SIST EN ISO 28721-2:2025

Vitreous and porcelain enamels - Glass-lined apparatus for process plants - Part 2: Designation and specification of resistance to chemical attack and thermal shock (ISO 28721-2:2025)

This document specifies requirements for the resistance of chemical enamels to chemical attack and thermal shock, as well as their designation, for ordering purposes.
It is applicable to enamels used in glass-lined apparatus, piping and other components, primarily used in process equipment in chemical plants, which are applied on to low-alloy carbon steels substrates.
NOTE            The main criteria for assessing enamel quality are its resistance to chemical attack and thermal shock, and the structure of the cover coat enamel.

Emails und Emaillierungen - Emaillierte Apparate für verfahrenstechnische Anlagen - Teil 2: Bezeichnung und Festlegung der chemischen und Temperaturschockbeständigkeit (ISO 28721-2:2025)

Dieses Dokument legt die Anforderungen an die chemische Beständigkeit und die Temperaturschockbeständigkeit von Chemie-Emails sowie die zur Bestellung zu verwendende Bezeichnung fest.
Es ist anwendbar für Emails, die in emaillierten Apparaten, Rohrleitungen und sonstigen Bauteilen verwendet werden, die vorwiegend für verfahrenstechnische Ausrüstung in Chemie-Anlagen eingesetzt werden und auf niedriglegierten Kohlenstoffstahlsubstraten aufgebracht werden.
ANMERKUNG   Die wesentlichen Kriterien für die Beurteilung der EmaiIqualität sind dessen chemische Beständigkeit und Temperaturschockbeständigkeit sowie die Struktur der Deckemailschicht.
WARNUNG — Dieses Dokument fordert entweder die Verwendung von Stoffen oder von Verfahren oder beidem, die gesundheitsgefährdend sein können, wenn keine angemessenen Sicherheitsmaßnahmen ergriffen werden. Dieses Dokument behandelt keine Gesundheitsrisiken, Sicherheits- oder Umweltaspekte, die mit seiner Anwendung verbunden sind. Es liegt in der Verantwortung des Anwenders dieses Dokuments, vor der Verwendung geeignete Gesundheits-, Sicherheits- und Umweltpraktiken festzulegen und die Geltung regulatorischer Beschränkungen zu bestimmen.

Émaux vitrifiés - Appareils émaillés pour les installations industrielles - Partie 2: Désignation et spécifications de la résistance à l'attaque chimique et au choc thermique (ISO 28721-2:2025)

Le présent document définit les exigences relatives à la résistance des émaux chimiques à l’attaque chimique et au choc thermique ainsi que leur désignation à des fins de commande.
Il est applicable aux appareils, éléments de tuyauterie et autres composants émaillés, principalement utilisés pour l’équipement industriel dans les usines chimiques, qui sont appliqués sur des substrats en aciers au carbone faiblement alliés.
NOTE            Les principaux critères pour évaluer la qualité de l’émail sont la résistance à l’attaque chimique et au choc thermique, ainsi que la structure du revêtement émaillé.

Steklasti in keramični emajli - Emajlirane naprave za procesno opremo - 2. del: Označevanje in specifikacija odpornosti proti kemični agresiji in toplotnemu udaru (ISO 28721-2:2025)

Ta dokument določa zahteve za odpornost kemičnih emajlov proti kemični agresiji in toplotnemu udaru ter njihovo označevanje za namene odreditve.
Uporablja se za emajle, ki se uporabljajo v emajliranih napravah, ceveh in drugih komponentah za uporabo predvsem v procesni opremi v kemičnih tovarnah, ter se nanesejo na podlage iz malolegiranih ogljikovih jekel.
OPOMBA: Glavni merili za ocenjevanje kakovosti emajla sta odpornost proti kemični agresiji in toplotnemu udaru ter struktura premaznega emajla.

General Information

• Status: Published
• Public Enquiry End Date: 28-Dec-2023
• Publication Date: 03-Mar-2025
• ICS: 25.220.50 - Enamels
• Technical Committee: IPKZ - Protection of metals against corrosion
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 03-Mar-2025
• Due Date: 08-May-2025
• Completion Date: 04-Mar-2025
• Ref Project: EN ISO 28721-2:2025 - Vitreous and porcelain enamels - Glass-lined apparatus for process plants - Part 2: Designation and specification of resistance to chemical attack and thermal shock (ISO 28721-2:2025)

Relations

• Revises: SIST EN ISO 28721-2:2016 - Vitreous and porcelain enamels - Glass-lined apparatus for process plants - Part 2: Designation and specification of resistance to chemical attack and thermal shock (ISO 28721-2:2015)
• Effective Date: 17-May-2023

Overview

EN ISO 28721-2:2025 specifies how to designate and specify the resistance of vitreous and porcelain enamels used in glass-lined apparatus for process plants to chemical attack and thermal shock. Applicable to enamels applied on low-alloy carbon steel substrates, this standard sets minimum, test-based quality requirements used for ordering, acceptance and classification of enamel coatings for chemical process equipment.

Key topics and technical requirements

• Scope and purpose
  • Defines designation elements and minimum performance requirements for enamel resistance to chemical corrosion and thermal shock.
  • Intended for glass-lined apparatus, piping and associated components in chemical plants.
• Designation elements
  • Rate of corrosion in hydrochloric acid (condensing HCl vapour).
  • Rate of corrosion in sodium hydroxide solution (0.1 mol/L, 80 °C, 24 h).
  • Crack formation temperature (thermal shock characteristic).
  • Structure of cover coat (e.g., all‑vitreous, semicrystalline combinations).
  • Enamel colour.
  • Standard designation label: “Enamel quality requirements in accordance with ISO 28721-2.”
• Quantified quality requirements
  • Resistance to condensing hydrochloric acid vapour: ≤ 0.08 mm/year.
  • Corrosion rate in 0.1 mol/L NaOH at 80 °C (24 h): ≤ 0.40 mm/year (volume:surface ratio 20 cm3:1 cm2 per ISO 28706-4).
  • Crack formation temperature: ≥ 190 °C (minimum 170 °C permitted for accessories such as agitators, thermometer wells, pumps and piping accessories).
  • Note: crack formation temperature is a specimen characteristic determined per ISO 13807 and does not directly represent the assembled apparatus.
• Referenced test methods
  • ISO 28706-2 (corrosion by boiling acids/neutral liquids)
  • ISO 28706-4 (alkaline corrosion using cylindrical vessel)
  • ISO 13807 (thermal shock / crack formation temperature)

Applications and who uses this standard

• Manufacturers of glass-lined reactors, vessels, piping and pumps to specify enamel performance.
• Procurement and specification engineers in the chemical, pharmaceutical and process industries to ensure material compatibility and durability.
• Quality assurance, inspection bodies and testing laboratories performing acceptance tests and verification.
• Designers and maintenance teams selecting enamel types for corrosion resistance and thermal-shock resilience.

Related standards

• ISO 28721 series (glass-lined apparatus)
• ISO 28721-3 (thermal shock resistance)
• ISO 28706-2, ISO 28706-4, ISO 13807 (test methods)
• EN adoption: CEN has endorsed ISO 28721-2:2025 as EN ISO 28721-2:2025.

EN ISO 28721-2:2025 is a practical reference for specifying and verifying enamel coating performance where corrosion resistance and thermal stability are critical to safe, long-lasting process equipment.

Standards Content (Sample)

SLOVENSKI STANDARD
01-april-2025
Steklasti in keramični emajli - Emajlirane naprave za procesno opremo - 2. del:
Označevanje in specifikacija odpornosti proti kemični agresiji in toplotnemu udaru
(ISO 28721-2:2025)
Vitreous and porcelain enamels - Glass-lined apparatus for process plants - Part 2:
Designation and specification of resistance to chemical attack and thermal shock (ISO
28721-2:2025)
Emails und Emaillierungen - Emaillierte Apparate für verfahrenstechnische Anlagen -
Teil 2: Bezeichnung und Festlegung der chemischen und
Temperaturschockbeständigkeit (ISO 28721-2:2025)
Émaux vitrifiés - Appareils émaillés pour les installations industrielles - Partie 2:
Désignation et spécifications de la résistance à l'attaque chimique et au choc thermique
(ISO 28721-2:2025)
Ta slovenski standard je istoveten z: EN ISO 28721-2:2025
ICS:
25.220.50 Emajlne prevleke Enamels
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 28721-2
EUROPEAN STANDARD
NORME EUROPÉENNE
February 2025
EUROPÄISCHE NORM
ICS 25.220.50 Supersedes EN ISO 28721-2:2015
English Version
Vitreous and porcelain enamels - Glass-lined apparatus for
process plants - Part 2: Designation and specification of
resistance to chemical attack and thermal shock (ISO
28721-2:2025)
Émaux vitrifiés - Appareils émaillés pour les Emails und Emaillierungen - Emaillierte Apparate für
installations industrielles - Partie 2: Désignation et verfahrenstechnische Anlagen - Teil 2: Bezeichnung
spécifications de la résistance à l'attaque chimique et und Festlegung der chemischen und
au choc thermique (ISO 28721-2:2025) Temperaturschockbeständigkeit (ISO 28721-2:2025)
This European Standard was approved by CEN on 3 February 2025.

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, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye 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
© 2025 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 28721-2:2025 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 28721-2:2025) 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 2025, and conflicting national standards shall
be withdrawn at the latest by August 2025.
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 28721-2:2015.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN website.
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, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the
United Kingdom.
Endorsement notice
The text of ISO 28721-2:2025 has been approved by CEN as EN ISO 28721-2:2025 without any
modification.
International
Standard
ISO 28721-2
Third edition
Vitreous and porcelain enamels —
2025-02
Glass-lined apparatus for process
plants —
Part 2:
Designation and specification of
resistance to chemical attack and
thermal shock
Émaux vitrifiés — Appareils émaillés pour les installations
industrielles —
Partie 2: Désignation et spécifications de la résistance à l'attaque
chimique et au choc thermique
Reference number
ISO 28721-2:2025(en) © ISO 2025

ISO 28721-2:2025(en)
© ISO 2025
All rights reserved. Unless otherwise specified, or required in the context of its implementation, 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
CP 401 • Ch. de Blandonnet 8
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Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
ISO 28721-2:2025(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Designation . 2
5 Quality requirements . 2
5.1 Rate of corrosion in hydrochloric acid .2
5.2 Rate of corrosion in sodium hydroxide solution .2
5.3 Crack formation temperature .2
Bibliography .
...