galvanisation en
TRANSCRIPT
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Corrosion protectionof rolled steel sections using hot-dip galvanization
Long Carbon EuropeSections and Merchant Bars
ArchitectsClaudeVasconi&JeanPetit-ChamberofCommerceLuxembourg
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Contents
1
Foreword 3
1. Risk o corrosion and protection period 5
2. Corrosion protection methods 8
3. Hot-dip galvanizing 10
4. Characteristics o hot-dip galvanizing o steel structures 17
5. Requirements or materials 21
6. Requirements o structures suitable or hot-dip galvanizing 25
7. Requirements or the abrication o steel structures 31
8. Requirements or hot-dip galvanizing 33
9. Duplex systems 35
10. Cost eectiveness 37
Reerences 39
Technical advisory & fnishing 42
Your partners 43
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Foreword
When it comes to choosing materials, steel,
because o its exceptional physical and
mechanical characteristics, is the most popularamongst designers. It can be used to rapidly
build economical, durable, and sae structures.
The steel used to make hot-rolled sections,
which can themselves be indenitely recycled,
is made rom recycled scrap. It is particularly
suitable or machining and shaping. However, it
tends to react with agents in the atmosphere
to orm stable thermodynamic bonds errous
oxides and/or salts.
The ability o steel to revert to its natural or
original state is called corrosion.
In laymans terms: steel rusts!
The primary quality o steel i.e. its ability to
retain its physical and mechanical strength, or
in the case o a steel structure, its load bearing
capacity, is generally long-lasting and is only
compromised when corrosion reduces its cross
section to such a degree that saety is adversely
aected.
The service lie o a structure depends on
the rate o reaction between the steel and itsenvironment. These reactions depend on the
nature and concentration o the corrosive agents
present.
Corrosion protection o structures must
thereore be considered as intervening in this
process in order to prevent the reaction or
greatly reduce the rate.
Large numbers o steel structures, some
o them a hundred years old, which have
beneted rom the combination o a suitablecorrosion protection treatment and regular
maintenance, show impressively the potential
o steel. However, these types o structures,
requiring high maintenance costs, are no longer
acceptable today.
New requirements govern the design o the
steel structures o the twenty-rst century:
l Environmental protection policies enorced
at both the national and international level
have lead to a considerable reduction in the
amount o corrosive load in the atmosphere
over the last twenty years. This has
resulted in a noticeable drop in the average
corrosion rate o steel and zinc as well as
improved resistance o coating systems.
l The design o steel structures is substantially
improved through the eectiveness o
welding procedures and the vast range o
rolled sections available thus contributing
positively to ensure that corrosion protection
systems have long service lives. Maintenance
and renovation costs continue to all becausethe amount o exposed surace area has
been greatly reduced and ease o access
improved. The ability o new coatings to
resist the stresses in their surroundings
has been increased considerably. New
inexpensive coating methods are employed in
abrication shops and on construction sites.
l Zinc baths have suicient capacity and
are large enough to allow widespread
hot-dip galvanization o steel structuresinvolving large components.
l Combining the hot-dip galvanization
technique with adapted paint systems or
zinc coatings - so called duplex systems
renders maintenance unnecessary with,
in most cases, the corrosion protection
not requiring any attention or the
entire service lie o the structure.
l Corrosion protection is becoming
an integral part o the abrication
process or steel structures.
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1. Risk of corrosion and protection period
1. Risk of corrosion
The risk o corrosion o steel structuresemanates rom the surrounding atmospheric
conditions.
The nature and extent o any corrosion is linked
to the amount o time that metal suraces are
exposed to moisture and to the amount o air
pollution.
The exposure time to moisture, which is the
amount o time that the relative humidity o the
air is > 80% at an ambient temperature of >0C,
is the main determinant as regards atmosphericcorrosion and corrosion rate o metals.
The absence o moisture considerably slows
down the corrosion rate o steel and zinc even in
the presence o high concentrations o gaseous
(SO2, NOx etc) or solid polluters (dust containing
aggressive particles).
Over the last ew years, the complex inluence
o atmospheric polluters on the corrosion rate o
unprotected structural steel and zinc has beenanalysed as part o several European research
programmes [1].
The result o this work has led to the drating
o the standard ISO 9223 Corrosion o metals
and alloys Corrosivity o atmospheres
Classiication. The basic inormation containing
the classiications or the corrosivity o
atmospheres and the corrosion rates o plain
carbon steel, zinc, copper, and aluminium,
determined as a unction o the corrosive load,
is suiciently accurate to allow the protection
period o paints and zinc coatings to be
calculated in a practical ashion.
This standard was also used as the basis or
the classiication o the corrosivity o ambient
atmospheric conditions in EN ISO 12994-2.
EN ISO 12944 characterises atmospheric
conditions in the orm o corrosivity categories
based on igures o the loss o mass or thicknessper unit surace area o steel or zinc during the
irst year o exposure to dierent atmospheric
conditions (Table 1).
Examples o characteristic ambient conditions
help to assign the appropriate corrosivity
category to the structures and acilitate
the determination o the required corrosion
protection, by emphasising the protection
period.
Apart rom unusual circumstances, this method
allows a suiciently reliable assessment to be
made o the corrosive load or the majority o
steel structures.
Corrosion riskcategory
Loss o thickness o zinc
in the
frst year (m)*
Examples o typical environments
External Internal
C 1 Very low Less than 0.1 Isolated building. Relative humidity o air:
less than 60%
C 2 Low 0.1 0 .7Slightly polluted atmosphere,
dry climate e.g. rural areas
Non-isolated building with temporary water
condensation e.g. warehouses, sports halls
C 3 medium 0.7 2.1
Urban or industrial atmosphere with low
level o SO2 pollution or coastal areas with
low salinity
Premises characterised by high relative
humidity o the air and impurities, e.g.
breweries, laundries, diaries
C 4 high 2.1 4.2Industrial or coastal atmosphere with low
salinitySwimming pools, chemical actories
C 5 Very high I 4.2 8.4Industrial atmosphere with considerable
humidity and aggressive atmospheresBuildings or areas with almost
continuous water condensation and high
levels o pollutionC 5 Very high M 4.2 8.4 Coastal area with high salinity
* can also be expressed in loss o mass (g/m2)
Table 1 Risk o corrosion - Classiication o ambient conditions according to EN ISO 12994-2.
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The levels o airborne SO2 are measured at numerous locations in Europe.
European research has also allowed the relationship between the corrosion
rate o zinc, the levels o airborne SO2 and the wetting time / amount orainall, to be analysed [2].
The loss o zinc as a unction o the concentration o airborne SO2 has
been plotted on a graph on the basis o this research (Figure 1). This
shows a simpliied, but perectly useable version or determining the
corrosivity category according to EN ISO 129442, on the basis o the
igures available or SO2 concentrations [g/m3] at various locations.
However, it should be emphasised that the corrosivity category
determined in this way characterises the corrosive load at the
macroclimatic level. Particular microclimatic eatures, perhaps deriving
rom emission sources in the vicinity o the steel structures, or the use o
an unsuitable design or ensuring corrosion protection, are not included
and must be speciied by the owner, or example, in the case o structures
built or the chemical industry.
In Europe, the considerable reduction in the amount o airborne SO2 has
resulted in a substantial decrease in the corrosive load. The average annual
corrosion rate o zinc or 1992/1993 was 8 g/m2 or 1.1m [3]. These
igures are still valid today.
Figure 1 Loss o zinc as a unction o SO2 pollution (according to Knotkova/Porter)
Loss o zinc/year [m]
Average annual igure o sulphur dioxide [g/m3]
0
100 20 30 40 50 60
0,5
1
1,5
2
2,5
3
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2. Protection period
The protection period o coatings is deined in EN ISO 12944-1 as theexpected service lie up until the moment where the system needs
attention or the irst time.
EN ISO 14713 deines the protection period up until attention is irst
needed o zinc coatings as being the time between the application o the
irst coating and the moment when it irst needs maintenance in order to
ensure the protection o the base material.
The protection period is a vital actor when selecting and deining
corrosion protection systems. This technical concept helps the owner o
the structure to speciy his maintenance schedule.
The protection period is not a guarantee period. Generally, the guarantee
period, a legal concept, is shorter than the protection period. There is no
link between these two concepts.
Nowadays, it is possible to imagine corrosion protection not requiring any
or hardly no attention or the entire service lie o hot-dip galvanized steel
structures, even i exposed to poor weather conditions.
The protection period o a zinc coating depends mainly, or a given
corrosive load, on the thickness o the applied coat. Figure 4 uses the
igures or loss o thickness o zinc indicated in Table 1 to show the
relationship between the protection period / the thickness o the zinc
coat and the corrosive load. It can be generally assumed that there is auniorm loss o zinc across the entire coated surace. I we consider the
macroclimatic corrosive charge o category C3, currently valid in Europe,
and characterised by a zinc loss o between 0.7 and 2.1 m during the
irst year, we obtain a protection period o at least 40 years or a minimum
zinc coat thickness o 85 m, as speciied in EN ISO 1461 (Table 3) or
steel product thicknesses o >6 mm.
Protection period (years)
Thickness o the zinc coating [m]
We have to once again state that the protection period determined in
accordance with the method above is only valid or the corrosive loads
considered at the macroclimatic level.
Special microclimatic eatures and higher loads particular to the structure,
such as an accumulation o dust with a prolonged exposure to moisture
can considerably reduce the protection period.
It is now possible, as a result of the clear definition of ambient atmospheric
conditions - corrosivity categories - and access to measurements used as
the basis or calculating the protection period, to properly design suitable
corrosion protection systems in accordance with EN ISO 12944-5 and
EN ISO 1461.
Figure 2 Protection period o zinc coatings as a unction o the thickness o the coatand the corrosive load
200 40 60 80 100 120 140
C5
100
80
60
40
20
0
C4
C3
C2
C1
Santiago-Bernabeu Stadium, Madrid, Spain
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2. Corrosion protection methods
ArchitectsEstudio
Lamela-PhotoEstudioLamela,FranciscoPabloLaso
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When considering the corrosion protection o
steel structures, a distinction is made between
active and passive measures.
Active corrosion protection aims at preventing
corrosion or reducing the rate o the corrosion
reaction by:
l interering in the corrosion process,
e.g. reducing air pollution
l choosing a suitable material, e.g. using
corrosion resistant materials
l using detailing appropriate or
corrosion protection
The goal o passive corrosion protection is
to shield the steel surace rom corrosive
substances.
Due to their broad range o application
possibilities and their eiciency, the ollowing
methods dominate the corrosion protection osteel structures:
l coatings based on liquid or powder coatings
l metallic coatings (zinc, aluminum or
zinc-/aluminum alloys) applied by hot-
dip galvanization or thermal spraying
l combination o metallic coatings
and paint systems
Optimal corrosion protection is achieved
by combining active and passive corrosion
protection methods, based on the appropriatedetailing prior to the application o the passive
corrosion protection.
In the ollowing, the most eicient passive
corrosion protection method or steel structures,
namely hot-dip galvanizing, will be presented
together with material-, design- and process-
related requirements.
Santiago-Bernabeu Stadium, Madrid, Spain
Cognac-Jay Foundation, Rueil-Malmaison, France
ArchitectsJeanNouvel&DidierBrault-PhotoPhilippeRuault
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3. Hot-dip galvanizing
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1. Method
Hot-dip galvanization is the application o zincor iron/zinc alloy coatings by immersing the
prepared steel in molten zinc.
A distinction must be made between:
l the continuous method (or sheets, wire
rod, etc.),
l the discontinuous method (or sections,
structural elements, and small parts).
Only the discontinuous method in accordancewith EN ISO 1461 may be used or steel
structures.
It is essential or hot-dip galvanizing, namely
the iron-zinc reaction, that the steel surace to
be galvanized shall be metallically clean, i.e. ree
rom grease, rust and scale.
This high level o surace preparation level Be
according to EN ISO 12944-4 is achieved by
irst conditioning the material to be galvanizedin acid or alkali degreasing baths, then pickling
in diluted hydrochloric acid, ollowed by luxing.
When the part to be galvanized is immersed in
the zinc bath (between 440 and 460C), the
lux, which is usually a mixture o zinc chloride
and ammonium chloride, protects the metallic
surace and improves its wettability as regards
the molten zinc.
Zinc is the main component o the zinc bath,
and the total amount o additional elements
(with the exception o iron and tin) shall not
exceed the sum o 1.5%.
The cleansed and luxed part can be dried prior
to galvanization in an oven at temperatures
between 80 and 100C.
During immersion in the zinc bath, layers o
iron-zinc alloys build up on the surace o the
steel element which are generally covered with
a coat o pure zinc upon removal rom the bath.
Figure 3 Principle o the discontinuous galvanization process
The speed o the iron-zinc reaction depends on
the galvanizing parameters and the chemical
composition o the steel, particularly its siliconand phosphorus content. Reactive steels
build up thick layers o iron-zinc alloys and the
residual heat in the galvanized material can even
transorm the pure zinc coat into a coat o iron-
zinc alloy.
This reaction can be interrupted or slowed down
considerably by an immediate quenching o the
galvanized part in a water bath.
Figure 3 schematically represents the principle of
the discontinuous galvanization process.
Degreasing bath Pickling bathRinsing bath Flux bath Drying oven Zinc bath Water bathRinsing bath
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2. The iron-zinc reaction
Nowadays, the usual structural steels arebasically all suitable or hot-dip galvanizing.
However, they possess individual characteristics
which inluence the result o the galvanizing
process.
Hot-dip galvanizing is a reaction between the
surace o steel and molten zinc which results in
a zinc coating whose thickness and appearance
are basically determined by the chemical
composition o the steel and the galvanization
parameters (zinc bath temperature, immersiontime). The surace condition o the steel element
may also inluence the result o galvanization.
The behaviour o steels during galvanization can
be divided into our groups on the basis o their
Si and P contents (Table 2).
The steels o the ArcelorMittal long products are
o the Sebisty type and have typically a silicon
content o between 0.15% and 0.25%, and a
phosphorous content o less than 0.040%.
There are overlaps between the groups,inluenced by the temperature o the zinc bath.
The iron-zinc reaction also depends on the
topography o the steels surace, especially
when using steels in the transition range
between the ones with a low Si and P content
and the ones rom the Sandelin group,. This may
result in local or widespread variations in the
thickness and appearance o the zinc coat.
Similar appearances can also be caused by local
thermal stresses at the surace o the steel,
as happens during oxygen-cutting or lamestraightening. Here, the cause is probably due to
localised changes o the chemical composition in
the heat aected zone close to the surace as a
result o the oxidation o the so-called reactive
elements in the steel (i.e. Si, P), which loose thus
their inluence on the iron-zinc reaction.
The variation in the galvanization behaviour o
welds vs. adjacent steel suraces is the result o
dierences in the chemical composition o the
welding consumables and the base material. The
zinc coating on grinded suraces o welds may
also be thicker or have a dierent appearance
with regard to adjacent areas.
Generally, blast-cleaned suraces, i.e. sand or
shot blasted prior to galvanization, react aster
on contact with molten zinc, resulting in thicker
zinc layers when compared to steel suraces that
are simply pickled.
Unevenness and imperections in the steel
surace deriving rom rolling, straightening and
other processes are usually not smoothed out
by the zinc coating, in most cases, they are evenvisually ampliied.
Galvanizers have very ew means at their
disposal or inluencing the quality o the zinc
coating, which depends mainly on the chemicalcomposition o the steel.
Theoretically, it is possible to inluence the
thickness o the zinc coat by controlling the
immersion time, the chemical composition
and the melting temperature o the zinc
bath. As shown in Figure 4, there is however
no consistent relationship between these
parameters
The thickness o the zinc coat increases
with temperature up to a Si + P content o
approximately 0.12%. Beyond this point, the
relationship is reversed up to a Si + P content o
0.27%; in case o Sebisty steels, the thickness
o the zinc coat decreases with an increase in
the bath temperature. It then increases again
with an increase in the melting temperature o
the zinc rom a Si + P content o approximately
0.27% and more.
Group silicon + phosphorous [%] Zinc coating
1 Steel with low
Si + P content< 0.03
Silvery bright, zinc spangles, thin
coat
2 Sandelin steels 0.03 < 0.13Grey, sometimes granular, very
thick coat
3 Sebisty steels0.13 < 0.28 Silvery bright to pale grey, coat o
average thickness coat
4 Steel with high
Si + P content 0.28 Pale grey, very thick coat
Table 2 Classiication o the galvanization behaviour o structural steels according to their silicon and phosphoruscontents.
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3. Adhesion capacity of zinc coatings
In accordance with EN ISO 1461, adhesionbetween the zinc coating and the substrate does
not normally need to be tested, because zinc
coatings have adequate adherence or resisting
mechanical impacts during normal handling
operations and use without spalling or laking
o.
I adhesion needs to be checked, e.g. in the case
o parts exposed to high mechanical stresses,
impact or notch tests may be perormed.
However, there is no European standard or thetesting o adhesion.
The methods routinely employed, such as
the cross-hatch test, ASTM hammer test
(ASTM A 123) and the impact tests in
accordance with DIN 50978, are restricted to a
maximum coat thickness o approximately 150
m, and provide only qualitative inormation.
Moreover, these methods mainly assess the
ductility and sensitivity to scaling o zinc
coatings rather than their adhesion capability.
The modiied test method used or organic
coatings i.e. Tear o test to assess adhesion
capability in accordance with EN ISO 26624[5] allows the adhesion o zinc coatings to be
determined with statistical reliability up to
45 MPa.
These characteristic adhesion values indicate
the tensile strength or uplit resistance o
zinc coatings, which, in conjunction with the
(adhesive or cohesive) ailure patterns, enable
the assessment o their adhesion capacity.
With the exception o Sebisty steels, measured
average values or the adhesion o zinc coatings
in accordance with EN ISO 1461 are generally
greater than 20 MPa. The values or Sebisty
steels vary rom 10 to 18 MPa.
Appropriate tests have conirmed the indication
given in EN ISO 1461 stating that undamaged
zinc coatings have suicient adhesion [6].
3. Hot-dip galvanizing
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4. Repair of damaged zinc coatings
In accordance with EN ISO 1461, theimperections in zinc coatings may not exceed
0.5% o the total surace o the building
component. A single deect may not exceed
10 cm2 and must to be repaired in accordance
with requirements.
The internal suraces o inaccessible hollow
structures are exempted rom this requirement,
because it is difficult or impossible to inspect and
because o poor access or repair purposes.
The standard considers three repair methods:
l Thermal spraying with zinc
l Use o zinc-rich paint
l Solder with a zinc-alloy stick
The repair techniques are not ranked in any
particular order.
Unless otherwise stipulated, the repair method is
at the galvanizers discretion.
The galvanizer shall advise the building owner
or end-user o the repair method that hasbeen used. Appropriate zinc powder-based
systems are mainly used. Single component
polyurethane/zinc powder-based primers are
recommended, provided their suitability has
been certiied by the manuacturer. This repair
method is practical, eective i implemented
correctly, and reasonably priced.
The repair o imperections using thermal zinc
spraying (with or without subsequent sealing)
is admittedly the most expensive and onerousrepair method, but it does oer a protection
period comparable to that o the original intact
zinc coating. Its technical easibility must be
checked in advance, particularly with regard
to the accessibility o the suraces to be
repaired. Also, the higher costs must be agreed
beorehand.
Repair using zinc-rich paint is eective as
well, but its quality very much depends on the
preparation o the surace, the suitability o
the paint itsel, the correct application and the
thickness o the coating.
The soldering repair technique with zinc alloy
is relatively expensive and the result obtained
is usually unsatisactory. In particular soldering
with tin, which is diicult to melt, gives poor
results. This method is thereore disappearing
rom the market.
The particular characteristics o the repair
method with respect to the application
o subsequent coats must be taken into
consideration. Compatibility between therepair coating and subsequent coats must
be guaranteed. For powder coatings, stoving
temperatures up to 200C have to be
considered.
Beore applying a repair coat, the aected
surace must be cleaned and, i necessary,
descaled. A high quality surace preparation canbe obtained by manually grinding to a surace
condition o PMa or by blasting to a surace
condition o Sa 2 or (EN ISO 12944-4). The
requirements relating to surace roughness must
be considered when selecting the repair method.
The coat thickness o the repaired area shall be
at least 30 m greater than the required local
thickness o the zinc coating as given in Table 3.
According to this standard, deects in the zinc
coating resulting rom the interventions by third
parties during abrication or erection must be
repaired in the same way. Zinc coatings have
a better resistance against mechanical loads
than organic paints. It is however technically
impossible to completely avoid damages or a
reduction o coat thickness in the areas where
handling gear is applied, even i all necessary
precautions are taken.
Deects with a surace area o more than
10 cm2 may also result rom modiications made
to the galvanized structure or rom mechanical
loads generated during erection. I the deectcan be repaired without compromising the
eectiveness o the corrosion protection e.g.
by thermal spraying with zinc, there is usually
no need or the structure to be dismantled and
regalvanized. Here, an equitable solution should
be sought between the contracting parties.
3. Hot-dip galvanizing
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Architect
sClaudeVasconi&JeanPetit,Luxembourg
Chamber o Commerce, Luxembourg
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4. Charasteristics of hot-dipgalvanizing of steel structures
1. Preliminaries
Hot-dip galvanizing is a highly eective andcost-eicient corrosion protection method or
steel structures.
The process-related speciicities o hot-dip
galvanization (surace preparation by pickling
in acid, immersion o steel structures into a
metal bath at 450C, uneven heating during
immersion) result however in higher technical
requirements than with other corrosion
protection methods with respect to:
l
Steel quality and material characteristicsl Detailing, structural design
l Fabrication o the steel structures
All these points have to be taken into account
by the contributing parties. As a matter o act,
an unavourable combination o these aspects
can result in the ormation o cracks during hot-
dip galvanization or during the treatment o the
steel components in the aqueous solutions like
degreasing, pickling and luxing. The state-o-
the-art considers today the zinc bath as the
leading action in relation with the ormation o
issures. Consequently, special attention has tobe paid to highly reactive chemical compositions
o the zinc bath as they increase the cracking
potential.
Basically, a distinction has to be made between
the liquid metal induced embrittlement (LME)
and the hydrogen-induced cracking or expansion
o cracks (hydrogen-induced corrosion) during
the hot-dip galvanizing process.
Extensive metallographic investigations have
shown that the cracking o usual structural
steels during hot-dip galvanizing is due to LME.Hydrogen-induced cracking o structural steel
structures during hot-dip galvanizing is much
less likely to occur [7].
In order to ulil the quality requirements o zinc
coatings according to EN ISO 1461, a close
collaboration between the steel manuacturer,
the abricator and the galvanizer is absolutely
necessary, especially when dealing with steel
constructions with a high degree o welding.
2. Hydrogen-induced cracking
On principle, the absorption o hydrogen into
the metals occurs in the presence o a suicient
amount o hydrogen, e.g. during the steel
production (blast urnace process, pickling), steel
processing (welding) or during the pretreatment
o the steel surace like degreasing, pickling, etc.
According to ISO 4964, the risk o hydrogen-
induced cracking mainly exists with a local tensile
strength >1200 N/mm2, a hardness >34 HRC or
a surace hardness >340 HV. Notches, presentin the microstructure o the surace, or material
inhomogeneities increase the risk o damage.
Usual steel grades are typically not subjected
to embrittlement through hydrogen absorption
during pickling, even i hydrogen remains in the
steel. In this case, the hydrogen escapes during
the immersion process in the molten zinc.
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3. Liquid metal-inducedembrittlement (LME)
Preconditions or LME to arise are:
l suicient static or dynamic tensile,
bending or torsional stresses (load
induced/ residual stresses)
l corrosive acting liquid metal
l solid metal vulnerable to LME
l critical temperature range
l mutual solubility o the involved metals
l good wettability o the solid metal by
the molten metal
l ormation o low melting intermetallic
phases/compounds.
Given the above-mentioned conditions during
the hot-dip galvanizing o steel structures, the
characteristics o steel can be unavourably
aected by wetting grain boundaries close to
the surace respectively suraces in notches orcracks with a corrosive acting liquid metal, zinc
and/or alloys o the zinc bath (or example lead
(Pb), tin (Sn) or bismuth (Bi)).
Tensile stresses in the steel can no longer be
transerred i:
l the deormation capacity (ductility)
is impaired, see also Figure 6,
l the resistance against crack
propagation is reduced.
When exceeding a critical stress level, the
development o inter-crystalline issures in
the steel, ramiied and branched out into the
material, results in the cracking o the remaining
section. The issure tips are usually illed
with zinc; in the case o alloyed zinc baths,
additional concentrations o alloying elements
may be present.
The order o magnitude o the critical stress,
above which steel is vulnerable to cracking
through LME in a zinc bath, is widely unknown
at present. On the one hand this is due to the
diiculty or deining and assessing the existing
and acting stresses in the structural element
and on the other hand it is due to the act that
stresses are generated through technological
parameters during the galvanizing process,
above all the dipping speed o the buildingcomponents and the heat transer rom the zinc
bath to the steel. Literature generally indicates
that the susceptibility to LME increases with
increasing hardness and resistance o the
structural steels. Observations in this regard
suggest that steel grades S275 and lower run a
very low LME-risk, whereas those above S460
are clearly more at risk.
Today, there is a general believe that the
potential risk o crack ormation due to LME
is substantially inluenced by the chemicalcomposition o the zinc bath, in particular the
contents o lead (Pb), tin (Sn) and bismuth (Bi).
Typical requirements on the maximum content
o these 3 elements are given in chapter 8.
4. Charasteristics of hot-dip galvanizing of steel structures
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5. Requirements for materials
19
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1. Chemical composition
The structural steels o ArcelorMittals longproducts are produced in accordance with part
2 or 4 o EN 10025:2004 and the option o
the suitability or hot-dip zinc-coating can be
agreed upon or all the steel grades up to a yield
strength o 460 MPa. It is clear here that this
option merely applies to the inluence o the
chemical composition o the steels regarding the
silicon (Si) and phosphorous (P) content on the
thickness and appearance o the zinc coating.
The perormance o the steels during hot-dip
galvanizing with regard to LME is not addressedin the European standards.
In Japan, extensive tests have been conducted
on the subject and a relation, similar to the
carbon equivalent as an indication or the
weldability, is proposed between the chemical
composition o some Japanese steels and their
LME risk potential,. [9] reports on this matter
in the context o a contribution to the current
state o knowledge regarding LME. Inquiries
about the causes o cracks in steel structures
in Europe, however, have lead to the conclusion
that optimal chemical compositions o the steelsalone according to the Japanese experience can
not prevent LME when other actors avouring
LME provoke a suiciently critical state. On a
general basis, it can nethertheless be stated that
a low carbon equivalent tends to counteract
LME.
5. Requirements for materials
ArchitectsClaudeVasconi&JeanPetit,Luxembourg
Chamber o Commerce, Luxembourg
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2. Mechanical properties of steel
The knowledge o the steel characteristicsis essential when designing the steel building
components suitable or hot-dip galvanizing.
The design or quasi-static loads is usually
based on the yield stress Re, This characteristic
is determined with the tensile strength Rm,
the Youngs modulus o elasticity E, the total
elongation at racture A, the uniorm elongation
Ag and the reduction o area Z, in a monoaxial
tensile test at ambient temperature at a gradual
loading rate.
The stress-strain diagram, obtained rom this
tensile test, shows that substantial deormation
occurs beyond the yield stress beore rupture
occurs. This means that racture o building
components is an indication that a large amount
o deormation has taken place. This ductility
has a major inluence on the assessment o
stress resistance, on the choice o the calculation
method and statical system, as well as the
application o the saety coeicients in steel
structures. In order to avoid brittle fracture, steel
needs to be suiciently ductile.
The plastic deormation also reduces stress
concentrations at notches or where residual
stresses are present. For example, residual
stresses (rom welding or rolling processes) are
either completely or partially disregarded when
designing steel structures.
Building components made rom a ductile
material may also be used or plastic design,
which means that elongation o the steel beyond
its yield stress is allowed.
Ductility however can vary considerably
between steel grades, as shown in Figure 5.
Also, it is important to note that the deormation
capacity o the steel is reduced during the hot-
dip galvanizing process (Figure 6).
Heating steel lowers its yield stress, modulus o
elasticity as well as its tensile strength.
The stress-temperature diagram in Figure 7
shows the typical reduction in yield stress or
the 3 usual steel grades S 235, HISTAR 355 /
S 355 and HISTAR 460 / S 460.
Hardness is another criterion used to assess
strength. The hardness value is used, or
example, or checking the uniormity o the
strength o semi-inished products, and can
be used or the approximate non-destructive
determination o the tensile strength.
The advantages o steel grades with high
elongation have already been mentioned.
In addition to total elongation A, uniorm
elongation Ag, and reduction o area Z, the notch
impact energy Kv is an important criterion whenassessing the toughness o a steel.
The toughness values may not be used as such
or structural design purposes, they rather
enable a qualitative comparison o various steels
with regard to their toughness. Combined with
the experience gained with steels whose stress
resistance and toughness have already been
determined, they enable an assessment o the
risk o brittle racture occurring in certain stress
conditions (i.e. plane, three-dimensional or
residual stresses, loads), at certain temperaturesor in particular loading modes (slow or ast).
Figure 5 Typical stress - strain diagram or various steels
Figure 6 Schematic stress strain diagram or structuralsteel S355 comparison o the characteristics o S355at room temperature (RT), at 460C in the air, and duringimmersion in the zinc bath at 460C
Figure 7 Typical yield stress - temperature diagram or
various steels
Yield stress [N/mm2]
Temperature [C]
HISTAR 355/S 355
S 235
HISTAR 460/S 460
0
100
200
300
400
500
0 100 200 300 400 500
Stress
Elongation
0
0
150
300
450
600
750
800
Stress [N/mm2]
HISTAR 460/S 460
HISTAR 355/S 355
S 235
6 12 18 24 3630
21
S355 RT
S355 460 C / air
S355 460 C / Zinc bath
Elongation [%]
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The toughness o hot-rolled sections is
measured in longitudinal rolling direction.
Without any special measures, toughnessvalues can be lower in transverse direction and
perpendicular to the surace o the section. The
reason or this deterioration is the presence o
non-metallic deormable inclusions positioned
parallel to the surace during the rolling process.
Stresses occurring perpendicular to the surace
(mainly in welded structures) combined with
insuicient toughness can then lead to a loss
o cohesion in the material similar to lamellar
tearing. These inclusions can be modiied or even
eliminated using special steel making techniques.
Thus, Z-quality steel is characterised by
superior deormation properties in a plane
perpendicular to the surace.
The limited possibilities or using the toughness
values in the assessment o crack potential is
due to the act that the state o stress (plane or
three-dimensional, residual) and the deformation
conditions o the structure are widely unknown.
It is mainly high stress levels at the end o
a surace or internal imperections, residual
stresses rom abrication, the temperature and
the loading rate that inluence the resistance tobrittle racture.
In order to better assess, rom a quantitative
point o view, the susceptibility o a steel
to brittle racture, racture resistance is
determined on the basis o the theory o
racture mechanics and special tests made on
samples pre-notched by atigue. Their condition
is similar to the one o building components
aected by issures. A critical temperature is
thus obtained at speciied stress levels. Below
this critical temperature, a crack propagatesrapidly resulting in the sudden racture o the
entire sample.
Speciic steel production processes (e.g. the
way o killing during casting) inluence the
toughness and susceptibility to lamellar tearing;
the designation o the notch toughness shows
dierent levels (or structural steels e.g. JR, J0,
J2, M, ML, etc.).
A ine grain microstructure, such as the one o
high strength ine grained structural steels, also
enables susceptibility to brittle racture to be
reduced and weldability to be improved. The
ine microstructure o these steels increases
their yield strength without compromising their
toughness.
3. Weldability
Structural steels are typically expected topossess a good weldability, which is usually the
case. This means that the welding technique
and iller materials must be selected in such a
way that there is no deterioration in either the
strength or the toughness in the heat aected
zone and in the weld.
During the production process o the steels, the
weldability can be improved by an increase o
the purity level, through an improved control
o the alloying elements as well as speciic
processes, like the controlled thermomechanicalrolling and the quenching and sel-tempering.
5. Requirements for materials
Grenoble Ice Rink, France
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4. Information on materials forfabricating building components
Figure 5 shows that the various steel qualities
have very high elongation capability. For design
purposes, only a small part o this potential is
used. The elongation capability o steel may
be reduced due to material embrittlement,
or generally due to local restrictions o
deormability as a result o two or three
dimensional (residual) stress states or through
the presence o micro structural impurities in
the steel. Exceeding the ductility limit obviously
results in brittle racture in the building
component. Experience shows that severalinluences can occur simultaneously.
These are very complex phenomena and
experimental results or the estimation o the
toughness. Respectively the tendency or brittle
racture are subject to very large variations.
Also, brittle racture is greatly inluenced by
the abrication processes (e.g. changes in the
microstructure in a welded area i excessively
cooled), the structural design (e.g. residual
stresses) and the way in which the structure
is used (e.g. the rate at which heavy loads are
applied).
Obviously, welded building parts may be
particularly aected by brittle racture.
The presence o hydrogen in the weld or in the
heat-aected zone, combined with residual
stresses rom welding, aects the susceptibilityo steel to hot and cold cracking. Besides hot
cracks during welding, cold cracks are to be
expected i hydrogen rom welding is present
in the weld or heat-aected zone and when
residual stresses rom shrinking take eect.
Here, hydrogen causes a reduction o the
deormation capacity.
Taking into account these considerations is
o outmost importance or the structural
design process o steel structures oreseen or
galvanization, as additional stresses during hot-
dip galvanizing and simultaneously reduced yield
stress and deormation capacities o the steels
can lead to LME or hydrogen induced crack
ormation.
This type o brittle racture during galvanizing
can occur in any type o steel. As already
indicated, susceptibility to racture is especially
inluenced by tensile stresses (mainly residual
stresses) in the building component.
5. Improving structural steels
Developments in structural steels are aimed at
increasing their yield strength and weldability
while keeping or even improving their toughness.
These improvements are achieved by eliminating
inclusions, by improving the microstructure
through the choice o alloying elements
avouring iner grains, the replacement o
ingot casting with continuous casting and the
adoption o reined rolling processes like the
thermomechanical rolling and the quenching andsel-tempering.
23
5. Requirements for materials
ArchitectsChemetov-
Huidobro-PhotosO.Wogenscki
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6. Requirements of structures suitablefor hot-dip galvanizing
1. General
The principles o the design o structures to begalvanized are similar to those or other steel
structures provided that the speciic demands
or the hot-dip galvanizing process are taken
into consideration.
Hot-dip galvanizing is a hot-immersion process
whose stages rom surace preparation
(degreasing, pickling, rinsing, and luxing) to
the galvanization process itsel take place in
an industrial-sized installation (e.g. tanks and
kettles) respectively in the zinc bath (440
460C). All the ollowing speciic demandso this procedure have to be taken into
consideration at the design stage:
l Technical demands associated
with the process
l Saety requirements
l Requirements imposed on the materials,
design, and fabrication of building components
to prevent deormations and cracks
Basic inormation on this subject can be ound inISO 1461 and in EN ISO 14713.
In addition, the shape o steel structures and
their design as regards corrosion protection
have a decisive inluence on the eectiveness
(protection period) and maintenance
(accessibility) o the corrosion protection.
In this respect, the basic rules or the design o
structures to be corrosion protected according
to EN ISO 12944-3 are also applicable to
galvanized structures.
2. Technical requirementsassociated with the process
2.1 Geometry o building components
The dimensions o building components that are
to be galvanized shall be chosen in such a way
that they can be immersed in a single operation.
It is thereore important or the designer to
determine in advance the maximum dimensions
o the available galvanizing tanks.
In the case o steel structures, the economically
viable dimensions o tanks are as ollows:
l Length: 7.00 16.50 m
l Width: 1.30 2.00 m
l Depth: 2.20 3.50 m
For building components that can not be
galvanized in one operation, (Figure 8 shows
an example or double immersion), special
measures have to be taken since the dierential
heating o the building component increases
the risk o deormation and/or cracking (see
also paragraph 6.2.4). In this situation, prior
discussions should be held with the galvanizer.
First immersion
Second immersion
Figure 8 Example o double immersion
Killesberg Tower, Stuttgart, Germany
ArchitectsHansLuzundPartner
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2.2 Vent holes, run-o openings,
ventilation openings
In order to ensure that the surace is correctly
pre-treated and high quality galvanization
is achieved, building components must be
designed in such a way that the pre-treatment
liquids and especially the molten zinc are in
contact with all the suraces, and that they can
reely run o when the part is removed rom
the bath.
Air pockets and air inclusions lead to uncoated
areas; constructional measures must thereore
be employed to prevent their ormation.
This does not only apply to structures made
rom hollow sections and tanks, but also to
structures comprising stieners, partition plates
and endplates, etc. in which air pockets may
orm during immersion i appropriate vent holes
are not incorporated.
The sizes o the run-o openings and vent holes
depend on the quantity o zinc that must low
through. The immersion velocity is an importantparameter or reducing the risk potential o
steel constructions with regard to LME. Further
details will be discussed in chapter 8. It has
been experimentally determined that the
susceptibility to LME decreases with an increase
in immersion velocity. An ideal immersion
velocity would be approximately 5 m/min [11].
Figure 9 shows examples o vent holes,
Figure 10 examples o run-o openings. In the
case o sections up to 300 mm high, l1 must be 20 mm, in the case o sections over 300 mm
high, l1 must be 30 mm. In order to achieve
the ideal immersion velocity or LME-critical
steel constructions, it is necessary to coordinate
the design o the vent holes with the abricator
and the galvanizer.
The run-o openings or the connection o
girders, base plates, corners o portal rames,
etc. must have a diameter between 10 mm and
approx. 35 mm. Examples can be ound in
Figure 10.
Figure 9 Examples o vent holes
Figure 10 Examples o run-o openings
l1
l1
l1
l1
Bevel cut Circular cut
6. Requirements of structures suitable for hot-dip galvanizing
D
D
D
D
Girder assembly Base plate Node o portal rame
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2.3 Saety issues associated
with the process
At the temperature o molten zinc (440
460C) the moisture contained in air pockets
(hollow parts, overlapping areas closed by
welds) generates pressurized water vapour
creating an explosion risk. Liquids rom the pre-
treatment process can also seep into overlapping
suraces i these are not perectly sealed, and
evaporate explosively when immersed in the
zinc bath.
Overlapping suraces should be avoided not
only or saety reasons, but also or corrosion
protection purposes. Table 4 provides some
suggestions, should overlapping suraces be
unavoidable.
The drilling o holes in large overlapping suraces
deinitely reduces the danger o explosion during
galvanization but it also reduces the eiciency
o the corrosion protection o the structure.
Indeed, iniltrated pre-treatment solutions do
not completely evaporate, leaving traces o salt
in gaps. In many cases, the zinc coat will not
completely cover the gaps ater evaporation
o the liquids, resulting in corrosion occurring inthese parts o the structure.
Maximum overlapping suraces Measures
Up to 100 cm2 (or product thicknesses < 12mm) Seal weld circumerence
Up to 400 cm2 (or product thicknesses 12mm) Seal weld circumerence
Table 4 Recommended maximum sizes o overlapping suraces
6. Requirements of structures suitable for hot-dip galvanizing
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2.4 Inormation on detailing
suitable or galvanization
The design and detailing o steel building
components must satisy the basic principles
or the design o structures requiring corrosion
protection, and in particular, o hot-dip
galvanization. This is the only way in which
adequate corrosion protection comprising
satisactory thickness o zinc layers can be
ensured, along with the elimination o the
potential risk of structural deformation, cracks or
any other damage to the building components.
Consultation with the galvanizer must be sought
as early as possible in the design process or
galvanized steel components.
Table 5 Structural details and abrication recommendations
Potential problems during hot-dip galvanization
o steel components may be solved by
implementation o the ollowing constructionaland technological measures:
l Already at the planning stage, the abricator
must try to minimise residual stresses
generated during abrication, particularly rom
welding. Here, appropriate welding procedures
are helpul. With increasing thicknesses o
building components, the risk o three-
dimensional stresses, aster cooling rates
and hence the risk o cracking increases.
l Strict compliance with requirements as
regards the design o structures intended
or hot-dip galvanization, especially when
using high strength steels with a low notch
toughness. The amount o vent holes and
drainage holes must be minimised. Also,
inappropriate abrication will increase the
risk o cracking. It is recommended to
seek agreement with the galvanizer.
l The ratio o plate thicknesses welded directly
together should not exceed a actor o 2.5.
With increasing thicknesses o the steelparts and or elements with a high degree o
welding, the ratio should even be smaller.
l The use o highly restrained building
components susceptible o generating
internal stresses during the galvanizing
process should be avoided.
l The actual characteristics and the
chemical composition o the material to
be galvanized must be identiied prior
to galvanization. The galvanizer must be
advised about the nature o the steels
used or the sections to be galvanized.
l Multiple immersions must be avoided.
The ollowing table shows a selection o
structural details which have to be considered
as critical with regard to LME during hot-dip
galvanization.
Nr Structural detail Description
1
Welding o hal end plates induces a concentration o residual stresses in the area indicated.
Recommendation: arrange the end plate over the ull height o the section or use a bolted
connection.
2Welding o the plate induces a concentration o residual stresses in the area indicated.
Recommendation: perorm stress relie annealing in the areas indicated, and/or round o.
3Welding induces concentrations o residual stresses at the our corners o the hollow section.
Recommendation: perorm stress relie annealing in the areas indicated.
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Nr Structural detail Description
4Welding induces concentrations o residual stresses at the our corners o the connection plate.
Recommendation: perorm stress relie annealing in the areas indicated.
5Welding induces concentrations o residual stresses at the ends o the plate.
Recommendation: perorm stress relie annealing in the areas indicated.
6
The dierences in stiness between the section, the thick base plate, and welds induce
concentrations o residual stresses.
Recommendation: perorm stress relie annealing in the area o the welds .
7
The dierences in stiness between the section and the endplate and welds induce concen-
trations o residual straining. Hardening at the edges o the bolt holes may also occur.
Recommendations: perorm stress relie annealing in the area o the welds, careully
drill bolt holes.
8
The dierences in stiness between the section and the endplate and welds induce
residual stresses.
Recommendation: perorm stress relie annealing in the area o the welds.
9The welding o stieners between the fanges o the section induces residual stresses.
Recommendation: perorm stress relie annealing in the area o the welds.
10
The system is internally highly restrained. The inevitable dierences in temperature to which
building components are heated lead to high residual stresses.
Recommendation: bolt the diagonals to the chords ater galvanization.
11
Inappropriate execution o the rounded areas may result in hardening and the creation
o notches.
Recommendation: round-o careully, perorm stress relie annealing in the abricated areas.
12Inappropriate execution o openings may result in hardening and the creation o notches.
Recommendation: round-o careully, perorm stress relie annealing in the abricated area.
6. Requirements of structures suitable for hot-dip galvanizing
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ArchitectsSRA,AnthonyBelluschi,OWP&P
Shopping Center 4 temps, Paris, France
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7. Requirements for the fabricationof steel structures
1. Residual stresses inbuilding components
Cracks rom hot-dip galvanizing o steel
constructions are oten generated in places with
high residual stresses (tensile stresses), notches
and/or hardness increases due to abrication
processes such as
l welding
l oxygen cutting
l grinding
l drilling
l punching
l
cold orming (ageing)l straightening
Residual stresses are also created in restrained
components in the zinc bath. The heat during
galvanization (450C) modiies both the
state o internal stresses and the mechanical
characteristics o the steel (reduction o yield
stress and modulus o elasticity), thereby
reducing the resistance o the building
components to elastic deormation. Stresses,
mainly localised, can decrease but also increase
and deormations may occur.
The diiculty lies, however, in determining the
magnitude o residual stresses, which in practice
can only be roughly estimated. The many
actors, inluenced by abrication and detailing,
cannot be determined with suicient accuracy
either qualitatively or quantitatively. Structural
engineers are usually unaware of the real amount
o residual stresses in the structure.
The plastic deormation capabilities o structural
steels generally allow to disregard the accurate
determination o residual stresses as they aremostly localised and tend to disappear through
plastiication when superposed with stresses
rom exterior loads. It is o course o outmost
importance here that the appropriate steel
is chosen with respect to toughness, taking
into account the dimensions o the building
component and the application temperature
(see prEN 1993-1-10). With components thatare to be hot-dip galvanized, special care must
be taken to minimise residual stresses. This is
usually achieved using constructional measures,
in order to avoid any subsequent stress relieving
beore galvanizing.
Fabrication also allows to prevent high residual
stresses and hardness increases by
l using multi-layer illet welds, which
could be welded in a single run with the
current state o welding techniques
l establishing a welding procedure
l avoiding long and thick welds
l avoiding cold deormation or reducing
the created residual stresses through
heat treatment (keeping in mind
however that not all the eects o
cold orming can be cancelled out)
l removing notches or restricting their presence
especially in thin building parts o welded
constructions and areas subject to changesin microstructure rom cold orming, welding,
oxygen cutting, drilling, punching, etc.
2. Surface condition ofrolled long products
Unless otherwise speciied in the order,
the suraces o hot rolled sections or hot-
dip galvanization shall normally conorm
to the basic requirements o EN 10163-
3:1991, class C, subsection 1.
The suraces to be galvanized must
be de-greased and any discontinuities
that could compromise the corrosion
protection properties o the zinc coat
must be removed beore galvanization.
ArchitectsMarkusOtt-PhotoAtelierKinold
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Rheda Wiederbrck Car Park, Germany
CourtesyofVollackManagementGmbH,Germany
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8. Requirements for hot-dip Galvanizing
As seen in paragraph 4.3, the presence o a
corrosive acting liquid metal in contact with a
solid metal prone to liquid metal embrittlementis the precondition or crack ormation in steels
due to LME. This prerequisite is inevitably
given or hot-dip galvanizing (liquid metal =
zinc bath, solid metal = steel), as this is the
only way that the zinc coat can be produced.
Similar to the requirements or the steel
production, or the structural design and or the
abrication o steel structures (in particular or
minimising residual stresses), speciic measures
have to be taken in the hot-dip galvanizing
process to keep the risk o hydrogen-induced
cracking and LME as low as possible.
Extensive investigations [9, 12, 13] have
shown that during hot-dip galvanizing, the
temperature gradient resulting rom the
immersion o structural elements into the
zinc bath and its time-related variation during
dipping is an important process parameter in
view o LME. Here, the risk potential or LME
is small or a low temperature gradient [14].
The heat transer coeicient and the
wetting ability o zinc baths increase withhigh concentrations o alloys, especially
tin (Sn), lead (Pb) and bismuth (Bi)
thereby reducing the heating time and
consequently increasing the risk o LME.
Based on the above mentioned indings,
investigations were conducted in order to lower
the temperature gradient by modiying process
parameters o hot-dip galvanizing [11].
The temperature gradient can be reduced by
l optimizing the chemical compositiono the zinc bath, especially with
respect to Sn, Pb and Bi,
l increasing the immersion velocity
(approx. 5 m/min)
l increasing the dipping angle
l increasing the salt concentration
in the lux (approx 500 g/l)
l adjusting the drying temperature ater
luxing to 100C, to ensure a high
temperature o the building components
prior to dipping in the zinc bath
l keeping the temperature o the zinc bath as
low as possible to minimise the temperature
dierence between the building part and thezinc bath.
Recent research results deine a new sate-
o-the-art. Nowadays, it can be assumed
that contents o tin up to 0.1% and/or
bismuth up to 0.1% do not detrimentally
inluence LME. Herewith, the content
o lead should be limited to 0.8%.
It must however be noted here that both
the classical zinc bath and the one modiied
as described above can be LME-critical,
especially i the LME-critical requirements or
the quality o material, design and abrication
(see paragraphs 5 to 7) are not met.
Chamber o Commerce, Luxembourg
ArchitectsClaudeVasconi&JeanPetit,Luxembourg
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BavarianModelHo
usingEstate,Ingolstadt,Germany
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9. Duplex systems
Many architects use hot-dip galvanized steel
structures because o their aesthetic qualities.
In addition, the use o liquid or powder paints on
top o the zinc coat, the well-known duplex-
system, has become very popular over the last
ew years.
Duplex systems have advantages when the
ollowing aspects are important:
l long protection period
Duplex systems have a service lie 1.2 to 1.5
times higher than the combined protection
periods o the hot-dip galvanization and paintcoats (synergy eect).
l large choice o colours
l need or signalling / identiication /
camoulage
l no or reduced release o zinc into the
environment
At least the irst coat o the paint system
should be applied in the workshop, i possible
immediately ater hot-dip galvanization thereby
rendering expensive surace preparation
on the construction site unnecessary.
High quality duplex systems require
optimal compatibility between the
galvanizing coat and the paint.
The choice o suitable coating materials is o
particular importance. Only coating systems with
proven compatibility with batch galvanizationin accordance with EN ISO 1461 shall be used.
The requirements or surace preparation /
pre-treatment depend on the nature o the
coating material.
Zinc suraces designed to be powder-coated
must be sweeped, phosphated or chromated
immediately prior to coating.
In the case o liquid paints, current technology
only requires the surace o the zinc coat
to be sweeped when large amounts o zinc
corrosion products (white rust) on the surace
compromise adhesion, or in unction o the
corrosion exposure categories as per the
speciications o the coat manuacturer.
The purpose o sweep blasting is simply to clean
and rough the surace o the coats. Sweeping
exerts great mechanical stress on zinc coatings
and may, i poorly executed, damage them
(i.e. cause cracks, laking).
The optimal parameters or sweeping are [15]:
l abrasive: non-metallic slags, aluminous
abrasive, or glass beads
l particle size o the abrasive grit: 0.25 -
0.50 mm
l jet pressure at the nozzle: 2.5 3.0 bars
l jet angle :
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Shopping Center 4 temps, Paris, France
ArchitectsSRA,AnthonyBelluschi,OWP&P
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10. Cost effectiveness
Hot-dip galvanization o structural steel
components exposed to atmospheric conditions
constitutes a highly eective durable corrosionprotection method. In many applications,
the corrosion protection lasts as long as the
structure itsel. Zinc coatings require no or
almost no maintenance. Hot-dip galvanizing,
in terms o lietime o the structures, including
maintenance and repair costs, is by ar the
most cost-eicient corrosion protection
system available or steel structures.
Contrary to the prevailing view that hot-dip
galvanization only becomes cost-eective over
time, it now oers substantial cost savings
when compared to other protection systems on
many types o structures, right rom the very
beginning. Studies have shown that, beyond a
speciic surace area o 15 to 20 m2/t, the initial
costs of hot-dip galvanizing are lower than those
o a three-coat paint system [17].
Architects and designers should more than ever
be aware o this act when selecting a corrosion
protection system.
Where hot-dip galvanizing cannot meet more
stringent appearance requirements, a simpleduplex system e.g. a coat o zinc and one coat
o paint that does not need sweeping, is worth
considering.
In any case, it is useul to perorm a cost-
comparison o the various options beore
selecting the appropriate corrosion protection
system.
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Bouillon Car Park, Luxembourg
ArchitectsRomainHoffmannArch
itectesetUrbanistes
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References
[7] Katzung, W. und Schulz, W. D.
On hot-dip galvanizing o steel
constructions Causes and solutionproposals reerring to cracking
[8] Pargeter, R.
Liquid metal penetration during hot-dip
galvanizing
Published: TWI Website
[9] Kinstler, Thomas J.
Current Knowledge o the Cracking o
Steels During Galvanizing
GalvaScience LLC, PO Box 501, Springville,
AL 35146
[10] Kikuchi, M.
Liquid Metal Embrittlement o Steels
during Hot Dip Galvanizing
Tetsu to Hagane, Iron and Steel, Volume
68, Number 14, 1982,
Pages 1870-1879
[11] Pankert, R., Dhaussey, D., Beguin, P., Gilles, M.
Three Years Experience with the
Galveco Alloy
Proceedings Twentieth International
Galvanizing ConerenceAmsterdam, 2003, European General
Galvanizers Association
[12] Interpretation zinc assisted cracking on
big scale steel structures and preventive
methods. 2001, reeriert in ILZRO
Project ZC 21 2.
[13] Poag, G., Zervoudis, J.
Inluence o various parameters on steel
cracking.AGA Tech Forum, Oct. 8. 2003. Kansas
City, Missouri.
[14] Pinger, T.
Avoidance o liquid metal induced
embrittlement o galvanized steel
constructions
[15] Schulz, W. D.; Schubert, P.; Katzung, W.;
Rittig, R.
Correct sweeping o hot-dip galvanized
parts according to DIN EN ISO 1461),
Der Maler- und Lackierer-meister 7/99
[16] Verbnde-Richtlinie Korrosions-schutz von
Stahlbauten Duplex-Systeme
Herausgegeben von Bundesverband
Korrosionsschutz e.V., Kln
Deutscher Stahlbauverband e. V.,
Dsseldor
Industrieverband Feuerverzinken e. V.,
Dsseldor
Verband der Lackindustrie e. V., Frankurt
[17] Dipl.-Ing. P. KleingarnCost-eective and reliable corrosion
protection using hot-dip galvanizing),
Feuer-verzinken (28 th year) n 3,
September 1999
1. Bibliography
[1] Dr.-Ing. D. KnotkovaAktuelle Erkenntnisse zum
Korrosionsverhalten von Zink und
Zinkberzgen
Vortrag 4. Deutscher Verzinkertag
1995 Kln
[2] Dr.-Ing. Knotkova und F. Porter
Longer lie o galvanized steel in the
atmosphere due to reduced SO2-pollution
in Europe
Proc. o Intergalva 1994, Paris
[3] F. von Assche
Atmospheric conditions and hot dip
galvanizing perormance
Proc. Intergalva 1997, Birmingham,
EGGA UK
[4] Katzung, W. und Mitarb.
Zum Einluss von Si und P au das
Verzinkungsverhalten von Bausthlen
Mat.-wiss. u. Werkstotech.
28, 575 587 (1997)
[5] Katzung, W. und Mitarbeiter; FuE-BerichtInstitut r Stahlbau Leipzig GmbH,
Arno-Nitzsche-Str. 45, D-04277 Leipzig
(unverentlicht)
[6] Katzung, W.; Rittig, R.; Schubert, P. und
Schulz, W. D.
Zum Einluss von Abkhlverlau und
Tauchdauer au die Hatestigkeit und das
Bruchverhalten von Zinkberzgen nach
DIN EN ISO 1461
Mat.-wiss. und Werkstotechnik 32,
483-492 (2001)
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2. Standards and further reading
l EN ISO 1461 : 1999Hot-dip galvanized coatings on abricated
iron and steel articles
l Katzung, W. und Marberg, D.
Beuth-Kommentare
Korrosionsschutz durch Feuerverzinken au
Stahl augebrachte Zinkberzge
(Stckverzinken), Kommentar zu
DIN EN ISO 1461 (2002)
l EN ISO 14713: 1999
Protection against corrosion o iron andsteel in structures Zinc and aluminium
coatings - Guidelines
l EN ISO 12944-1-8 : 1998
Corrosion protection o steel structures by
protective paint systems
l DIN 267, PART 10
Mechanical assembly components -
Technical delivery conditions
Galvanized parts
l EN 10025 : 2004Hot rolled products rom structural steels
l EN 1993-1-10
Design o steel structures Selection o
materials
l DASt Guideline 009
Selection o steel grades or welded steel
structures
l Korrosionsschutz durch Feuerverzinken
(Stckverzinken)
Corrosion protection by hot-dipgalvanizing batch galvanizing
Institut Feuerverzinken GmbH,
Sohnstrae 70, D-40237 Dsseldor
l Maa, P. und Peiker, P.
Hot-dip galvanization manual
Deutscher Verlag r Grundstoindustrie
Leipzig, Stuttgart 1993
l Arbeitsbltter Feuerverzinken
Technical sheets or hot-dip galvanizing
Institut Feuerverzinken GmbH, Sohnstrae
70, D-40237 Dsseldor
References
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Notes
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Technicaladvisory& Finishing
Technical advisory
We are happy to provide ree technical advice to
optimise the use o our products and solutions
in your projects and to answer your questions
about the use o sections and merchant bars.
This technical advice covers the design o
structural elements, construction details, surace
protection, ire saety, metallurgy and welding.
Our specialists are ready to support yourinitiatives anywhere in the world.
To acilitate the design o your projects, we also
oer sotware and technical documentation that
you can consult or download rom our website:
www.arcelormittal.com/sections
Finishing
As a complement to the technical capacities
o our partners, we are equipped with
high-perormance inishing tools and
oer a wide range o services, such as:
l drilling
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l T cut-outs
l notching
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l curving
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l cold sawing to exact length
l welding and itting o studs
l shot and sand blasting
l surace treatment
Building & ConstructionSupport
At ArcelorMittal we also have a team o
multi-product proessionals specialising in
the construction market: the Building and
Construction Support (BCS) division.
A complete range o products and
solutions dedicated to construction in all
its orms: structures, aades, rooing,
etc. is available rom the website
www.constructalia.com
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Your partners
ArcelorMittal
Commercial Sections
66, rue de Luxembourg
L-4221 Esch-sur-Alzette
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Tel: +352 5313 3014
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ArcelorMittal
Commercial Sections
66, rue de Luxembourg
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LUXEMBOURG
Tel.: + 352 5313 3014
Fax: + 352 5313 3087
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