WHY WOULD ANYONE NOT GALVANIZE STEEL IF THEY CAN?
Francis Gerace, P.E., Market Development
Hubbell Galvanizing
New York Mills, NY
November 30,2010
Abstract: There are many products which protect structural steel from corrosion. There
is also an intense focus on sustainability. Hot-dip galvanizing is one product that provides
economical, long-lived, and sustainable corrosion protection. It is also more durable than most
other barrier systems. Not all steel can be galvanized because sometimes the elements are too
long and/or too heavy to be placed in the baths. Also, at times the intended environment is not
conducive for zinc longevity such as acidic environments or immersed in salt water. But for
those applications where galvanizing is appropriate, why would anyone not choose to hot-dip
galvanize steel?
INTRODUCTION
In the public sector, most levels of government are feeling budget constraints. In the
private sector, most businesses are watching every dollar to insure the “biggest bang for the
buck”. Both sectors are very concerned with initial costs. Nevertheless, they are aware of
downstream implications on operational and maintenance costs as well. Both initial and life
cycle impacts are being taken into account when deciding on capital investments. In addition,
with the growing consciousness of our surroundings and the effect we are having on the
environment, there is also an intense focus on sustainability. Steel is one of the most economical
choices for construction. Compared to other materials, it often provides initial cost savings over
competitive materials. However, the use of steel has a major drawback. Left unprotected, it rusts,
which shortens its service life. In a 2001 paper, jointly authored by the Federal Highway
Administration (FHWA) and the NACE International, the total annual direct cost of corrosion
was estimated at $121 billion, which is 1.38 percent of the U.S. GDP of $8.79 trillion in 1998.
The largest portion (88.3 percent) of this cost is the organic coatings group at $107.2 billion.
Galvanizing and metalizing accounted for $1.4 billion.1 Corrosion most often affects metal
structures such as bridges, steel reinforced concrete, storage tanks, and pipelines. Corrosion
problems often are not obvious but can lead to extensive structural failure and loss of capital
investment. As the average age of facilities and structures continues to rise, corrosion problems
will inevitably worsen. However, related expenses can be minimized by using proven
technologies in the design, construction installation, maintenance, and repair of structures.2
However, these technologies have a cost, both initial and cyclical. In order to achieve economic
and sustainable goals, enterprises are seeking solutions that are low in initial costs, low in cost
over the life of the element, have extended service life, and have a minimum effect on the
environment.
Hot-dip galvanizing (HDG) is one product that protects steel from corrosion while
providing economical, long-lived, and sustainable corrosion protection. It is also more durable
1
“Corrosion Costs and Preventive Strategies in the United States”,
Publication No. FHWA-RD-01-156, 2001
2
“Corrosion and Corrosion Control”
By Jorge E. Costa and Leandro Etcheverry
Concrete Repair Bulletin, September/October 2005
Why Would Anyone NOT Galvanize Steel If They Can?
Francis Gerace, P.E., Market Development
Hubbell Galvanizing
than most other barrier systems. In this paper we will examine the protective qualities of HDG.
We will also explore the economics, both initial and life-cycle costs, of using HDG compared to
competitive materials. Finally we will look at the effect of HDG on the environment and address
the sustainability of HDG in comparison to paint, the most common alternative to HDG for steel
corrosion protection.
It is a fact not all steel can be galvanized; members may be too long or too heavy. But for
those elements that can be, why would anyone not choose to galvanize steel?
PROTECTIVE QUALITIES OF HDG
There is a common perception that Hot-dip galvanizing protects steel by providing a
sacrificial coating on the steel surface. Many also perceive the main benefit of HDG to be that
the zinc provides cathodic protection, since zinc will corrode before iron. While these both are
true, the main benefit of HDG is it presents an extremely robust barrier between the steel and the
environment.
Metal corrosion can be defined as the destructive attack of a metal through interaction
with its environment.3 Metals are defined as being capable of conducting heat and electricity.
Metals have free electrons which have the potential
to move between positively charged areas (anode)
to negatively charged areas (cathode) within the
Cathode
Electrolyte structure of the metal. However, this movement is
possible only through the presence of an electrolyte
which transfers the electrons on the surface,
resulting in corrosion. In the schematic, The
Anode
Corrosion Triangle, electrons migrate within the
metal through an electron path from anodic areas to
The Corrosion Triangle
cathodic areas. The circuit is completed by the
return current path provided by the electrolyte.
.
The most common method of corrosion protection is to isolate the metal from the
electrolyte. This is done by creating a barrier between the two. Once the electrolyte is separated
from the metal, the circuit is broken and no corrosion can take place. Corrosion protection is
afforded as long as the barrier remains intact. Should the barrier be breached, corrosive attack of
the underlying metal will take place. In the case of steel, barrier breaches create pockets of
oxidation, i.e. rust. Since rust is more voluminous than iron, pressure is created as the rust
expands. The breach then expands and is further exploited, lifting and undercutting the
surrounding barrier allowing more exposure to the electrolyte and compounding the corrosion.
3
Fundamental of Corrosion Chemistry
"Corrosion Control", NAVFAC MO-307, September 1992
<http://www.corrosionist.com/Corrosion_Fundamental.htm> (accessed September 1, 2010)
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Why Would Anyone NOT Galvanize Steel If They Can?
Francis Gerace, P.E., Market Development
Hubbell Galvanizing
Soon the barrier becomes compromised and results in section loss and the ultimate failure of the
member.
Remedies for barrier compromise are: the installation of a robust barrier that is resistant
to breaching; providing a barrier that is extremely adherent to the steel to minimize undercutting
of the barrier should a breach occur; and strict adherence to a cyclic preventive maintenance
regiment to insure barrier integrity.
Hot-dip galvanized steel addresses all of those remedies: the galvanized coating is
extremely hard and durable; the galvanized coating is metallurgically bonded to the steel; and
finally, the coating is extremely durable. We will examine each of these attributes in the
following sections.
The Galvanizing Process and Zinc Coating
The galvanizing process is a documented, timed sequence and is done in a controlled
environment, outside weather conditions are not a factor. Galvanizing is a process where, after
preparatory steps (degreasing, acid cleaning, and fluxing), clean, bare steel is submerged in
molten zinc. Galvanizing is complete when the temperature of the steel equalizes with the
temperature of the molten zinc, typically 830 °F or higher (435 °C +) with the observable
formation of a metallurgical bond of the zinc to the steel. The bond is extremely tenacious, with
strip strength of greater than 3,000 psi. (This is in contrast with other barrier systems with strip
strengths of approximately 600 psi.) In addition to the metallurgical bond, three alloy layers and
a layer of pure zinc form. A micrograph of the zinc layer is shown below.
As can be seen, the inter-metallic
layers are composed of various
percentages of iron and zinc. Using
the diamond pyramid number
(DPN) hardness scale, it can be
seen that these layers are harder
than the base steel. When coupled
with the ductility of the pure zinc
Eta layer, the result is a very hard,
durable coating that resists
breaching. While the coating can
be removed by abrading, blasting or similar actions, the coating stands up to normal handling
during construction without damage.
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Why Would Anyone NOT Galvanize Steel If They Can?
Francis Gerace, P.E., Market Development
Hubbell Galvanizing
The Longevity of Galvanized Coatings
While the galvanized coating is unaffected by ultraviolet ray exposure, the corrosion rate
of zinc is directly influenced by atmospheric conditions. Certain factors that specifically affect
the corrosion of zinc include: temperature, humidity, rainfall, sulfur dioxide (pollution)
concentration in the air, and air salinity. None of these factors can be singled out as the main
contributor to zinc corrosion, but they all play a role in determining the corrosion protection hotdip galvanized (zinc) coatings can provide in certain environments. 4
For corrosion classification purposes, atmospheres are generally divided into five groups
rural, suburban, temperate marine, tropical marine, and industrial. Rural environments are
usually the least aggressive of the five atmospheric types. This is primarily due to the relatively
low level of sulfur and other emissions found in such environments. Suburban atmospheres are,
as the term suggests, found in the largely residential, perimeter communities of urban or city
areas with little or no heavy industry. Temperate marine atmospheres are influenced by
proximity to the coastline and prevailing wind direction and intensity. In marine air, chlorides
from sea spray can react with the normally protective zinc corrosion products to form soluble
zinc chlorides. When these chlorides are washed away, fresh zinc is exposed to corrosion.
Temperate marine atmospheres usually are more corrosive than suburban atmospheres. Tropical
marine atmospheres are similar to temperate marine atmospheres except they are found in
warmer climates. Tropical marine climates tend to be somewhat more corrosive than temperate
marine climates. Finally, industrial environments are generally the most aggressive in terms of
corrosion. Air emissions may contain some sulfides and phosphates that cause the most rapid
consumption of the zinc coating. Automobiles, trucks, and industrial plant exhaust are examples
of these emission sources. Most city or urban area atmospheres are classified as industrial.
Independent and industry testing
of galvanized steel samples over decades
in industrial, urban, rural, and marine
environments, with varying degrees of
chlorides, sulfides and other corrosive
elements, has yielded performance data
for galvanized steel in real world
applications. This data is portrayed in the
Time to First Maintenance chart. The
chart is a plot of the data accumulated
Time to First Maintenance
4
Galvanizing Performance in the Atmosphere
American Galvanizer’s Association, n. d.
http://www.galvanizeit.org/aga/about-hot-dip-galvanizing/how-long-does-hdg-last/in-the-atmosphere accessed
September 1, 2010
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Why Would Anyone NOT Galvanize Steel If They Can?
Francis Gerace, P.E., Market Development
Hubbell Galvanizing
from galvanized steel samples performance in real-world applications. The chart was generated
for the various environments listed above from the Zinc Coating Life Predictor5 developed by
Dr. X. G., Zhang, Ph.D. of Teck Cominco Metals Ltd. for the International Zinc Association.
The predictor performs calculations based on models developed using statistical methods, neural
network technology, and an extensive corrosion database. The resulting chart estimates the
anticipated time to first maintenance for HDG steel of varying coating thicknesses in a wide
array of environments. First maintenance is when there is 5% red rust evident on the substrate
steel. Options at that point are: touchup via one of the methods specified in ASTM A780
Practice for Repair of Damaged and Uncoated Areas of Hot-Dip Galvanized Coatings, painting
or, if the feature can be taken out of service, re-galvanizing.
Cathodic Protection
In addition to the protection afforded by a superb barrier provided by the HDG coating,
the presence of zinc in contact with iron provides cathodic protection from corrosion which
means zinc will preferentially corrode to protect the underlying base steel. The Romans were
aware of the protective qualities of zinc, with the first recorded use of zinc as a construction
material in 79 A.D.
The table on the left shows a series of metals arranged in order of
electrochemical activity in seawater (the electrolyte). This arrangement of
metals determines what metal will be the anode and cathode when the two
are put in an electrolytic cell. Metals higher on the scale provide cathodic
or sacrificial protection to the metals below them. Therefore, zinc protects
steel.
The scale indicates magnesium, aluminum, and cadmium also
should protect steel. In most normal applications, magnesium is highly
reactive and is too rapidly consumed. Aluminum forms a resistant oxide
coating and its effectiveness in providing cathodic protection is limited.
Cadmium provides the same cathodic protection for steel as zinc, but for
technical and economic reasons, its applications are limited. Since zinc is
anodic to steel, the galvanized coating will provide cathodic protection to
exposed steel as well. When zinc and steel are connected in the presence of an electrolyte, the
zinc is slowly consumed while the steel is protected. The zinc’s sacrificial action also offers
protection where small areas of steel may be exposed due to cut edges, drill holes, scratches, or
as the result of severe surface abrasion during rough handling or job site erection. Cathodic
protection of the steel from corrosion continues until all the zinc is consumed.
5
“Zinc Coating Life Predictor”, Dr. X. G. Zhang, teckcominco and International Zinc Association, 2002
<http://www.galvinfo.com:8080/zclp/> accessed September 10, 2010
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Francis Gerace, P.E., Market Development
Hubbell Galvanizing
Zinc Patina
As with many metals, the outer, pure zinc layer passivates over time with the formation
of a patina. Passivation is the spontaneous formation of a hard non-reactive surface film that
inhibits further corrosion. The galvanized outer surface converts from pure zinc to zinc oxide
immediately after removal from the zinc bath and exposure to oxygen. After a few days,
depending on humidity and storage, exposure to moisture converts the zinc oxide coating to zinc
hydroxide. This coating develops over months and after exposure to carbon dioxide, the zinc
hydroxide coating converts to zinc carbonate. This is the final patina film and it is a thin,
compact and tightly adherent layer of corrosion products consisting mainly of basic zinc
carbonate. Zinc carbonate is flannel grey in color. (All galvanized product, whether shiny or dull
as it is removed from the kettle, turns grey after six months to a year.) The final patina is
passivated and serves to retard further corrosion. The final rate of corrosion of the zinc patina is
considerably below that of ferrous materials, some 10 to 100 times slower, depending upon the
environment. The patina is stable and non-reactive unless exposed to aggressive chlorides or
sulfides, and is a key component to HDG’s long life. The result is a long-lived barrier and
cathodic coating protecting the steel for decades.
Long Lasting Protection
Working together, the three factors provide galvanizing its
long-lasting protection because:
• The zinc coating acts as a barrier against the
penetration of water, oxygen, and atmospheric pollutants.
• The zinc coating cathodically protects the steel from
coating imperfections caused by accidental abrasion,
cutting, drilling, or bending.
• The zinc carbonate patina is passive, which slows the
corrosion rate of the zinc.6
Additional Benefits of HDG7
In addition to barrier and cathodic protection, there are several other beneficial
characteristics of the HDG. These include complete coverage and edge protection.
Complete Coverage:
Because the galvanizing process involves total immersion of the
material into cleaning solutions and molten zinc, all interior and exterior surfaces are coated.
6
7
“Galvanize It! Seminar”, American Galvanizer’s Association, 2009
“Galvanize It! Seminar”, American Galvanizer’s Association, 2009
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Why Would Anyone NOT Galvanize Steel If They Can?
Francis Gerace, P.E., Market Development
Hubbell Galvanizing
This includes the insides of hollow and tubular structures, and the threads of fasteners. Complete
coverage is important because corrosion tends to occur at an increased rate on the inside of some
hollow structures where the environment can be extremely humid and condensation occurs.
Hollow structures that are painted have no corrosion protection on the inside. Additionally,
fasteners with no protection on the threads are susceptible to corrosion, and corroded fasteners
can lead to concerns about the integrity of structural connections.
Edge Protection:
As depicted in the photomicrograph of a cross-section of the edge of a
galvanized part, the galvanizing process naturally produces coatings at least as thick at the
corners and edges as the coating on the rest of the part. This is because the reaction between iron
and zinc is a diffusion reaction and thus the crystalline structure of the coating forms
perpendicular to the steel surface. As coating damage is most likely to occur at the edges, this is
where added protection is needed most. Brush- or spray-applied coatings such as paints have a
natural tendency to thin at corners and edges.
WHEN GALVANIZING MAY NOT BE APPROPRIATE
Large steel elements do not lend themselves easily to galvanizing. The average kettle size
in the US is approximately 40 feet. Nevertheless, galvanizing plants capable of galvanizing
pieces 95 feet long and weighing 55,000 pounds are available. Architects/Engineers should
explore kettle capacities before specifying HDG to examine the economics of the coating.
In addition, certain environments are not conducive to HDG longevity. Factors such as
pH have a profound effect on HDG life. When galvanized
steel is used in contact with liquids, a different set of
conditions determines its resistance. A liquid’s degree of
acidity or alkalinity is the factor of greatest importance.
Zinc coatings dissolve in liquids with a pH below 4.5 or
above 12.5. This should not be considered a hard and fast
rule because such factors as agitation, aeration,
temperature, polarization, and the presence of inhibitors
may also change the rate of corrosion. However,
generally at intermediate pH values, a protective film is formed on the zinc surface and the rate
of corrosion is very slow. Since many liquids fall within this pH range, galvanized steel
containers are widely used in storing and transporting many chemical solutions.
Galvanizing is successfully used to protect steel in fresh water exposure. “Fresh water” is
used loosely here to refer to all forms of water except sea water. Water with relatively high free
oxygen or carbon dioxide content is more corrosive than water containing less of these gases.
Hard water is much less corrosive toward zinc than soft water.
Galvanized coatings provide considerable protection to steel when immersed in sea water
and exposed to salt spray. However, it is the dissolved salts (primarily sulfides and chlorides) in
Page 7 of 12
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Francis Gerace, P.E., Market Development
Hubbell Galvanizing
sea water that are the prime determinants of the corrosion behavior of the zinc immersed in sea
water. Other negative factors are water temperature and the amount of oxygen in the water.
Although anticipated galvanized coating life is shorter in sea water than in many other
exposures, galvanizing performs much better than many other coating systems in this
environment. The negative effects of extreme pH values, sulfides and chlorides may be
ameliorated by application of a duplex coating over the zinc surface. This coating, usually a zinc
compatible paint or powder coating retards the deterioration of the zinc, extending longevity by
one and one half to two times the expected life under harsh conditions.
Welding galvanized surfaces directly is not recommended due to health and safety
concerns. However, welding galvanized steel without removing the surrounding zinc coating can
be accomplished provided the welder is experienced in doing so. Special breathing apparatuses
and/or adequate ventilation must be in place to avoid inhalation of zinc fumes. Nevertheless, the
American Welding Society recommends removing the galvanized coating 2 to 4 inches way
from the weld area. The damaged area (caused by the burn of the weld torch) can be repaired
using one of the accepted touch-up and repair compounds listed in ASTM A 780, which is the
specification that governs repair of galvanized articles. It is also important to mention that when
welding galvanized steel the surrounding coating in the Heat Affected Zone (HAZ) may be
damaged from the heat applied by welding. Repair work may be necessary to remediate these
areas to ensure the corrosion protection is not compromised.
HOT-DIP GALVANIZING
COSTS LESS
We have discussed how HDG protects against corrosion, and how long it will last. The
next area to explore is cost in relation to other coatings. Many people have heard galvanizing is a
logical choice when looking at cost from a life-cycle basis; however, there is a common
misconception galvanizing is cost-prohibitive on an initial basis. The following will provide a
cost comparison of hot-dip galvanizing to a number of common paint systems on both an initial
and life-cycle basis.
Initial costs for paint systems include four components: material, shop cleaning labor,
shop/field application, and field labor. All of these costs are included in the initial price for
galvanizing as the cleaning process is a built-in part of the galvanizing process.
The following table shows various paint systems and the equivalent cost of HDG for a
typical project. The data sources (costs, time to first maintenance based on in-field performance)
for the paint systems are from KTA Tator, Inc., NACE Paper Number 08279 (2008). HDG costs
were derived from the American Galvanizers Association National Survey (2009). Project
parameters are a structure less than 50 feet high; 100,000 ft2 to be coated consisting of a typical
medium structural shapes (200 ft2/ton); and the corrosion environment is moderate industrial
(C3). For the life-cycle cost analysis, a 7% interest rate was assumed with 4% inflation and a 35
year service life. Performing economic analyses including initial and life-cycle assessments can
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Francis Gerace, P.E., Market Development
Hubbell Galvanizing
be a difficult and cumbersome practice, but the online calculator www.galvanizingcost.com8 was
used to automate the process.
Economic Analysis Project Size 100,000SF
Coating System
Initial
Cost
2
/ft
Initial
Project
Cost
$125,000
$220,000
LifeCycle
Cost/
2
ft
$4.74
$2.20
LifeCycle
Project
Cost
$474,000
$220,000
Initial
Project
Difference
to HDG
($95,000)
$0
Life Time
Project
Difference to
HDG
$254,000
$0
Inorganic Zinc
HDG
Inorganic Zinc primer/
Epoxy top coat
Acrylic WB primer/
midcoat/ topcoat
Epoxy zinc primer/Epoxy
midcoat/Polyurethane
topcoat
$1.25
$2.20
$2.15
$214,800
$4.56
$456,000
($5,200)
$236,000
$2.69
$269,000
$7.01
$701,000
$49,000
$481,000
$3.30
$330,100
$5.13
$513,000
$101,000
$293,000
As mentioned before, it is not recommended to analyze only the initial cost for a
corrosion protection system. However, if initial cost is the only analysis, galvanizing is still a
solid choice, as it is initially less expensive than all but the minimal protection the one-coat
inorganic zinc paint system provides and competitive when an epoxy top coat is added to the
primer.
Smaller projects with many components and light structural steel sections will yield an
initial galvanizing cost lower than most paint systems, as the galvanizing process efficiently
accommodates bundles and groups of steel.
Economic Analysis Project Size 10,000SF
8
Coating System
Initial
Cost
2
/ft
Inorganic Zinc
HDG
Inorganic Zinc primer/
Epoxy top coat
Acrylic WB primer/
midcoat/ topcoat
Epoxy zinc primer/Epoxy
midcoat/Polyurethane
topcoat
$1.44
$1.76
Initial
Project
Cost
$14,400
$17,600
LifeCycle
Cost/
2
ft
$3.99
$1.76
LifeCycle
Project
Cost
$39,900
$17,600
Initial
Project
Difference
to HDG
($3,200)
$0
Life Time
Project
Difference to
HDG
$22,200
$0
$2.47
$24,702
$6.01
$60,100
$7,102
$42,500
$3.10
$30,970
$8.07
$80,700
$13,370
$63,100
$3.80
$37,960
$5.90
$59,000
$20,360
$31,400
Galvanizing Cost Life-Cycle Cost Calculator,< www.galvanizingcost.com>, American Galvanizer’s Association, 2010
Page 9 of 12
Why Would Anyone NOT Galvanize Steel If They Can?
Francis Gerace, P.E., Market Development
Hubbell Galvanizing
When life-cycle costs are considered, hot-dip galvanizing is the most economical system
for corrosion protection. In fact, this analysis does not even include the hidden (or indirect) costs
associated with paints when there is loss of use, traffic delays that may result when a bridge or
road is closed or partially closed, and interruption of local commerce. Also, if deviations from
the practical paint maintenance schedule used in the analysis above occur, life-cycle costs could
be significantly higher than indicated.
Sustainability
There is a growing awareness of how our actions impact our surroundings and the
environment, as well as the future implications of those actions. A commonly accepted definition
of sustainable development (SD) is the social, economic, and environmental commitment to
growth and development that meet the needs of the present without compromising the ability of
future generations to meet their own needs.
There are a number of systems used to measure how sustainable a product or process may
be, and they are often highly subjective. Some systems such as LEED® presented by the US
Green Building Council are prescriptive in that they assign values through a rigid formulation to
assess the achievement towards meeting goals in prescribed categories. HDG, at 30% recycled
content, contributes to LEED® credit in the Materials and Resources category since it contains
so much recycled content.
However, other methods such as Life Cycle Inventory (LCI) and Life Cycle Assessment
(LCA) are more analytical and serve to assist designers and specifiers as to the effect of choices
of materials on the environment. LCI is the study and measurement of the material flows, energy
flows, and environmental releases for the production of a defined amount of a product. LCI does
not consider energy consumed or environmental impact during use or end-of-life. It can be
described as a cradle to gate analysis. In other words, it is the impact of preparing a material for
construction. LCA goes beyond the manufacture of material and is a standardized scientific
method for the systematic analysis of all mass and energy flows as well as environmental
impacts attributed to a product system, from raw material acquisition to end-of-life management.
LCA includes a product’s LCI as well as the downstream impacts of operations and maintenance
and disposal at the end of the element’s life.
As a part of the Zinc for Life program, the International Zinc Association (IZA)
sponsored a study of the LCI and LCA of hot-dip galvanized steel by Five Winds International
and PE International. Galvanizing data was collected from: the American Galvanizers
Association (AGA), the European General Galvanizing Association (EGGA), the Galvanizers
Association of Australia, and the Hot-Dip Galvanizers Association of South Africa. The study
examined four criteria with which the LCI and LCA of Hot-Dip Galvanizing can be measured


Primary Energy Demand (PED), the total energy consumed;
Global Warming Potential (GWP), the Carbon footprint;
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Francis Gerace, P.E., Market Development
Hubbell Galvanizing


Acidification Potential (AP), the creation of acid rain;
Photochemical Ozone Creation Potential (POCP), the creation of smog.
Using the above criteria and
Complete
PED
GWP
AP (SO2
POCP (C2H2
defining universal boundary
LCA
(CO2
equiv.)
equiv.)
conditions, the net effect of
equiv.)
1 kg of HDG on the
environment was
1 kg of HDG
17.3 MJ
1.80 kg 0.00615 kg
0. 000824 kg
determined and is shown.9
†
PED (primary energy demand) reflects production, use, and end-of-life
The term net effect is used
credit.
because the LCA considered
the entire life of HDG. At the end of life both the steel and zinc are 100% recyclable and are
reclaimed with no loss of physical properties. Thus there is a credit assigned to the PED as it
takes less energy to produce recycled HDG steel than from virgin sources.
†
There is a procedure defined by ISO to address the differences between competitive
materials. In this case, the difference between HDG and paint on the environment would require
both industries to reconcile parameters, boundary conditions, methods of measurement, etc.
While there has been no such agreement, some conclusions can be made regarding the
differences between the two on a qualitative basis. First, steel is the primary component for both
LCA’s. Steel’s high recyclability and low environmental impact have large impact on LCA
numbers. Nevertheless, a galvanized coating provides more advantages since there are no
additional direct or indirect environmental costs during use since there is zero maintenance.
Also, the zinc coating is recycled during end-of-life phase, leaving no permanent waste.
However, painted steel will produce additional environmental costs because it will require
regular maintenance on a predetermined cycle of 12 to 20 years. At the end of life, steel is the
primary component recovered, whether it is galvanized or painted. However, unlike the
recyclable zinc of the galvanized coating, the paint coating will become a permanent part of the
waste stream.
Nevertheless, there have been quantitative comparative studies done. VTT Technical
Research in Finland conducted a life-cycle assessment study for a hot-dip galvanized balcony
system compared with an identical constructed painted balcony system10. That study quantified
the principal environmental impacts for a galvanized steel balcony and painted balcony. For the
impact categories discussed above, the efficiency and durability of the galvanized balcony
9
“Hot-dipped Galvanizing is Green”,
<http://www.galvanizeit.org/images/uploads/publicationPDFs/HDG_is_Green_Email.pdf>, the American
Galvanizer’s Association, 2009
10
"Life-cycle Assessment Study for Hot-dip Galvanized Balcony System Compared with Painted Balcony System",
VTT Technical Research Centre of Finland, April 2004
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provided for significantly lower life-cycle environmental indicators than the painted system
balcony.
So, of the two barrier systems, galvanizing, or paint, HDG is the sustainable choice. In
the production phase 30% of all zinc is from recycled sources. During the use phase, HDG is
maintenance free and has no energy requirements, effectively a zero impact on the environment.
Finally, at the end of life, 80% of all remaining zinc HDG products are reclaimed and put back to
use with no degradation of mechanical and physical properties. With paint systems, by contrast,
the amount of recycled material during the production phase is unknown, the required cyclical
repainting represents an environmental impact, and at the end of life the spent paint is landfilled
CONCLUSION
From the above, Hot-dip galvanizing is clearly a superb corrosion protection system for steel.





As a barrier from electrolytes, the coating has a metallurgic bond with 3000 psi strip
strength, it is unaffected by UV rays, and provides complete coverage and edge
protection.
The zinc provides cathodic protection, since zinc is more anodic than iron.
The galvanized coating provides long lasting protection since the zinc patina passivates
the corrosion process.
Economically, HDG compares favorably to all but the most simple paint systems on an
initial cost basis. Since it is maintenance-free, it outshines all systems on a life-cycle cost
basis.
Compared to other systems, HDG is sustainable due to its 100% recyclability and its
reclamation properties.
So, if an element can be galvanized, why would anyone NOT choose HDG for steel
corrosion protection?
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