ISO 8504-4:2022

INTERNATIONAL ISO
STANDARD 8504-4
First edition
2022-08
Preparation of steel substrates before
application of paints and related
products — Surface preparation
methods —
Part 4:
Acid pickling
Préparation des subjectiles d'acier avant application de peintures et
de produits assimilés — Méthodes de préparation des subjectiles —
Partie 4: Décapage à l'acide
Reference number
ISO 8504-4:2022(E)
© ISO 2022

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ISO 8504-4:2022(E)
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© ISO 2022
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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Published in Switzerland
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  © ISO 2022 – All rights reserved

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ISO 8504-4:2022(E)
Contents Page
Foreword .iv
Introduction .v
1 S c op e . 1
2 Nor m at i ve r ef er enc e s . 1
3 Terms and definitions . 1
4 G ener a l . 2
4.1 P ickling liquid . 2
4.1.1 Requirements to the chemical materials . 2
4.1.2 Requirements to the formulation and process conditions of a pickling liquid . 2
4.1.3 Example of formulation and process conditions of a pickling liquid . 2
4.2 General requirements . 2
4.2.1 R equirements to the bath equipment materials . 2
4.2.2 R equirements to the bath analysis . 2
4.3 H ealth and safety . . 2
5 M ethod of acid pickling . 3
5.1 P rocedure for acid pickling . 3
5 . 2 P r ep a r at ion . 3
5 . 3 D e g r e a s i ng. 3
5.3.1 Components and conditions . 3
5 . 3 . 2 I m mer s ion me t ho d . 4
5 . 3 . 3 P a r t pl ac ement . 4
5 . 3 .4 I m mer s ion t i me . 4
5 . 3 . 5 P r o c e s s t emp er at u r e . 4
5.4 F resh water rinsing and/or washing . 4
5.4.1 F resh water rinsing process. 4
5.4.2 R insing water temperature . 4
5.4.3 Fresh water washing process . 4
5 . 5 P ic k l in g . 4
5.5.1 I mmersion requirement . . . 4
5 . 5 . 2 P a r t placement . 4
5 . 5 . 3 I m mer s ion t i me . 4
5 . 5 .4 P r o c e s s t emp er at u r e . 4
5 . 6 Po s t t r e at ment . 5
5.6.1 C onversion layer . 5
5 . 6 . 2 Su r f ac e neut r a l i z at ion . 5
5.6.3 Improvement of the phosphate layer . 5
5.6.4 Q uality check and assurance . 5
5.6.5 Drying . 5
6 A ssessment of cleaned surface . 5
Annex A (informative) Formulation and condition of common process liquids .6
Bibliography . 8
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ISO 8504-4:2022(E)
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
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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).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any 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 of the voluntary nature of standards, the meaning of ISO specific terms and
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www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 35, Paints and varnishes, Subcommittee
SC 12, Preparation of steel substrates before application of paints and related products.
A list of all parts in the ISO 8504 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.
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ISO 8504-4:2022(E)
Introduction
The performance of protective coatings of paint and related products applied to steel is significantly
affected by the state of the steel surface immediately prior to painting. The principal factors that are
known to influence this performance are:
— the presence of rust and mill scale;
— the presence of surface contaminants, including salts, dust, oils and greases;
— the surface profile.
The ISO 8501 series, the ISO 8502 series and the ISO 8503 series provide methods for assessing these
factors. The ISO 8504 series however provides guidance on the preparation methods that are available
for cleaning steel substrates, indicating the capabilities of each in attaining the specified levels of
cleanliness.
This document describes acid pickling, which is an effective method for surface preparation. It is widely
applicable because this method of surface preparation has a number of versatile features listed below.
a) In general, the equipment is stationary but can be mobile.
b) The method is applicable to most types and forms of steel surface, especially those that would
deform by abrasive blast-cleaning.
c) It is possible to remove rust or mill scale and non-steel metal traces from internal, external and
complex structures surfaces.
d) Acid pickling can be performed for decorative and or aesthetic purposes.
There are several items that should be included in the purchaser's procurement documents to
supplement this document. Surface imperfections should be considered before surface preparation
and coating application. The ISO 8504 series does not contain recommendations for surface cleaning of
equipment and cleaning of pipelines (such as chemical pipelines, petroleum pipelines).
The ISO 8504 series does not contain recommendations for the protective coating system to be
applied to the steel
...