ISO/TR 22861:2025

Technical
Report
ISO/TR 22861
First edition
Guidance on marine environment
2025-10
zonation for steel corrosion
embedded in concrete
Recommandations relatives au zonage de l'environnement marin
pour la corrosion de l'acier encastré dans le béton
Reference number
© ISO 2025
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: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Fundamental . 2
4.1 Transfer mechanisms .2
4.2 Environmental action .2
4.3 Exposure zone .2
5 Investigation . . 2
5.1 Investigation object .2
5.2 Investigation content .2
6 Exposure zone division . 2
7 Exposure zone determination based on environmental action measurement of standard
specimens . 3
7.1 Specimen fabrication .3
7.2 Specimen placement .3
7.3 Test procedure .4
7.4 Exposure zone determination .4
Annex A (informative) Influence factor of marine environmental action and normative
estimation process of typical exposure zones . 6
Annex B (informative) A case of exposure zone determination with the corrosion potential of
the reinforcement . 8
Annex C (informative) A case of exposure zone determination with the surface chloride ion
concentration .11
Annex D (informative) A case of exposure zone determination with the concrete electrical
resistivity.15
Bibliography . 17

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 156, Corrosion of metals and alloys.
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
Introduction
Due to the different exposure zones encountered by reinforced concrete structures within marine
environments, the mechanisms of chloride penetration vary, resulting in various levels of steel corrosion.
It is imperative to design the durability of reinforced concrete structures in these distinct exposure zones
to satisfy specific requirements and implement appropriate anti-corrosion strategies. Underestimating the
environmental effects without implementing sufficient protective measures can precipitate premature
degradation of reinforced concrete. Conversely, overestimating environmental effects and adopting excessive
protective measures can incur superfluous construction costs. Therefore, it is essential to accurately identify
the boundaries of exposure zones to categorize the effect of the actual environmental action.
The division of exposure zones is based on the assessment of the durability of marine reinforced concrete
structures. From the outcomes of exposure zone division, the intensity of environmental effects can also
be broadly categorized. However, similar levels of environmental effect can manifest across different
exposure zones, indicating the necessity for a more refined categorization tailored specifically to marine
environments.
This document aims to highlight the main exposure zones that infrastructure services need to consider
when providing corrosion protection for reinforced concrete structures. It provides a general method for
determining the exposure zone of marine reinforced concrete structures. The identified exposure zones
are used for durability analyses of corrosion damage and for making informed decisions about corrosion
protection measures. This document is a supplement to existing specifications, such as ISO 13823, ISO 16204
and ISO 12696.
v
Technical Report ISO/TR 22861:2025(en)
Guidance on marine environment zonation for steel corrosion
embedded in concrete
1 Scope
This document sets out a methodology for the exposure zone division of reinforced concrete structures in
marine environments, based on a test procedure that is provided in this document.
This document is applicable to the division of coastal and offshore marine environment areas. It is not
applicable to typhoon, strong tide and other marine environment areas.
Annexes B, C, and D provide examples of marine environment zonation to illustrate the methodology.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology 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
durability
capability of a structure or any component to satisfy, with planned maintenance, the design performance
requirements over a specified period of time under the influence of environmental action, or as a result of a
self-ageing process
3.2
environmental action
chemical, electrochemical, biological, physical and/or mechanical action causing material degradation of a
component
Note 1 to entry: For the purposes of this document, the term "environment" mainly refers to the marine environment
and related influence factors.
3.3
category of location
conventionally defined typical exposure conditions of a component or structure
Note 1 to entry: Exposure can mean in the open, under seawater, in an aggressive salt spray environment, etc. The
typical exposure conditions include the atmospheric zone, splash zone, tidal zone and submerged zone.

4 Fundamental
4.1 Transfer mechanisms
Transfer mechanisms, including gravity, condensation and drainage, either promote or prevent the
transfer of environmental influences into the agents (e.g. moisture, oxygen and temperature) that cause
environmental action on or within the components of the structural system.
4.2 Environmental action
Environmental action, such as corrosion, decay or shrinkage, result from chemical, electrochemical,
biological (e.g. insect attack), physical (e.g. UV) or mechanical action that causes material deterioration or
deformation. The environmental action considered in this document is chloride-induced corrosion.
NOTE The influence factor under different environmental actions is outlined in Clause A.1.
4.3 Exposure zone
The term "exposure zone" refers to a specific zone within the surface area of a concrete element that is
exposed to the marine environment. The category of location is standardized in relation to the effects of
environmental action.
The workflow of the exposure zone division method includes investigation (Clause 5), exposure zone division
(Clause 6) and exposure zone determination based on environmental action measurement of standard
specimens (Clause 7). For any component of marine structures, the method requires an understanding of
the transfer mechanisms (4.1) and environmental action (4.2) leading to the difference in each exposure
zone (4.3).
NOTE 1 The spatial location is divided into the horizontal platform and vertical platform according to the respective
directions. Both the horizontal platforms and vertical platforms consist of several different exposure points.
NOTE 2 The horizontal platforms are categorized based on their minimum distance from the
...