See Hot-Dip Galvanizing brochure

HOT-DIP
GALVANIZING
TABLE OF CONTENT
The company
3
Affiliations
4
Mission & values
5
Services
Specialties
7
7
Research & Development
7
Seminar
8
Hot-dip galvanizing
10
Sustainable development
17
Technical information
19
Design
21
Prevent distortion
26
Post-galvanizing treatments
27
THE COMPANY
With over 40-years experience in hot-dip galvanizing and a solid commitment towards its
customers, Corbec inc. has become the leading galvanizer in central and eastern Canada.
Our two installations, conveniently located in the east-end of Montreal and in Quebec
City, are equipped with kettle sizes allowing for the galvanizing of a wide range of steel
products, such as:
•
•
•
•
•
Engineered structures such as bridges, wind mills, electrical towers, etc.
Exposed architectural steel structures
Fences and farming equipment
Original Manufactured Equipment (OEM)
A variety of metal pieces and hardware
For many years, Corbec participates and is involved with galvanizing associations
as well as technical and engineering societies throughout the world. Operations
staff and management are up to date on developing technologies and
general improvements in our industry.
3
Our coatings are in conformity with international standards and our turn-around time will
respect your tightest schedules.
4
AGA – American Galvanizers Association. www.galvanizeit.org
ICCA – Canadian Institute of Steel Construction. www.icca.ca
OIQ – Ordre des Ingénieurs du Québec. www.oiq.qc.ca
ACRGTQ – Association des constructeurs de routes et grands travaux du
Québec. www.acrgtq.ca
MISSION AND VALUES
Corbec Galvanizing the standard…
As a leading hot dip galvanizer, we are committed to offering
consistently superior quality, at a competitive price with reliable
service. Our excellence is built on employee expertise and our ability
to surpass industry expectations.
5
Corbec builds on its skills…
With a view to becoming the leader in the Canadian market, Corbec
will expand to meet emerging needs. To facilitate the implementation
of its management model, Corbec will promote participative
management and knowledge transfer. In the interest of remaining
a leading-edge and innovative company, Corbec is committed to
maintaining its involvement in research and development and
enabling its employees to develop new capabilities.
Corbec Our values...
Corbec has built a reputation for reliability founded on its
fundamental values, which the company has imparted to its
employees, suppliers and other business partners.
AFFILIA
6
ATIONS
FAIRNESS
OPEN-MINDE DNESS
R ELIABILITY
C OOPERATION
E FFICIENCY
SERVICES SPECIALTIES R&D
SERVICES OFFERED
7
•
•
•
•
Packing according to specifications
Timelines and deadlines according to your needs (advanced production scheduling)
Fast delivery (upon request)
Technical support
OUR SPECIALTIES
• Galvanizing process for bent rebar
• Galvanizing large parts
• Trailer galvanizing
RESEARCH AND DEVELOPMENT
Our research and development department works in conjunction with our client projects to develop new
procedures and methodology adapted to their needs. We also work with specifier’s such as Ministère
des Transports du Québec and Hydro Québec to improve contracts and specifications.
SEMINARS
8
Corbec is pleased to offer training seminars, tailored to the
needs of your production and design teams. At your offices or
ours this activity will be customized for the size and goals of
your group.
Also, you can address your own set of questions prior to
the seminar and we will prepare a presentation where your
concerns will be at the forefront. Seminars are typically one to
four hours and include an overview of the hot-dip galvanizing
process.
Seminars can, at your request, include a tour of one of our
plants. Your team will be able to see, up-close, the production
process and better understand the details surrounding hot-dip
galvanizing.
This activity sounds interesting?
Please contact our coordinator of sales & marketing at
514-364-4000 or send a written request to
[email protected].
HISTORY OF GALVANIZING
9
Hot-dip galvanized steel has been effectively used for more
than 150 years. The value of hot-dip galvanizing stems from
the relative corrosion resistance of zinc, which, under most
service conditions, is considerably better than iron and steel.
In addition to forming a physical barrier against corrosion,
zinc, applied as a hot-dip galvanized coating, cathodically
protects exposed steel. Furthermore, galvanizing for
protection of iron and steel is favoured because of its low
cost, the ease of application, and the extended maintenancefree service it provides.
HOT-DIP GALVANIZING
Galvanic Series of Metals
CORRODED END
(Anodic or less noble)
Magnesium
Zinc
Aluminium
Cadmium
Steel
Lead
Tin
Nickel
Brass
Bronzes
Copper
Nickel-Copper Alloys
Stainless Steels (passive)
Silver
Gold
Platinum
10
Protected End
(Cathodic or more noble)
Processus de galvanization
Galvanization process
Caustic
Cleaning
Rinsing
Pickling
Rinsing
Flux
Solution
Drying
Zinc
bath
Cooling and
Finition
What is hot-dip galvanizing
Hot-dip galvanizing is a metallurgical bond between steel and molten zinc, produced in specific installations
and under controlled conditions. The process, of molecular adhesion between two metals is unique and
simple, yet provides excellent molecular adherence and cathodic protection.
THE ADVANTAGES
Galvanizing provides great resistance
Once the freshly cleaned material is submerged in the molten zinc bath @ 450C (840 degrees F), a metallurgical bond
is created composed of inter-metallic layers and a pure zinc layer.
The first inter-metallic layer is actually harder than the base steel. This quality is what gives galvanized steel its great
impact and abrasion resistance. The soft, pure zinc layer helps absorb some of the shock and the inter-metallics protect
the base material.
11
Microphotography of metallic coating
Coat ETA 100% Zn
Index of hardness 70 DPN
Coat Zeta 94% Zn 6% Fe
Index of hardness 179 DPN
Coat Delta 90% Zn 10% Fe
Index of hardness 244 DPN
Coat ETA 100% Zn
Index of hardness 70 DPN
Coat Gamma 75% Zn 25% Fe
Base steel
Index of hardness159 DPN
Hot-Dip Galvanized Steel’s Estimated Service Life in Soil
Hot-Dip Galvanized
Steel’s Estimated Service Life in Soil
High Chlorides (>20 PPM) Low Moisture (<17.5%)
pH=9.4 H 2O=5.0%
Service life (years)
250
300
200
pH
H 2O
150
pH=6.6 H 2O=17.5%
100
High Chlorides (>20 PPM) High Moisture (<17.5%)
250
pH=7.9 H 2O=10.5%
pH
H 2O
Service life (years)
300
200
150
pH=8.6 H 2O=17.6%
100
pH pH=7.4 H 2O=26.8%
H 2O
pH
H 2O
50
50
pH=6.0 H 2O=40.0%
0
1.0
2.0
3.0
4.0
5.0
0
1.0
6.0
2.0
Zinc Coating Thickness (mils)
Low Chlorides (<20 PPM) High Moisture (>7.0)
300
4.0
5.0
6.0
Low Chlorides (<20 PPM) Low Moisture (<7.0)
pH=7.0H 2O=5.0%
250
pH
H 2O
200
pH=7.8 H 2O=19.3%
pH
H 2O
150
100
pH=7.0 H 2O=40.0%
Service life (years)
Service life (years)
300
pH=9.0 H 2O=5.0%
250
3.0
Zinc Coating Thickness (mils)
200
pH
H 2O
150
pH=6.0 H 2O=19.4%
100
pH
H 2O
50
50
pH=5.0 H 2O=40.0%
0
1.0
2.0
3.0
4.0
5.0
6.0
Zinc Coating Thickness (mils)
Service life is defined as the time to necessary part replacement
or underground maintenance.
0
1.0
2.0
3.0
4.0
Zinc Coating Thickness (mils)
3
1 mil=25.4 pm=056 oz/ft
5.0
6.0
12
HDG coatings have a foreseeable service-life
Coating service-life is foreseeable as long as climate conditions - in which the coatings are exposed - are known.
The ASTM has published the results of a research conducted in different environments where zinc coatings
could be exposed to a variety of climate conditions.
13
Time to First Maintenance* (years)
100
90
80
Key
70
Rural
60
Suburban
Temperate Marine
50
Tropical Marine
40
Industrial
30
20
10
0
1. 0
1.5
2.0
2.5
3.0
3.5
Average Thickness of Zinc (mils)
4.0
4.5
5.0
1 mil = 25.4μm = 0.56oz/ft2
*Time to first maintenance is defined as the time to 5% rusting of the steel surface.
Rust takes its toll on painted surfaces
Here is what happens to painted steel when scratched…The
exposed steel corrodes and forms a rust « bubble ». This “bubble”,
larger than the surface occupied by the steel will expand and lift
the paint off the surface, creating a blister. In the meantime, the
cavity of corrosion and the blister continue to progress.
Zinc coating
Steel discovered
is protected
Base steel
14
Galvanizing offers sacrificial protection
Here is what happens in the case of galvanized steel when scratched…Thanks to its galvanic protection, the zinc coating
sacrifices itself to protect the steel to which it is bonded. This sacrificial protection will prevail as long as zinc is within
proximity.
Should the hot-dip galvanized coating
be damaged or scratched, the steel will
find protection against corrosion thanks
to the surrounding zinc that has higher
electrochemical properties than those of steel.
Since corrosion is an electrochemical process,
it will attack the surrounding zinc rather
than the exposed steel. Thus said, contrary to
other types of processes claiming to corrosion
protection, it is not required to touch-up
noticeable cracks, flaws or gaps on galvanized
coatings.
Conventional Current
Electrons
External Circuit
Cathode
Electrons
Anode
Electrolyte
Figure 1 : Bi-metallic couple
Galvanizing is a
15
Studies have shown that HDG is highly competitive when it comes
to cost-comparison as a whole: each type of coating product
has its set of characteristics to battle corrosion (and ultimately
protect steel). However, these products often entail particular
application, as well as relative life-span and relative savings.
cost-efficient process
When compared to other types of products labeled anti-corrosive and subject to
environmental standards, HDG costs have risen at a slower pace: Initial HDG costs
are competitive with the costs of other products. Life-cycle cost analysis show that
HDG is a wise investment compared to other products simply by considering the
low/no-maintenance costs required over the project’s life-span.
Please consult the calculation tool to compare the costs
of galvanization against other available protection
systems online at the American Galvanizers Association
website by visiting : www.galvanizingcost.com
16
SUSTAINABLE DEVELOPMENT
Hot-dip galvanizing is a responsible choice.
• Raw materials are preserved because steel does not corrode, therefore, no spending is incurred for the usual
recycling of scrap metal;
• Nearly maintenance free, HDG cannot be compared to paint-protection: in this case, protection is a thin
barrier that, once broken, is an open door to corrosion. Galvanizing helps maintain steel’s structural integrity
and saves taxes when prescribed for public construction;
• Very little metal is re-introduced in the environment and when recycling occurs, the energy used to melt zinc
is inversely related to the amount of zinc recycled.
LCA of galvanized steel
17
Raw Material &
Energy Inputs
Inputs for Maintenance = 0
Energy Inputs
Production
Use
End-of-Life
Steel
Zinc Metal
Galvanizing Process
Bridges
Light Poles
Parking Garages
Truck Frames
Sign Structures
Émissions
2
CO
SO2
etc.
Zinc Corrosion Products
Steel & Zinc Recycle Loop (100%)
For all but the most aggressive, corrosive environmental conditions, there are no energy or raw
material inputs during use (75 + years).
For hot-dip galvanized steel, naturally occurring zinc oxide, zinc hydroxide, and zinc carbonate.
Think about it… Zinc is a natural and vital substance. Galvanizing does not modify the environment’s balance.
Whether it be nutritional supplements, sunscreens, medication or diaper creams, all contain beneficial amounts
of zinc, primarily in the form of zinc oxide.
The industry generally works towards the promotion of sustainable development by ensuring that its production
and use is in harmony with the natural environment and the needs of society. Corbec Corporation is the first
galvanizing company in Canada to fully process all polluted airs from its installations. Our newly installed
energy efficient covers also contribute to the health and security of our workers.
Zinc Production
Energy Input
Energy Input
Energy Input
Zinc Ore from Mines
(raw material)
Emissions
Solid Waste
Zinc Concentration
Other Refined Primary Metals
(Cu, Cd, Etc.)
Emissions (SO 2, CO 2, Etc.)
Solid Waste
Zinc Refining
Zinc EAF Dust
End-of-Life Recycling
Automobiles, appliances,
galvanizied products, etc.
Recycled
Process Residues
Skimmings and dross from
galvanizing process
Zinc Metal Ingots
(Ready for galvanizing
kettle)
Recycled Sulphuric Acid
Emissions (CO2 )
18
Hot-Dip Galvanizing
The final step to determining the LCA production phase for hot-dip galvanizing is to evaluate the energy
demands and emissions generated by the hot-dip galvanizing process itself. The gate-to-gate study considers the
additional energy and emissions of the process beyond the inputs of the steel and zinc. Figure 10 below depicts
the additional products and enegy required to coat the steel with zinc.
Figure 10
Energy Input
Cleaning Materials
acids, water, flux
Steel Product
energy inputs counted
in steel production
Energy Input
Surface Preparation
degreasing, pickling,
and fluxing
Recycled Sulphuric Acid
Wastes (solid, acid)
Emissions ( CO 2 , acid
mist)
Zinc Metal Ingots
energy inputs counted
in zinc production
Energy Input
Galvanizing
Kettle
Emissions
(CO 2 )
HDG Steel Product
ready for use
Recyclable Process
Residus
skimmings, dross
in zinc production
Zinc metal production
and oxides into
cosmetics, tires, etc.
TECHNICAL INFORMATION
Steel Selection
For an optimal coating, steel has to be selected wisely. Following information is based on ASTM A 385.
Generally, galvanized coatings are chosen for their anti-corrosive properties, not for their appearance. The relative
corrosion resistance of the normal or abnormal coating is, in all considerations, equal.
Types of zinc coatings
Type of coating zinc
1 mil
19
Metallized
Hot-Dip Galvanized
Zinc Paint
Galvanized Sheet
Electroplated
STEEL SELECTION
4 basic elements that can affect the galvanized coating:
1. Carbon in excess of about 0.25%
2. Silicon in the range of 0.04% to 0.15% or above 0.22% can produce galvanized coating growth rates
much higher than those for steels with silicon levels below 0.04% and between 0.15% and 0.22%.
3. Phosphorus in excess of 0.04%
4. Manganese in excess of about 1.3%
ETA
(100% Zn)
70 DPN hardness
ZETA
(94% Zn 6% Fe)
179 DPN Hardness
DELTA
(90% Zn 10% Fe)
GAMMA
(75% Zn 25% Fe)
250 DPN hardness
BASE STEEL
159 DPN Hardness
Fig. 1 Photomicrograph of Normal Galvanized Coating
Zinc Grip (Arbitrary Unit)
9
8
7
6
5
4
3
2
1
A
0
Dispersion zone values
related to different authors
B
0
0,1
0,04
20
C
0,2
0,3
0,4
0,15
0,5
0,6
Si (Mass %)
a Silicon effect
Coating Thickness (um)
400
Coating Thickness (um)
350
400
300
250
300
200
150
200
100
50
100
A
0
B
0,05
C
0,1
0,12
0,15
b Phosphorus Effect
0
0,2
P (Mass %)
A
0,05
B
0,1
0,09
0,15
C
0,2
0,25
0,3
Si + 2,5 (Mass %)
c Combined effect of silicon and phosphorus
CONCEPTION
Vent and draining holes
Thicker coating at weld due to
higher silicon content of weld
metal
Weld splatter will be galvanized into
the coating and should be removed
during fabrication to avoid unsightly
appearance.
Zinc drips off causing spikes
(dags) and a very rough
surface
21
Combination of
good drainage
angles
Natural drain to one point
Combination of
good and bad
drainage angles
Size of fame and head height of
hoists affect quality of drain
Multiple hanging
points for best
drainage angles
On immersion, the air travels up the
underside surfaces causing air
pockets at each plate
On withdrawal, zinc travels or flows
down the upper surfaces, pooling at
each plate
22
There will always be air or
zinc traps even on channels.
Angles
crop plates before welding
Remember, where zinc pools so will flux
Angle fabrications
zinc or air trap
air pockets
zinc pockets
hole or cut
corners
VENT HOLE CORRECT
AIR
Vent hole prevents air traps and
resulting ungalvanized internal areas
or even floatation
A
Optional hole
position
Preferred fill/drain
hole position
Larger opening for faster
flow of zinc into unit
B
AIR
Incorrect vent
hole
Trapped zinc sloshes out
and runs solidify during
cooling causing heavy,
unsightly buildup from
incorectly positioned hole
Vent hole
Fill/drain
hole
Correct drain hole
Zinc
23
Suggested design for
flanged hollow sections
Center hole drainage is
not recommended
C
Vent hole
ZINC
Preferred vent
hole position
D
Zinc run
Optional
hole position
Residual zinc
Open end or drain hole
at the correct position
and size
E
If no lug is possible opposite
holeing will be required for
jigging
Open end
full/drain facility
Space matching surfaces?
Avoid welding units
back to back.
Suggested
design
Do not forget to vent and
drai hollow sections
Vent and drain holes too small!
24
Vent and drain hole size.
Vent and drain holes that are too
small in hollow sections increase
immersion time and may cause
unsightly excessive zinc
drainage runs as the zinc freezes
during the draining period.
Zinc will flow around and down
circular units leaving drainage runs
along units.
Chart 1. – Drainage holes for overlapping surfaces – steel thickness ≤ 1/2” (1.25 cm)
Overlapping surface po2 [cm2] Holes
Unwelded surfaces
< 16 [< 103]
None
None
> 16 et < 64 [> 103 &< 413]
3/8" [1 cm]
1" [2.5 cm]
> 64 et < 400 [> 413 &< 2580]
1/2" [1.25 cm]
2" [5 cm]
each increment of 400 [2580]
3/4" [2 cm]
4" [10 cm]
Chart 2. – Drainage holes for overlapping surfaces – steel thickness ≥ 1/2” (1.25 cm)
25
Overlapping surface po2 [cm2] Holes
Unwelded surfaces
< 16 [< 103]
None
None
> 16 et < 64 [> 103 &< 413]
None
None
> 64 et < 400 [> 413 &< 2580]
1/2" [1.25 cm]
2" [5 cm]
each increment of 400 [2580]
3/4" [2 cm]
4" [10 cm]
PREVENTING DISTORTION
Bolted and welded assemblies varying in thickness can cause deformities or distorsion. This is caused by the variations in
heating and cooling of the pieces.
It is recommended to galvanize these structures prior to assembly. Assembly can then be completed by welding and
reconditioning or by means of bolting or riveting with pre-galvanized hardware.
Distortion can also occur during the release of welding stresses in the kettle.
Therefore, proceed with welding within guidelines to balance out these stresses.
Reasons for distortion
Distortion is almost always attributable to:
• Release of existing or created stresses in the steel (welding, laminating, forming);
• Expansion constraints for assemblies of varying thicknesses when galvanizing;
• Assemblies requiring different immersion speeds.
26
This can be avoided by:
Folding of plate will introduce a certain
amount of strentgh and reduce the
possibility of distortion
• Design symmetry and proper sequencing of assembly;
• A design that allows for quick immersion and
withdrawal in the zinc kettle.
In thin-wall applications,
when possible, use
reinforcements that are
omega or diamondshaped. When in doubt,
request advice from your
galvanizer
Large sheets can be break pressed which
will reduce the distortion to smaller areas.
Twisting may occure even though
the measures have been taken
POST-GALVANIZING TREATMENT
Although the look of galvanized steel is gaining in popularity, namely for residential applications, painting over
galvanized steel is often required. Thankfully, this practice is widely used and its technique, usually mastered by
paint professionals.
Here is an overview of the specific conditions that need to be followed in order to proceed with post-galvanizing
painting. The following content addresses surface preparation in relation to painting over galvanized steel.
27
Why paint?
The first answer that comes to mind is « for the look »! Paint can simply be prescribed by the architect but, it can
also serve as identification or extra protection in a hostile environment.
Painting over galvanized steel is known as Duplex system
Benefits are ….
•
•
•
•
Paint acts as a protection barrier for galvanized steel;
Galvanizing’s corrosion protection properties are enhanced and optimized by the application of paint;
Scaling of paint is reduced thanks to the presence of the underlying galvanized steel;
Galvanizing and paint together offers longer-lasting surface protection, 1.5 to 2.5 times their individual
service-life.
Galvanized steel goes through a process of oxidation (or aging) that is
illustrated with the help of what is called « passivation cycle »:
Ellapsed time
Free flowing air 02
0 - 48 h
Zinc Oxide
ZnO
Moisture from rain (dew) H O2
48 h - 6 months
28
Zinc Hydroxide
Zn (OH) 2
Free flowing air
02 + CO 2
6 months - 2 years
Fully developed patina
Zinc Carbonate
27nCO 3
Zn(OH)2
When should paint be applied?
Galvanized steel has three (3) “stages of aging” (when oxides are present) and painting can be executed
at any stage, providing that the proper surface preparation is applied…
•
•
•
•
Immediately after the galvanizing treatment.
When the galvanized steel is at 50% of its life span
When the thickness of the galvanized sheet is ≤1mils
At the first sign of rust
29
STANDARDS
COMPLETE LIST OF ASTM AND CSA STANDARDS
GOVERNING HOT-DIP GALVANIZING
The following documents are not available on our web site. However, you
can contact ASTM and purchase them directly.
A 123/A 123M-02
A143/A 143M-03
A 153/A 153M-03
A 384/A 384M-02
A 385-03
A 767/A 767M-00b
A 780-01
B 6-0
D 6386-99
E 376-03
CAN/CSA
G 164-M92
Specification for Zinc (Hot-Dip Galvanized) Coatings on Iron and Steel
Products.
Practice for Safeguarding Against Embrittlement of Hot-Dip Galvanized
Structural Steel Products and Procedure for Detecting Embrittlement.
Specification for Zinc Coating on Iron and Steel Hardware.
Practice for Safeguarding Against Warpage and Distortion During Hot-Dip
Galvanizing of Steel Assemblies.
Practice for Providing High-Quality Zinc Coatings
(Hot-Dip).
Specification for Zinc-Coated (Galvanized) Steel Bars for Concrete
Reinforcement.
Practice for Repair of Damaged and Uncoated Area of Hot-Dip Galvanized
Coatings.
Specification for Zinc.
Practice for Preparation of Zinc (Hot-Dip Galvanized) Coated Iron and
Steel Products and hardware Surfaces for Painting.
Practice for Measuring Coating Thickness by Magnetic Field or EddyCurrent Exam Method.
Hot-dip Galvanizing of Irregular Shaped Products.
30
HEAD OFFICE
Telephone: 514.364.4000
Toll free: 1 800 463.8313
Fax. : 514.365.9222
Montreal plant
Quebec plant
400 George V (corner Victoria)
Lachine
(Quebec) H8S 2R7
50, rue Lisbonne
St-Augustin-de-Desmaures
(Québec) G3A 0M6
Telephone: 514.637.7076
Fax: 514.639.4630
Telephone: 418.628.1055
Fax: 418.628.3031
Kettle size
Kettle size
6’
6’
48’
56’
10’6’’
12’
WWW.CORBECGALV.COM | 1 800 463.8313