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PRESENTATION ON

“BOND STRENGTH INCREASE&

CORROSION RESISTANCE OF STEEL REBARS”

By Use of

NANOPRETREAT ™

- Rust Resistant Compound and Bond Strength Increaser…

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Introduction Corrosion of Steel is a matter of global

concern

Rusting of steel is noticed in every type of construction – structures, RCC, factory sheds, bridges etc

Protective steel coatings now available have a few limitations

It is noted that all buildings and MS structures in coastal areas need repair after 7-8 years of construction!

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THE PROCESS OF CORROSION

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THE CORROSION CYCLE

Rust expanding on uncoatedsteel surface

Cracking near concrete-steel interface

More cracking of concrete with high pressure by corrosion

product

Concrete separates from steel

Eventually causing spalling

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NANOPRETREAT- An Anti-Rust Compound

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The PRODUCT Water-based patented

formulation Inorganic in nature Eco-Friendly

(Complies with ROHS standards)

Non-inflammable Coated structures

stable even at -196o to

+400o C

0.5 to 2 micron coat thickness , so practically no change in gauge of substrate

Coated rebars and MS structures show nearly 100% bond strength increase

Coated steel can be painted, powder-coated & electroplated very well

Easy to use - paint, spray or dip methods

Excellent Corrosion Resistance properties

Non-toxic

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PROTECTS STEEL :

nanopretreat prevents corrosion in 3 ways:-

Stops Formation of free Fe 2+ & Fe 3+ ions by formation of insoluble micro crystals all over the surface.

  Forms a Fine and Tenacious coat on the

Surface of Steel. There by stopping Ingress of Water.

  Fights Against Atmospheric Pollution.  

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BASIC DATA: Viscosity = 13 seconds @30º Celsius

Sp. Gravity = 1.12 gm/cc

Ph. Value: 3.5 - 4

Conforms to ROHS Standard (Reduction of Hazardous Substance - DIRECTIVE 2002/95/EC)

nanopretreat does not contain Lead, hexavalent Chromium, Mercury, Cadmium, polybrominated Biphenyls & diphenylethers.

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When nanopretreat ™ is applied on a steel surface there is a formation of millions of nuclei on activated  surface. And coat is "generated"

through the surface in due course and becomes inseparable part which is stable through

temperature range from +400º to -196º Celsius.

What happens on application of nanopretreat?

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Reasons for increasing “Bonding Strength” of the coating

construction rebars with concrete

Application of nanopretreat forms DENSE FOREST of micro-crystals on TMT rebar surface.

This dense forest acts as ‘Activator’ for crystal formation.

the coating also acts as a cement crystallisation accelerator around the coated TMT Rebar.

This process helps hydrated cement crystal to form ‘crystal-crystal’ contact instead of ‘metal – crystal’ contact. Homogenous attraction between two different crystals is always greater.

Nanocoat prevents rusting of rebars even in cases of fine cracks that are commonly found in RCC .

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Importance of Bonding of Rebar With Concrete

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In case of RCC beam ..the compression load

is taken by concrete and tensile load is taken by steel when beam is loaded .These compression stresses in concrete and tensile stresses in steel act as a balancing couple to counteract the applied load but this happens only when there is perfect grip between steel and concrete. Hence bond strength is important.

If such bonding strength between the concrete and steel is not achieved, it happens just as a steel rod is pierced into an over sized bore of concrete. which ultimately decreases power and strength of beam and consequently collapse.

BEAM

LOAD

STEEL REINFORCEMEN

T

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Bonding & Role of nanopretreat

When the regular rebars come in direct contact with moisture and water, that results in direct corrosion on the surface of steel rebar which separates the rebar and the bonding cement slurry ,that ultimately results into bond or grip stresses. So "stress transfer phenomenon" cannot take place. Hence the beam looses its strength and becomes demolished even if sufficient reinforcement is provided .The nanopretreat ™ prevents all such recurrences only because nanopretreat prevents rusting process and keeps bond stress intact.

Present coatings available in the market are in the form of thin layer of epoxy and polymers which cause a loose coat between steel and concrete (construction wants bond of concrete with steel and not with other lose film) ,over which during loading condition, rebar gets separated from concrete hence there is decrease in bond stresses but the nanopretreat ™ applied on steel rebar provides rust resistance as wel as good bond stress as steel guard acts as a part and parcel of steel.

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HEAT RESISTANT: Image of athe

coatinged steel sample - magnified 1000 times. The white particles are the densely formed crystals on the steel surface on applying Steel Guard -the coating.

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The steel sample shown was heated to 400

o C and

hammered. The sample was chiseled to remove coating from the surface of steel and observed under the microscope. Crystals visible show efficacy ofthe coating

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ECO-FRIENDLY

In view of the present Environmental Concern all over the world nanopretreat is an appropriate application as it does not contain any environmental hazardous substance of any kind.

'Steel Guard nanocoat' 20

Nanoptrtreat Performance Study Report

DFT :0.2 - 2 MICRONS

IMPACT TEST :250 Kg Passed.

BEND TEST : 170 Kg Passed.

SCRATCH RESISTANT : 5 Kg Passed.

SALT SPARY : 120 Hours passed.

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To conclude….

the crystal arrangement on the TMT rebar after coating is so close and interwoven that water and gases cannot penetrate through the coat thus preventing rust.

In addition, it helps in developing massive and tenacious bond with concrete, improving strength and life of the construction

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