Session C5
Paper 195
Disclaimer—This paper partially fulfills a writing requirement for first year (freshman) engineering students at the
University of Pittsburgh Swanson School of Engineering. This paper is a student, not a professional, paper. This paper is
based on publicly available information and may not be provide complete analyses of all relevant data. If this paper is used
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ZINC-ALUMINUM-MAGNESIUM ALLOY PAINTS: A CRUCIAL
RENOVATION FOR BRIDGES
Kevyn Mitchell, [email protected], Vidic 2:00, Mike Winiarczyk, [email protected], Mahboobin 10:00
Abstract — Corrosion is a big problem for bridges as it
weakens the structures and causes potential for failure. It is
important for engineers to keep bridges as safe as possible
because many people rely on them every day. There are
practical solutions that can be used to combat the effects of
corrosion, with one of the most common methods being
paint. We will look at the use of Zinc-Aluminum-Magnesium
(Zn-Al-Mg) alloy paints to slow and prevent corrosion.
In general, galvanizing paints use layers of zinc to create
a nonpermeable barrier on top of the structure. This barrier
protects the structure from exposure to moisture, which in
turn drastically slows corrosion. Zn-Al-Mg paints have
potential to be better performing than traditional
galvanizing paints.
While the paint can efficiently prevent corrosion when it
is applied to structures, the impact it has on the environment
must be considered as well so that it does not cause
excessive pollution and damage to the surroundings. In this
paper, the usefulness of Zn-Al-Mg paint will be scrutinized,
we will perform an in-depth analysis on how it works, we
will determine whether it is sustainable, and its tested data
will be analyzed to determine if its overall effectiveness is
worth the cost.
According to the U.S. Department of Transportation’s
Federal Highway Administration (FHWA), bridges that are
considered to be in the range of excellent to fair condition
and bridge elements that are considered either good or fair
qualify to receive preventive maintenance [3]. The FHWA
classifies preventive maintenance as “a planned strategy of
cost-effective treatments to an existing roadway system and
its appurtenances that preserves the system, retards future
deterioration, and maintains or improves the functional
condition of the structure (without substantially increasing
structural capacity)” [3]. One preventive maintenance
method is the application of a painting or coating to the
surface of bridges.
Coatings that are applied to bridges help protect the
structure underneath from weather and other sources of
water that can lead to corrosion of the structure. There are
more types of corrosion than the process of water interacting
with iron, including bimetallic corrosion and environmental
corrosion. According to Whirlwind Steel, bimetallic
corrosion “occurs when a chemical reaction is caused by two
metals coming in contact - or close contact - with one
another,” and environmental corrosion occurs because
certain environmental pollutants, toxins and compounds can
exacerbate either one of the [previously mentioned] forms of
corrosion” [4]. Weather greatly contributes to corrosion as
well, simply by causing the presence of water on a structure,
especially in locations with “freeze-thaw cycles [which]
create… greater weathering damage” [5]. While coatings are
effective in slowing the process of corrosion, the
effectiveness can be improved. This would, in turn, reduce
the frequency of application of the paints and allow for the
paints to have maximum effectiveness. The use of zincaluminum-magnesium based paints could help to increase
this effectiveness, and create savings in the long run.
Key Words—Paint, Galvanization, Corrosion, Bridges, Rust
control, Chemical engineering, Preventive maintenance
CORROSION IS CRIPPLING
INFRASTRUCTURE
Infrastructure has been in a poor place in the United
States recently, and infrastructure spending has been at its
lowest point since 1947 [1]. One part of infrastructure that
has been suffering is bridges. In the American Society of
Civil Engineer’s Report Card for America’s Infrastructure,
bridges got a rating of C+, meaning that bridges are in a
mediocre state. Factors that contribute to this rating include
structural deficiency and functional obsolescence, along with
funding and expected future attention to bridges. Structural
deficiency is a big problem that can lead to potential failure
of bridges which in turn could lead to loss of life and high
amounts of damages [2].
Depending on the condition that bridges are in, different
measures can be taken to improve their conditions.
CORROSION AND GALVANIZATION
Corrosion is a significant issue that is affecting the
structural integrity of bridges, and thankfully, methods to
control and reduce corrosion have been developed. The
process of galvanization is a method that provides protection
by applying a coating to a metal base, and is the primary
method investigated. To investigate methods of stopping
corrosion, the process of corrosion must be understood first.
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that the structure is in. The electric potential differences will
switch positions on the surface, when anodes become
cathodes and vice-versa (seen in the last two images in the
diagram), which causes the process to continue, and it may
do so until the iron is entirely consumed, which would lead
to a lack of structural integrity in a bridge. Because it is a
process that will not stop after a certain point, prevention is a
necessity.
The Process of Corrosion
Corrosion occurs, on a basic level, due to the reaction of
iron and water. When investigated further, it is seen that
differences in electrochemical potential are caused on
surfaces of exposed steel due to non-uniformity of surface
composition [6]. Because of the electric potential
differences, electrons flow and iron atoms are converted to
positively charged ions [6]. The positively charged iron ions
will react with hydroxide ions, which come from water or
any other electrolyte that is in contact with the surface, and
form iron oxide, which is more commonly referred to as rust
[6]. This diagram shows how the process of corrosion
Galvanization to Prevent Corrosion
Galvanization is defined by the U.S. General Services
Administration as the “process of coating iron or steel with
zinc in order to provide greater protection against corrosion
for the iron or steel base” [7]. There are many different
methods of galvanization that exist, including hot-dip
galvanizing, electrogalvanizing, sherardizing, metallic
spraying, and painting. These methods are all similar in the
fact that their result is a galvanized surface, but they differ
through how they achieve said galvanization.
Hot-dip galvanization, the oldest type, is done by
immersing iron or steel with a cleaned surface into molten
zinc, which forms multiple layers of iron- or steel-zinc
alloys [7]. Electrogalvanization is achieved through
immersing iron or steel into an electrolyte solution
comprised of zinc sulfate or cyanide, which then creates a
pure zinc coating on the surface [7]. Sherardization is the
placing of a small object into an air-free environment that is
instead filled with metallic zinc dust, and when heated, a
thin zinc coating is produced on the object [7]. Metallic
spraying is “the application of a fine spray of molten zinc to
a clean iron or steel element… [that] can then be heated and
fused with the surface of the iron or steel to produce an
alloy” [7]. The use of paints with zinc in them can also be
used to protect structures.
These different methods of galvanization each have their
own benefits and drawbacks, but the majority of
galvanizations
done
today
occur
through
electrogalvanization, rather than the traditionally popular
method of hot-dip galvanization [7]. Galvanization features
many problems that arise due to corrosion, the exact issue
that causes these techniques to be employed. Because
galvanization is not a completely effective process,
preventive maintenance must occur in to keep the coatings at
their highest effectiveness. When looking at structures used
in high-stress environments, such as bridges, which
experience the constant effects of rain and the environment
and more drastic side effects of extreme weather as well,
maintenance will have to occur at a higher frequency to keep
the galvanized coating at maximum effectiveness.
With a high frequency of required reapplications of a
coating,
some
methods,
including
hot-dip,
electrogalvanizing, and sherardizing are out of the picture
for the sake of practicality, as it is far from reasonable to
recast pieces of a bridge and replace them or to disassemble
a bridge for reapplication of a coating. This leads us to
occurs.
FIGURE 1 [6]
The process of corrosion shown visually, with included
chemical equations of the creation of iron oxide
The electric potential differences occur on exposed surfaces,
which happen to be the places that water or other solutions
will come in contact with the structure as well. Corrosion
can occur at different rates, depending on the environment
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conclude that paints, while featuring many drawbacks, may
indeed be the most practical and cost-effective method of
keeping up with the requirements of preventive maintenance
simply due to the ease of application that comes with them.
of insoluble zinc oxides, hydroxides, carbonates and basic
zinc salts depending on the nature of the environment” the
structure is in [6]. This is the layer that will truly slow the
effects of corrosion, and even as it is damaged it will not
lose all functionality at that point.
Patinas can slowly regenerate themselves by consuming
some of the zinc coating, located under the patina, which
helps to increase the lifespan of the barriers [6]. On the
Galvanizer’s Association of Australia’s website, the
formation of the patina is described as follows: “the zinc
patina begins its development with exposure to oxygen in
the atmosphere. Moisture from rain or humid air reacts with
this layer to form zinc hydroxide. This layer then reacts with
carbon dioxide present in the atmosphere to form the tightly
adherent, insoluble zinc patina” [6]. This process is
illustrated in the following figure:
The Drawbacks of Galvanizing Paints
One of the biggest drawbacks to galvanizing paint is that
it is the “least effective method of zinc coating” when
compared to all other methods of galvanization according to
the U.S. General Services Administration [7]. Paint tends to
peel completely from metal along with any primers applied,
which leads to a bare metal surface being exposed after any
paint falls off. Paint can fall off due to either natural
deterioration, or due to uncontrollable interactions with it.
Chemical corrosion will occur due to contact with things
such as plasters, cements, acidic rainwater, contact with
dissimilar metals in the presence of moisture, and certain
organic growth such as moss or lichen [7]. Any human
activity that leads to contact with the surface of the metal
will lead to some paint being removed as well.
The loads that bridges bear have effects on the metal that
makes up bridges, which can in turn lead to an effect on any
coatings applied to them. For example, loads on bridges can
create friction which in turn causes heat, which will cause
thermal expansion to occur, even if it is at a relatively tiny
scale. Looking at the effects of thermal expansion linearly, it
causes the length of objects to increase as per the following
equation:
FIGURE 2 [8]
Equation for change in length due to linear thermal
expansion
FIGURE 3 [6]
This figure illustrates the formation of the patina, and
shows the different chemicals that exist in each step
Here, 𝛼𝐿 denotes the coefficient of linear thermal expansion.
The coefficient of cast iron is 10.4*10-6 m/(m*K), the
coefficient of steel is 12.0*10-6 m/(m*K), and the coefficient
of zinc is 29.7*10-6 m/(m*K) [9]. While these numbers do
not mean much by themselves, applying them to the
equation for change in length due to linear thermal
expansion shows that zinc will expand at a rate more quickly
than either steel or iron will expand. These differing rates of
expansion will lead to the thinner portion (the coating, as it
is primarily made of zinc) being damaged. This damage will
lead to the paint coating breaking up and failing to protect
the bridge underneath.
Step 1 of figure 3 shows the formation of zinc oxide due to
the presence of oxygen in the atmosphere. Step 2 of figure 3
shows the formation of zinc hydroxide due to water coming
into contact with the surface. Step 3 of figure 3 shows the
patina is developed with zinc carbonate. The presence of
carbon dioxide in the air combines with the zinc oxide to
form the zinc carbonate, and the zinc hydroxides are still
present here as well. These reactions show that the patina
will be present as long as the zinc coating is present on the
surface of the metal, but if the coating is not, the patina is
not either. In summary, the barriers work by providing a
layer themselves, and allowing for a patina to form and
regenerate from itself which adds further protection.
How Barriers Work to Prevent Corrosion
ZN-AL-MG BASED PAINTS FOR
GALVANIZATION
As discussed previously, any method of galvanization
will provide a barrier to prevent and reduce any oxidation
from occurring. Galvanization does in fact create a physical
barrier on the surface of the metal, but it also creates a
protective patina on the surface as well [6]. According to the
Galvanizers Association of Australia, the patina “is made up
While galvanizing paints do have downsides to them,
there is always room to improve and minimize the
downsides present. One method that could potentially aid
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and improve the paints would be adding other components to
the paints themselves. Adding zinc, aluminum, and
magnesium alloys to galvanizing paints could help to
increase corrosion resistance, the longevity of the coating it
creates, and the patina that is formed or other similar side
effects. The biggest benefit to adding other materials to the
paint is that everything that already occurs in normal
galvanizing paints will still be present in Zn-Al-Mg paint,
only with changes to the qualities of those features.
To create Zn-Al-Mg paints, different amounts of each
respective element must be mixed into the paints. Beyond
that, however, the process of creating the mixture should be
considered as well. Different percentages of Zn, Al, and Mg
have been created in the past, with different results from the
different combinations. Shimoda et al. found that “the higher
the Al%, the longer the corrosion resistance lasts, [and] that
the addition of Mg significantly enhances the level of
corrosion resistance” [10]. While their research was carried
out on Zn-Al-Mg alloy coated steels, which were created
using a hot-dip galvanization method, their findings are still
relevant as it is the mixture of Zn, Al, and Mg that are being
looked at here as opposed to what medium they are in.
The different elements tend to show different effects as
well. The zinc is present in all samples tested, so the patina
is still able to form to protect the structure as explained
previously. In order to observe the effects of aluminum
content, Shimoda et al. compared mass loss to percent of
aluminum content during corrosion tests, and obtained the
following data:
plane corrosion resistance corresponded to a lower loss of
mass per area. The top set of points are the data after the 45 th
cycle of the process, the middle set are after the 30th cycle,
and the bottom set are after the 12th cycle. Looking from left
to right across the graph, it can be seen that higher
percentages of aluminum content do lead to a lower amount
of mass lost to corrosion.
Shimoda et al. also did tests to see the effects of
magnesium. They compared mass loss to percent of
aluminum content during corrosion tests, and obtained the
following data:
FIGURE 5 [10]
This chart shows the mass loss in g/m2 compared to the
percent magnesium content in the coating, with percent
aluminum coating to control
The data shows that increasing percent magnesium will
reduce mass loss after the JASO-CCT method of testing
plane corrosion resistance. Looking at the data when the
percent aluminum is fixed shows that higher percentages of
magnesium corresponds to lower mass loss. It has already
been shown that aluminum increases the length of time that
the corrosion resistance will be present (it can also be seen
here), so that leaves magnesium as the explaining factor for
what causes the change, and it is a change in effectiveness
rather than that of longevity.
When controlling zinc, it is shown that the addition of
aluminum to the mixture causes the length of effective
corrosion resistance to increase for the coating. It is also
shown that magnesium increases the effectiveness of the
resistance, without an effect on the length it has. Through
testing, Shimoda et al. found that the best makeup of the
coating contained “more than 6-8%” Al, and “3%” Mg to
provide the optimal amount of corrosion resistance and
amount of time that the resistance lasts [10].
FIGURE 4 [10]
This chart shows the mass loss in g/m2 compared to the
percent aluminum content in the coating
Their research showed that a higher percentage of aluminum
present in a mixture during the JASO-CCT method of testing
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the steel exposed to the elements. This would lead to the
steel to become corroded much faster than it would have
with the protective coating. This problem, however, is
avoidable as long as proper maintenance is performed on the
bridges and they are not left alone long after the coating
needs to be reapplied. In theory, this is an extremely easy
fix, but other issues such as lack of funding could get in the
way of reapplication of paint, which would lead to an
unprotected surface.
Another issue that may arise when using paints on
bridges is that “paint does not adhere well…to galvanized
iron or steel” [7]. While the Zn-Al-Mg coating has lessened
this issue by improving upon its ability to bind with steel, it
can still be a problem in some cases. If the paint cannot be
easily applied, professionals should be hired to ensure the
painting is properly done. Hiring professionals is just
another expenditure that could deter the use of paints, more
specifically the Zn-Al-Mg paint, on bridges.
Other downsides to adding aluminum or magnesium to
the paints is a potential for the downsides of the added
elements to show up in the new paint. According to Khan et
al. of the Nagaoka University of Technology of The
University of Tokyo, “significant corrosion fatigue damages
[on magnesium alloys] have been reported under NaCl
solution or high humidity” [14]. If, in creation of the Zn-AlMg paint, the mixture is not created evenly, different
elements of the paint could pool unevenly. Due to this, and
assuming the effects of a humid environment are present,
once applied, any magnesium-dense areas could potentially
be prone to higher levels of deterioration. Because of this, it
must be assured that homogenous mixture of the paint is
achieved during its creation.
One more disadvantage that the Zn-Al-Mg coating faces
is that it is slightly more difficult to produce. The ratios of
the three elements need to be adjusted to properly perform a
designated task, which takes more time than just using a zinc
alloy alone. However, the extra work beforehand could pay
off in the long run. Therefore, the Zn-Al-Mg coating has
drawbacks like any other product, but there is one that
should be further analyzed to truly understand the extent of
its effect.
ARE ZN-AL-MG PAINTS BETTER THAN
NORMAL GALVANIZING PAINTS?
The Advantages of Zn-Al-Mg Paints
There is a myriad of advantages that come along with
using zinc, aluminum, and magnesium in galvanizing paints,
and they should not be overlooked. These paints are not only
effective for the structures they are applied to, but they are
also beneficial for the consumers and the market as a whole.
One reason the Zn-Al-Mg paint, specifically, is so effective
is due to the presence of aluminum. As opposed to some of
its competitors, which do not contain aluminum, the
aluminum present in the Zn-Al-Mg paint “provides anodic
protection unlike zinc-rich formulations” [11]. The
combination of zinc and aluminum, therefore, significantly
helps the effectiveness of the product. The addition of
magnesium, however, aids the paint even more.
Another reason these paints are effective on a structural
level is because adding magnesium to a zinc-aluminum alloy
coating has a significantly positive influence on corrosion
protection (up to 8%) [12]. This was demonstrated by
comparing the rust-resistant capabilities of zinc-aluminum
alloy infused with magnesium to zinc alloys with other, less
effective, substances. The zinc-aluminum alloy with
magnesium proved to resist corrosion far better than the rest
as it could withstand corrosion for weeks longer than its
competitors [12]. Therefore, the results were clear that this is
a successful formula. Upon further analysis of the Zn-Al-Mg
corrosion protection model, a better understanding of its
abilities can be found. The Zn-Al-Mg model demonstrates
its cathodic protection. The products from the corrosion
reaction form inhibition layers, thus slowing down zinc
dissolution. This, as a result, expands the lifespan of the
product far beyond its less sophisticated predecessors.
One more advantage of the Zn-Al-Mg coating is that it
has proven to be very successful in the market since its
creation in 2007. When it was first created, its index for
market growth was around 100. In just four years, its index
for market growth had steadily increased to nearly 1,900
[13]. Therefore, the Zn-Al-Mg coating has been consistently
demonstrating its legitimacy in the market.
Despite having numerous advantages and benefits,
however, there will be disadvantages that take away from
the paint’s positive image, as there are with any product.
THE PRACTICALITY OF ZN-AL-MG
PAINTS
The Fancourt Bridge
The Disadvantages of Zn-Al-Mg Paints
While the idea of galvanization to prevent corrosion is a
good one, real applications of it must be considered as well.
To consider this, the replacement of the Fancourt Bridge in
Pittsburgh, Pennsylvania in 2012 will be analyzed. The
Fancourt Bridge is a located over bypass ramps between two
larger bridges: the Fort Duquesne and Fort Pitt Bridges.
Because of the proximity to these high-traffic bridges, and
its location near downtown Pittsburgh, the Fancourt Bridge
Like any product on the market, Zn-Al-Mg paints come
with downsides related to application and production.
Despite how many advancements were made with the ZnAl-Mg based paints, it is still a paint. Therefore, it still faces
some of the same issues that ordinary corrosion-preventive
paints do. For instance, when paints approach the end of
their lifespan, they will chip away from the bridge, leaving
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receives an ample load of traffic. Prior to the rehabilitation
project on the bridge, it had been rated “structurally and
functionally obsolete” [15].
The bridge was given an 85 day construction period,
meaning there was little room for error and work had to be
done quickly. To be rehabilitated, it was decided that parts
of the bridge should be galvanized. Nine of the bridges
girders and 40 of its diaphragms were galvanized during this
project [15]. The bridge has since been in better condition
than before the construction project, partly thanks to the fact
that it was galvanized.
materials in the paints and primers. Therefore, if the
production goes unregulated, there can be adverse effects on
society. In this sense, using paints is not as sustainable as
other non-paint-based methods of galvanization, but if the
production of the paints is regulated, there can be some
visible economic and community development.
Overall Practicality of the Paints
The practicality of the zinc-aluminum-magnesium can be
determined by looking both at how well it can be
implemented in the world and how sustainable the paints are
themselves. As seen through the Fancourt Bridge,
galvanization is indeed a good method to control corrosion
that occurs on bridges. When looking at sustainability, the
Zn-Al-Mg paints perform better than other galvanizing
paints, showing its economic feasibility, and through this
better performance they are also safer, which shows how
they work towards more sustainable community
development.
Sustainability itself could be treated as a relative
definition, depending on what objects are being compared.
When comparing the Zn-Al-Mg paints to traditional
galvanizing paints, it is easy to say that the Zn-Al-Mg paints
are indeed more sustainable. As discussed earlier, the
presence of aluminum and magnesium in the paint causes it
to both last longer and be more effective at preventing
corrosion. We believe that this alone allows the paints to be
more sustainable than traditional ones. Sustainability of the
Zn-Al-Mg paints can be brought into question when
comparing it to that of other methods of galvanization. Other
methods often require less reapplication or maintenance,
which would lead to them being more sustainable.
Are Zn-Al-Mg Paints Sustainable?
When analyzing the sustainability of different methods
of corrosion prevention, many factors must be considered.
To be sustainable, a method should ideally have as little of a
negative impact as possible. In other words, the system or
product created should operate at a rate that does not
compromise the natural environment, or the ability of future
generations to meet their own needs. Sustainability,
however, is not limited to strictly environmental standards.
There are more areas that are affected by the sustainability
of a system or product. Some of these include economic
development, community development, and environmental
protection.
From an economic point of view, Zn-Al-Mg paints are to
be commended. In addition to its superior performance, the
Zn-Al-Mg paint also has its competitors beat in another
regard. When compared to other zinc-based alloys, the ZnAl-Mg alloy proved to require less of it to cover structures
than other paints. In fact, this alloy results in 161 g/m2 in
weight loss [12]. In other words, the zinc-aluminum alloy
performs better at half the coating weight of alloys
containing only zinc [12]. This reduction in weight is not
only beneficial for the structure but also for the businesses
that purchase and use it (In the case of bridges, those
companies would be the government.). The fact that less of
it is required to perform a task will reduce expenditures for
companies and, in turn, maximize profits. Additionally, the
enhanced corrosion protection results in longer service life
and is complementary to other corrosion prevention
measures [12]. Both are aspects that lead to a more
profitable and successful company by cutting down on
maintenance costs.
Community development refers to the ability of a system
or product to keep people safe and ensure there is no
infringement on their quality of life or overall wellbeing.
Since the purpose of Zn-Al-Mg paints is to prevent the
corrosion of bridges, they do not hinder the wellbeing of
society in that sense. In fact, the fact that these paints
prevent corrosion, something that is detrimental to the health
and safety of society, can be considered a positive
community development. However, the process to make
these paints has to be strictly regulated due to the toxicity
and possible carcinogenic properties of some of the
ENVIRONMENTAL IMPACTS OF
CORROSION AND THE PAINTS
When analyzing any product, it is important to also
analyze the effects it can have on the environment. While the
Zn-Al-Mg coating is less detrimental to the environment
than other paints, such as ones based with lead, it can still
have a negative impact. As mentioned above, when paints
approach the end of their lifespan, they tend to chip away
and leave steel exposed to the elements. This plays into the
environmental impact because those chips of paint go
somewhere, and they usually end up in the river or body of
water the bridge is transporting people over, along with any
rust particles that end up there. This contributes to the
inadvertent pollution of water systems and overall marine
ecosystems. In other words, paint and rust could adversely
affect the environment because a “major drawback of…
solvent-based paint is the emission of volatile organic
compounds” [12]. In order for a method of corrosion
prevention to be sustainable, it should have as little of an
impact as possible on the environment as well.
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This data was also collected in a tropical climate, so these
effects will be seen where the previously discussed pH data
are seen. The mass of zinc that is lost comes from the
coating on the galvanized steel. As would be normally
expected, more mass is lost as time goes by. The more
interesting part of the data shows that mass loss is much
higher in urban environments compared to rural
environments. The biggest difference between the two
environments can be seen between the 306-day period,
where urban environments had around 7.25 g/m2 of zinc
loss, and the 365-day period, where the rural environment
had only around 6.50 g/m2 of zinc loss. This could lead to
the inference, although it is extrapolating, that the rate of
mass loss in an urban environment is higher than that in a
rural environment. Urban environments tend to have more
bridges (and other structures) that would get galvanizing
paints applied to them as well. Combining this higher rate of
mass loss with the higher density of paint use, urban
environments would expect to see a much higher amount of
pollution in their environments than rural areas do.
Runoff Rainwater from Galvanized Steel
Zinc is a metal that is often looked for in soil, as it has
detrimental effects on the environment. Veleva et al. studied
the effects of zinc runoff from galvanized steel in humid
tropical climates, which are recognized as an “aggressive
environment for metals” [16]. This group collected data on
pH in rural environments in precipitation, as seen here:
Limited Natural Resources
Another potential issue that could arise from
development of paints that contain more minerals is that
natural resources could be depleted from the Earth too
quickly. Even though zinc, aluminum, and magnesium are
not necessarily scarce resources, they are resources
nonetheless. Zinc is present in all types of galvanizing
paints, so it is already used a lot for galvanization.
According to L. Veleva et al., “nearly one-half of the annual
world zinc production, about three million tons, is consumed
for galvanisation [sic] of steel” [16]. To produce the Zn-AlMg coating, these resources will be depleted and used in an
industrial facility, which also produces byproducts that may
be harmful to the environment.
FIGURE 6 [16]
This graph compares pH of galvanized steel to that of
runoff rainwater (pluvial precipitation)
From the data, which was collected over the span of a year,
it can be seen that the runoff rainwater, referred to as pluvial
precipitation, has a lower pH value, and is more acidic than
the galvanized steel. The increase in runoff rainwater pH
values is due to dissolution of basic zinc corrosion products
into the water from contact with the galvanized steel [16].
The group also analyzed the mass loss of zinc on
galvanized steel samples, as seen here:
Preventing Pollution from Galvanizing Paints
Although pollution does and will occur, as it cannot be
completely mitigated, great strides have been made to
minimize the effects of the paint chips on the environment.
NACE, the National Association of Corrosion Engineers,
explains that “in response to environmental concerns,
primers have changed from those that relied on lead and
chromate to zinc-based materials, and organic solvents have
been replaced” [5]. Bridges are being looked at as well, as
the Oregon Department of Transportation is monitoring the
Yaquina Bay Bridge in Newport, Oregon, which has 84 tons
of Zn applied to it, in order to make sure that zinc in the
water underneath is under the U.S. Environmental Protection
Agency’s standard of 5000 µg per liter of water [16]. The
paints have potential to impact the environment, so it must
be prevented.
FIGURE 7 [16]
This graph compares the mass of zinc lost over time in an
urban and a rural environment
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Kevyn Mitchell
Mike Winiarczyk
sustainable solely due to the fact that they are more
effective, as they are more economically feasible and
promote safer community development due to their
effectiveness. When comparing the paints to other
galvanization methods, it is slightly easier to argue that the
other methods will be more sustainable due to both less
reapplication and maintenance and the environmental
impacts of the paint.
The environmental effects do affect the sustainability,
but it is important to understand how and why it affects it.
Although there may be some harmful side effects to creating
the coatings, the purpose of these coatings is to protect the
nation’s infrastructure. If the infrastructure, more
specifically, a bridge was left exposed to the elements, the
corrosion that would occur would be far more detrimental to
the environment than creating the technology to prevent it.
For instance, if a bridge were left uncovered, it would rust
rather quickly and deposit large quantities of rust particles
into the water. Prolonged exposure could even result in
chunks of the bridge itself chipping off into the water.
Therefore, the relatively small environmental impact of the
paints could be overlooked in the long run if they are
protecting the environment from a greater threat of more
rust.
Ultimately, the Zn-Al-Mg paint has numerous
advantages that outweigh its disadvantages. As demonstrated
by its index for market growth, this technology is gaining
traction and is starting to be used on a more widespread
basis. This coating should be implemented more frequently
on bridges as it is a relatively inexpensive and efficient
product that is the result of a plethora of tests and trials. The
Zn-Al-Mg paint has proven and is continuing to prove itself
today as a more sustainable alternative to other galvanizing
paints. Perhaps it can be the solution to America’s mediocre
infrastructure grade.
The Environment and Sustainability
When looking at our definition of sustainability, keeping
environmental impacts to a minimum is important.
Manufacturers are cognizant of the issue of pollution and
work to minimize environmental impacts and make sure
their products are sustainable. They are doing this by
creating more advanced paints, including ones with added
zinc, aluminum, and magnesium. When comparing
galvanizing paints to other galvanizations and only
considering environmental impacts, other methods are more
likely to be more sustainable by having a smaller
environmental impact. Overall, it can be seen that zinc and,
by extension, galvanizing paints do have an impact on the
environment.
IS FURTHER DEVELOPMENT OF ZN-ALMG PAINTS WORTH IT?
If all the positive and negative aspects of the Zn-Al-Mg
paints are taken into consideration and analyzed, an accurate
representation of this product can be made. On the positive
side, this coating provides both anodic and cathodic
protection against corrosion with the addition of aluminum
and magnesium to the zinc-based alloy. As a result of this
increased protection, the paint lasts longer than others
lacking these elements. This augmented longevity sets this
product above its competitors in three regards. The first is
that it would be better for infrastructure, more specifically
for bridges. The second is that it would be better for
companies because their product would last longer and they
could use less to accomplish the same task, thus cutting
down on expenditures and maximizing profits. Finally, this
product would be better for the environment despite being
categorized as a protective paint. However, the Zn-Al-Mg
coating is not a perfect product. It has flaws that detract from
its noble intentions.
One of the disadvantages of the Zn-Al-Mg coating is the
fact that it would require maintenance to ensure it is holding
up against its environment and serving its purpose to make
sure the bridge keeps from corroding. That may be a
deterrent from using it, but it would require less maintenance
than other paints currently being used. Another disadvantage
is that paints, in general, can be difficult to get to adhere to
galvanized iron or steel. This, in turn, would require
specialized professionals to apply it to bridges. One more
issue some may find with this technology is that it is slightly
more difficult to manufacture than the standard, zinc-based
paint. There are more precise measurements of different
elements that go into making the paint to ensure it performs
at the optimal level.
To decide whether or not Zn-Al-Mg paints are
sustainable, we concluded that in comparison to other types
of galvanizing paints that do not feature zinc or aluminum,
the paints that do contain those elements are more
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ACKNOWLEDGEMENTS
We would like to thank our co-chair Harrison Lawson
for being helpful and keeping us track for this assignment,
and our writing instructor Dr. Zelesnick for giving us good
advice on how to make the paper sound better. Although
other groups may have had session chairs to help them
through the writing process alongside their co-chairs and
writing instructors, we would like to doubly thank our cochair and writing instructor for doing a great job filling in for
that role as well.
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