BS EN ISO 28706-5-2011 Vitreous and porcelain enamels Determination of resistance to chemical corrosion Determination of resistance to chemical corrosion in closed systems《釉瓷和搪瓷 耐化.pdf

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1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS EN ISO 28706-5:2011Vitreous and porcelain enamels Determination of resistanceto chemical corrosionPart 5: Determination of resistance tochemical corrosion in closed systems (I

2、SO28706-5:2010)BS EN ISO 28706-5:2011 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of EN ISO28706-5:2011. It is identical to ISO 28706-5:2010. It supersedes BS EN14483-5:2004 which is withdrawn.The UK participation in its preparation was entrusted to TechnicalCommi

3、ttee 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 include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. BSI 2011ISBN 978 0 580 7313

4、9 6ICS 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 July 2011.Amendments issued since publicationDate Text affectedEUROPEAN STANDARD NORME EUROPENNE

5、 EUROPISCHE NORM EN ISO 28706-5 July 2011 ICS 25.220.50 Supersedes EN 14483-5:2004English Version Vitreous and porcelain enamels - Determination of resistance to chemical corrosion - Part 5: Determination of resistance to chemical corrosion in closed systems (ISO 28706-5:2010) Emaux vitrifis - Dterm

6、ination de la rsistance la corrosion chimique - Partie 5: Dtermination de la rsistance la corrosion chimique en milieux ferms (ISO 28706-5:2010) Emails und Emaillierungen - Bestimmung der Bestndigkeit gegen chemische Korrosion - Teil 5: Bestimmung der Bestndigkeit gegen chemische Korrosion in geschl

7、ossenen Systemen (ISO 28706-5:2010) This European Standard was approved by CEN on 17 June 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 national standard without any alteration. Up-to-d

8、ate 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 translatio

9、n 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, Fr

10、ance, 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 COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE

11、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 28706-5:2011: EBS EN ISO 28706-5:2011EN ISO 28706-5:2011 (E) 3 Foreword The text of ISO 28706-5:2010 has been

12、prepared by Technical Committee ISO/TC 107 “Metallic and other inorganic coatings” of the International Organization for Standardization (ISO) and has been taken over as EN ISO 28706-5:2011 by Technical Committee CEN/TC 262 “Metallic and other inorganic coatings” the secretariat of which is held by

13、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 January 2012, and conflicting national standards shall be withdrawn at the latest by January 2012. Attention is drawn to the possibility that s

14、ome 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 14483-5:2004. According to the CEN/CENELEC Internal Regulations, the national standards organizations

15、of the following countries are 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, Ro

16、mania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. Endorsement notice The text of ISO 28706-5:2010 has been approved by CEN as a EN ISO 28706-5:2011 without any modification. BS EN ISO 28706-5:2011ISO 28706-5:2010(E) ISO 2010 All rights reserved iiiContents Page Foreword i

17、v Introduction.v 1 Scope1 2 Normative references1 3 Principle1 4 Apparatus.2 5 Test specimens3 6 Procedure.3 7 Expression of results4 8 Autoclave test with hydrochloric acid.5 9 Test with hot sodium hydroxide solution .6 10 Tests with simulated solutions 7 11 Tests with process fluids7 Annex A (info

18、rmative) Explanatory notes.9 Bibliography11 BS EN ISO 28706-5:2011ISO 28706-5:2010(E) iv ISO 2010 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 Stand

19、ards is normally carried out 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 ta

20、ke part in the work. ISO collaborates closely 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 i

21、s to prepare International Standards. 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 % of the member bodies casting a vote. Attention is drawn to the possibili

22、ty 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. ISO 28706-5 was prepared by Technical Committee ISO/TC 107, Metallic and other inorganic coatings. This second edition cancels and repla

23、ces the first edition (ISO 28706-5:2008), of which it constitutes a technical revision. ISO 28706 consists of the following parts, under the general title Vitreous and porcelain enamels Determination of resistance to chemical corrosion: Part 1: Determination of resistance to chemical corrosion by ac

24、ids 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 a hexagonal vessel Part 4: Determination of resistance to chemical corr

25、osion by alkaline liquids using a cylindrical vessel Part 5: Determination of resistance to chemical corrosion in closed systems BS EN ISO 28706-5:2011ISO 28706-5:2010(E) ISO 2010 All rights reserved vIntroduction Corrosion of vitreous and porcelain enamels by aqueous solutions is a dissolution proc

26、ess. The main component of the enamel, silicon dioxide (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 hydrolysed as well and form the corre

27、sponding 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; for other aqueous solution

28、s, 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/m2), as well as a corrosion rate (mm/year), be calculated. The most important parameters influencing aqueous

29、 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 conditions. a) In aqueous alkali solutions

30、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 other hydrolysed components are soluble in the alkali. Attack proceeds linearly during regular test times. Therefore, test results are expressed in term

31、s 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 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)

32、, there is only minor attack on the 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 enamels, some staining or surface roughening will occur. c) In boiling aqueous acids

33、 (see ISO 28706-2), the silica network of the enamel is being attacked, 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 dissolved silica and will then only leach

34、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 effectively prevented in vapour phase tests. The condensate formed on the test speci

35、men is free of any dissolved enamel constituents. Examples of enamel corrosion proceeding in a logarithmic manner see 1) and linearly see 2) are as follows. 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

36、 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 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 uni

37、t area is calculated. BS EN ISO 28706-5:2011ISO 28706-5:2010(E) vi ISO 2010 All rights reserved2) Boiling 20 % hydrochloric acid (see Clause 12 of ISO 28706-2:2008) Since this is an azeotropic boiling acid, its concentration in the liquid and the vapour phase are identical, and liquid phase testing

38、need not be performed. Vigorous boiling supplies an uninhibited condensate, and the attack proceeds linearly with time of exposure. Therefore, 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 yea

39、r). 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 of attacking acid to attacked enamel surface is chosen so that it is comparatively high (sim

40、ilar to that in a chemical-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 28706-5:2010), simulated

41、 test solutions (see Clause 10 of ISO 28706-5:2010) or process fluids (see Clause 11 of ISO 28706-5:2010) 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 s

42、table. The enamel surface 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 vitreous and porcelain enamel being tested i

43、s weak, leached alkali from the vitreous and porcelain enamel can 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 te

44、rms 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 i

45、s therefore not included in the test report. h) For other acids (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. Calcula

46、tion 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 part of ISO 28706 are not appropriate. For such enamels, for exa

47、mple 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. BS EN ISO 28706-5:2011INTERNATIONAL STANDARD ISO 28706-5:2010(E) ISO 201

48、0 All rights reserved 1Vitreous and porcelain enamels Determination of resistance to chemical corrosion Part 5: Determination of resistance to chemical corrosion in closed systems WARNING This part of ISO 28706 calls for the use of substances and/or procedures that may be injurious to health if adeq

49、uate safety measures are not taken. This part of ISO 28706 does not address any health hazards, safety or environmental matters associated with its use. It is the responsibility of the user of this part of ISO 28706 to establish appropriate health, safety and environmentally acceptable practices and take suitable actions for any national and international regulations. Compliance with this part of ISO 28706 does not in itself confer immunity from legal obligations. 1 Scope This part of ISO 28706 specifies a test method for the