Zinc – High Grade (HG) is a commercially refined zinc metal with a minimum purity of 99.95% Zn. It is produced through electrolytic or advanced pyrometallurgical refining and cast into ingots, bars, slabs, or pigs for industrial use.
HG zinc is widely used where high purity is required but ultra-low impurity control is not critical, making it a cost-effective alternative to Special High Grade zinc in many applications.
Metallurgical & Strengthening Behavior
HG zinc exhibits limited ductility at room temperature
Becomes ductile at 100–150°C
Cannot be heat-treated or precipitation hardened
Strengthening is achieved only through:
Alloying (Al, Cu, Mg)
Grain refinement during solidification
Impurities like Pb and Fe can slightly affect:
Fluidity
Surface finish
Corrosion behavior
Key Characteristics of Zinc – High Grade (HG)
1. High Purity with Economic Advantage
Suitable for most industrial uses
Lower cost than SHG zinc
2. Good Corrosion Resistance
Forms a stable oxide/carbonate layer
Effective sacrificial protection
3. Excellent Castability
Good fluidity in molten state
Compatible with batch and continuous melting
4. Reliable Alloying Base
Widely used for brass, galvanizing zinc, and zinc compounds
Refining & Processing Properties
Produced via electrolytic refining
Lower refining cost compared to SHG zinc
Slightly higher oxidation losses during melting
Compatible with:
Hot-dip galvanizing
Zinc oxide production
Zinc alloy manufacturing
Available Forms
Zinc ingots (20–25 kg)
Jumbo ingots (500–1,000 kg)
Zinc bars
Zinc slabs
Zinc pigs
Applications of Zinc – High Grade (HG)
General galvanizing
Brass manufacturing
Zinc oxide production
Chemical salts and compounds
Batteries (non-critical grades)
Metallurgical additives
Difference Between Zinc – High Grade (HG) and Zinc – Special High Grade (SHG)
| Grade | Description |
|---|---|
| High Grade Zinc (HG) | Commercially refined zinc with high purity, used for general industrial purposes. |
| Special High Grade Zinc (SHG) | Ultra-high purity electrolytic zinc, produced under strict control for critical applications. |
Purity Level (Most Important Difference)
| Grade | Minimum Zinc Content |
|---|---|
| HG Zinc | ≥ 99.90% Zn |
| SHG Zinc | ≥ 99.995% Zn |
Refining & Production Method
| Aspect | HG Zinc | SHG Zinc |
|---|---|---|
| Refining process | Electrolytic / Pyrometallurgical | Electrolytic only |
| Impurity control | Moderate | Very strict |
| Batch consistency | Standard | Extremely consistent |
| LME registration | ❌ Not mandatory | ✅ Mandatory |
Key Performance Differences
HG Zinc
Slightly higher impurity-driven hardness
Greater dross formation
Acceptable for non-critical applications
More economical
SHG Zinc
Ultra-clean metallurgy
Better corrosion performance
Higher coating adhesion
Improved electrical and chemical behaviour.
Applications
High Grade (HG) Zinc – Typical Uses
General galvanizing
Construction hardware
Low-spec zinc alloys
Agricultural & utility components
Roofing sheets (basic grades)
Special High Grade (SHG) Zinc – Typical Uses
Automotive galvanizing
Continuous galvanizing lines (CGL)
Zinc die-casting alloy production (ZAMAK)
Battery-grade zinc
Chemical & pharmaceutical zinc compounds
Zinc oxide (high purity grades)
Export-grade zinc products
Cost Difference
| Factor | HG Zinc | SHG Zinc |
|---|---|---|
| Price | Lower | 5–15% higher |
| Yield loss | Higher | Lower |
| Long-term cost | Moderate | Lower due to less waste |
Standards & Certification
| Grade | Common Standards |
|---|---|
| HG Zinc | IS 209, ASTM B6 (High Grade) |
| SHG Zinc | ASTM B6 (SHG), ISO 752, EN 1179, LME |