Corrosion Resistant Alloy Steel Rebar

High-quality Fe 500CRS and Fe 550CRS grades for durable construction and enhanced longevity in structures.

Maintaining Strength, Ductility, and Toughness over Long Service Life

AISCO 500CRS and AISCO 550CRS Corrosion-Resistant Alloy TMT Deformed Steel Rebars

Corrosion-Resistant Alloy (CRA) TMT deformed rebars are specially engineered reinforcement steels designed to withstand aggressive environments where conventional rebars are prone to rust and deterioration. By combining low carbon content, thermo-mechanical treatment, and special corrosion-resistant alloying elements, these rebars offer superior durability, ductility, and structural safety.

Standards Compliance

Indian Standards: IS 1786:2008 (High strength deformed steel bars for concrete reinforcement).
Seismic Detailing: IS 13920:2016 (Ductile detailing of RC structures subjected to seismic forces).
International Standards:
- ASTM A615/A615M (Grade 80) – USA.
- DIN 488 (BST 500 M) – Germany/Europe.
- BS 4449:1997 (GR 460 B) – UK.

Chemical Composition (Typical Range)

Carbon (C): 0.15 - 0.27% (for ductility & weldability).
Manganese (Mn): 0.80 – 1.60% (strength & toughness).
Chromium (Cr): 0.20 – 0.60% (corrosion resistance).
Copper (Cu): 0.20 – 0.35% (chloride-induced corrosion resistance).
Phosphorus (P) & Sulphur (S): ≤ 0.04% (controlled for improved toughness).

Metallurgical Features

Thermo-Mechanical Treatment (TMT):
- Quenching + self-tempering → Hard martensitic surface + ductile ferrite-pearlite core.
Alloy Protection:
- Chromium and Copper improve resistance against chloride, carbonation, and industrial pollution.
Low Carbon Design:
- Ensures toughness, ductility, and superior weldability.

Mechanical Properties

Yield Strength: 500 – 600 MPa (Fe 500/Fe 550 grades).
Ultimate Tensile Strength (UTS): ≥ 1.08 × Yield Strength.
Elongation (Uniform): ≥ 14.5% (as per IS 13920:2016).
Fatigue Resistance: Excellent under cyclic loading.

Key Advantages

✅ Corrosion Resistance – Enhanced service life in coastal, marine, and industrial environments.
✅ Seismic Safety – High ductility & elongation ensures energy absorption during earthquakes.
✅ Low Maintenance – Reduces lifecycle cost of structures.
✅ Weldable & Bendable – No preheating required during fabrication.
✅ High Bond Strength – Deformed ribs ensure superior grip with concrete.

Applications

Coastal and marine structures (ports, jetties, bridges).
Industrial plants (chemical, fertilizer, power).
Urban infrastructure (flyovers, high-rise buildings, metros).
Structures in chloride & sulphate-rich soils.

AISCO 500CRS and AISCO 550 Corrosion-Resistant Alloy TMT Rebars combine the strength and ductility of low-carbon TMT rebars with special alloying for corrosion resistance, ensuring longer service life, reduced maintenance costs, and superior safety in aggressive environments.

Corrosion-Resistant Alloy Steel Deformed Bars for Concrete Reinforcement

Code: HSN 72142090, NIC 24105

Indian Standards: IS 1786:2008 (Grade Fe 550) = American Standards: ASTM A706/A706M (Grade 80) = Euro Standards DIN 488 (BST 500 M) and = British Standards: BS4449:1997 (GR 460 B)

Benefits of Corrosion-Resistant Alloy (CRA) elements in steel rebars used for construction:

✅ 1. Significantly Higher Corrosion Resistance

Alloying elements such as Chromium (Cr), Copper (Cu), Nickel (Ni), Molybdenum (Mo) form stable oxide layers on the steel surface.

These protect the rebar from chloride-induced corrosion, especially in:

Coastal areas
High groundwater salt concentration (>300 ppm)
Water treatment plants
Bridges, flyovers & marine structures

✅ 2. Longer Structural Life

Corrosion-resistant rebars prolong the service life of concrete structures by preventing:

Rust expansion
Cracking of concrete
Spalling (chunks of concrete breaking off)

This reduces the need for frequent repairs over the structure’s lifespan.

✅ 3. Lower Life-Cycle Cost

Even though CRA rebars may cost more upfront, they offer:

Reduced maintenance
Extended durability
Fewer repairs

Overall, the life-cycle cost becomes much lower for long-term infrastructure.

✅ 4. Improved Bond Strength With Concrete

Alloy elements help maintain:

Rib integrity
Surface condition
No rust-induced weakening of bond

Meaning the rebar maintains better load transfer with concrete for decades.

✅ 5. Better Performance Under Harsh Conditions

CRA rebars perform well in:

Marine and coastal environments
Industrial areas with chemical exposure
Sewage & desalination plants
High humidity zones

They resist pitting, chloride penetration, and stress corrosion cracking.

✅ 6. Enhanced Strength & Toughness

Some alloying elements improve mechanical properties:

Cr, Mo → Higher strength & hardenability
Ni → Better toughness at low temperatures
Cu → Increases corrosion resistance without affecting ductility

Thus, the rebar remains strong and ductile even in aggressive environments.

✅ 7. Protects Against Microstructural Deterioration

Corrosion-resistant alloys prevent:

Loss of cross-sectional area
Brittleness due to rust buildup
Weakening of microstructure over time

This ensures greater structural reliability.

Corrosion-resistant alloy elements make steel rebars more durable, reliable, and cost-effective—especially for structures exposed to saltwater, chemicals, or moisture.

Comparison Table (Normal TMT vs. Corrosion-Resistant TMT)

Application of CRR / Low-Alloy Corrosion-Resistant TMT Bars in High-Rise Building

Basements of high-rise buildings are continuously exposed to moisture, groundwater chlorides/sulphates, and low-oxygen environments, making them highly corrosion-prone.

🔶 Why CRR Rebars are Used in Basements

High Groundwater Chlorides (>300 ppm)

Cu–Cr–Ni–Mo alloying significantly slows chloride penetration and reduces pitting corrosion.

Constant Dampness / Water Seepage

Basements remain wet or humid, causing rapid rusting in normal rebars.
Alloy rebars maintain passivation even under intermittent wet–dry cycles.

Protection Against Sulphates & Chemical Impurities

Urban groundwater often contains aggressive ions. Mo and Cr enhance chemical resistance.

Prevents Concrete Spalling in Underground Areas

Corrosion causes cracking and detachment of covering concrete.
CRR rebars reduce rust expansion, thus improving long-term durability.

🔶 Typical Basement Applications

Raft foundation
Pile & pile caps
Shear walls
Retaining walls
Lift wells and core walls
Underground parking structures
Water sumps, STP/UGT rooms

🔶 Key Benefit for High-Rise Towers

High-rise buildings demand 100+ year service life. CRR bars reduce long-term structural maintenance and prevent early deterioration of foundation systems.

Application of CRR / Low-Alloy TMT Bars in Air-Polluted Urban Areas

Air pollution accelerates corrosion even in above-ground structures—especially in metro cities with high SO₂, NOₓ, CO₂ and particulate contaminants.

🔶 Why CRR Rebars Improve Durability in Polluted Cities

Protection Against Carbonation

Polluted air increases CO₂ concentration → faster carbonation → reduced concrete alkalinity.
Alloying elements help keep the steel surface passivated even if pH drops.

Resistance to Acidic Rain

SO₂ & NOₓ emissions cause acid rain which increases chloride mobility in concrete.
Cr and Mo greatly improve resistance to such acidic environments.

Reduced Corrosion in High-Humidity Cities

Coastal metros (Mumbai, Chennai, Kolkata) and industrial zones have moist, contaminated air.

Copper alloying decreases uniform corrosion and atmospheric corrosion rate.

Better Performance in Areas Near Traffic Corridors

Dense traffic emissions contain chlorides and sulphur compounds.
Ni and Cr improve film stability on steel, slowing the corrosion attack.

🔶 Application Zones in Urban Buildings

Podiums & parking decks
Lower floors and external beams/columns
Boundary walls, podium slabs
Utility areas exposed to pollution
Metro rail stations, malls, commercial towers

Benefits of CRR / Low-Alloy Corrosion-Resistant TMT Bars Compared to Carbon Steel Rebar

1. Significantly Higher Corrosion Resistance

CRR / Low-Alloy Rebar

Alloy elements (Cu, Cr, Ni, Mo) form a stable passive film on steel surface.
Slows rust formation, even in chloride, sulphate, and acidic environments.
Reduces corrosion rate by 40–70% compared to carbon-only steel.

Carbon Steel Rebar