EN ISO 14713-1:2009

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Zinc coatings - Guidelines and recommendations for the protection against corrosion of
iron and steel in structures - Part 1: General principles of design and corrosion resistance
(ISO 14713-1:2009)
Zinküberzüge - Leitfäden und Empfehlungen zum Schutz von Eisen- und
Stahlkonstruktionen vor Korrosion - Teil 1: Allgemeine Konstruktionsgrundsätze und
Korrosionsbeständigkeit (ISO 14713-1:2009)
Revêtements de zinc - Lignes directrices et recommandations pour la protection contre
la corrosion du fer et de l'acier dans les constructions - Partie 1: Principes généraux de
conception et résistance à la corrosion (ISO 14713-1:2009)
Ta slovenski standard je istoveten z: EN ISO 14713-1:2009
ICS:
25.220.40 Kovinske prevleke Metallic coatings
91.080.10 Kovinske konstrukcije Metal structures
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN ISO 14713-1
NORME EUROPÉENNE
EUROPÄISCHE NORM
December 2009
ICS 25.220.40; 91.080.10 Supersedes EN ISO 14713:1999
English Version
Zinc coatings - Guidelines and recommendations for the
protection against corrosion of iron and steel in structures - Part
1: General principles of design and corrosion resistance (ISO
14713-1:2009)
Revêtements de zinc - Lignes directrices et Zinküberzüge - Leitfäden und Empfehlungen zum Schutz
recommandations pour la protection contre la corrosion du von Eisen- und Stahlkonstruktionen vor Korrosion - Teil 1:
fer et de l'acier dans les constructions - Partie 1: Principes Allgemeine Konstruktionsgrundsätze und
généraux de conception et résistance à la corrosion (ISO Korrosionsbeständigkeit (ISO 14713-1:2009)
14713-1:2009)
This European Standard was approved by CEN on 18 November 2009.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the CEN Management Centre or to any CEN member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as the
official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2009 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 14713-1:2009: E
worldwide for CEN national Members.

Contents Page
Foreword .3

Foreword
This document (EN ISO 14713-1:2009) has been prepared by Technical Committee ISO/TC 107 "Metallic and
other inorganic coatings" in collaboration with Technical Committee CEN/TC 262 “Metallic and other inorganic
coatings” the secretariat of which is held by BSI.
This European Standard shall be given the status of a national standard, either by publication of an identical
text or by endorsement, at the latest by June 2010, and conflicting national standards shall be withdrawn at
the latest by June 2010.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 14713:1999.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the United Kingdom.
Endorsement notice
The text of ISO 14713-1:2009 has been approved by CEN as a EN ISO 14713-1:2009 without any
modification.
INTERNATIONAL ISO
STANDARD 14713-1
First edition
2009-12-15
Zinc coatings — Guidelines and
recommendations for the protection
against corrosion of iron and steel in
structures —
Part 1:
General principles of design and
corrosion resistance
Revêtements de zinc — Lignes directrices et recommandations pour la
protection contre la corrosion du fer et de l'acier dans les
constructions —
Partie 1: Principes généraux de conception et résistance à la corrosion

Reference number
ISO 14713-1:2009(E)
©
ISO 2009
ISO 14713-1:2009(E)
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ii © ISO 2009 – All rights reserved

ISO 14713-1:2009(E)
Contents Page
Foreword .iv
1 Scope.1
2 Normative references.1
3 Terms and definitions .2
4 Materials .3
4.1 Iron and steel substrates.3
4.2 Zinc coatings .3
5 Selection of zinc coating .3
6 Design requirements.4
6.1 General principles of design to avoid corrosion .4
6.2 Design for application of different zinc coating processes.5
6.3 Tubes and hollow sections.5
6.4 Connections.5
6.5 Duplex systems .6
6.6 Maintenance.7
7 Corrosion in different environments .7
7.1 Atmospheric exposure.7
7.2 Exposure to soils.10
7.3 Exposure to water .12
7.4 Abrasion .12
7.5 Exposure to chemicals .12
7.6 Elevated temperatures.13
7.7 Contact with concrete.13
7.8 Contact with wood.14
7.9 Bimetallic contact.14
8 Accelerated test methods applied to zinc coatings.16
Bibliography.17

ISO 14713-1:2009(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 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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 14713-1 was prepared by Technical Committee ISO/TC 107, Metallic and other inorganic coatings,
Subcommittee SC 4, Hot dip coatings (galvanized, etc.).
This first edition, together with ISO 14713-2 and ISO 14713-3, cancels and replaces ISO 14713:1999, which
has been technically revised.
ISO 14713 consists of the following parts, under the general title Zinc coatings — Guidelines and
recommendations for the protection against corrosion of iron and steel in structures:
⎯ Part 1: General principles of design and corrosion resistance
⎯ Part 2: Hot dip galvanizing
⎯ Part 3: Sherardizing
iv © ISO 2009 – All rights reserved

INTERNATIONAL STANDARD ISO 14713-1:2009(E)

Zinc coatings — Guidelines and recommendations for the
protection against corrosion of iron and steel in structures —
Part 1:
General principles of design and corrosion resistance
1 Scope
This part of ISO 14713 provides guidelines and recommendations regarding the general principles of design
which are appropriate for articles to be zinc coated for corrosion protection and the level of corrosion
resistance provided by zinc coatings applied to iron or steel articles, exposed to a variety of environments.
Initial protection is covered in relation to
⎯ available standard processes,
⎯ design considerations, and
⎯ environments for use.
This part of ISO 14713 applies to zinc coatings applied by the following processes:
a) hot dip galvanized coatings (applied after fabrication);
b) hot dip galvanized coatings (applied onto continuous sheet);
c) sherardized coatings;
d) thermal sprayed coatings;
e) mechanically plated coatings;
f) electrodeposited coatings.
These guidelines and recommendations do not deal with the maintenance of corrosion protection in service
for steel with zinc coatings. Guidance on this subject can be found in ISO 12944-5 and ISO 12944-8.
NOTE There are a variety of product-related standards (e.g. for nails, fasteners, ductile iron pipes, etc.) which
provide specific requirements for the applied zinc coating systems which go beyond any general guidance presented in
this part of ISO 14713. These specific product-related requirements will take precedence over these general
recommendations.
2 Normative references
The following referenced documents are indispensable for the application 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 1461, Hot dip galvanized coatings on fabricated iron and steel articles — Specifications and test methods
ISO 14713-1:2009(E)
ISO 2063, Thermal spraying — Metallic and other inorganic coatings — Zinc, aluminium and their alloys
ISO 2064, Metallic and other inorganic coatings — Definitions and conventions concerning the measurement
of thickness
ISO 2081, Metallic and other inorganic coatings — Electroplated coatings of zinc with supplementary
treatments on iron or steel
ISO 8044:1999, Corrosion of metals and alloys — Basic terms and definitions
ISO 9223, Corrosion of metals and alloys — Corrosivity of atmospheres — Classification
ISO 9224, Corrosion of metals and alloys — Corrosivity of atmospheres — Guiding values for the corrosivity
categories
ISO 9226, Corrosion of metals and alloys — Corrosivity of atmospheres — Determination of corrosion rate of
standard specimens for the evaluation of corrosivity
ISO 11844-1, Corrosion of metals and alloys — Classification of low corrosivity of indoor atmospheres —
Determination and estimation of indoor corrosivity
ISO 12683, Mechanically deposited coatings of zinc — Specification and test methods
ISO 12944-5, Paints and varnishes — Corrosion protection of steel structures by protective paint systems —
Part 5: Protective paint systems
ISO 12944-8, Paints and varnishes — Corrosion protection of steel structures by protective paint systems —
Part 8: Development of specifications for new work and maintenance
ISO 14713-2, Zinc coatings — Guidelines and recommendations for the protection against corrosion of iron
and steel in structures — Part 2: Hot dip galvanizing
ISO 14713-3, Zinc coatings — Guidelines and recommendations for the protection against corrosion of iron
and steel in structures — Part 3: Sherardizing
EN 10240, Internal and/or external protective coatings for steel tubes — Specification for hot dip galvanized
coatings applied in automatic plants
EN 10346, Continuously hot-dip coated steel flat products — Technical delivery conditions
EN 13438, Paints and varnishes — Powder organic coatings for galvanized or sherardized steel products for
construction purposes
EN 13811, Sherardizing — Zinc diffusion coatings on ferrous products — Specification
EN 15520, Thermal spraying — Recommendations for constructional design of components with thermally
sprayed coatings
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 1461, ISO 2063, ISO 2064,
ISO 8044, ISO 12683, EN 13811 and the following apply.
3.1
atmospheric corrosion
corrosion with the earth’s atmosphere at ambient temperature as the corrosive environment
(see ISO 8044:1999, 3.04)
2 © ISO 2009 – All rights reserved

ISO 14713-1:2009(E)
3.2
elevated temperatures
temperatures between + 60 °C and + 200 °C
3.3
exceptional exposure
special cases, such as exposure that substantially intensifies the corrosive exposure and/or places increased
demands on the corrosion protection system
3.4
life to first maintenance
the time interval that can elapse after initial coating before coating deterioration reaches the point when
maintenance is necessary to restore protection of the basis metal
4 Materials
4.1 Iron and steel substrates
In hot dip galvanizing, the reactivity of the steel is modified by its chemical composition, particularly by the
silicon plus phosphorus contents (see ISO 14713-2). The metallurgical and chemical nature of the steel is
irrelevant to protection by thermally sprayed or sherardized coatings.
The broad range of steels likely to be subject to zinc coating will commonly fall into the following categories:
⎯ carbon steel, composed simply of iron and carbon, accounts for 90 % of steel production [e.g.
EN 10025-2 and EN 10080 (steel reinforcement)];
⎯ high strength, low-alloy (HSLA) steels have small additions (usually < 2 % by weight) of other elements,
typically 1,5 % manganese, to provide additional strength for a modest price increase (e.g. EN 10025-6);
⎯ low-alloy steel is alloyed with other elements, usually molybdenum, manganese, chromium, or nickel, in
amounts of up to 10 % by weight to improve the hardenability of thick sections (e.g. EN 10083-1).
Steel can be hot rolled or cold formed. Hot rolling is used to produce angle, “I”, “H” and other structural
sections. Some structural sections, e.g. safety barriers, cladding rails, and cladding panels, are cold formed.
Cast and wrought irons are of various metallurgical and chemical compositions. This is irrelevant to protection
by thermally sprayed or sherardized coatings but special consideration is needed regarding the cast irons
most suitable for hot dip galvanizing (see ISO 14713-2).
4.2 Zinc coatings
The application of zinc coatings provides an effective method of retarding or preventing corrosion of ferrous
materials (see Clause 1 for the range of zinc coatings/processes covered by this part of ISO 14713). Zinc
coatings are used in this regard because they protect iron and steel both by barrier action and by galvanic
action.
5 Selection of zinc coating
The zinc coating system to be used should be selected by taking the following items into account:
a) the general environment (macro-climate) in which it is to be applied;
b) local variations in the environment (micro-climate), including anticipated future changes and any
exceptional exposure;
ISO 14713-1:2009(E)
c) the required life to first maintenance of the zinc coating system;
d) the need for ancillary components;
e) the need for post-treatment for temporary protection;
f) the need for painting, either initially (duplex system) or when the zinc coating is approaching the end of its
life to first maintenance to achieve minimal maintenance cost;
g) the availability and cost;
h) if the life to first maintenance of the system is less than that required for the structure, its ease of
maintenance.
NOTE The life for a zinc coating in any particular atmospheric exposure condition is approximately proportional to the
thickness of the coating.
The operational sequence for applying the selected system should be determined in consultation with the
steel fabricator and the applier of the zinc coating system.
6 Design requirements
6.1 General principles of design to avoid corrosion
Design of structures and products should influence the choice of protective system. It may be appropriate and
economic to modify the design to suit the preferred protective system.
The items in a) to j) should be considered.
a) Safe and easy access for cleaning and maintenance should be provided.
b) Pockets and recesses in which water and dirt can collect should be avoided; a design with smooth
contours facilitates application of a protective coating and helps to improve corrosion resistance.
Corrosive chemicals should be directed away from structural components, e.g. drainage tubes should be
used to control de-icing salts.
c) Areas which are inaccessible after erection should be given a coating system designed to last the
required life of the structure.
d) If bimetallic corrosion (corrosion due to contact between dissimilar materials: metals and/or alloys) is
possible, additional protective measures should be considered (see ISO 14713-2).
e) Where the coated iron and steel are likely to be in contact with other building materials, special
consideration should be given to the contact area; e.g. the use of paint, tapes or plastic foils should be
considered.
f) Hot dip galvanizing, sherardizing, mechanical coating, zinc flake coating or electroplating can be provided
only in works; thermal spraying can be applied in works or on site. When paint is to be applied to a zinc
coating, the application is more readily controlled in works but, where there is a likelihood of substantial
damage occurring during transportation and erection, specifiers may prefer to apply the final paint coat on
site. The application of a powder coating on metal coated steel can only be done in works.
Where the total system is applied offsite, the specification has to cover the need for care at all stages to
prevent damage to the finished iron and steel and set out repair procedures to the coating once the
steelwork is erected.
4 © ISO 2009 – All rights reserved

ISO 14713-1:2009(E)
g) Hot dip galvanizing (in accordance with ISO 1461), sherardizing (in accordance with EN 13811) or
thermal spraying (in accordance with ISO 2063) should take place after bending and other forms of
fabrication.
h) Methods of marking parts shall not have an influence on the quality of the pre-treatment operations prior
to coating.
i) Precautions may be required to minimize the likelihood of deformation during processing or subsequently.
j) The conditions experienced by the articles during coating application may also need to be considered.
6.2 Design for application of different zinc coating processes
The design practice for hot dip coating differs from that for other zinc coating systems. ISO 14713-2 provides
guidance on the design for hot dip coatings. This supplements the general principles of good design for steel
structures.
The design practice for sherardized coatings can be found in ISO 14713-3.
The design for zinc thermal spraying should be discussed with the thermal sprayer at an early stage so that
adequate provision is made for access to all areas of the article (see EN 15520).
The design for electroplating with zinc follows the general design principles for electroplating and these are
not given here. The design for mechanical coating is best discussed with specialist applicators; in general,
these processes are most suitable for small parts which can be tumbled in a barrel but specialist plants may
be available for other shapes.
6.3 Tubes and hollow sections
6.3.1 General
If they are dry and hermetically sealed, the internal surfaces of tubes and hollow sections will not need
protection. Where hollow sections are fully exposed to the weather, or interior environments that might give
rise to condensation, and are not hermetically sealed, consideration should be given to the need for both
internal and external protection.
6.3.2 Corrosion protection of internal and external surfaces
Hot dip galvanizing gives equal thickness internally and externally. There are some special products where
the thickness of the coating is different on internal and external surfaces, e.g. tubes for water distribution
systems (see EN 10240). When tubes and hollow sections are hot dip galvanized after assembly into
structures, drainage/venting holes should be provided for processing purposes (see ISO 14713-2).
Sherardizing gives equal thickness internally and externally. No precautions are needed for hollow sections.
When tubes are sherardized, the zinc dust and sand mixture should be loaded into the tubes before starting
the thermal diffusion process (see ISO 14713-3)
6.4 Connections
6.4.1 Fastenings to be used with hot dip galvanized, sherardized or thermal sprayed coatings
The protective treatment of bolts, nuts and other parts of the structural connections should be given careful
consideration. Ideally, their protective treatment should provide a similar performance to that specified for the
general surfaces. Specific requirements are given in the appropriate product International Standards (e.g.
ISO 10684) and in a series of International Standards for coatings on fasteners which are in the course of
preparation/publication.
ISO 14713-1:2009(E)
Hot dip galvanized (see, for example, ISO 1461 which covers specified minimum coating thicknesses up to
55 µm), sherardized, or other coatings on steel fasteners should be considered. Alternatively, stainless steel
fasteners can be used; for precautions to take in order to minimize the potential for bimetallic corrosion,
see 7.9.
The mating surfaces of connections made with high-strength friction-grip bolts should be given special
treatment. It is not necessary to remove thermally sprayed, sheradized or hot dip coatings from such areas to
obtain an adequate coefficient of friction. However, consideration has to be given to any long-term slip or
creep-avoidance requirements and to any necessary adjustments to the assembly dimensions.
6.4.2 Welding considerations related to coatings
It is recommended to weld prior to hot dip galvanizing, sherardizing or thermal spraying. The use of welding
anti-spatter sprays that cannot be removed in the pretreatment process at the galvanizers' works should be
avoided. For this reason, where welding sprays are used, low silicone, water-soluble sprays are
recommended. After welding, the surface should be prepared to the standard specified for preparing the
steelwork overall before applying the protective coating process. Welding should be balanced (i.e. equal
amounts on each side of the main axis) to avoid introducing unbalanced stresses in a structure. Welding
residues have to be removed before coating. The normal pretreatments for thermal spraying are usually
sufficient for this purpose but extra pretreatment may be needed for hot dip galvanizing; in particular, weld
slag should be removed separately. Some forms of welding leave alkaline deposits behind. These have to be
removed by blast-cleaning followed by washing with clean water before applying thermally-sprayed coatings.
(This does not apply to hot dip galvanizing and sherardizing where the pretreatment process removes alkaline
deposits.)
It is desirable that fabrication takes place without the use of a blast primer, as this has to be removed before
hot dipping, sherardizing or thermal spraying.
Where welding takes place after hot dip galvanizing, sherardizing or thermal spraying, it is preferable, before
welding, to remove the coating locally in the area of the weld to ensure the highest quality weld. After welding,
protection should be appropriately restored locally by thermal spraying, “solder sticks” and/or zinc dust paints.
It is not recommended to weld sherardized articles, but spot-welding may be possible in certain applications.
After welding of coated steels, the surface should be prepared to the standard specified for preparing the
steelwork overall before applying paint or fusion-bonded powder coatings.
Assemblies comprising different metals needing different pretreatments should be discussed with the
processor.
Welding of zinc coated parts must be done with appropriate local air ventilation in accordance with health and
safety regulations.
6.4.3 Brazing or soldering
Soft soldered assemblies cannot be hot dip galvanized or sherardized and brazing should be avoided if
possible — many types of brazing are unsuitable for hot dip galvanizing or sherardizing. The galvanizer or
sherardizer should be consulted if brazing is being considered.
Since corrosive fluxes may be used in these processes, removal of flux residues after the coating process is
essential to avoid corrosion of the coated parts; the design of these parts should facilitate this.
6.5 Duplex systems
ISO 12944-5 and EN 13438 give information on organic coatings which are applied to hot dip galvanized or
sherardized coatings. When such an organic coating has been applied, the term “duplex system” is used to
describe the combination of coatings — historically, this term was most commonly used to describe organic
coatings on hot dip galvanized articles.
6 © ISO 2009 – All rights reserved

ISO 14713-1:2009(E)
NOTE EN 15773 deals with quality and communications requirements in the supply chain when specifying the supply
of duplex systems.
The life of a zinc coated steel structure is longer than the life of the zinc coating system that is initially applied
to it, as some steel can be lost by corrosion before a structure becomes unserviceable. If it is necessary to
prolong the life of the zinc coating, maintenance has to take place before any steel rusting occurs and
preferably while at least 20 µm to 30 µm of zinc coating remains. This gives a maintained zinc coating plus
organic coating system a longer total life than a simple organic coating.
The total life of a zinc coating plus organic coating system is usually significantly greater than the sum of the
lives of the zinc coating and protective organic coating. There is a synergistic effect, i.e. the presence of zinc
coatings reduces under-rusting of the paint film; the paint preserves the zinc coating from early corrosion.
Where it is desired to retain a reasonably intact layer of paint as a basis for maintenance, the initially applied
paint system should have extra thickness.
Maintenance usually takes place when the zinc coating loses its appearance or becomes degraded. Zinc
coatings usually take longer to degrade than paint. Hence a zinc coating may be recommended for 20 years
or more up to first maintenance, whereas the same coating when covered by paint is, for reasons of
appearance of the paint, recommended for only 10 years up to first maintenance. It should also be noted that
an area of degraded paint can retain moisture and hence hasten the corrosion of metal, particularly on a
surface not washed by rain.
If maintenance is delayed until the zinc coating has been consumed and rusting has started, the iron and steel
have to be maintained in the same way as rusted painted steel.
6.6 Maintenance
Zinc coatings may be left unmaintained if the corrosion rate of the coating is insufficient to affect the
performance of the structure in its designed period of use. If a longer life span is required, maintenance of the
coating should be carried out by stripping and re-galvanizing (part of) the structure or by painting while some
original coating remains.
7 Corrosion in different environments
7.1 Atmospheric exposure
The corrosion rate of a zinc coating is affected by the time for which it is exposed to wetness, air pollution and
contamination of the surface, but the corrosion rates are much slower than for steel and often decrease with
time. General information on the atmospheric corrosion rate for zinc is given in ISO 9224.
Table 1 gives basic groups of environments (related to ISO 9223). Where the relative humidity is below
60 %, the corrosion rate of iron and steel is negligible and they may not require zinc coating, e.g. inside
many buildings. Zinc coating with or without painting may, however, be required for appearance or for
reasons of hygiene, e.g. in a food factory. When the relative humidity is higher than 60 % or where they
are exposed to wet or immersed conditions or prolonged condensation then, like most metals, iron and
steel are subject to more serious corrosion. Contaminants deposited on the surface, notably chlorides
and sulfates, accelerate attack. Substances that deposit on the surface of the iron and steel increase
corrosion if they absorb moisture or go into solution on the surface of the iron and steel. The temperature
also influences the corrosion rate of unprotected iron and steel and temperature fluctuations have a
stronger effect than the average temperature value.
The micro-environment, i.e. the conditions prevailing around the structure, is also important because it allows
a more precise assessment of the likely conditions than study of the basic climate alone. It is not always
known at the planning stage of a project. Every effort should be made to identify it accurately, however,
because it is an important factor in the total environment against which corrosion protection is required. An
example of a micro-climate is the underside of a bridge (particularly over water).
ISO 14713-1:2009(E)
The corrosion of steelwork inside buildings is dependent upon the internal environment but in “normal”
atmospheres, e.g. dry and heated, it is insignificant. Steelwork in the perimeter walls of buildings is influenced
by the configuration within the perimeter wall, e.g. steelwork without direct contact with the outer leaf of a wall
comprising two parts separated by an air space is at less risk of corrosion than steelwork in contact with or
embedded in the outer leaf. Buildings containing industrial processes, chemical environments, wet or
contaminated environments should be given special consideration. Steelwork which is partially sheltered, e.g.
farm barns and aircraft hangars, should be considered as being subject to the exterior environment.
Table 1 also sets out an indication of the likely range of corrosion rates which are applicable to zinc coatings
exposed to the different types of corrosivity category dealt with in ISO 9223.
8 © ISO 2009 – All rights reserved

ISO 14713-1:2009(E)
Table 1 — Description of typical atmospheric environments
related to the estimation of corrosivity categories
Corrosivity category C Typical environments (examples)
Corrosion rate for zinc
(based upon one year
Indoor Outdoor
−1
exposures), r (µm⋅a )
corr
and corrosion level
C1 Heated spaces with low relative humidity Dry or cold zone, atmospheric environment with very low
and insignificant pollution, e.g. offices, pollution and time of wetness, e.g. certain deserts, central
r u 0,1
corr
schools, museums Arctic/Antarctica
Very low
Unheated spaces with varying Temperate zone, atmospheric environment with low
C2
temperature and relative humidity. Low pollution (SO < 5 µg/m ), e.g.: rural areas, small towns.
0,1 < r u 0,7
corr
frequency of condensation and low Dry or cold zone, atmospheric environment with short time
Low
pollution, e.g. storage, sport halls of wetness, e.g. deserts, sub-arctic areas
Spaces with moderate frequency of Temperate zone, atmospheric environment with medium
C3
3 3
condensation and moderate pollution from pollution (SO : 5 µg/m to 30 µg/m ) or some effect of
0,7 < r u 2 production process, e.g. food-processing chlorides, e.g. urban areas, coastal areas with low
corr
plants, laundries, breweries, dairies deposition of chlorides, subtropical and tropical zones with
Medium
atmosphere with low pollution
Spaces with high frequency of Temperate zone, atmospheric environment with high
3 3
condensation and high pollution from pollution (SO : 30 µg/m to 90 µg/m ) or substantial effect
C4
production process, e.g. industrial of chlorides, e.g. polluted urban areas, industrial areas,
2 < r u 4
corr
processing plants, swimming pools coastal areas without spray of salt water, exposure to
High
strong effect of de-icing salts, subtropical and tropical
zones with atmosphere with medium pollution
Spaces with very high frequency of Temperate and subtropical zones, atmospheric
condensation and/or with high pollution environment with very high pollution (SO : 90 µg/m to
C5
from production process, e.g. mines, 250 µg/m ) and/or important effect of chlorides, e.g.
4 < r u 8
corr
caverns for industrial purposes, industrial areas, coastal areas, sheltered positions on
Very high
coastline
unventilated sheds in subtropical and
tropical zones
Spaces with almost permanent Subtropical and tropical zones (very high time of wetness),
condensation or extensive periods of atmospheric environment with very high pollution (SO
exposure to extreme humidity effects higher than 250 µg/m ), including accompanying and
CX
and/or with high pollution from production production pollution and/or strong effect of chlorides, e.g.
8 < r u 25
corr
process, e.g. unventilated sheds in humid extreme industrial areas, coastal and offshore areas with
Extreme
tropical zones with penetration of outdoor occasional contact with salt spray
pollution including airborne chlorides and
corrosion-stimulating particulate matter
NOTE 1 Deposition of chlorides in coastal areas is strongly dependent on the variables influencing the transport inland of sea-salt, such as wind
direction, wind velocity, local topography, wind sheltering islands beyond the coast, distance of the site from the sea, etc.
NOTE 2 Extreme influence of chlorides, which is typical of marine splashing or heavy salt spray, is beyond the scope of ISO 9223.
NOTE 3 Corrosivity classification of specific service atmospheres, e.g. in chemical industries, is beyond the scope of ISO 9223.
NOTE 4 Sheltered and not rain-washed surfaces, in a marine atmospheric environment where chlorides are deposited, can experience a higher
corrosivity category due to the presence of hygroscopic salts.
NOTE 5 In environments with an expected “CX category”, it is recommended to determine the atmospheric corrosivity classification from one year
corrosion losses. ISO 9223 is currently under revision; category “CX” will be included in the revised document.
NOTE 6 The concentration of sulfur dioxide (SO ) should be determined during at least 1 year and is expressed as the annual average.
NOTE 7 Detailed descriptions of types of indoor environments within corrosivity categories C1 and C2 is given in ISO 11844-1. Indoor corrosivity
categories IC1 to IC5 are defined and classified.
NOTE 8 The classification criterion is based on the methods of determination of corrosion rates of standard specimens for the evaluation of corrosivity
(see ISO 9226).
NOTE 9 The thickness-loss values are identical to those given in ISO 9223, except that, for rates of 2 µm (per year) or more, the figures are rounded to
whole numbers.
NOTE 10 The zinc reference material is characterized in ISO 9226.
NOTE 11 Corrosion rates exceeding the upper limits in category C5 are considered as extreme. Corrosivity category CX refers to specific marine and
marine/industrial environments.
NOTE 12 To a first approximation, the corrosion of all metallic zinc surfaces is at the same rate in a particular environment. Iron and steel will normally
corrode 10 to 40 times faster than zinc, the higher ratios usually being in high-chloride environments. The data is related to data on flat sheet given in
ISO 9223 and ISO 9224.
NOTE 13 Change in atmospheric environments occurs with time. For many regions, the concentrations of pollutants (particularly SO ) in the atmosphere
have reduced with time. This has lead to a lowering of the corrosivity category for these regions. This has, in turn, lead to the zinc coatings experiencing
lower corrosion rates compared to historical corrosion performance data. Other regions have experienced increasing pollution and industrial activity and
therefore would be expected to develop environments more accurately described by higher corrosivity categories.
NOTE 14 The corrosion rate for zinc and for zinc-iron alloy layers are approximately the same.
ISO 14713-1:2009(E)
Table 2 indicates the life to first maintenance for a selection of zinc coatings exposed to the range of these
corrosivity categories. The minimum and maximum life expectancies are indicated for each chosen system
and durability class indicated. Durability is classified into the following classes:
a) Very low (VL): 0 to < 2 years
b) Low (L): 2 to < 5 years
c) Medium (M): 5 to < 10 years
d) High (H): 10 to < 20 years
e) Very high (VH): W 20 years
7.2 Exposure to soils
The wide range in physical and chemical properties of soils (e.g. the pH variation from 2,6 to 12 and resistivity
from tens of ohms to approximately 100 kΩ) and the gross inhomogeniety of soils means that corrosion of zinc
coatings in soils is rarely uniform in nature. Corrosion in soil is dependent on the mineral content, on the
nature of these minerals and on the organic components, water content and oxygen content (aerobic and
anaerobic corrosion). Corrosion rates in disturbed soil conditions are usually higher than in undisturbed soil.
General guidance on the corrosion likelihood in soil can also be found in EN 12501-1.
Lime-containing soils and sandy soils (provided that they are chloride-free) are, in general, least corrosive,
whilst clay soils and clay marl soils are corrosive to a limited extent. In bog and peat soils, the corrosiveness
depends on the total acid content.
Where major iron and steel structures such as pipelines, tunnels, and tank ins
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