EN ISO 29601:2026

Paints and varnishes - Corrosion protection by protective paint systems - Assessment of porosity in a dry film (ISO 29601:2026)

ISO 29601:2011 specifies procedures for detecting the presence of porosity in a protective paint system of any thickness on a steel or other metallic substrate. The procedures given are based on methods using two different types of test equipment, the choice of equipment depending on the dry film thickness. These procedures are only applicable to the testing of electrically non-conductive parts of a paint system.
The test methods specified are mainly intended for use with new coatings, but can also be used for coatings which have been in service for some time. In the latter case, it is important to bear in mind that the coating might have been penetrated by substances in contact with the coating during service.

Beschichtungsstoffe - Korrosionsschutz durch Beschichtungssysteme - Beurteilung der Porosität einer trockenen Beschichtung (ISO 29601:2026)

Diese Internationale Norm legt Verfahren zur Feststellung von Porosität in Beschichtungssystemen jeder
Schichtdicke für den Korrosionsschutz auf einem Stahlsubstrat oder anderen Substraten aus Metall fest. Die
in dieser Internationalen Norm angegebenen Vorgehensweisen basieren auf Verfahren, die zwei
verschiedene Prüfgerätetypen verwenden. Die Auswahl des Gerätes richtet sich nach der
Trockenschichtdicke. Diese Verfahren sind nur für die Prüfung elektrisch nichtleitender Schichten eines
Beschichtungssystems anwendbar.
Die festgelegten Prüfverfahren werden hauptsächlich für neue Beschichtungen angewendet, sie können
jedoch auch für Beschichtungen angewendet werden, die bereits in der Praxis gebraucht wurden. Im letzteren
Fall ist zu beachten, dass in das Beschichtungssystem Substanzen während der Lagerung eingedrungen sein
könnten.

Peintures et vernis Anticorrosion par systèmes de peinture - Évaluation de la porosité d'un feuil sec (ISO 29601:2026)

L'ISO 29601:2011 spécifie des modes opératoires permettant de détecter l'existence de porosité dans un système de revêtement de peinture, quelle qu'en soit l'épaisseur, appliqué sur un subjectile en acier ou sur tout autre métal. Les modes opératoires fournis dans la présente Norme internationale sont basés sur des méthodes faisant appel à deux types d'équipement d'essai, le choix de l'équipement étant fonction de l'épaisseur du feuil sec. Ces modes opératoires ne s'appliquent qu'aux essais des couches électriquement non conductrices d'un système de peinture.
Les méthodes d'essai spécifiées sont destinées principalement aux revêtements neufs mais peuvent aussi être employées pour les revêtements déjà mis en service. Dans ce dernier cas, il est important de garder à l'esprit le fait que des substances en contact avec le revêtement ont pu y pénétrer pendant la période en service.

Barve in laki - Korozijska zaščita z zaščitnimi premaznimi sistemi - Ocenjevanje poroznosti suhega filma (ISO/FDIS 29601:2026)

General Information

• Status: Not Published
• Publication Date: 28-Apr-2026
• ICS: 87.020 - Paint coating processes
• ICS: 87.040 - Paints and varnishes
• Technical Committee: CEN/TC 139 - Paints and varnishes
• Drafting Committee: CEN/TC 139 - Paints and varnishes
• Current Stage: 6055 - CEN Ratification completed (DOR) - Publishing
• Start Date: 27-Apr-2026
• Completion Date: 27-Apr-2026
• Ref Project: kSIST FprEN ISO 29601:2026 - Paints and varnishes - Corrosion protection by protective paint systems - Assessment of porosity in a dry film (ISO/FDIS 29601:2026)

Relations

• Referred By: EN ISO 13506-1:2024 - Protective clothing against heat and flame - Part 1: Test method for complete garments - Measurement of transferred energy using an instrumented manikin (ISO 13506-1:2024)
• Effective Date: 28-Jan-2026
• Consolidated By: ISO 29601:2026 - Paints and varnishes — Corrosion protection by protective paint systems — Assessment of porosity in a dry film
• Effective Date: 12-Feb-2026
• Revises: EN ISO 29601:2011 - Paints and varnishes - Corrosion protection by protective paint systems - Assessment of porosity in a dry film (ISO 29601:2011)
• Effective Date: 18-Jan-2023

Overview

EN ISO 29601:2026, titled Paints and varnishes - Corrosion protection by protective paint systems - Assessment of porosity in a dry film, is a European standard developed by CEN. This standard defines procedures for detecting porosity in protective paint and varnish systems on steel or other metallic substrates. Porosity assessment is essential in ensuring the long-term corrosion protection provided by coatings applied in demanding industrial and infrastructure environments.

The standard applies to paint systems of any thickness, provided they contain electrically non-conductive components. It details two principal testing methods - the use of low-voltage pinhole detectors and high-voltage holiday detectors - to suit different dry film thicknesses. The guidance is relevant for both newly applied coatings and, with care, coatings that have been in service.

Key Topics

Porosity Detection Methods

• Low-voltage pinhole detectors: Typically used for coatings up to 500 µm. These use a wetted sponge and battery-powered device to detect discontinuities.
• High-voltage holiday detectors: Required for dry film thickness above 500 µm. These systems generate a spark to reveal defects, using a probe and calibrated voltage settings.

Test Procedure Highlights

• Test method selection depends on dry film thickness.
• Proper surface preparation and grounding are critical for accurate results.
• Test voltages must be set according to film thickness for reliable detection.
• Results are reported as the number of discontinuities found in the inspection area.

Applications

EN ISO 29601:2026 serves a range of sectors where corrosion protection of metals is crucial, including:

• Industrial Infrastructure: Bridges, storage tanks, pipelines, and offshore platforms rely on protective coating systems to prevent corrosion-related failures.
• Manufacturing and Maintenance: New installations and maintenance operations benefit from quality assurance through porosity assessment.
• Quality Control: Paint manufacturers, applicators, and inspection agencies use these methods to verify the integrity of protective coatings before and after deployment.
• Regulatory Compliance: Reference in national and project specifications ensures coatings meet required performance standards.

Practical use of this standard helps identify holidays, pinholes, cracks, voids, and other discontinuities that can compromise corrosion protection, thus supporting durability and reducing lifecycle costs.

Related Standards

EN ISO 29601:2026 complements several international and European standards for protective paint and varnish systems:

• ISO 12944 series: Addresses all aspects of corrosion protection by paint systems, including design, implementation, and maintenance.
• ISO 19840: Specifies measurement and acceptance criteria for dry film thickness of protective paints on rough surfaces.
• ISO 16276-1/2: Covers assessment and acceptance criteria for the adhesion/cohesion strength of coatings.
• ISO 4628 series: Provides methods for evaluating degradation of coatings, such as blistering, rusting, and cracking.
• ISO 2808: Outlines methods for determining coating film thickness.

Referencing these standards in combination ensures comprehensive and standardized evaluation of protective coating performance, from surface preparation through to long-term inspection.

---

Keywords: EN ISO 29601:2026, porosity assessment, protective paint systems, corrosion protection, dry film testing, pinhole detector, holiday detector, industrial coatings, quality control, paint and varnish standards, steel protection.

Standards Content (Sample)

SLOVENSKI STANDARD
oSIST prEN ISO 29601:2025
01-maj-2025
Barve in laki - Korozijska zaščita z zaščitnimi premaznimi sistemi - Ocenjevanje
poroznosti suhega filma (ISO/DIS 29601:2025)
Paints and varnishes - Corrosion protection by protective paint systems - Assessment of
porosity in a dry film (ISO/DIS 29601:2025)
Beschichtungsstoffe - Korrosionsschutz durch Beschichtungssysteme – Beurteilung der
Porosität einer trockenen Beschichtung (ISO/DIS 29601:2025)
Peintures et vernis - Anticorrosion par systèmes de peinture – Évaluation de la porosité
d'un feuil sec (ISO/DIS 29601:2025)
Ta slovenski standard je istoveten z: prEN ISO 29601
ICS:
25.220.20 Površinska obdelava Surface treatment
87.040 Barve in laki Paints and varnishes
oSIST prEN ISO 29601:2025 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

oSIST prEN ISO 29601:2025
oSIST prEN ISO 29601:2025
DRAFT
International
Standard
ISO/DIS 29601
ISO/TC 35/SC 14
Paints and varnishes — Corrosion
Secretariat: DIN
protection by protective paint
Voting begins on:
systems — Assessment of porosity
2025-03-13
in a dry film
Voting terminates on:
2025-06-05
Peintures et vernis — Anticorrosion par systèmes de peinture —
Évaluation de la porosité d'un feuil sec
ICS: 87.020
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
ISO/CEN PARALLEL PROCESSING
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS.
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION.
Reference number
ISO/DIS 29601:2025(en)
oSIST prEN ISO 29601:2025
DRAFT
ISO/DIS 29601:2025(en)
International
Standard
ISO/DIS 29601
ISO/TC 35/SC 14
Paints and varnishes — Corrosion
Secretariat: DIN
protection by protective paint
Voting begins on:
systems — Assessment of porosity
in a dry film
Voting terminates on:
Peintures et vernis — Anticorrosion par systèmes de peinture —
Évaluation de la porosité d'un feuil sec
ICS: 87.020
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2025
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
STANDARDS MAY ON OCCASION HAVE TO
ISO/CEN PARALLEL PROCESSING
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
BE CONSIDERED IN THE LIGHT OF THEIR
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
or ISO’s member body in the country of the requester.
NATIONAL REGULATIONS.
ISO copyright office
RECIPIENTS OF THIS DRAFT ARE INVITED
CP 401 • Ch. de Blandonnet 8
TO SUBMIT, WITH THEIR COMMENTS,
CH-1214 Vernier, Geneva
NOTIFICATION OF ANY RELEVANT PATENT
Phone: [phone]
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION.
Email: [e-mail]
Website: www.iso.org
Published in Switzerland Reference number
ISO/DIS 29601:2025(en)
ii
oSIST prEN ISO 29601:2025
ISO/DIS 29601:2025(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Test equipment . 2
5.1 Low-voltage pinhole detectors .2
5.1.1 General .2
5.1.2 Electric path .2
5.1.3 Sensitivity and alarm .2
5.1.4 Conductive liquid .2
5.2 High-voltage holiday detectors .3
5.2.1 General .3
5.2.2 Electrical source .3
5.2.3 Equipment shall be operated either by DC or pulsed DC. High-voltage AC
generators shall not be used for testing. .3
5.2.4 Electrical path .3
5.2.5 Alarm .3
5.2.6 Controlled output voltage.3
6 Procedure . 3
6.1 Selection of test method .3
6.2 Low-voltage pinhole detection .4
6.2.1 Test voltage.4
6.2.2 Paint conditions before testing .4
6.2.3 Wetting agent .4
6.2.4 Preparation before testing .4
6.2.5 Testing .4
6.3 High-voltage holiday detection .4
6.3.1 Paint conditions before testing .4
6.3.2 Test voltage settings and calculation .5
6.3.3 output voltage verification .5
6.3.4 preparation before testing .5
6.3.5 Testing .5
7 Expression of results . 5
8 Test report . 6
Annex A  Table of mean dry film thicknesses and their corresponding recommended test
voltages . 7
Bibliography . 9

iii
oSIST prEN ISO 29601:2025
ISO/DIS 29601:2025(en)
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).
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/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 [or Project Committee] ISO/TC 35, paints and varnishes,
Subcommittee SC 14, Protective paint systems for steel structures.
This third edition cancels and replaces the second edition (ISO 29601:2012), which has been technically
revised.
The main changes are as follows:
— editorial update
A list of all parts in the ISO ##### 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
oSIST prEN ISO 29601:2025
ISO/DIS 29601:2025(en)
Introduction
This International Standard supplements the ISO 12944 series (see the Bibliography) with regard to the
detection of porosity in a dry film. If specified or agreed, the standard can also be used for other applications.
The objective of this International Standard is to achieve uniformity of practice for the detection of porosity
in a dry film. The methods chosen entail the detection of porosity using one of two types of equipment, a
low-voltage pinhole detector or a high-voltage holiday detector.
This International Standard complements ISO 19840, which concerns the measurement of the thickness
of dry films on rough surfaces, and ISO 16276 1 and ISO 16276 2, which concern the measurement of the
adhesion of a coating by pull-off testing (Part 1) and by cross-cut and X cut testing (Part 2).

v
oSIST prEN ISO 29601:2025
oSIST prEN ISO 29601:2025
DRAFT International Standard ISO/DIS 29601:2025(en)
Paints and varnishes — Corrosion protection by protective
paint systems — Assessment of porosity in a dry film
1 Scope
This International Standard specifies procedures for detecting the presence of porosity in a protective paint
system of any thickness on a steel or other metallic substrate. The procedures given in this International
Standard are based on methods using two different types of test equipment, the choice of equipment
depending on the dry film thickness. These procedures are only applicable to the testing of electrically non-
conductive parts of a paint system.
The test methods specified are mainly intended for use with new coatings, but can also be used for coatings
which have been in service for some time. In the latter case, it is important to bear in mind that the coating
might have been penetrated by substances in contact with the coating during service.
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 19840, Paints and varnishes — Corrosion protection of steel structures by protective paint systems —
Measurement of, and acceptance criteria for, the thickness of dry films on rough surfaces
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
porosity
presence of one or more discontinuities in a coating
3.2
discontinuity
hole, pit, pinhole, void, crack, thin spot, inclusion, contamination or other flaw in a coating that significantly
lowers the dielectric strength of the coating
Note 1 to entry: Certain types of discontinuity can also be described as a holiday.
3.3
nominal dry film thickness
NDFT
dry film thickness specified for each coat or for the whole paint system
[SOURCE: ISO 19840:2004]
3.4
mean dry film thickness
arithmetic mean of all the individual dry film thicknesses in the inspection area
[SOURCE: ISO 19840:2004]
...