GREEN PROTECTION
CORROSION
The construction chemicals industry now provide such
technologies and products to provide additional performance and endurance to
structure and hence reduce the impact of corrosion . India loses INR 2 trillion
(USD 40 billion) which is roughly about 4% of our national GDP every year due
to corrosion of infrastructure, industrial equipment and other vital
installations, according to last estimates from CII. Chemicals including
surface coatings, floorings, concrete admixtures, corrosion inhibitors, grouts
and sealants, repair mortars protect the surface from corrosion by restricting
the ingress of moisture and providing a 'sealed' structure.
Concrete spalling is usually caused by corrosion of
the steel reinforcement bar embedded in the concrete, but can be caused by
other ferrous elements either fully or partially embedded in the structure.
Corrosion is the cause of spalling and splitting in older concrete structures.
Corrosion is typically caused by carbonation (which lowers the pH in the
concrete) and chloride ions from salt-laden air combined with water, moisture
and oxygen which creates a corrosive environment.
The corrosion on rebar is due to the growth of ferrous
oxide scale (rust) on the rebar as shown in figure above which could lead to
cracking and spalling. The ferrous oxide scale can expand 5-10x in volume and
exerts enough force on the surrounding material that it splits the concrete.
This splitting is what we refer to as spalling.
PROTECTION
The construction chemical industries have developed
such chemicals which act as corrosion inhibitors. Apple Chemie has come with
one such product named as AC-COROGUARD. It’s a specially formulated corrosion
inhibitor solution to increase chloride threshold value, reducing corrosion
rate, thereby minimizing the corrosion & ensuring life of reinforcement
structure.AC-CORROGUARD, corrosion inhibitor, is mixed type of inhibitor
solution which retards anodic as well as cathodic reactions and forms an
impervious layer on metal surface. Economical compared to costly concrete.
Enhances strength & durability of concrete.
Application: Remove all loose rust / iron oxide
remanants if any on the rebar by using wire brush. The treatment shall be given
to reinforcement only after cutting and bending the same as per the bar bending
schedule. Make a slurry of cement by adding inhibitor solution to OPC in the
ratio of 0.5 to 0.6 : 1 (Inhibitor Solution : OPC Cement) Apply uniform coat of
slurry on surface of reinforcement, iron and steel by brushing or dipping. Keep
coated bars for drying on the drying platform. Apply second coat after 12 to 24
hrs interval and dry again.
Advantages
1) Inhibits
the corrosion and protects the rebars from corrosive environment.
2) It maintains high alkalinity around the
metal surface in concrete, therefore controls corrosion to carbonation.
3) It
increases the resistance of natural passivating film on the metal surface from
chloride attack.
4) It
creates thin protective film on metal surface
5) The
passivating film blocks the contact of
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