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Treatment Prevents
Corrosion in Steel and Concrete Structures
Environmental and Agricultural Resources
Originating Technology/NASA Contribution
NASA’s Kennedy Space Center is located on prime beachfront
property along the Atlantic coast of Florida on Cape Canaveral.
While beautiful, this region presents several challenges,
like temperamental coastal weather, lightning storms, and
salty, corrosive, sea breezes assaulting equipment and
the Center’s launch pads. The constant barrage of salty
water subjects facility structures to a type of weathering
called spalling, a common form of corrosion seen in porous
building materials such as brick, natural stone, tiles,
and concrete. In spalling, water carries dissolved salt
through the building material, where it then crystallizes
near the surface as the water evaporates. As the salt crystals
expand, this creates stresses which break away chips, or
spall, from the surface, causing unsightly and structural
damage.
The potential for corrosion heightens as concrete structures
age, because over time concrete loses its acidity, or pH.
When it starts out, poured concrete has a high pH value,
between 11 and 13, which helps to inhibit corrosion. Over
time, though, this value drops, and when the pH value dips
into the 8 to 9 range, there is potential for corrosion
of the steel reinforcing bars, or rebar, causing further
structural concerns.
In the mid-1990s, to protect the rebar, NASA developed
an electromigration technique that sends corrosion-inhibiting
ions into rebar to prevent rust, corrosion, and separation
from the surrounding concrete. An ounce of prevention is
worth a pound of cure, and with the help of Florida’s Technological
Research and Development Authority, an independent state
agency that partnered with Kennedy on technology transfer
initiatives, the Center began working with Surtreat
Holding LLC, of Pittsburgh, Pennsylvania, a company that had developed
a chemical option to fight structural corrosion in 1997.
Surtreat’s method was to apply its anti-corrosive solution
product, TPS-II, to the surface of a corroding concrete
slab, where it would then seep through to the rebar, coating
it and preventing further corrosion.
Combining Surtreat’s TPS-II with electromigration fit well
in the Kennedy dual-use program, part of NASA’s technology
transfer and commercialization effort. The cooperative
effort involved Surtreat providing NASA with the corrosion-inhibiting
chemical and concrete test slabs, along with technical
support as needed. Kennedy provided testing specifications
and procedures, then prepared the concrete with the Surtreat
chemical and carried out an environmental evaluation of
the treatment. Kennedy’s materials scientists reviewed
the applicability of the chemical treatment to the electromigration
process and determined that it was an effective and environmentally
friendly match, suitable for use at the NASA facility.
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The
Surtreat coating is environmentally friendly and
lasts 10 years or more, reducing maintenance costs
over the lifetime of the structure. |
Ten years later, NASA is still using this combined approach
to fight concrete corrosion, and it has also developed
a new technology that it believes will further advance
these efforts. The technology is a liquid galvanic coating,
applied to the outer surface of reinforced concrete, to
protect the embedded rebar from corrosion. The coating
contains one of several types of metallic particles—magnesium,
zinc, or indium. An electrical current established between
metallic particles in the applied coating and the surface
of the steel rebar produces cathodic protection of the
rebar. The current forces a flow of electrons from the
coating (anode) to the rebar along a separate metallic
connection. This surplus of electrons at the rebar (cathode)
prevents the loss of metal ions that would normally occur
as part of the natural corrosion process. The technology,
made of inexpensive, commercially available ingredients,
can be applied to the outside surface of reinforced concrete
(most rebar corrosion prevention must be applied directly
to the rebar) and with a conventional brush or spray, eliminating
the need for expensive, specialized labor.
This new technology is currently in use at Kennedy, but
NASA also saw the immediate benefits that could be gained
by transferring this technology to the private sector,
where decay and corrosion of concrete structures costs
billions of dollars per year.
Partnership
Ten years after its initial partnership, Surtreat has partnered
with NASA again by licensing the new liquid galvanic coating
technology and has already put it to use. Its first test,
in early 2007, was completed at the U.S. Army Naha Port,
in Okinawa, Japan, a coastal facility built during the
Korean War and subject to much of the same environmental
stressors as those found at Kennedy.
Product Outcome
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Surtreat uses topically
applied, chemically reactive, migrating formulations
unique to each project. |
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This
parking structure was suffering from water and
deicing salt infiltration, causing a number of
corrosion-related problems throughout the structure.
The Surtreat chemicals migrated over 2 inches below
the surface, halting corrosion. |
The NASA-developed coating may be used to prevent corrosion
of steel in concrete in several applications, including
highway and bridge infrastructures, piers and docks, concrete
balconies and ceilings, parking garages, cooling towers,
and pipelines, to name just a few.
Surtreat is the ideal partner to bring this technology
to the public, as the company has a proven record of providing
full-service, innovative, and technical solutions for the
restoration and prevention of deterioration and corrosion
in steel-reinforced concrete structures. Their Total Performance
System provides diagnostic testing and site analysis to
identify the scope of problems for each project, manufactures
and prescribes site-specific solutions, controls material
application, and verifies performance through follow-up
testing and analysis.
The coating lasts 10 years or more, reducing maintenance
costs over the lifetime of the structure; and testing has
proven that the treatment yields reductions in rebar corrosion
potential, water penetration, chemical reactivity, and
water-soluble chloride, while generating increases in hardness,
flexural strength, and pH levels. The treatment also provides
resistance to chloride penetration and problems associated
with freezing and thawing of the porous structures.
Surtreat treatments are environmentally friendly, and the
company focuses on preventing and minimizing adverse environmental
impacts by identifying and controlling potential environmental
risks in advance. The solutions used are water-soluble
and environmentally safe, and in testing have shown no
effect on the turbidity, pH, or dissolved oxygen content
levels in water. Surtreat’s formulations bond inorganic
compounds to structures, where they become part of the
steel and concrete matrix indefinitely. It leaves no residues,
coatings, or materials that could potentially harm humans,
animals, fish, or
the environment.
Total Performance System™ is a trademark of Surtreat
International.
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