Galvanizing Zinc refers to high-purity zinc metal used as a protective coating on steel and iron to prevent corrosion. When applied through processes like hot-dip galvanizing, electro-galvanizing, or thermal spraying, the zinc forms a robust barrier that protects the base metal from rust and environmental damage.
Zinc protects steel in two ways:
1. Physical Barrier Protection
It creates a tough, adherent coating that stops moisture, oxygen, and chemicals from reaching the steel surface.
2. Cathodic (Sacrificial) Protection
Even if the coating is scratched, zinc will corrode first instead of the steel, ensuring long-term durability.
Galvanizing Zinc is widely used in construction, infrastructure, automotive, electrical, marine, and household applications.
Chemical Composition
Typical Galvanizing Zinc Composition
| Element | Typical Content |
|---|---|
| Zinc (Zn) | ≥ 99.95% |
| Aluminum (Al) | 0.005 – 0.20% |
| Nickel (Ni) | 0.04 – 0.06% (optional) |
| Bismuth (Bi) | 0.02 – 0.10% (lead-free fluidity agent) |
| Lead (Pb) | ≤ 0.005% (or zero in eco grades) |
| Iron (Fe) | ≤ 0.003% |
| Cadmium (Cd) | ≤ 0.003% |
Key Mechanical Properties
Galvanizing zinc is not used as a structural metal, but its mechanical behavior affects coating durability.
| Property | Typical Value |
|---|---|
| Tensile Strength | 100–150 MPa |
| Yield Strength | 30–50 MPa |
| Elongation | 10–30% |
| Hardness | ~30–40 HB |
| Modulus of Elasticity | ~108 GPa |
| Adhesion to Steel | Excellent (metallurgical bond) |
Mechanical Relevance
Zinc coating absorbs impact and abrasion
Acts as a ductile sacrificial layer
Coating remains intact during forming and bending of steel
Physical Properties
| Property | Value |
|---|---|
| Density | 7.13 g/cm³ |
| Melting Point | 419.5°C |
| Boiling Point | 907°C |
| Thermal Conductivity | ~116 W/m·K |
| Electrical Conductivity | ~28% IACS |
| Coefficient of Thermal Expansion | 30.2 µm/m·°C |
| Appearance | Bright silver (fresh), dull grey (aged) |
Strengthening & Metallurgical Behavior
Intermetallic Layer Formation
In hot-dip galvanizing, zinc reacts with iron to form intermetallic layers:
Gamma (Γ) – Fe₃Zn₁₀
Delta (δ) – FeZn₇
Zeta (ζ) – FeZn₁₃
Eta (η) – Pure zinc outer layer
These layers:
Create a true metallurgical bond
Provide superior adhesion compared to paint or plating
Control coating hardness and durability
Strengthening Mechanism
Galvanizing zinc:
Is not heat treatable
Relies on intermetallic phase formation for functional strength
Alloying additions control layer growth and surface finish
Key Characteristics
1. Sacrificial Corrosion Protection
Zinc corrodes preferentially to steel
Protects even when coating is scratched or damaged
Offers long-term protection in harsh environments
2. Self-Healing Behavior
Zinc corrosion products seal exposed areas
Prevents under-film corrosion
3. Excellent Coating Uniformity
Controlled fluidity ensures even thickness
Reduced dross and ash formation
4. Compatibility with Various Steels
Optimized for:
Mild steel
High-silicon steel
Automotive-grade steel
Refining & Processing Properties
Produced from electrolytic zinc (SHG)
Alloyed in controlled melting furnaces
Strict impurity monitoring (Pb, Cd, Fe)
Processing Behavior in Galvanizing
Low viscosity molten zinc
Stable bath chemistry
Minimal oxidation
Good wetting of steel surface
Bath Additive Roles
Aluminum – oxidation control & adhesion
Nickel – reduces excessive coating thickness on silicon steel
Bismuth/Lead – improves drainage and surface smoothness
Available Forms
SHG zinc ingots
Galvanizing-grade alloy ingots
Jumbo blocks
Zinc slabs
Zinc shot / pellets
Custom bath alloy formulations
Applications of Galvanizing Zinc
1. Construction & Infrastructure
Structural steel
Transmission towers
Bridges
Handrails and guardrails
2. Automotive & Transportation
Body panels
Chassis components
Fasteners
3. Energy & Utilities
Power transmission structures
Wind turbine towers
Solar mounting structures
4. Agriculture & Water
Fencing
Irrigation pipes
Water tanks
Advantages of Galvanizing Zinc
✔ Long-lasting corrosion protection (20–100+ years)
✔ Complete coverage including edges and interiors
✔ Sacrificial protection even after damage
✔ Low maintenance cost
✔ Fast coating process
✔ Fully recyclable
Limitations
❌ Not a load-bearing material
❌ Performance decreases above 200°C
❌ Coating thickness influenced by steel chemistry
❌ Requires controlled bath management
Why Choose Galvanizing Zinc?
Galvanizing zinc is selected when long-term steel protection, reliability, and cost efficiency are critical.
Industries choose galvanizing zinc because it:
Extends steel life multiple times
Reduces life-cycle maintenance cost
Performs in marine, industrial, and rural environments
Offers predictable, standardized performance
Meets ASTM, ISO, EN, and IS specifications
Galvanizing zinc is a purpose-engineered zinc grade optimized for coating steel through metallurgical bonding. Its high purity, controlled alloying, sacrificial corrosion behavior, and excellent processing characteristics make it the most effective and economical solution for long-term steel protection across infrastructure, automotive, energy, and industrial sectors.