BS en Iso 14713-1 2017

BS EN ISO 14713‑1:2017

BSI Standards Publication

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

BS EN ISO 14713‑1:2017

BRITISH STANDARD

National foreword

This British Standard is the UK implementation of EN ISO 14713‑1:2017. It is identical to ISO 14713‑1:2017. It supersedes BS EN ISO 14713‑1:2009, which is withdrawn. The UK participation in its preparation was entrusted to Technical Committee STI/34, Hot dip galvanized coatings. A list of organizations represented on this committee can be obtained on request to its secretary. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. © The British Standards Institution 2017 Published by BSI Standards Limited 2017 ISBN 978 0 580 94155 9 ICS 25.220.40 Compliance with a British Standard cannot confer immunity from legal obligations .

This British Standard was published under the authority of the Standards Policy and Strategy Committee on 30 June 2017. Amendments/corrigenda issued since publication

Date

Text affected

BS EN ISO 14713‑1:2017

EN ISO 14713-1

EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM

May 2017

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 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)

Zinküberzüge - Leitfäden und Empfehlungen zum Schutz von Eisen- und Stahlkonstruktionen vor Korrosion - Teil 1: Allgemeine Konstruktionsgrundsätze und Korrosionsbeständigkeit (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 C O M I TÉ E URO P É E N D E N O RM ALI S ATI O N E U RO P ÄI S C H E S KO M I T E E F Ü R N O RM U N G

CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels © 2017 CEN

All rights of exploitation in any form and by any means reserved worldwide for CEN national Members.

Ref. No. EN ISO 14713-1:2017 E

BS 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.

3

BS EN ISO 14713‑1:2017 ISO 1 471 3 -1 : 2 01 7(E)

Contents

Page

Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv 1

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

2

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

3

Terms and definitions

4

Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

.....................................................................................................................................................................................

2

4. 1

I ro n an d s te e l s u b s trate s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

4. 2

Z i n c co ati n gs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

5

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

6

Design requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 6.1

G e n e ral p ri n ci p l e s o f d e s i gn to avo i d co rro s i o n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

6.2

D e s i gn fo r ap p l i cati o n o f d i ffe re n t z i n c co ati n g p ro ce s s e s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

6.3

Tu b e s an d h o l l o w s e cti o n s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

6.4

6.3 .1

G e n e ral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

6.3 .2

C o rro s i o n p ro te cti o n o f i n te rn al an d exte rn al s u rface s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

C o n n e cti o n s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

6.4.1

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

6. 4. 2

We l d i n g co n s i d e rati o n s re l ate d to co ati n gs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

6. 4. 3

B raz i n g o r s o l d e ri n g . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

........................................................................................................................................... ....................

7

8

5

6.5

Duplex systems

6.6

M ai n te n an ce . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

.......................................................................................................................................................................................

6

Corrosion in different environments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 7.1

Atm o s p h e ri c exp o s u re . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

7.2

E xp o s u re to s o i l s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

7.3

E xp o s u re to wate r . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2

7.4

Ab ras i o n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2

7.5

E xp o s u re to ch e m i cal s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2

7.6

E l evate d te m p e ratu re s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 3

7.7

C o n tact wi th co n cre te . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 3

7.8

C o n tact wi th wo o d . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 4

7.9

B i m e tal l i c co n tact . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 4

Accelerated test methods applied to zinc coatings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 6

Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 7

© I S O 2 0 1 7 – Al l ri gh ts re s e rve d

iii

BS EN ISO 14713‑1:2017 ISO 1 471 3 -1 : 2 01 7(E)

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fic

te r m s

ad he re nc e

a nd

to

the

s e e the fo l l o w i n g

U R L : w w w. i s o . o r g/ i s o/fo re wo rd . htm l .

Hot dip coatings (galvanized, etc.)

T h i s do c u me n t wa s p re p a re d b y Te c h n ic a l C o m m i t te e I S O/ T C 1 0 7, S ub c o m m i t te e S C 4 ,

This a

s e c o nd

m i no r

e d i tio n

re v i s i o n

c a nc e l s

fo l l o w i n g

a nd

the

re p l ac e s

the

p ub l ic atio n

fi r s t

of I S O

Metallic and other inorganic coatings

,

.

e d i tio n

(I SO

176 6 8 : 2 0 1 6

1471 3 -1 : 2 0 0 9 ) ,

a nd

ISO

o f wh i c h

9 2 2 3 : 2 01 2 ,

w i th

it

c o n s ti tu te s

the

fo l l o w i n g

c h a n ge s :

—

I S O 176 6 8 h a s re p l ac e d E N 1 3 8 1 1 ;

—

re v i s io n s ISO

to

Tab l e

92 2 3 : 2 01 2 ,

1

Tab l e

to C .1

al ign a nd

to

w i th m a ke

c o r re s p o nd i n g c l e a re r

th at the

de s c r i p ti o n s c o r ro s i o n

of

rate s

t y p ic a l

e nv i ro n me n ts

p re s e n te d

a re

fo r

the

in

fi r s t

ye a r o f e x p o s u re .

A l i s t o f a l l p a r ts i n the I S O 1471 3 s e r i e s c a n b e fo u nd o n the I S O we b s i te .

iv

© I S O 2 0 1 7 – Al l ri gh ts re s e rve d

BS EN ISO 14713‑1:2017 INTERNATIONAL STANDARD

ISO 1 471 3 -1 : 2 01 7(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

T his

do c u me n t

de s i g n

wh ic h

p ro v ide s

a re

g u i de l i ne s

ap p ro p r i ate

c o r ro s io n re s i s t a nc e

fo r

a nd

a r tic l e s

re c o m me n d ati o n s

to

be

p ro v ide d b y z i nc c o ati n gs

z i nc

c o ate d

ap p l ie d to

re ga rd i n g

fo r

c o r ro s i o n

the

ge ne ra l

p ro te c tio n

i ro n o r s te e l a r tic l e s ,

p r i nc ip l e s

a nd

e x p o s e d to

the

l e ve l

of of

a va r i e t y o f

e nv i ro n m e nt s . I n i ti a l p ro te c tio n i s c o ve re d i n re l atio n to

—

ava i l ab l e s ta nd a rd p ro c e s s e s ,

—

de s i g n c o n s ide r ati o n s , a n d

—

e nv i ro n me n ts fo r u s e .

T h i s do c u me n t ap p l ie s to z i nc c o ati n gs ap p l ie d b y the fo l l o w i n g p ro c e s s e s :

a)

ho t d ip ga l va n i z e d c o ati n gs (ap p l i e d a fte r fab r ic atio n) ;

b)

ho t d ip ga l va n i z e d c o ati n gs (ap p l i e d o n to c o nti nuo u s s he e t) ;

c)

s he ra rd i z e d c o ati n gs ;

d)

the r m a l s p raye d c o ati n gs ;

e)

me c h a n i c a l l y p l ate d c o ati n gs ;

f)

e l e c tro de p o s i te d c o ati n gs .

T he s e in

g u i de l i ne s

s er vice

fo r

a nd

s te e l

re c o m m e nd atio n s

w i th

z i nc

c o ati n gs .

do

no t

de a l

G u id a nc e

on

w i th th i s

the

m a i n te n a nc e

s ub j e c t

can

be

of

c o r ro s i o n

fo u n d

in

ISO

p ro te c tio n

1 2 9 4 4 -5

a nd

ISO 1 2 944-8 .

NO TE

T here

a re

wh i c h p r o v i de s p e c i

a

fi c

va r i e t y

of

p r o du c t- r e l a te d

s ta nd a rd s

(e . g.

fo r

nails ,

fa s te n e r s ,

duc ti l e

i ron

pip e s ,

e tc .)

r e q u i r e m e n ts fo r th e ap p l i e d z i n c c o a ti n g s ys te m s wh i c h go b e yo n d a n y ge ne r a l g u i d a n c e

p r e s e n te d i n th i s d o c u m e n t . T he s e s p e c i

fi c

p r o du c t- r e l a te d r e q u i r e m e n ts w i l l t a ke p r e c e d e n c e o ve r the s e ge n e r a l

r e c o m me n d ati o n s .

2

Normative references

I S O 14 61 ,

I SO 2 063 ,

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

Thermal spraying — Metallic and other inorganic coatings — Zinc, aluminium and their alloys

Metallic and other inorganic coatings — Definitions and conventions concerning the measurement

of thickness I S O 2 0 6 4,

Corrosion of metals and alloys — Basic terms and definitions Mechanically deposited coatings of zinc — Specification and test methods

I S O 8 0 4 4: 2 01 5 ,

ISO 1 2683 ,

© I S O 2 0 1 7 – Al l ri gh ts re s e rve d

1

BS EN ISO 14713‑1:2017 ISO 1 471 3 -1 : 2 01 7(E)

I S O 176 6 8 ,

Zinc diffusion coatings on ferrous products — Sherardizing — Specification

3 Terms and definitions For the purposes of this document, the terms and de finitions given in ISO 1461, ISO 2063, ISO 2064, ISO 8044, ISO 12683 and ISO 17668 and the following apply. I S O a n d I E C m a i n ta i n te r m i no l o g i c a l d at ab a s e s fo r u s e i n s t a n d a rd i z atio n at the fo l l o w i n g add re s s e s :

—

I E C E l e c tro p e d i a :

ava i l ab l e at h t tp : // w w w. e l e c tro p e d i a . o r g/

—

I S O O n l i ne b ro ws i n g p l atfo r m : ava i l ab l e at ht tp : // w w w. i s o . o r g/o b p

3 .1 atmospheric corrosion c o r ro s i o n w i th the e a r th’s atmo s p he re at a m b ie n t te mp e ratu re a s the c o r ro s i ve e nv i ro n me n t

[S O U RC E : I S O 8 0 4 4 : 2 0 1 5 , 3 . 4]

3.2 elevated temperatures te mp e r atu re s b e t we e n + 6 0 ° C a nd +2 0 0 ° C

3.3 exceptional exposure

special cases such as exposure that substantially intensi fies the corrosive exposure and/or places increased demands on the corrosion protection system 3 .4

li fe to first maintenance ti me

i nte r va l

th at c a n

e l ap s e

a fte r

i n i ti a l

c o ati n g b e fo re

c o ati n g de te r i o ratio n

re ac he s

the

p o i n t whe n

maintenance is necessary to restore protection of the basis metal 4 4.1

Materials Iron and steel substrates

In hot dip galvanizing, the reactivity of the steel is modi fied 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 c ate go r i e s :

— carbon steel, composed simply of iron and carbon, accounts for 90 % of steel production [e.g. E N 1 0 0 2 5 -2 a n d E N 1 0 0 8 0 (s te e l re i n fo rc e me n t) ] ;

— high-strength, low-alloy (HSLA) steels have small additions (usually 100 67/>100 95/>100 10/29 20/60

VH VH VH H VH

20/40 33/67 48/95 5/10 10/20

VH VH VH M H

10/20 17/33 24/48 2/5 5/10

H VH VH L M

3/10 6/17 8/24 1/2 2/5

M H H VL L

55

26/79

VH

13/26

H

7/13

H

2/7

L

10 15 30 45 60 75 5 25

5/14 7/21 14/43 21/65 29/86 36/>100 2/7 12/36

M H VH VH VH VH L H

2/5 4/7 7/14 11/25 14/29 18/36 1/2 6/12

L M H H VH VH VL M

1/2 2/4 4/7 5/11 7/14 9/18 1/1 3/6

VL L M M H H VL M

0/1 1/2 2/4 3/6 2/7 3/9 0/1 1/3

VL VL VL L L M VL VL

© ISO 2017 – All rights reserved

BS EN ISO 14713‑1:2017 ISO 1 471 3 -1 : 2 01 7(E)

Table 2

(continued) Selected corrosivity category (I SO 92 2 3 )

M inimum Sys tem

Reference

µm

M e c h a n i c a l p l ati n g

life minimum/ma ximum (years)

thickness

and durability class ( VL , L , M , H , VH )

s tandard

ISO 1 2683

C3

C4

C5

CX

8

4/1 1

M

2 /4

L

1 /2

VL

0/1

VL

25

1 2 /3 6

H

6/1 2

M

3 /6

L

1 /3

VL

NOTE 1 The figures for life have been rounded to whole numbers. The allocation of the durability designation is based upon the average of the minimum and maximum of the calculated life to first maintenance, e.g. 85 µm zinc coating in corrosivity category C4 (corrosion rate for zinc between 2 ,1 µm per annum and 4,2 µm per annum), gives expected durability of 85/2,1 = 40,476 years (rounded to 40 years) and 85/4,2 = 20,238 years (rounded to 20 years). Average durability of (20 + 40)/2 = 30 years (designated “VH”). NOTE 2 Life to first maintenance of protective coating systems: The list of systems given in this table, clas si fied by environment and typical time to first maintenance, indicates the options open to the speci fier. The recommended treatments listed for longer lives will always protect for shorter periods and are often also

-

e c o n o m i c a l fo r th e s e s h o r te r p e r i o d s .

NOTE 3 This table can be applied to any zinc coating to determine the life to first maintenance. The corrosion rate for any given environment is indicated by the corrosivity classi fication category, C3 to CX. The minimum and maximum life to first maintenance for the selected system is set out in the body of this table. NOTE 4 It is impossible to achieve an exactly uniform thickness of any type of coating. The third column of this table indicates the minimum average coating thickness for each system. In practice, the overall mean is likely to be substantially in excess of this minimum, which is important as the zinc coatings are able to provide protection to adjacent areas which can lose their coating prematurely. NO TE 5

T h i c k n e s s r e qu i r e m e n t s i n E N 1 0 2 4 0 a r e m i n i mu m l o c a l th i c k n e s s r e qu i r e me n t s . F u r th e r m o r e , th e

thickness quoted for coatings in these tables may not match speci fied coating thicknesses in some standards. NO TE 6

I n th i s ta b l e , g u i d a n c e i s g i ve n fo r c o a ti n gs ap p l i e d to s tr u c t u r a l a n d c o l d- fo r m i n g g r ade s o f h o t d i p

galvanized sheet and cold-rolled sections, on zinc electroplated sheet, on coatings thermally sprayed with zinc, on mechanically plated coatings, on sherardized coatings and for articles hot dip galvanized after manufacture. H o t d i p g a l va n i z e d fa b r i c ate d a n d s e m i - fab r i c a te d p r o du c t s m ade fr o m th i n m a te r i a l a n d fa s te n e r s a n d o the r

centrifuged work usually have intermediate thicknesses of coating (see also relevant product standards). As the life of all zinc coatings is approximately proportional to the thickness or mass of zinc coating present, the relative performance of such intermediate thicknesses can readily be assessed. NOTE 7 Zinc/aluminium alloy coatings (with 5 % to 55 % aluminium) usually last longer than pure zinc; pend ing wider use, they are not included in this table. There is widespread technical literature available on these

-

c l a s s e s o f m ate r i a l s .

NOTE 8 Thickness of hot dip galvanizing on products: ISO 1461 speci fies the standard hot dip galvanized coat ing at the equivalent of 85 µm minimum for steel >6 mm thick. Thinner steel, automatically hot dip galvanized tubes and centrifugal work (usually threaded work and fittings) have thinner coatings, but these are usually

-

g r e a te r th a n 45 µ m . W h e r e i t i s de s i r e d to u s e c o a ti n gs o f d i ffe r e n t th i c k n e s s e s to tho s e s t ate d , th e i r l i ve s c a n

be ascertained by calculation; the life of a zinc coating is (to a first approximation) proportional to its thick ness. For tubes, EN 10240 includes an option for the purchaser to specify a thicker coating requirement which will give an extended service life. Hot dip galvanized coatings thicker than 85 µm are not speci fied in ISO 1461 but the general provisions of that International Standard apply and, together with speci fic thickness figures, may form a speci fication capable of veri fication. It is essential to know the composition of the steel to be used and the galvanizer should be consulted before specifying, as these thicker coatings may not be available for all types of steel. Where the steel is suitable, thick coatings may be speci fied. -

NOTE 9 Thickness of sherardizing on products: ISO 17668 speci fies coating thickness of 6 classes up to 75 µm, The sherardizer should be consulted where thicker coatings are required, as a thicker coating may not be avail able for all types of steel.

-

NOTE 10 Thermal spray coatings. These coatings are normally used as part of a corrosion protection system after receiving a sealing coat. The performance of the coating system is highly dependent upon this being carried out effectively. No data is provided for performance in this document. Further guidance can be found in E N 1 5 52 0 .

© I S O 2 0 1 7 – Al l ri gh ts re s e rve d

11

BS EN ISO 14713‑1:2017 ISO 1 471 3 -1 : 2 01 7(E)

7.3

Exposure to water

T he

typ e

o f wate r

—

s o ft o r

h a rd

fre s h

wate r/ b rac ki s h

wate r/s a l t wate r

—

has

a

m aj o r

in

f l ue nc e

on

the c o r ro s io n o f i ro n a nd s te e l i n wate r a nd the s e l e c tio n o f p ro te c ti ve z i nc c o ati n gs . Wi th z i nc c o ati n gs , c o r ro s i o n

is

flo w

a g i tatio n

r ate ,

a ffe c te d

primarily

a nd

by

o x yge n

the

c he m ic a l

ava i l ab i l i t y a re

c o mp o s i ti o n all

o f the

i mp o r ta n t.

Fo r

wate r,

b ut

e x a mp l e ,

te mp e ratu re ,

z i nc

s ho u l d

p re s s u re ,

no t b e

used

in

ho t no n- s c a l e - fo r m i n g wate r s ; he av y c o r ro s io n o f z i nc c a n a l s o o c c u r i n c o nde n s ate , e s p e c i a l l y b e t we e n ab o u t

55

°C

a nd

80

°C

(e . g.

in

s au n a s) .

O the r w i s e ,

b a r r ie r

p ro te c ti o n

can

o cc u r

at

all

te mp e rat u re s ;

b e l o w ab o u t 6 0 ° C , z i nc c a n a l s o p ro v ide c atho d ic p ro te c ti o n . T he du ratio n o f l i fe o f z i nc s u r fac e s i n c o l d s c a l e - fo r m i n g wate r s i s u s u a l l y h i ghe r th a n i n no n- s c a l e - fo r m i n g wate r s ( Ry z n a r ’s o r L a n ge l i e r ’s i nde x s ho u l d

be

used

to

c a l c u l ate

whe the r

the

wate r

is

s c a l e - fo r m i n g) .

S i nc e

the

c o mp o s i tio n

o f no n- s a l i ne

wate r s c a n va r y g re atl y, p re v io u s e x p e r ie nc e o r e x p e r t ad v ic e s ho u l d b e s o u gh t.

Fo r

ho t wate r,

used

fo r a l l

s p e c i a l i s t ad v ic e

s tr uc tu re s

s ho u l d

a l ways

(i nc l ud i n g p ip e s ,

be

fi t ti n gs ,

s o u ght (s e e

ta n ks

a nd

also

fo r

e x a mp l e

ta n k c o ve r s)

in

EN

1 2 5 0 2 -3 ) .

c o n tac t w i th

C o ati n gs

p o tab l e

wate r

s ho u l d b e no n- to x i c a n d s ho u l d no t i mp a r t a ny ta s te o r o do u r, c o l o u r o r tu rb id i t y to the wate r, no r fo s te r

fic ie nt c o ats

m i c ro b i a l at t ac k. Wi th ta n k s , i f add i tio n a l p ro te c tio n to ho t d i p ga l va n i z i n g i s ne c e s s a r y, s u f o f h i gh- b u i l d b i tu me n p a i n t s ho u l d b e ap p l i e d .

Z o ne s

f l uc tu ati n g

of

f l uc tu atio n s re s e r vo i r s)

—

e . g.

wate r tid a l

l e ve l

(i . e .

the

mo ve me nt s ,

o r s p l a s h z o ne s

a re a

or

a r ti

in

wh ic h

fi c i a l

the

wate r

a l te r ati o n

s ho u l d b e g i ve n s p e c i a l

of

l e ve l

the

c o n s i de rati o n a s ,

c h a n ge s

wate r

as

l e ve l

a

in

i n add i ti o n to

re s u l t

lo ck

o f n atu ra l

c h a mb e r s

wate r at tac k,

or

the re

c a n a l s o b e atmo s p he r i c at t ac k a n d ab ra s io n .

T he m a ny fac to r s S o me

g u ide l i ne s

a ffe c ti n g c o r ro s io n i n fre s h wate r m a ke i t i mp rac tic ab l e to fo r

s e awate r

a re

set

out

b elow

b ut

it

is

e mp h a s i z e d

p re s e n t s i mp l e g u id a nc e .

th at,

fo r

all

wate r

e x p o s u re s ,

s p e c i a l i s t ad v i c e s ho u l d b e s o u ght fo r fu l l g u i d a nc e o n a l l c o nd i ti o n s i nvo l ve d .

In

te mp e rate

a nd

20

µm

fi t ti n gs h ave

sea

p er

w i th

wate r,

a n nu m .

the

ga l va n i z e d ,

add i ti o n a l

ave r a ge

Hot

d ip

z i nc

c o r ro s io n

ga l va n i z e d

s he ra rd i z e d ,

tub e ,

rate

ho t

wi l l

d ip

e l e c tro de p o s i te d

p ro te c ti o n whe n u s e d i n s e a wate r (s e e

us ual ly

l ie

ga l va n i z e d/ Z n or

ISO

b e t we e n

me c h a n i c a l l y

1 2 9 4 4 -5

10

µm

p er

e l e c tro de p o s i te d p l ate d

a nd I S O

c o ati n gs

12944-8

a n nu m

s he e t

a nd

no r m a l l y

a nd E N

1 3 43 8 ) .

B rac ki s h wate r m ay b e m o re o r l e s s c o r ro s i ve th a n s e a wate r a n d no ge ne ra l e s ti m ate s o f du rab i l i t y c a n b e g i ve n .

Gu i d a nc e

on

the

c o r ro s i o n

l i ke l i ho o d

fo r

ho t

d ip

ga l va n i z e d

c o ati n gs

by

of

used

in

wate r

s to ra ge

a nd

d i s tr i b u ti o n s ys te m s c a n b e fo u n d i n E N 1 2 5 0 2 - 3 .

7.4

Abrasion

N atu ra l

me c h a n ic a l

e x p o s u re

can

o cc u r

in

wate r s

s h i fti n g

b o u l de r s ,

ab ra s io n

by

s a nd ,

wave

s p l a s h i n g , e tc . P a r ti c l e s e n tra i ne d b y the w i nd (fo r e xa mp l e , s a nd ) c a n a l s o c au s e i nc re a s e d at tac k. Z i nc c o ati n gs

h ave

muc h

h i ghe r

ab ra s io n

re s i s ta nc e

(a

fac to r

of 10

or

mo re)

th a n

mo s t c o nve n ti o n a l

p a i nt

c o ati n gs . T he z i nc- i ro n a l l o ys a re p a r tic u l a rl y h a rd . A re a s wa l ke d o n o r d r i ve n o n , o r wh ic h r u b to ge the r, c a n b e s ub j e c t to s e ve re ab r a s i o n . A re a s u n de r c o a r s e g rave l a re s u b j e c te d to s e ve re e ro s io n b y i mp ac t a nd

ab r a s i o n .

T he

go o d

b o nd

b e t we e n

z i nc

c o ati n gs

s he ra rd i z i n g whe re the re i s a n a l l o y i n g re ac tio n)

7.5

a nd

s te e l

( p a r tic u l a rl y i n

ho t d i p

ga l va n i z i n g a nd

he lp s to l i m i t s uc h e ffe c ts .

Exposure to chemicals

A p r i m a r y fac to r go ve r n i n g c o r ro s io n b e h av io u r o f z i nc c o ati n gs i n l iqu id c he m i c a l e nv i ro n me nt s i s the pH

o f the

5,5

a nd

c he m ic a l

b elow 1 2 , 5 .

s o l u tio n . Fac to r s

Z i nc s uc h

c o ati n gs , as

i n h i b i to r s m ay a ffe c t the s p e c i

fic

Wi th i n

12 ,5,

is

the

pH

ve r y s l o w.

s peci

12

fic

ra n ge

of 5 , 5

to

s uc h

a g i t atio n ,

as

ga l va n i z i n g ,

ae r ati o n ,

e nv i ro n me n t.

we l l

in

s o lu ti o n s

p o l a r i z ati o n

a nd

of pH

the

ab o ve

p re s e nc e

of

rate o f c o r ro s i o n e x p e r i e nc e d b y the c o ati n g.

a

p ro te c ti ve

fi l m

fo r m s

on

the

T he p re c i s e c he m i c a l c o mp o s i tio n o f the p ro te c ti ve

c he m ic a l

p e r fo r m

te mp e ratu re ,

S i nc e

m a ny

l i qu id s

fa l l

w i th i n

z i nc

fi l m

the

is

pH

s u r fac e

a nd

the

c o r ro s io n

r ate

s o me wh at de p e nde n t up o n the

ra n ge

of 5 , 5

to

12 ,5,

ga l va n i z e d

© I S O 2 0 1 7 – Al l ri gh ts re s e rve d

BS EN ISO 14713‑1:2017 ISO 1 471 3 -1 : 2 01 7(E)

steel containers are widely used in storing and transporting many chemical solutions. Prolonged or fre que nt d i re c t c o nt ac t w i th ac id s o r s tro n g a l ka l i s i s no t re c o m me n de d .

Many organic solvents have little effect on non-ferrous metals but speci fic advice should be sought for e ac h c he m i c a l .

7.6

Elevated temperatures

All the zinc coatings described are usually suitable for elevated temperatures. Separate advice has to be sought regarding any organic materials/coatings. Te mp e ratu re s ab o ve 2 0 0 ° C a re no t c o n s i de re d i n th i s do c u m e nt.

Temperatures between +200 °C and +500 °C occur only under special conditions of construction and operation, e.g. in steel chimneys, flue gas ducts and gas take-off mains in coking plants. Specialist advice s ho u l d b e s o u gh t fo r the c o ati n g o f s u r fac e s s o e x p o s e d .

S he ra rd i z e d c o ati n gs h ave a te mp e r atu re re s i s ta nc e up to 6 0 0 ° C .

7.7

Contact with concrete

U np ro te c te d

s te e l

a r tic l e s

in

c o n tac t

w i th

c o nc re te

can

c o r ro de

as

mo i s tu re

p e ne trate s

i n to

the

c o nc re te th ro u gh c rac ks a n d p o re s . T he o x id ati o n p ro duc ts fro m the re ac tio n b e t we e n the s te e l a n d the

oxygen/moisture present can create sufficient pressure to cause damage to the concrete (spalling). Zinc coatings (usually applied in the form of a hot dip galvanized coating to reinforcement — see ISO 14657), can be used to prevent this type of deterioration for long periods of time, dependent upon the speci fic e x p o s u re e nv i ro n me n t.

The corrosion protection afforded by galvanized rebar in concrete is due to a combination of bene ficial effects. Of primary importance is the substantially higher chloride threshold (2 to 4 times) fo r pH

z i nc

c o ati n gs

p a s s i vati o n

to

s ta r t

ra n ge

c o r ro d i n g

th a n

s te e l ,

c o mp a re d

m a ki n g

to

u nc o ate d

ga l va n i z e d

s te e l .

re b a r

In

add i tio n ,

re s i s ta n t

to

z i nc

the

pH

has

a

muc h

l o we r i n g

g re ate r

e ffe c ts

of

c a rb o n ati o n a s the c o nc re te a ge s . E ve n whe n the z i nc c o ati n g do e s s ta r t to c o r ro de , i ts c o r ro s i o n rate i s

considerably less than that of uncoated steel. Zinc remains passive at signi ficantly lower pH levels than for black steel (9,5 versus 11,5) making ga l va n i z e d re b a r fa r l e s s s u s c e p tib l e to c o r ro s io n due to c a rb o n atio n o f the c o nc re te .

Zinc reacts with wet concrete to form calcium hydroxyzincate accompanied by the evolution of hydrogen. This corrosion product is insoluble and protects the underlying zinc (provided that the s u r ro u n d i n g c o nc re te m i x tu re i s b e l o w a p H o f ab o u t 1 3 , 3 ) .

Re s e a rc h

has

s ho w n

th at

du r i n g

th i s

i n i ti a l

re ac ti o n

p e r io d

u n ti l

c o ati n g

p a s s i vatio n

a nd

c o nc re te

hardening occurs, some of the pure zinc layer of the coating is dissolved. However, this initial reaction ceases once the concrete hardens and the hydroxyzincate coating has formed. Studies of galvanized rebar recovered from field structures indicate that the coating remains in this passive state for e x te n de d p e r i o d s o f ti m e , e ve n whe n e x p o s e d to h i gh c h l o r ide l e ve l s i n the s u r ro u n d i n g c o nc re te .

Fo r

c o nc re te s

o f h i gh

pH ,

or

whe re

s o me

b ac kg ro u nd

c h l o r i de s

a re

e x p e c te d ,

the

z i nc

s u r fac e

can

be

passivated, using a range of proprietary post-treatments, as a safeguard against excessive hydrogen evolution that may, in serious cases, reduce the pullout strength of the bar. For normal concrete c o nd i tio n s ,

re s e a rc h

has

s ho w n

no

s t ati s tic a l

d i ffe re nc e

in

b o nd

s tre n g th

b e t we e n

ga l va n i z e d

re b a r

th at wa s p a s s i vate d o r no t p a s s i vate d .

S he ra rd i z e d

c o ati n gs

in

ac c o rd a nc e

w i th

ISO

176 6 8

a re

p a s s i vate d

a nd

the re fo re

wi l l

be

p re p a re d

fo r

e i the r l o w o r h i gh l e ve l s o f c h l o r ide adde d to c o nc re te . I n a l l o the r re s p e c ts , s he ra rd i z i n g w i l l ac t i n the

same way as hot dip galvanizing in contact with concrete.

© I S O 2 0 1 7 – Al l ri gh ts re s e rve d

13

BS EN ISO 14713‑1:2017 ISO 1 471 3 -1 : 2 01 7(E)

7.8

Contact with wood

Z i nc- c o ate d

p ro duc t s

a re

w i th a va r ie t y o f wo o d s .

used

C a re

ve r y

s uc c e s s fu l l y

s ho u l d b e

t a ke n ,

in

m a ny

ho we ve r,

ap p l ic atio n s

to

wh ic h

bri ng

the m

i n to

c o nt ac t

avo id d i re c t c o n tac t b e t we e n z i nc c o ati n gs

a n d ti m b e r s wh ic h h ave b e e n fre s h l y tre ate d w i th ac i d ic p re s e r vati ve s . O nc e the wo o d h a s d r i e d a n d the

fi xe d ,

p re s e r vati ve s h ave b e e n

c o nt ac t i s ac c e p tab l e , e ve n whe n the wo o d o nc e mo re b e c o m e s we t. Ve r y

ac id i c wo o d s , s uc h a s o a k, s we e t c he s tnu t, we s te r n re d c e d a r a nd D o u gl a s w i th

z i nc- c o ate d

a r ti c l e s ,

a l tho u gh

s o me

i n i ti a l

c o r ro s io n

wo u l d

be

fi r

c a n b e u s e d i n c o nj u nc ti o n

e x p e c te d .

In

the s e

cases,

i s o l ati o n

te c h n ique s m ay b e c o n s ide re d , e . g. ap p l ic ati o n o f a n o r ga n ic c o ati n g o ve r the a re a o f c o n tac t .

S he ra rd i z i n g

c o ati n gs

co n s i s t

o f z i nc- i ro n

a l l o ys ,

fic ie n t

p ro duc e a s u r fac e wh i c h h a s a h i gh c o e f

wh ic h ,

b e c au s e

o f the

the r m a l

d i ffu s i o n

te c h n ique ,

o f fr ic ti o n s i m i l a r to a l l - a l l o y l aye r c o ati n gs de ve l o p e d o n

m a ny ho t d ip ga l va n i z e d a r ti c l e s . T he s e c o ati n gs wo u l d te nd to re qu i re h i gh w i thd r awa l l o ad s to b re a k the b o nd w i th the wo o d whe re u s e d o n n a i l s , fo r i n s ta nc e .

7.9

Bimetallic contact

W he n

t wo

dissimilar

me ta l s

c o me

i n to

d i re c t c o n t ac t a n d

an

e l e c tro l y te

s uc h

as

mo i s tu re

is

p re s e nt,

the re i s a p o te n ti a l fo r b i me ta l l i c c o r ro s io n to ta ke p l ac e w i th the m o re e l e c tro ne gati ve o r a no d ic me ta l , as

de te r m i ne d

fro m

the

e l e c tro - c he m i c a l

s e r ie s ,

c o r ro d i n g

p re fe re n ti a l l y

to

p re ve n t

c o r ro s i o n

o f the

o the r me ta l (s e e Tab l e 3 ) .

Table 3 — Galvanic series (based upon electrode potentials in sea water) showing relative position of zinc to other metals Anodic — more prone to corrosion M a gne s iu m

Z i nc

Alu m i n iu m

C a rb o n a n d l o w- a l l o y s te e l s

C a s t i ro n

L e ad

Tin

C o p p e r, b r a s s , b r o n z e

N i c ke l ( p a s s i ve)

T i ta n iu m

S ta i n l e s s s te e l

Cathodic — less prone to corrosion

T he b i me ta l l i c e ffe c t i s the b a s i s fo r the s ac r i o ffe r s

to

smal l

a re a s

of

exposed

s te e l

if

fi c i a l

the

p ro te c ti o n th at a z i nc c o ati n g (e . g. ho t d ip ga l va n i z i n g)

c o ati n g

b e c o me s

d a m a ge d .

Z i nc

c o ati n gs

wi l l

c o r ro de

p re fe re nti a l l y to p ro te c t a ny me ta l b e l o w i t i n the e l e c tro - c he m i c a l s e r ie s .

T he l e ve l o f b i m e ta l l i c c o r ro s io n th at w i l l ta ke p l ac e w i l l de p e nd up o n a nu m b e r o f fac to r s , i nc l ud i n g: the s peci

fic

me t a l s i n c o n tac t, the ratio o f the s u r fac e a re a o f the t wo me t a l s a n d the e x p o s u re c o nd i tio n s .

G e ne ra l l y, the l e ve l o f b i me t a l l ic c o r ro s i o n w i l l i nc re a s e w i th a g re ate r d i ffe re nc e i n e l e c tro de p o te n ti a l b e t we e n H o we ve r,

the the

de te r m i ne

t wo

me ta l s ,

e l e c tro de

e . g.

the

p o te nti a l

i f a nd at wh at l e ve l

fu r the r

m ay

va r y

ap a r t due

the

to

t wo

o x ide

me ta l s

l aye r

o f s e ve r i t y b i me ta l l i c c o r ro s i o n

in

the

fo r m ati o n

a nd

wi l l

a re

ta ke

p l ac e ,

e l e c tro - c he m ic a l c a n no t b e as

used

s erie s .

a l o ne

o the r fac to r s

to

s uc h a s

tho s e de s c r i b e d b e l o w a re a l s o i mp o r ta nt .

T he

ratio

me ta l s

o f the

s ho u l d

s u r fac e

be

h i gh .

a re a o f the

t wo

W he re

r atio

the

me ta l s is

is

e s s e n ti a l

re duc e d ,

a nd ,

p ro b l e m s

ide a l l y, m ay

the

o cc u r

ratio due

o f a no d ic- to - c atho d ic

to

the

g re ate r

l e ve l

of

o x yge n re duc tio n wh ic h m ay t a ke p l ac e , l e ad i n g to i nc re a s e d c o r ro s io n o f the a no d ic m e ta l .

14

© I S O 2 0 1 7 – Al l ri gh ts re s e rve d

BS EN ISO 14713‑1:2017 ISO 1 471 3 -1 : 2 01 7(E)

T he e x p o s u re c o n d i tio n s a re c r i tic a l , a s fo r b i me ta l l i c c o r ro s io n to ta ke p l ac e , a n e l e c tro l y te mu s t b r id ge the t wo m e ta l s p re s e n t. A s a re s u l t, i n d r y i n te r n a l e nv i ro n m e nt s , the p o te n ti a l fo r b i me ta l l i c c o r ro s i o n is

ve r y

l o w,

o f wate r

wh i l e

in

the

in

e x te r n a l

fo r m

o f ra i n

atmo s p he r ic

a nd

e nv i ro n me n ts ,

c o nde n s ati o n .

T he

the

wo r s t

p o te n ti a l

e x p o s u re

i nc re a s e s

c o n d i ti o n s ,

due

to

the

ho we ve r,

p re s e nc e

a re

tho s e

of

i m me r s io n i n a s o l u tio n whe re a n e l e c tro l y te i s p e r m a ne n tl y b r i d g i n g the t wo m e ta l s .

N o r m a l l y,

a ny

p o te nti a l

fo r

b i m e ta l l i c

c o r ro s io n

m ay

be

a l l e v i ate d

by

e l e c tr i c a l l y

i n s u l ati n g

the

t wo

m e ta l s fro m o ne a no the r. Fo r b o l te d c o n ne c ti o n s , th i s m i gh t b e do ne b y u s i n g p o l yc h l o ro p re ne o r p l a s ti c wa s he r s , wh i l e fo r o ve rl ap p i n g s u r fac e s , i t m i ght b e ac h ie ve d b y u s i n g p l a s tic s p ac e r s o r p a i n ti n g o ne o f the s u r fac e s w i th a s u i tab l e p a i n t s ys te m .

G e ne ra l l y, whe n

in

ho t

an

ga l va n i z e d

d ip

ga l va n i z e d

atmo s p he r ic

s te e l

c o r ro s io n i s s i g n i

to

o the r

fi c a n tl y

s te e l

p e r fo r m s

e nv i ro n me n t m e ta l

is

as

h i gh .

we l l

in

c o nt ac t

i l lu s tr ate d

C o nve r s e l y,

in

in

w i th

Tab l e

4,

mo s t

c o m mo n

p ro v i de d

i m me r s e d

th at

c o nd i ti o n s ,

e n g i ne e r i n g the

the

ratio

e ffe c t

of

of

me ta l s ho t

d ip

b i m e ta l l ic

i nc re a s e d a n d s o me fo r m o f i s o l atio n w i l l no r m a l l y b e re qu i re d .

Table 4 — Indication of additional corrosion expected due to direct contact between zinc and other metallic materials Atmospheric exposure Metal

I mmersed

I ndus trial/

Rural

urban

Marine

Fresh water

Sea water

Aluminium

a

a to b

a to b

b

b to c

Brass

b

b

a to c

b to c

c to d

Bronze

b

b

b to c

b to c

c to d

C as t iron

b

b

b to c

b to c

c to d

Copper

b

b to c

b to c

b to c

c to d

Lead

a

a to b

a to b

a to c

a to c

a to b

a to b

a to b

b

b to c

Stainless s teel a

T he

z i nc

co ati n g

wi l l

s u ffe r

e i ther

no

add i tio n a l

co r ro s io n

o r,

at

wo r s t,

only

ve r y

s l i ght

add i tio n a l

co r ro s io n

wh i c h

is

u s u a l l y to l e r a b l e i n s e r v i c e .

b

c

d

T h e z i n c c o a t i n g w i l l s u ffe r s l i g h t o r m o d e r a te a d d i t i o n a l c o r r o s i o n wh i c h m a y b e to l e r a b l e i n s o m e c i r c u m s t a n c e s .

T h e z i n c c o a t i n g m a y s u ffe r fa i rl y s e ve r e a d d i t i o n a l c o r r o s i o n a n d p r o te c t i ve m e a s u r e s w i l l u s u a l l y b e n e c e s s a r y.

T h e z i n c c o a t i n g m a y s u ffe r s e ve r e a d d i t i o n a l c o r r o s i o n a n d c o n t ac t s h o u l d b e a vo i d e d .

T he

fo l l o w i n g

g u id a nc e

re l ate s

to

speci

fi c

ap p l i c atio n s

c o nc e r n i n g

z i nc- c o ate d

s te e l wo rk

in

c o n tac t

w i th the de s i g n ate d me ta l o r a l l o y.

a)

A lu m i n iu m

—

T he

a l u m i n iu m

is

re l ati ve l y

s e ve r i t y

o f i nc re a s e

l o w.

in

H o we ve r,

b i me t a l l ic

it

s ho u l d

c o r ro s io n

be

due

re me m b e re d

to

atmo s p he r ic

th at

o ne

c o n tac t

ap p l i c ati o n

w i th

whe re

ga l va n i z e d s te e l a nd a l u m i n iu m a re u s e d i n c o nj u nc tio n w i th o ne a no the r i s a l u m i n iu m c l add i n g. I n th i s i n s ta nc e , i s o l atio n i s ad v i s e d due to the l a r ge s u r fac e a re a o f the a l u m i n iu m p a ne l s .

b)

C opp er a nd

—

D ue

to

the

l a r ge

c o p p e r- c o n ta i n i n g

e nv i ro n me n t. c o ate d

W he re

a r tic l e s ,

as

p o te n ti a l

a l l o ys ,

p o s s ib l e ,

s ma l l

set

e l e c tr ic a l de s i g n

a mo u nt s

up

by

c o n tac t

i s o l atio n

s ho u l d

o f co p p er

also

is

b e t we e n

a l ways

avo i d

d i s s o l ve d

in

z i nc- c o ate d

ad v i s e d ,

e ve n

r u n- o ff o f wate r the

wate r

m ay

fro m be

s te e l

in

an

a nd

copp er

atmo s p he r i c

copp er

de p o s i te d ,

o n to

z i nc-

l e ad i n g

to

b i m e ta l l i c c o r ro s i o n .

c)

L e ad

—

P o te n ti a l

p ro b l e m s

h ave

fo r b i me ta l l ic c o r ro s io n

b e en

re p o r te d

c o nc e r n i n g ,

c o ate d p ro duc ts a nd the u s e o f l e ad i n

d)

Sta i n le s s

s te e l

—

T he

mo s t c o m mo n

w i th fo r

fi x i n g

use

l e ad

is

low i n

e x a mp l e ,

the

an

use

atm o s p he r ic o f l e ad

e nv i ro n m e n t a nd

fl a s h i n g

w i th

z i nc

or

no

z i nc-

ga l va n i z e d p o s ts .

o f s ta i n l e s s

s te e l

w i th

z i nc- c o ate d

s te e l

is

in

the

fo r m

of

nu t s a n d b o l ts i n a n atm o s p he r ic e nv i ro n me n t. Gi ve n the l o w p o te n ti a l fo r b i me ta l l ic c o r ro s io n a nd the

s ma l l

s u r fac e

a re a

o f s ta i n le s s

s te e l

fa s te ne r s ,

b i me ta l l i c

c o r ro s i o n

wo u l d

no t no r m a l l y b e

an

i s s ue , a l tho u gh , a s a l ways , b e s t p rac tic e re m a i n s i s o l atio n u s i n g i n s u l ati n g wa s he r s .

© I S O 2 0 1 7 – Al l ri gh ts re s e rve d

15

BS EN ISO 14713‑1:2017 ISO 1 471 3 -1 : 2 01 7(E)

P rac tic a l rati n g

e x p e r ie nc e

o f “a”

c o n tac t.

or

“a

s u g ge s ts

to

H o we ve r,

b”

is

whe re

th at

whe re

i n d ic ate d , the

ratio

l i t tl e

of

the or

s u r fac e

no

s u r fac e

a re a

add i ti o n a l

a re a s

is

r ati o

o f z i nc

c o r ro s i o n

re duc e d

or

wi l l

the

to

o the r

t a ke

rati n g

me ta l

p l ac e is

as

h i ghe r,

is

a

h i gh

a nd

a

re s u l t o f the

s o me

fo r m

of

i n s u l ati o n m ay b e re qu i re d .

8

Accelerated test methods applied to zinc coatings

S a l t s p ray te s ts fa i l u re

c a n no t b e

me c h a n i s m .

used

Wi tho u t

a

to

ac c u rate l y te s t z i nc- c o ate d

p ro p e r

we t/d r y

c yc l e ,

the

z i nc

s te e l

b e c au s e

c o ati n g

the y ac c e l e rate

c a n no t

fo r m

p ati n a

the

w ro n g

l aye r s .

T he

ab s e nc e o f a p ati n a l aye r a l l o ws c o n s t a n t at t ac k o f the z i nc me t a l a nd g i ve s a ve r y l o w p re d ic tio n o f the z i nc c o ati n g l i fe ti me .

NO TE to is

AS T M

AS T M “A S T M to

E ffo r ts

de te r m i n e

B 1 1 7.

B117

AS T M

a nd

G -1

b e en

m ade

in

“ac c e l e r ate d ”

C o m m i t te e

AS TM

s ta nd a rd

C o m m i t te e

h ave

p ro p er

C o m m i t te e

AS T M

the

a

G85 . on

T he

th e

G -1

on

B 1 1 7,

th at th e

z i nc- c o ate d O ne

te s t

C o rro s io n

C o m m i t te e

C o r ro s io n

de s i g n a ti o n

re co m mend s

m a ny

l i fe ti m e .

pas sed

o f M e ta l s

s e l do m

of

used

has

fo l l o w i n g

fi r m s

c o r r e l a te

te s t n o t b e

ap p l i c ati o n s

co r ro s io n

M e ta l s

th e

con

s te e l

fo r

w i th

to

j u r i s d i c ti o n

r e s o l u ti o n

th at r e s u l ts

in

in

th e

s ys te m s

o ve r

the

r e ga r d i n g

o f s a l t s p r ay

p e r fo r m a n c e

o r r e fe r e n c e d

de ve l o p

p r e ve n ti o n

n at u r a l

co r re c t in

th e

s alt

the

(fo g)

te s t

s p r ay

use

run

S ta te s

s ta nd a rd s

of AS T M

te s t s ,

e n v i r o n me n t s .

o th e r s t a n d a r d s

m e tho d

U n i te d

B 1 1 7:

ac c o r d i n g T h e r e fo r e ,

fo r th a t p u r p o s e ,

u n le s s

ap p r o p r i a te c o r r o b o r a ti n g l o n g- te r m a tm o s p h e r i c e x p o s u r e s h ave b e e n c o n du c te d”.

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© I S O 2 0 1 7 – Al l ri gh ts re s e rve d

BS EN ISO 14713‑1:2017 ISO 1 471 3 -1 : 2 01 7(E)

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F. C . ,

“C o r ro s i o n

Re s i s ta nc e

o f Z i nc

a nd

Z i nc

A l l o ys ”,

P ub l .

M a rc e l

D e k ke r

I nc ,

New

York, 1994

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© ISO 2017 – All rights reserved

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