oSIST prEN ISO 21227-4:2026

Paints and varnishes - Evaluation of defects on coated surfaces using digital image processing - Part 4: Evaluation of filiform corrosion on coated corrosion test samples (ISO/DIS 21227-4:2026)

ISO 21227-4:2008 describes a method for evaluating filiform corrosion by means of digital optical imaging. Only the evalution procedure is described. The filiform corrosion itself is produced in accordance with other standards.

Beschichtungsstoffe - Beurteilung von Beschichtungsschäden mittels digitaler Bildverarbeitung - Teil 4: Beurteilung von Filiformkorrosion an beschichteten Korrosionsprüfkörpern (ISO/DIS 21227-4:2026)

Peintures et vernis - Évaluation des défauts sur des surfaces revêtues par traitement numérique d'images - Partie 4: Évaluation de la corrosion filiforme sur des échantillons d'essai de corrosion revêtus (ISO/DIS 21227-4:2026)

L'ISO 21227‑4:2008 spécifie une méthode permettant d'évaluer la corrosion filiforme au moyen de l'imagerie optique numérique. Seul le mode opératoire d'évaluation est spécifié. La corrosion filiforme elle-même est produite conformément à d'autres normes.

Barve in laki - Vrednotenje napak na premazanih površinah z uporabo digitalne obdelave slik - 4. del: Vrednotenje filiformne korozije na premazanih vzorcih za korozijske preskuse (ISO/DIS 21227-4:2026)

ISO 21227-4:2008 opisuje metodo za ocenjevanje nitaste korozije s pomočjo digitalnega optičnega slikanja. Opisan je le postopek ocenjevanja. Sama nitasta korozija se proizvaja v skladu z drugimi standardi.

General Information

• Status: Not Published
• Public Enquiry End Date: 01-May-2026
• ICS: 87.040 - Paints and varnishes
• Technical Committee: IBLP - Paints and varnishes
• Current Stage: 4020 - Public enquire (PE) (Adopted Project)
• Start Date: 11-Mar-2026
• Due Date: 29-Jul-2026
• Completion Date: 29-May-2026
• Ref Project: prEN ISO 21227-4 - Paints and varnishes - Evaluation of defects on coated surfaces using digital image processing - Part 4: Evaluation of filiform corrosion on coated corrosion test samples (ISO/DIS 21227-4:2026)

Relations

• Revises: SIST EN ISO 21227-4:2009 - Paints and varnishes - Evaluation of defects on coated surfaces using optical imaging - Part 4: Evaluation of filiform corrosion (ISO 21227-4:2008)
• Effective Date: 01-Apr-2026

Overview

oSIST prEN ISO 21227-4:2026:2026 is a draft international standard developed by CEN and ISO that defines a method for evaluating filiform corrosion on coated corrosion test samples using digital image processing. As part of the ISO 21227 series on paints and varnishes, this document focuses specifically on providing objective and quantitative assessment procedures for filiform corrosion detected on coated surfaces subjected to corrosion testing.

Filiform corrosion refers to a form of corrosion that propagates under protective coatings, like paints or varnishes, typically appearing as thread-like filaments. Accurate and standardized evaluation is essential for quality control in the coatings industry. This standard provides guidance on using digital optical imaging to analyze and measure the extent of filiform corrosion, ensuring reproducible and reliable results.

Key Topics

• Objective Evaluation Using Digital Imaging
  The standard outlines methods for using digital image processing to accurately measure and evaluate the spread and severity of filiform corrosion on coated surfaces.

• Calibration of Digital Imaging Systems
  Detailed calibration procedures for image sensors are described to ensure precise measurement in both horizontal and vertical directions.

• Image Enhancement Techniques
  Common digital image processing methods are documented, including:

  • Gamma correction for dynamic range adaptation
  • Sigmoid function to enhance contrast
  • Histogram-based contrast improvement
  • Median and Gaussian filters for noise reduction and smoothing
  • Binarisation to create binary images for further analysis

• Measurement and Evaluation Process
  The procedure describes:

  • How to determine corrosion area and filament lengths
  • The process of measuring longest and most frequent filament lengths
  • How to calculate filament frequency and the index for filiform attack

• Comprehensive Test Reporting
  The standard specifies required reporting components, such as original and processed images, data tables, applied image processing steps, and complete measurement results.

Applications

oSIST prEN ISO 21227-4:2026:2026 is vital for organizations and laboratories involved in the quality inspection and research of protective coatings. Key applications include:

• Coating Performance Evaluation
  Enables manufacturers and testing labs to assess the resistance of paint and varnish coatings against filiform corrosion, supporting product development and verification.

• Quality Control and Assurance
  Ensures consistency and comparability in the evaluation of defects on coated surfaces, which is essential for compliance with industry requirements and customer specifications.

• Corrosion Testing and Research
  Provides research institutions and industrial labs with a standardized digital method for quantifying corrosion phenomena, facilitating the development of improved protective coatings.

• Regulatory and Certification Processes
  The standard can be referenced in regulatory documents and certification schemes to demonstrate compliance with recognized international practices for evaluating coated surfaces.

Related Standards

For comprehensive corrosion evaluation and coating quality assessment, oSIST prEN ISO 21227-4:2026:2026 should be used alongside related standards, including:

• ISO 21227-1: Paints and varnishes - Evaluation of defects on coated surfaces using optical imaging - General guidance
• ISO 4628-10: Assessment of degree of filiform corrosion on painted substrates
• ISO 4623-1: Determination of resistance to filiform corrosion - Steel substrates
• ISO 4618: Paints and varnishes - Vocabulary
• ISO 129-1: Technical product documentation - Presentation of dimensions and tolerances

These standards provide a complete framework for the evaluation of coatings, from terminology and definitions to specific evaluation techniques and criteria.

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By implementing oSIST prEN ISO 21227-4:2026:2026, organizations can enhance the reliability and repeatability of their filiform corrosion assessments, leading to better product quality and compliance with international coatings standards.

Standards Content (Sample)

SLOVENSKI STANDARD
01-april-2026
Barve in laki - Vrednotenje napak na premazanih površinah z uporabo digitalne
obdelave slik - 4. del: Vrednotenje filiformne korozije na premazanih vzorcih za
korozijske preskuse (ISO/DIS 21227-4:2026)
Paints and varnishes - Evaluation of defects on coated surfaces using digital image
processing - Part 4: Evaluation of filiform corrosion on coated corrosion test samples
(ISO/DIS 21227-4:2026)
Beschichtungsstoffe - Beurteilung von Beschichtungsschäden mittels digitaler
Bildverarbeitung - Teil 4: Beurteilung von Filiformkorrosion an beschichteten
Korrosionsprüfkörpern (ISO/DIS 21227-4:2026)
Peintures et vernis - Évaluation des défauts sur des surfaces revêtues par traitement
numérique d'images - Partie 4: Évaluation de la corrosion filiforme sur des échantillons
d'essai de corrosion revêtus (ISO/DIS 21227-4:2026)
Ta slovenski standard je istoveten z: prEN ISO 21227-4
ICS:
87.040 Barve in laki Paints and varnishes
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
International
Standard
ISO/DIS 21227-4
ISO/TC 35/SC 9
Paints and varnishes — Evaluation
Secretariat: BSI
of defects on coated surfaces using
Voting begins on:
digital image processing —
2026-03-02
Part 4:
Voting terminates on:
2026-05-25
Evaluation of filiform corrosion on
coated corrosion test samples
ICS: ISO ics
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 21227-4:2026(en)
DRAFT
ISO/DIS 21227-4:2026(en)
International
Standard
ISO/DIS 21227-4
ISO/TC 35/SC 9
Paints and varnishes — Evaluation
Secretariat: BSI
of defects on coated surfaces using
Voting begins on:
digital image processing —
Part 4:
Voting terminates on:
Evaluation of filiform corrosion on
coated corrosion test samples
ICS: ISO ics
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 2026
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 21227-4:2026(en)
ii
ISO/DIS 21227-4:2026(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Calibration . 1
5 Image enhancement . 2
5.1 General .2
5.2 Examples of image enhancement: .2
5.2.1 Gamma correction .2
5.2.2 Sigmoid function . . .2
5.2.3 Histogram-based contrast increase .2
5.2.4 Median filter .2
5.2.5 Gaussian filter .2
5.2.6 Binarisation .2
6 Evaluation . 3
7 Test report . 5
Bibliography . 7

iii
ISO/DIS 21227-4:2026(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 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 35, Paints and varnishes, Subcommittee
SC 9, General test methods for paints and varnishes in collaboration with the European Committee for
Standardization (CEN) Technical Committee CEN/TC 139, Paints and varnishes, in accordance with the
Agreement on technical cooperation between ISO and CEN (Vienna Agreement).
This second edition cancels and replaces the first edition (ISO 21227-4:2008), which has been technically
revised.
The main changes are as follows:
— the title of the document has been changed to “Part 4: Evaluation of filiform corrosion on coated corrosion
test samples”;
— the text has been revised considering the new methods for digital image processing added in
ISO 21227-1:—;
— the calibration (Clause 4) has been changed;
— the normative references have been updated.
A list of all parts in the ISO 21227 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
ISO/DIS 21227-4:2026(en)
Introducti
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