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 14713-1:2017)

ISO 14713-1:2017 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.
ISO 14713-1:2017 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.

Zinküberzüge - Leitfäden und Empfehlungen zum Schutz von Eisen- und Stahlkonstruktionen vor Korrosion - Teil 1: Allgemeine Konstruktionsgrundsätze und Korrosionsbeständigkeit (ISO 14713-1:2017)

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 14713-1:2017)

ISO 14713-1:2017 fournit des lignes directrices et des recommandations concernant les principes généraux de conception appropriés pour les pièces revêtues de zinc pour la protection contre la corrosion et le niveau de résistance à la corrosion assuré par les revêtements de zinc appliqués aux pièces en fer ou en acier, exposées à de nombreux environnements. La protection initiale est traitée en relation avec
- les procédés normalisés existants,
- les considérations théoriques, et
- les environnements d'utilisation.
ISO 14713-1:2017 s'applique aux revêtements de zinc appliqués au moyen des procédés suivants:
a) revêtements obtenus par galvanisation à chaud (appliqués après fabrication);
b) revêtements obtenus par galvanisation à chaud (appliqués sur tôle en continu);
c) revêtements obtenus par shérardisation;
d) revêtements obtenus par projection thermique;
e) revêtements obtenus par voie mécanique (matoplastie);
f) revêtements obtenus par galvanoplastie.
Ces lignes directrices et recommandations ne traitent pas de l'entretien de la protection contre la corrosion en service pour l'acier revêtu de zinc. Des lignes directrices correspondantes sont fournies dans l'ISO 12944‑5 et dans l'ISO 12944‑8.

Cinkove prevleke - Smernice in priporočila za zaščito železnih in jeklenih konstrukcij proti koroziji - 1. del: Splošna načela za projektiranje in korozijsko odpornost (ISO 14713-1:2017)

Ta dokument določa smernice in priporočila glede splošnih načel za projektiranje, ki so primerna za izdelke s cinkovimi prevlekami za zaščito proti koroziji in stopnjo
odpornosti na korozijo, ki jo zagotavljajo cinkove prevleke, nanesene na železne ali jeklene izdelke, ki so izpostavljeni različnim okoljskim dejavnikom. Prvotna zaščita je zajeta v povezavi z:
– razpoložljivimi standardnimi postopki;
– napotki za projektiranje in
– okolji za uporabo.
Ta dokument se uporablja za cinkove prevleke, nanesene z naslednjimi postopki:
a) vroče galvanizirane prevleke (nanesene po izdelavi);
b) vroče galvanizirane prevleke (nanesene na neprekinjeno ploščo);
c) šerardirane prevleke;
d) prevleke, nanesene z vročim brizganjem;
e) mehansko obdelane prevleke;
f) elektrogalvanske prevleke.
Te smernice in priporočila ne obravnavajo vzdrževanja protikorozijske zaščite
jekel s cinkovimi prevlekami. Smernice o tem je mogoče najti v standardih ISO 12944-5 in
ISO 12944-8.
OPOMBA: Obstajajo različni standardi, ki se nanašajo na izdelke (npr. za žeblje, pritrdilne elemente, cevi iz duktilne litine itd.) in podajajo posebne zahteve za nanesene sisteme cinkovih prevlek, ki presegajo vse splošne smernice, predstavljene v tem dokumentu. Te zahteve, povezane s specifičnimi izdelki, imajo prednost pred temi splošnimi priporočili.

General Information

Status
Published
Publication Date
09-May-2017
Current Stage
6060 - Definitive text made available (DAV) - Publishing
Due Date
10-May-2017
Completion Date
10-May-2017

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SLOVENSKI STANDARD
SIST EN ISO 14713-1:2017
01-september-2017
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NRQVWUXNFLMSURWLNRUR]LMLGHO6SORãQDQDþHOD]DSURMHNWLUDQMHLQNRUR]LMVNR

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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 14713-1:2017)
Zinküberzüge - Leitfäden und Empfehlungen zum Schutz von Eisen- und

Stahlkonstruktionen vor Korrosion - Teil 1: Allgemeine Konstruktionsgrundsätze und

Korrosionsbeständigkeit (ISO 14713-1:2017)

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/FDIS 14713-1:2016)
Ta slovenski standard je istoveten z: EN ISO 14713-1:2017
ICS:
25.220.40 Kovinske prevleke Metallic coatings
91.080.10 Kovinske konstrukcije Metal structures
91.080.13 Jeklene konstrukcije Steel structures
SIST EN ISO 14713-1:2017 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 14713-1:2017
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SIST EN ISO 14713-1:2017
EN ISO 14713-1
EUROPEAN STANDARD
NORME EUROPÉENNE
May 2017
EUROPÄISCHE NORM
ICS 25.220.40 Supersedes EN ISO 14713-1:2009
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 14713-1:2017)

Revêtements de zinc - Lignes directrices et Zinküberzüge - Leitfäden und Empfehlungen zum

recommandations pour la protection contre la Schutz von Eisen- und Stahlkonstruktionen vor

corrosion du fer et de l'acier dans les constructions - Korrosion - Teil 1: Allgemeine

Partie 1: Principes généraux de conception et Konstruktionsgrundsätze und Korrosionsbeständigkeit

résistance à la corrosion (ISO 14713-1:2017) (ISO 14713-1:2017)
This European Standard was approved by CEN on 3 May 2017.

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-CENELEC 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-CENELEC Management

Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,

Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels

© 2017 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 14713-1:2017 E

worldwide for CEN national Members.
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SIST EN ISO 14713-1:2017
EN ISO 14713-1:2017 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

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SIST EN ISO 14713-1:2017
EN ISO 14713-1:2017 (E)
European foreword

This document (EN ISO 14713-1:2017) 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, including for corrosion protection and corrosion testing of

metals and alloys” 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 November 2017, and conflicting national standards

shall be withdrawn at the latest by November 2017.

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 14713-1:2009.

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,

Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia,

France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,

Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and the United Kingdom.
Endorsement notice

The text of ISO 14713-1:2017 has been approved by CEN as EN ISO 14713-1:2017 without any

modification.
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SIST EN ISO 14713-1:2017
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SIST EN ISO 14713-1:2017
INTERNATIONAL ISO
STANDARD 14713-1
Second edition
2017-04
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 14713-1:2017(E)
ISO 2017
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SIST EN ISO 14713-1:2017
ISO 14713-1:2017(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2017, Published in Switzerland

All rights reserved. Unless otherwise specified, 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
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2017 – All rights reserved
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SIST EN ISO 14713-1:2017
ISO 14713-1:2017(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 2

4 Materials ....................................................................................................................................................................................................................... 2

4.1 Iron and steel substrates ................................................................................................................................................................ 2

4.2 Zinc coatings ............................................................................................................................................................................................. 3

5 Selection of zinc coating................................................................................................................................................................................ 3

6 Design requirements ........................................................................................................................................................................................ 3

6.1 General principles of design to avoid corrosion ......................................................................................................... 3

6.2 Design for application of different zinc coating processes ............................................................................... 4

6.3 Tubes and hollow sections............................................................................................................................................................ 4

6.3.1 General...................................................................................................................................................................................... 4

6.3.2 Corrosion protection of internal and external surfaces ................................................................. 4

6.4 Connections ............................................................................................................................................................................................... 5

6.4.1 Fastenings to be used with hot dip galvanized, sherardized or thermally

sprayed coatings............................................................................................................................................................... 5

6.4.2 Welding considerations related to coatings ............................................................................................. 5

6.4.3 Brazing or soldering ..................................................................................................................................................... 6

6.5 Duplex systems ....................................................................................................................................................................................... 6

6.6 Maintenance .............................................................................................................................................................................................. 6

7 Corrosion in different environments .............................................................................................................................................. 6

7.1 Atmospheric exposure ..................................................................................................................................................................... 6

7.2 Exposure to soils ................................................................................................................................................................................... 9

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 2017 – All rights reserved iii
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SIST EN ISO 14713-1:2017
ISO 14713-1:2017(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.

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

constitute an endorsement.

For an explanation on 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 the following

URL: w w w . i s o .org/ iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 107, Metallic and other inorganic coatings,

Subcommittee SC 4, Hot dip coatings (galvanized, etc.).

This second edition cancels and replaces the first edition (ISO 14713-1:2009), of which it constitutes

a minor revision following the publication of ISO 17668:2016 and ISO 9223:2012, with the following

changes:
— ISO 17668 has replaced EN 13811;

— revisions to Table 1 to align with corresponding descriptions of typical environments in

ISO 9223:2012, Table C.1 and to make clearer that the corrosion rates presented are for the first

year of exposure.
A list of all parts in the ISO 14713 series can be found on the ISO website.
iv © ISO 2017 – All rights reserved
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SIST EN ISO 14713-1:2017
INTERNATIONAL STANDARD ISO 14713-1:2017(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 document 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 document 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 document. These specific product-related requirements will take precedence over these general

recommendations.
2 Normative references

ISO 1461, Hot dip galvanized coatings on fabricated iron and steel articles — Specifications and test methods

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 8044:2015, Corrosion of metals and alloys — Basic terms and definitions

ISO 12683, Mechanically deposited coatings of zinc — Specification and test methods

© ISO 2017 – All rights reserved 1
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SIST EN ISO 14713-1:2017
ISO 14713-1:2017(E)

ISO 17668, Zinc diffusion coatings on ferrous products — Sherardizing — Specification

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 and ISO 17668 and the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— IEC Electropedia: available at http:// www .electropedia .org/
— ISO Online browsing platform: available at http:// www .iso .org/ obp
3.1
atmospheric corrosion

corrosion with the earth’s atmosphere at ambient temperature as the corrosive environment

[SOURCE: ISO 8044:2015, 3.4]
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

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).
2 © ISO 2017 – All rights reserved
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SIST EN ISO 14713-1:2017
ISO 14713-1:2017(E)
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 document).

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;
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.
© ISO 2017 – All rights reserved 3
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SIST EN ISO 14713-1:2017
ISO 14713-1:2017(E)

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.

g) Hot dip galvanizing (in accordance with ISO 1461), sherardizing (in accordance with ISO 17668) or

thermal spraying (in accordance with ISO 2063) should take place after bending and other forms of

fabrication.

h) Methods of marking parts should 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).
4 © ISO 2017 – All rights reserved
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SIST EN ISO 14713-1:2017
ISO 14713-1:2017(E)
6.4 Connections

6.4.1 Fastenings to be used with hot dip galvanized, sherardized or thermally 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.

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, sherardized 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 par
...

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