SIST EN ISO 28706-3:2018

Vitreous and porcelain enamels - Determination of resistance to chemical corrosion - Part 3: Determination of resistance to chemical corrosion by alkaline liquids using a hexagonal vessel or a tetragonal glass bottle (ISO 28706-3:2017)

This document describes a test method for the determination of the resistance of vitreous and porcelain
enamelled articles to attack by alkaline liquids at temperatures between 25 °C and 95 °C. The apparatus
used is a hexagonal vessel in which six enamelled specimens or a tetragonal glass bottle in which four
enamelled specimens are simultaneously tested.
NOTE 1 The resistance to any alkaline liquid can be determined. However, the test method was originally used
for the determination of the resistance to hot detergent solutions, within the neutral and alkaline range, used for
washing textiles.
NOTE 2 Since detergents are continually subject to alterations in their composition, a standard test solution
is specified which, in respect to its alkalinity, wetting properties and complexing behaviour, can be considered
as a typical composition for the detergents present on the market. The pH value and alkalinity of the standard
test solution depend on the proportions of sodium tripolyphosphate, sodium carbonate and sodium perborate
present; sodium tripolyphosphate acts simultaneously as a complexing agent. The wetting properties of the
standard test solution are obtained by the addition of alkylsulfonate. A higher sodium perborate content is not
considered necessary since the effect of oxygen on enamel is unimportant and an increase in the perborate
content does not cause any significant alteration in the alkalinity of the standard test solution. The testing of
different enamels using this standard test solution and other test solutions (including 5 % sodium pyrophosphate
solution) has justified the use of this standard test solution for determining the resistance of enamels to hot
detergent solutions.

Emails und Emaillierungen - Bestimmung der Beständigkeit gegen chemische Korrosion - Teil 3: Bestimmung der Beständigkeit gegen chemische Korrosion durch alkalische Flüssigkeiten unter Verwendung eines Gerätes mit hexagonalem Gefäß oder einer tetragonalen Glasflasche (ISO 28706-3:2017)

Dieses Dokument legt ein Prüfverfahren zur Bestimmung der Beständigkeit von emaillierten Gegenständen gegen den Angriff alkalischer Flüssigkeiten bei Temperaturen zwischen 25 °C und 95 °C fest. Das verwendete Gerät ist ein hexagonales Gefäß, in dem sechs emaillierte Proben gleichzeitig geprüft werden können, oder eine tetragonale Glasflasche, in der vier emaillierte Proben gleichzeitig geprüft werden können.
ANMERKUNG 1 Die Beständigkeit gegen sämtliche alkalische Flüssigkeiten kann bestimmt werden. Das Prüfver-fahren wurde jedoch ursprünglich zur Bestimmung der Beständigkeit gegen heiße Waschmittellösungen im neutralen und alkalischen Bereich erarbeitet, die zum Waschen von Textilien verwendet werden.
ANMERKUNG 2 Da Waschmittel laufend Rezepturänderungen unterliegen, ist eine Standard-Prüflösung festgelegt worden, die hinsichtlich Alkalität, Benetzungsvermögen und Komplexbildungsverhalten als eine typische Rezeptur für die auf dem Markt befindlichen Waschmittel gelten kann. Der pH-Wert und die Alkalität der Standard-Prüflösung ergeben sich aus den vorhandenen Anteilen an Natriumtripolyphosphat, Natriumcarbonat und Natriumperborat; Natriumtripolyphosphat dient gleichzeitig als Komplexbildner. Das Benetzungsvermögen der Standard-Prüflösung wird durch den Zusatz von Alkylsulfonat erreicht. Ein höherer Gehalt an Natriumperborat wird nicht für notwendig gehalten, da die Wirkung von Sauerstoff auf Email unbedeutend ist und eine Erhöhung des Gehaltes an Perborat keine wesentliche Änderung der Alkalität der Standard-Prüflösung zur Folge hat. Die Prüfung verschiedener Emails mit dieser Standard-Prüflösung und anderen Prüflösungen (einschließlich Natriumpyrophosphat-Lösung mit einem Massenanteil von 5 %) rechtfertigt die Verwendung dieser Standard-Prüflösung zur Bestimmung der Beständigkeit von Emails gegen heiße Waschmittellösungen.

Émaux vitrifiés - Détermination de la résistance à la corrosion chimique - Partie 3: Détermination de la résistance à la corrosion chimique par des liquides alcalins dans un récipient hexagonal ou une bouteille en verre tétragonale (ISO 28706-3:2017)

ISO 28706-3:2017 spécifie une méthode d'essai permettant de déterminer la résistance d'articles en émail vitrifié à l'attaque par des liquides alcalins à des températures comprises entre 25 °C et 95 °C. L'appareillage utilisé est un récipient hexagonal dans lequel six éprouvettes émaillées sont soumises à essai simultanément ou une bouteille en verre tétragonale dans laquelle quatre éprouvettes émaillées sont soumises à essai simultanément.
NOTE 1    La résistance à n'importe quel liquide alcalin peut être déterminée. Toutefois, la méthode d'essai a été à l'origine utilisée pour la détermination de la résistance à des solutions chaudes de détergent, dans la gamme neutre et basique, utilisées pour le lavage des textiles.
NOTE 2    Étant donné que les détergents subissent continuellement des modifications dans leur composition, une solution d'essai normalisée est spécifiée qui, compte tenu de son alcalinité, de ses propriétés mouillantes et de son aptitude à agir comme complexant, peut être considérée comme une composition type des détergents actuellement sur le marché. La valeur du pH et l'alcalinité de la solution d'essai normalisée résultent des proportions de tripolyphosphate de sodium, de carbonate de sodium et de perborate de sodium présentes; le tripolyphosphate de sodium agit également comme complexant.  Les propriétés mouillantes de la solution d'essai normalisée sont obtenues par addition d'alkylsulfonate. Une teneur plus élevée en perborate de sodium n'est pas jugée nécessaire car l'effet de l'oxygène sur l'émail est sans importance et une augmentation de la teneur en perborate ne modifie pas de façon significative l'alcalinité de la solution d'essai normalisée. Des essais effectués sur différents émaux, en utilisant cette solution d'essai normalisée et d'autres solutions d'essai (y compris une solution à 5 % de pyrophosphate de sodium), ont justifié l'emploi de la solution d'essai normalisée pour déterminer la résistance des émaux aux solutions chaudes de détergent.

Steklasti in porcelanski emajli - Ugotavljanje odpornosti proti kemični koroziji - 3. del: Ugotavljanje odpornosti proti kemični koroziji z alkalnimi tekočinami z uporabo šesterokotne posode ali trikotne steklenice (ISO 28706-3:2017)

Ta dokument opisuje preskusno metodo za ugotavljanje odpornosti steklastih in porcelanskih emajliranih izdelkov na napade z alkalnimi tekočinami pri temperaturah od 25 °C do 95 °C. Uporabljena naprava je šesterokotna posoda za hkratno preskušanje šest emajliranih primerkov ali trikotna steklenica za hkratno preskušanje štirih emajliranih primerkov.
OPOMBA 1: Mogoče je določiti odpornost na vse vrste alkalnih tekočin, toda preskusna metoda je bila prvotno uporabljena v nevtralnem in alkalnem območju za ugotavljanje odpornosti proti vročim raztopinam detergentov, ki se uporabljajo za pranje tkanin.
OPOMBA 2: Ker se sestava detergentov nenehno spreminja, je določena standardna preskusna raztopina, ki se lahko glede na svojo alkalnost, vlažilne lastnosti in obnašanje med kompleksiranjem obravnava kot značilna sestava detergentov, ki so prisotni na trgu. Vrednost pH in alkalnost standardne preskusne raztopine sta odvisni od prisotnih deležev natrijevega tripolifosfata, natrijevega karbonata in natrijevega perborata; natrijev tripolifosfat sočasno deluje kot kompleksirajoči reagent. Vlažilne lastnosti standardne preskusne raztopine se pridobijo z dodajanjem alkilsulfonata. Višja vsebnost natrijevega perborata se ne obravnava kot nujna, saj je vpliv kisika na emajl nepomemben in povečana vsebnost perborata ne povzroča večjih sprememb pri alkalnosti standardne preskusne raztopine. Preskušanje različnih emajlov s standardno preskusno raztopino in drugimi preskusnimi raztopinami (vključno s 5-odstotno raztopino natrijevega pirofosfata) je upravičilo uporabo te standardne preskusne raztopine za določanje odpornosti emajlov proti vročim raztopinam detergentov.

General Information

• Status: Published
• Public Enquiry End Date: 02-Jan-2017
• Publication Date: 18-Mar-2018
• ICS: 25.220.50 - Enamels
• Technical Committee: IPKZ - Protection of metals against corrosion
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 01-Mar-2018
• Due Date: 06-May-2018
• Completion Date: 19-Mar-2018
• Ref Project: EN ISO 28706-3:2018 - Vitreous and porcelain enamels - Determination of resistance to chemical corrosion - Part 3: Determination of resistance to chemical corrosion by alkaline liquids using a hexagonal vessel or a tetragonal glass bottle (ISO 28706-3:2017)

Relations

• Replaces: SIST EN ISO 28706-3:2012 - Vitreous and porcelain enamels - Determination of resistance to chemical corrosion - Part 3: Determination of resistance to chemical corrosion by alkaline liquids using a hexagonal vessel (ISO 28706-3:2008)
• Effective Date: 01-Apr-2018
• Replaces: SIST EN ISO 28706-3:2012 - Vitreous and porcelain enamels - Determination of resistance to chemical corrosion - Part 3: Determination of resistance to chemical corrosion by alkaline liquids using a hexagonal vessel (ISO 28706-3:2008)
• Effective Date: 08-Jun-2022

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN ISO 28706-3:2018
01-april-2018
1DGRPHãþD
SIST EN ISO 28706-3:2012
6WHNODVWLLQSRUFHODQVNLHPDMOL8JRWDYOMDQMHRGSRUQRVWLSURWLNHPLþQLNRUR]LML
GHO8JRWDYOMDQMHRGSRUQRVWLSURWLNHPLþQLNRUR]LML]DONDOQLPLWHNRþLQDPL]
XSRUDERãHVWHURNRWQHSRVRGHDOLWULNRWQHVWHNOHQLFH,62
Vitreous and porcelain enamels - Determination of resistance to chemical corrosion -
Part 3: Determination of resistance to chemical corrosion by alkaline liquids using a
hexagonal vessel or a tetragonal glass bottle (ISO 28706-3:2017)
Emails und Emaillierungen - Bestimmung der Beständigkeit gegen chemische Korrosion
- Teil 3: Bestimmung der Beständigkeit gegen chemische Korrosion durch alkalische
Flüssigkeiten unter Verwendung eines Gerätes mit hexagonalem Gefäß oder einer
tetragonalen Glasflasche (ISO 28706-3:2017)
Émaux vitrifiés - Détermination de la résistance à la corrosion chimique - Partie 3:
Détermination de la résistance à la corrosion chimique par des liquides alcalins dans un
récipient hexagonal ou une bouteille en verre tétragonale (ISO 28706-3:2017)
Ta slovenski standard je istoveten z: EN ISO 28706-3:2018
ICS:
25.220.50 Emajlne prevleke Enamels
SIST EN ISO 28706-3:2018 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 28706-3:2018

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SIST EN ISO 28706-3:2018


EN ISO 28706-3
EUROPEAN STANDARD

NORME EUROPÉENNE

February 2018
EUROPÄISCHE NORM
ICS 25.220.50 Supersedes EN ISO 28706-3:2011
English Version

Vitreous and porcelain enamels - Determination of
resistance to chemical corrosion - Part 3: Determination of
resistance to chemical corrosion by alkaline liquids using a
hexagonal vessel or a tetragonal glass bottle (ISO 28706-
3:2017)
Émaux vitrifiés - Détermination de la résistance à la Emails und Emaillierungen - Bestimmung der
corrosion chimique - Partie 3: Détermination de la Beständigkeit gegen chemische Korrosion - Teil 3:
résistance à la corrosion chimique par des liquides Bestimmung der Beständigkeit gegen chemische
alcalins dans un récipient hexagonal ou une bouteille Korrosion durch alkalische Flüssigkeiten unter
en verre tétragonale (ISO 28706-3:2017) Verwendung eines Gerätes mit hexagonalem Gefäß
oder einer tetragonalen Glasflasche (ISO 28706-
3:2017)
This European Standard was approved by CEN on 1 December 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-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
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, 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, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and United Kingdom.





EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2018 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 28706-3:2018 E
worldwide for CEN national Members.

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SIST EN ISO 28706-3:2018
EN ISO 28706-3:2018 (E)
Contents Page
European foreword . 3
2

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SIST EN ISO 28706-3:2018
EN ISO 28706-3:2018 (E)
European foreword
This document (EN ISO 28706-3:2018) 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, including for corrosion protection and corrosion testing of
metals and alloys” 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 August 2018, and conflicting national standards shall
be withdrawn at the latest by August 2018.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 28706-3:2011.
According to the CEN-CENELEC Internal Regulations, the national standards organisations 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, Malta,
Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.
Endorsement notice
The text of ISO 28706-3:2017 has been approved by CEN as EN ISO 28706-3:2018 without any
modification.


3

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SIST EN ISO 28706-3:2018

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SIST EN ISO 28706-3:2018
INTERNATIONAL ISO
STANDARD 28706-3
Second edition
2017-11
Vitreous and porcelain enamels —
Determination of resistance to
chemical corrosion —
Part 3:
Determination of resistance to
chemical corrosion by alkaline
liquids using a hexagonal vessel or a
tetragonal glass bottle
Émaux vitrifiés — Détermination de la résistance à la corrosion
chimique —
Partie 3: Détermination de la résistance à la corrosion chimique par
des liquides alcalins dans un récipient hexagonal ou une bouteille en
verre tétragonale
Reference number
ISO 28706-3:2017(E)
©
ISO 2017

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SIST EN ISO 28706-3:2018
ISO 28706-3:2017(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2017, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. [phone]
Fax [phone]
[e-mail]
www.iso.org
ii © ISO 2017 – All rights reserved

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SIST EN ISO 28706-3:2018
ISO 28706-3:2017(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Reagents . 2
6 Apparatus and materials. 2
7 Test specimens. 9
8 Procedure. 9
8.1 General . 9
8.2 Hexagonal vessel . 9
8.3 Tetragonal glass bottle .10
9 Expression of results .10
10 Standard detergent solution test .10
10.1 General .10
10.2 Test solution .11
10.3 Test temperature .11
10.4 Duration of the test .11
10.5 Test report .11
11 Other test solutions and/or conditions .12
11.1 General .12
11.2 Test solution .12
11.3 Test temperature .12
11.4 Duration of the test .12
11.5 Test report .12
Bibliography .13
© ISO 2017 – All rights reserved iii

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SIST EN ISO 28706-3:2018
ISO 28706-3:2017(E)

Foreword
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 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 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 approval 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 the 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).
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 ISO's 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 the first edition (ISO 28706-3:2008), which has been
technically revised.
A list of all parts in the ISO 28706 series can be found on the ISO website.
iv © ISO 2017 – All rights reserved

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SIST EN ISO 28706-3:2018
ISO 28706-3:2017(E)

Introduction
Corrosion of vitreous and porcelain enamels by aqueous solutions is a dissolution process. The
main component of the enamel, SiO , forms a three-dimensional silica network. After hydrolysis, it
2
decomposes and forms silicic acid or silicates. These are released into the attacking medium. Other
components, mainly metal oxides, are hydrolyzed 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;
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
2
area (g/m ⋅h) 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 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 ISO 28706-4:2016, Clause 9), the silica
network of the enamel is considerably attacked at 80 °C. Silicates and most of the other hydrolyzed
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 weak aqueous acids like citric acid (see ISO 28706-1:2008, Clause 9) or also
in stronger acids like sulfuric acid (see ISO 28706-1:2008, Clause 10), 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 (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 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
specimen 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 ISO 28706-2:2017, Clause 11) and boiling 30 % sulfuric acid (see
ISO 28706-2:2017, Clause 12)
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 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 ISO 28706-2:2017, Clause 13)
Since this is an azeotropic 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
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).
© ISO 2017 – All rights reserved v

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SIST EN ISO 28706-3:2018
ISO 28706-3:2017(E)

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 (similar 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 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 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 ISO 28706-2:2017, Clause 14), the silica network is fairly stable. 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 enamel being tested is weak, leached alkali from the
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 terms of loss in mass
per unit area, and the test time should be indicated.
g) For standard detergent solution (see Clause 10), 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 (see ISO 28706-2:2017, Clause 16) and other alkaline solutions (see Clause 11 and
ISO 28706-4:2016, Clause 11), it will also not be known if a linear corrosion rate will be reached
during the test period. Calculation of the corrosion rate is therefo
...

SLOVENSKI STANDARD
oSIST prEN ISO 28706-3:2016
01-december-2016
6WHNODVWLLQSRUFHODQVNLHPDMOL8JRWDYOMDQMHRGSRUQRVWLSURWLNHPLþQLNRUR]LML
GHO8JRWDYOMDQMHRGSRUQRVWLSURWLNHPLþQLNRUR]LML]DONDOQLPLWHNRþLQDPL]
XSRUDERãHVWHURNRWQHSRVRGHDOLWULNRWQHVWHNOHQLFH,62',6
Vitreous and porcelain enamels - Determination of resistance to chemical corrosion -
Part 3: Determination of resistance to chemical corrosion by alkaline liquids using a
hexagonal vessel or a tetragonal glass bottle (ISO/DIS 28706-3:2016)
Emails und Emaillierungen - Bestimmung der Beständigkeit gegen chemische Korrosion
- Teil 3: Bestimmung der Beständigkeit gegen chemische Korrosion durch alkalische
Flüssigkeiten unter Verwendung eines Gerätes mit hexagonalem Gefäß oder einer
tetragonalen Glasflasche (ISO/DIS 28706-3:2016)
e: Émaux vitrifiés - Détermination de la résistance à la corrosion chimique - Partie 3:
Détermination de la résistance à la corrosion chimique par des liquides alcalins dans un
récipient hexagonal ou une bouteille en verre tétragonale (ISO/DIS 28706-3:2016)
Ta slovenski standard je istoveten z: prEN ISO 28706-3
ICS:
25.220.50 Emajlne prevleke Enamels
oSIST prEN ISO 28706-3:2016 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
oSIST prEN ISO 28706-3:2016

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oSIST prEN ISO 28706-3:2016
DRAFT INTERNATIONAL STANDARD
ISO/DIS 28706-3
ISO/TC 107 Secretariat: KATS
Voting begins on: Voting terminates on:
2016-11-01 2017-01-23
Vitreous and porcelain enamels — Determination of
resistance to chemical corrosion —
Part 3:
Determination of resistance to chemical corrosion by
alkaline liquids using a hexagonal vessel or a tetragonal
glass bottle
Émaux vitrifiés — Détermination de la résistance à la corrosion chimique —
Partie 3: Détermination de la résistance à la corrosion chimique par des liquides alcalins dans un récipient
hexagonal ou une bouteille en verre tétragonale
ICS: 25.220.50
THIS DOCUMENT IS A DRAFT CIRCULATED
This document is circulated as received from the committee secretariat.
FOR COMMENT AND APPROVAL. IT IS
THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
ISO/CEN PARALLEL PROCESSING
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
BE CONSIDERED IN THE LIGHT OF THEIR
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NATIONAL REGULATIONS.
ISO/DIS 28706-3:2016(E)
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COPYRIGHT PROTECTED DOCUMENT
© ISO 2016, Published in Switzerland
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Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Principle . 2
4 Reagents . 2
5 Apparatus and materials. 2
6 Test specimens. 9
7 Procedure. 9
7.1 General . 9
7.2 Hexagonal vessel . 9
7.3 Tetragonal glass bottle .10
8 Expression of results .10
9 Standard detergent solution test .10
9.1 General .10
9.2 Test solution .11
9.3 Test temperature .11
9.4 Duration of the test .11
9.5 Test report .11
10 Other test solutions and/or conditions .12
10.1 General .12
10.2 Test solution .12
10.3 Test temperature .12
10.4 Duration of the test .12
10.5 Test report .12
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Foreword
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 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 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 approval 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 the 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).
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 meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical
Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information
ISO 28706-3 was prepared by Technical Committee ISO/TC 107, Metallic and other inorganic coatings .
This second cancels and replaces the first edition (ISO 28706-3:2008), which has been technically
revised.
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 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 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
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Introduction
Corrosion of vitreous and porcelain enamels by aqueous solutions is a dissolution process. The
main component of the enamel, SiO , forms a three-dimensional silica network. After hydrolysis, it
2
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 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 series of solutions can a scientifically exact rate of loss in mass per unit
2
area (g/m ⋅h) 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 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 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 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 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 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 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 specimen 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 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 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 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,
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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 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 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 28706-5:2008), artificial test solutions
(see 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
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 enamel being tested is weak, leached alkali from the
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 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 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. 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, 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.
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oSIST prEN ISO 28706-3:2016
DRAFT INTERNATIONAL STANDARD ISO/DIS 28706-3:2016(E)
Vitreous and porcelain enamels — Determination of
resistance to chemical corrosion —
Part 3:
Determination of resistance to chemical corrosion by
alkaline liquids using a hexagonal vessel or a tetragonal
glass bottle
1 Scope
This part of ISO 28706 describes a test method for the determination of the resistance of vitreous and
porcel
...