therefore not included in the test reportsof those parts of this docume