oSIST prEN ISO 4969:2026

• Abstract:

  ISO 4969:2015 establishes guidelines for the macroscopic examination of steel by hot etching, room temperature etching and electrolytic etching.; The method has very wide application. Selection of the type, concentration and temperature of the reagent, the etching apparatus and the conditions of surface preparation of the test piece make it possible to achieve the required aim.; NOTE It might be difficult to see fine voids and cracks and discriminate between them and determine their nature by macroetching.

• Status: Not Published
• Public Enquiry End Date: 29-Nov-2026
• ICS: 77.040.99 - Other methods of testing of metals
• ICS: 77.080.20 - Steels
• Technical Committee: PKG - Testing of metallic materials
• Ref Project: prEN ISO 4969 - Steel - Etching method for macroscopic examination (ISO 4969:2015)

oSIST prEN ISO 4969:2026 is a CEN reference for steel - etching method for macroscopic examination, aligned with ISO 4969:2015. It specifies guidelines for revealing the macrostructure of steel by hot etching, room temperature etching and electrolytic etching, so inspectors and metallography laboratories can examine steel test pieces in a controlled way.

What does oSIST prEN ISO 4969:2026 specify?

oSIST prEN ISO 4969:2026 specifies how to prepare, etch, preserve and report steel specimens for macroscopic examination. It is written for use with steel products where the aim is to reveal gross physical or chemical irregularities, and it organizes the method into Clauses 1 to 8 plus a bibliography.

The main clauses are:

• Clause 1 - Scope
• Clause 2 - Principle
• Clause 3 - Sampling
• Clause 4 - Preparation
• Clause 5 - Solutions
• Clause 6 - Procedure
• Clause 7 - Preservation of test pieces
• Clause 8 - Test report

In practice, this means the standard is not just about the etchant itself. It also covers how the sample is taken, how the surface is prepared, how the etch is applied, and what must be recorded afterward.

What are the key requirements of oSIST prEN ISO 4969:2026?

oSIST prEN ISO 4969:2026 makes the results depend on the product, the specimen preparation and the etching method chosen. The standard gives enough control points to make the examination repeatable, but it also expects the operator to judge when the structure has been developed adequately.

What the method is meant to reveal

Clause 2 says macroetching reveals the macrostructure of a metal test piece and gross irregularities such as segregation, cracks, porosity, decarburization and case hardening. Observation is by the unaided eye, a magnifying glass or a stereomicroscope. In practice, this tells the reader what kinds of discontinuities the method can show and why fine voids and cracks may still be difficult to separate clearly.

How to choose and take samples

Clause 3 says the position and number of samples are set by the product standard, specification, contract or order. If nothing special is stated, sampling is planned from the manufacturing process and the grade being assessed. Specimens are usually slices 13 mm to 25 mm thick, often cut to expose a transverse surface, with longitudinal surfaces used when required.

How to prepare the surface

Clause 4 says the preparation level depends on the precision needed. Rough machining can be enough for routine checks, but finer defects need more careful machining and often polishing. The clause also warns against heavy tool marks, excessive cold work and contamination, because these can distort the etched pattern or create uneven attack.

How to handle solutions safely

Clause 5 says the solutions are listed with each method and that commercial-quality reagents are usually acceptable if they are clean and free from particles. Mixing must be done slowly, especially with strong acids, and hydrofluoric acid requires polyethylene vessels. For practice, this means the reagent choice and its condition directly affect both safety and etch quality.

How the etching is performed

Clause 6 covers hot etching, room temperature etching and electrolytic etching. For immersion etching, the bath must be large enough and deep enough, and specimens must not touch each other. Large pieces can be swab etched when immersion is not practical.

For electrolytic etching, the standard gives separate AC and DC arrangements with schematics. It identifies the power connection, electrode arrangement, current and voltage conditions, and the room-temperature solutions to use. In practice, this is the section a laboratory follows when it needs a more controlled, electrically assisted etch.

How to preserve and report the result

Clause 7 recommends neutralization or brief passivation after etching, followed by rinsing, brushing and drying. For longer storage, the etched surface should be protected with a plastic film, cellulose varnish or a similar coating. Clause 8 requires the report to identify the steel grade, cast number, examined surface position, etch type and result, including a description or photograph.

What terms does oSIST prEN ISO 4969:2026 define?

• Macroetching - Etching a steel surface so the macrostructure and gross irregularities become visible.
• Segregation - Non-uniform distribution of elements in the steel, which may appear after etching.
• Desmutting - A follow-up treatment used to remove residue from the etched surface.
• Passivation - A brief nitric acid treatment that helps slow later corrosion and can brighten the surface.
• Electrolytic etching - Etching carried out with an electrical current, an electrode arrangement and an electrolyte.
• AC - Alternating current, used in one of the electrolytic etching arrangements.
• DC - Direct current, used in the other electrolytic etching arrangement.

Who uses oSIST prEN ISO 4969:2026?

oSIST prEN ISO 4969:2026 is used by steelmakers, metallography laboratories, quality control teams and inspection staff who need to examine steel macrostructure or defects. It is also relevant to welding and heat-treatment work, because the standard explicitly covers structures such as hardening, decarburization, weld zones and case hardening.

It is useful wherever product acceptance depends on the appearance of a cut and etched surface, including plain steels, alloy steels, stainless steels and high-alloy steels. Buyers, specifiers and contract writers use it when they need sampling, preparation and reporting rules to be fixed in a product standard, order or contract.

What changed in oSIST prEN ISO 4969:2026 from the previous edition?

oSIST prEN ISO 4969:2026 corresponds to the second edition of ISO 4969 and replaces ISO 4969:1980. The foreword states that it has been technically revised.

Which standards are used with oSIST prEN ISO 4969:2026?

The bibliography lists related standards that can be used alongside this method:

• ASTM E3 - specimen preparation for metallography
• ASTM E7 - metallography terminology
• ASTM E340 - macroetching of metals and alloys
• ASTM E381 - macroetch testing of steel bars, billets, blooms and forgings
• GB/T 226 - etch test for macrostructure and defects of steels
• JIS G 0553 - macroscopic examination of steel by etching

These references show where users can find related specimen-preparation guidance, terminology and comparable macroetch test methods.

What does the oSIST prEN ISO 4969:2026 document contain?

The document contains a procedure-based method for macroetching steel, plus practical guidance on sampling, surface preparation, reagent handling, etching and preservation. Table 1 gives hot-etching solutions with their temperature and time ranges, and Table 2 gives room-temperature etchants and their application scopes.

Figure 1 shows the AC electrolytic etching setup, and Figure 2 shows the DC setup. Those figures support laboratory arrangement and equipment checks, while the tables support method selection for different steel grades and inspection aims.

The document also includes instructions for swab etching of large specimens, cleaning after etching, and the minimum content of the test report.

SLOVENSKI STANDARD
01-oktober-2026
Jeklo - Metoda jedkanja za makroskopsko preiskavo (ISO 4969:2015)
Steel - Etching method for macroscopic examination (ISO 4969:2015)
Acier - Méthode d'attaque pour examen macroscopique (ISO 4969:2015)
Ta slovenski standard je istoveten z: prEN ISO 4969
ICS:
77.040.99 Druge metode za Other methods of testing of
preskušanje kovin metals
77.080.20 Jekla Steels
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

INTERNATIONAL ISO
STANDARD 4969
Second edition
2015-07-01
Steel — Etching method for
macroscopic examination
Acier — Méthode d’attaque pour examen macroscopique
Reference number
ISO 4969:2015(E)
©
ISO 2015
ISO 4969:2015(E)
© ISO 2015, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
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ii © ISO 2015 – All rights reserved

ISO 4969:2015(E)
Contents Page
Foreword .iv
1 Scope . 1
2 Principle . 1
3 Sampling . 1
4 Preparation . 2
5 Solutions . 2
6 Procedure. 3
7 Preservation of test pieces . 5
8 Test report . 6
Bibliography . 9
ISO 4969:2015(E)
Foreword
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bodies (ISO member bodies). The work of preparing International Standards is normally carried out
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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
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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
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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
The committee responsible for this document is ISO/TC 17, Steel, Subcommittee SC 7, Methods of testing
(other than mechanical tests and chemical analysis).
This second edition cancels and replaces the first edition (ISO 4969:1980), which has been technically revised.
iv © ISO 2015 – All rights reserved

INTERNATIONAL STANDARD ISO 4969:2015(E)
Steel — Etching method for macroscopic examination
1 Scope
This International Standard establishes guidelines for the macroscopic examination of steel by hot
etching, room temperature etching and electrolytic etching.
The method has very wide application. Selection of the type, concentration and temperature of the
reagent, the etching apparatus and the conditions of surface preparation of the test piece make it
possible to achieve the required aim.
NOTE It might be difficult to see fine voids and cracks and discriminate between them and determine their
nature by macroetching.
2 Principle
2.1 The use of the test and the conditions for interpreting the results observed depend on the particular
case, details are presented in product standards or shall be subject to special agreement.
2.2 Macroscopic etching reveals the macrostructure of a metal test piece and any gross physical or
chemical irregularities present.
2.3 The reagent acts by dissolving different parts of the metal surface at unequal rates, and thus,
produces differences in level which makes observation possible.
2.4 Macroscopic examination after etching reveals lack of chemical uniformity (segregation of elements),
lack of physical uniformity (cracks, porosity), and any intentional or accidental structural variations such
as those caused, for instance, by hardening, decarburization or case hardening.
2.5 In addition, enhanced sensitivity can be achieved by altering the conditions of preparation and
attack. For instance, it is possible to reveal the dendritic structure of a metal or the presence of inclusions
or very small defects.
2.6 Observation of the etched surface is carried out with the unaided eye and/or with a magnifying
glass, or with a stereomicroscope.
3 Sampling
3.1 The position and number of sampling shall be determined according to the requirements of the
product standard, specification, contract or order. In the absence of any special requirements, sampling
must be planned according to the details of the manufacturing process and the grade being evaluated.
3.2 The macroetching test, as applied to the inspection of steel products of this method, is carried out
on slices, usually 13 mm to 25 mm in thickness. Disks or specimens are usually cut to reveal a transverse
surface, but the requirements of the specification, contract, or order can include the preparation and
examination of a longitudinal surface. In most cases, a longitudinally-oriented macroetching disc is taken
with the plane to be etched along the centre line of the wrought product and it includes both outside
surfaces with a length in the longitudinal direction, usually 1,5 times greater than the thickness or diameter.
ISO 4969:2015(E)
3.3 Samples may be cold cut from the source by any convenient fashion; saws and abrasive cut-off
wheels are particularly effective. The use of torch cutting or hot cutting should be used only when
necessary to cut a sample from a large piece. It is advisable to locate the test surfaces well, away from the
hot-cut surface avoiding sampling defects, such as deformations, heat affected zone, cracks, and so on.
3.4 Large cross sections can be cut into smaller pieces to facilitate handling and to comply with safety
requirements. The sectioning of the large specimens should be done so as not to disturb the central
portion of the section.
4 Preparation
4.1 The degree of surface preparation necessary depends on the precision required for macroscopic
examination by acid etching.
4.2 While rough machining, resulting in relatively coarse surfaces, can be sufficient in certain cases
(routine inspection to reveal shrinkage holes, for example), more careful machining is generally required.
4.3 The criteria to be observed when machining are as follows:
a) cutting-tool marking should not be pronounced, for example, as the result of incorrect adjustment,
excessively deep cuts or heavy feeds on the lathe or the shaping machine; good results are generally
obtained with a feed of approximately 0,1 mm;
b) there should be as little cold working of the surface as possible, due for instance
1) to a type of tool which is not suitable for the metal, or which is badly sharpened, and
2) to the use of unsuitable grinding wheels (less than 100 grit).
4.4 The main types of machining generally used are the following:
a) grinding, with or without preliminary machining;
b) shaping or turning, provided that the lathe is fitted with a speed adjuster.
4.5 Where acid etching is used to reveal very fine defects or structural irregularities (different welding
zones for instance), careful polishing is recommended; the finer the polishing, the better the definition. In
general, it is recommended that a machined surface finish with a Ra less than 30 μm be obtained.
4.6 After surface preparation, the sample is cleaned carefully with suitable solvents. Any grease, oil,
or other residue will produce uneven attack. Once cleaned, care s
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