ISO 24131-4:2026

Internal protection by polymeric lining for ductile iron pipes — Requirements and test methods — Part 4: Ceramic epoxy lining

This document specifies the requirements and test methods applicable to factory applied ceramic epoxy lining for ductile iron pipes conforming to ISO 2531, ISO 7186 and ISO 16631, excluding potable water, for operating temperature up to 50 °C.

Protection interne des tuyaux en fonte ductile par revêtement polymérique — Exigences et méthodes d'essai — Partie 4: Revêtement époxy céramique

General Information

• Status: Published
• Publication Date: 11-Jun-2026
• ICS: 23.040.10 - Iron and steel pipes
• Technical Committee: ISO/TC 5/SC 2 - Cast iron pipes, fittings and their joints
• Drafting Committee: ISO/TC 5/SC 2/WG 24 - Internal Protection
• Current Stage: 6060 - International Standard published
• Start Date: 12-Jun-2026
• Due Date: 16-Jul-2027
• Completion Date: 12-Jun-2026

Overview

ISO 24131-4:2026 sets out the requirements and test methods for factory-applied ceramic epoxy linings on ductile iron pipes used for non-potable water and sewerage applications, with operating temperatures up to 50°C. Developed by the International Organization for Standardization (ISO), this standard is a key reference for manufacturers, engineers, and quality assurance professionals working with ductile iron pipelines as specified in ISO 2531, ISO 7186, and ISO 16631.

The standard addresses both technical performance and quality control for internal polymeric protection systems utilizing ceramic epoxy. Excluded from scope are pipes for potable water and applications exceeding the specified temperature limit.

Key Topics

• Lining Material: Ceramic epoxy lining, factory-applied, containing at least 20% by volume of ceramic quartz, with a two-component amine-cured epoxy base.
• Surface Preparation: Clean, moisture-free pipe surfaces, typically prepared by blasting or grinding to achieve a roughness (Ra) of 12.5 μm or more.
• Lining Properties:
  • Uniform color and appearance, free from defects such as pinholes, blisters, and cracks.
  • Minimum localized thickness of 900 μm and average thickness of 1000 μm.
• Adhesion and Non-Porosity:
  • High adhesion strength (minimum 8.0 MPa).
  • Non-porous performance proven by electrical puncture tests.
• Performance Criteria:
  • Abrasion and chemical resistance for sewerage applications.
  • Resistance to impact (direct and indirect).
  • Resistance to deformation (ovalization) and hot water exposure.
• Quality Control: Regular routine and performance testing, covering surface, appearance, thickness, adhesion, cross-linkage, and porosity.

Applications

ISO 24131-4:2026 is relevant for various industrial and municipal water and sewer infrastructure projects where ductile iron pipes are exposed to aggressive contents or corrosive sewerage, excluding potable water transport. Specific applications include:

• Sewage Systems: Ensuring resistance to abrasion and corrosive chemicals found in wastewater.
• Industrial Water Conveyance: Where high durability and lining integrity are critical under chemical or thermal stress.
• Infrastructure Repair and Replacement: When integrating with existing plastic or metal pipeline systems as specified in ISO 16631.
• Quality Assurance in Pipe Manufacturing: For producers of ductile iron pipes, the standard serves as a guideline for in-factory linings, covering process and performance validation.

By complying with ISO 24131-4:2026, specifiers and manufacturers can enhance the longevity and reliability of ductile iron pipes in demanding environments, minimize maintenance, and reduce lifecycle costs.

Related Standards

Professionals working with ISO 24131-4:2026 will also benefit from familiarity with complementary standards, including:

• ISO 2531: Ductile iron pipes, fittings, and accessories for water applications.
• ISO 7186: Ductile iron products for sewerage (key for abrasion and chemical resistance requirements).
• ISO 16631: Compatibility and connection with plastic pipeline systems.
• ISO 4624: Pull-off test for adhesion (essential for testing lining adherence).
• ISO 8503-1: Surface roughness characteristics for paint and lining applications.
• ISO 9001: Quality management systems for manufacturing control.

Practical Value

Adopting ISO 24131-4:2026 ensures consistent, high-quality internal protection of ductile iron pipes through strict requirements and clear, reproducible test methods. The standard delivers critical benefits:

• Enhances pipe lifespan by reducing internal corrosion and degradation risks.
• Improves safety and reliability in wastewater and industrial water transport.
• Facilitates compliance in international markets by providing a recognized benchmark.
• Supports quality assurance and process control throughout manufacturing and installation.

ISO 24131-4:2026 is an indispensable standard for ensuring durable, efficient, and compliant ductile iron pipeline systems, especially in demanding non-potable and sewage service environments.

Standards Content (Sample)

International
Standard
ISO 24131-4
First edition
Internal protection by polymeric
2026-06
lining for ductile iron pipes —
Requirements and test methods —
Part 4:
Ceramic epoxy lining
Protection interne des tuyaux en fonte ductile par revêtement
polymérique — Exigences et méthodes d'essai —
Partie 4: Revêtement époxy céramique
Reference number
© ISO 2026
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
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Technical requirements . 3
4.1 General .3
4.2 Surface preparation .3
4.3 Surface roughness .3
4.4 Lining appearance .3
4.5 Lining thickness .3
4.6 Adhesion .4
4.7 Cross linkage (MIBK/ΔTg) .4
4.8 Non-porosity .4
4.9 Protection of pipe ends .4
4.10 Repairs .4
5 Performance requirements . . 5
5.1 General .5
5.2 Abrasion resistance only for sewage applications .5
5.3 Impact resistance .5
5.4 Indirect impact resistance .5
5.5 Resistance to hot water .5
5.6 Chemical resistance only for sewage applications .5
5.7 Resistance to ovalization .5
6 Test methods . 6
6.1 Routine tests . .6
6.1.1 Surface preparation .6
6.1.2 Surface roughness .6
6.1.3 Lining appearance . .6
6.1.4 Lining thickness .6
6.1.5 Adhesion .6
6.1.6 Cross linkage (MIBK/ΔTg).6
6.1.7 Non-porosity .6
6.2 Performance test .7
6.2.1 Impact resistance .7
6.2.2 Indirect impact resistance . .7
6.2.3 Resistance to hot water .7
6.2.4 Chemical resistance .7
6.2.5 Resistance to ovalization .8
Annex A (normative) Quality assurance . 9
Annex B (informative) Handling, transportation and storage .11
Bibliography .12

iii
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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of 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 www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 5, Ferrous metal pipes and metallic fittings,
Subcommittee SC 2, Cast iron pipes, fittings and their joints.
A list of all parts in the ISO 24131 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
International Standard ISO 24131-4:2026(en)
Internal protection by polymeric lining for ductile iron
pipes — Requirements and test methods —
Part 4:
Ceramic epoxy lining
1 Scope
This document specifies the requirements and test methods applicable to factory applied ceramic epoxy
lining for ductile iron pipes conforming to ISO 2531, ISO 7186 and ISO 16631, excluding potable water, for
operating temperature up to 50 °C.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 2531, Ductile iron pipes, fittings, accessories and their joints for water applications
ISO 7186, Ductile iron products for sewerage applications
ISO 16631, Ductile iron pipes, fittings, accessories and their joints compatible with plastic (PVC or PE) piping
systems, for water applications and for plastic pipeline connections, repair and replacement
ISO 4624, Paints and varnishes — Pull-off test for adhesion
ISO 8503-1, Preparation of steel substrates before application of paints and related products — Surface
roughness characteristics of blast-cleaned steel substrates — Part 1: Specifications and definitions for ISO
surface profile comparators for the assessment of abrasive blast-cleaned surfaces
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 2531 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
ceramic epoxy lining
factory applied lining which consists of at least 20% by volume of ceramic quartz, and the lining material is
two-component amine cured epoxy which is mixed together in the proportion specified by the manufacturer
before application
3.2
routine test
test carried out to control the manufacturing process
Note 1 to entry: The frequency of the test is defined by this document or the manufacturer.

3.3
cross linkage
chemical reaction between epoxy resin and hardener to form the final cured lining
3.4
non-porosity
absence of electrical puncture in a high voltage test (holiday test) under defined test condition
3.5
designated zone
area of a casting where, because of jointing tolerance restrictions, testing difficulties or enveloping by a
gasket, etc., a lower standard of coating performance is inevitable
Note 1 to entry: For the purpose of this document, their areas are defined as:
— joint areas;
— bolt holes;
— permitted markings;
— ribs;
— edges.
Note 2 to entry: Where necessary, these zones can be protected by appropriate additional corrosion protection actions
during or after installation. However, such actions are not covered in this document.
3.6
abrasion resistance
ability of materials and structures to withstand abrasion
3.7
impact resistance
energy which a lining can withstand without damage under defined test conditions
3.8
indirect impact resistance
impact energy applied from outside of the pipe with deformation to which a lining can withstand without
damage under defined test conditions
3.9
ovalization
100 times the measured vertical deflection, (caused by the applied load) divided by the measured pipe
external diameter
3.10
pull off test
force per unit area, applied perpendicular to the surface, which is necessary to separate the lining from its
substrate
3.11
performance test
test which is done once and thereafter only when there is a change in the lining material or lining process
3.12
hardness
resistance of the lining to the penetration of a ball under defined test conditions

3.13
chalking
superficial reaction of ceramic epoxy lining due to exposure to UV-radiation
Note 1 to entry: The process is confined to the surface only and results in a dulling of the surface.
3.14
localized minimum thickness
minimum thickness measured at any one point of one lined product
4 Technical requirements
4.1 General
The following technical requirements shall be demonstrated by routine tests applied in production, on in-
process and finished lined products with defined frequency. Routine tests shall be in accordance with the
overview of requirements provided in Table A.2.
Quality assurance for ceramic epoxy lining shall be in accordance with Annex A.
4.2 Surface preparation
Prior to lining application, all surfaces to be lined shall be substantially clean and free from oil, grease and
moisture.
In cold weather, or anytime when moisture tends to condense on the surface of the pipe, it shall be uniformly
warmed for sufficient time to dry before cleaning. The surface temperature shall be maintained at least 3 °C
above the dew point.
Surface preparation shall be designed to reach the required performances specified in this document. It
is the responsibility of the manufacturer to demonstrate the fitness for purpose of surface preparation
technology and to put in place a quality control procedure to ensure the stability of those performances.
NOTE The requirements of Class Sa 2.5 of ISO 8501-1 and ≤ Rating 3 dust quantity and Class 2 for dust size of
ISO 8502-3 can be applied.
4.3 Surface roughness
The surface roughness Ra shall be at leas
...