What Is GI Sheet? (Galvanized Iron Sheet)
GI sheets are low-carbon steel sheets coated with zinc for corrosion protection. Available in both plain and corrugated forms, they're produced through hot-dip galvanizing (HDG) or electro-galvanizing (EG) processes, offering varying levels of durability and cost-effectiveness.
Thickness & Gauge Chart
Our Galvanized sheets are available in thicknesses ranging from 0.2mm to 4.0mm, with the most popular range being 0.2mm to 1.5mm for most construction and industrial applications.
| Gauge | Millimeters (mm) | Inches |
|---|---|---|
| 30 | 0.30 | 0.0118 |
| 28 | 0.40 | 0.0157 |
| 26 | 0.50 | 0.0197 |
| 24 | 0.60 | 0.0236 |
| 22 | 0.80 | 0.0315 |
| 20 | 1.00 | 0.0394 |
| 18 | 1.20 | 0.0472 |
| 16 | 1.50 | 0.0591 |
Recommended Thickness for Common Applications
- Roofing: 0.4mm to 0.7mm (26-24 gauge) for residential, 0.7mm+ for industrial
- Wall Cladding: 0.4mm to 0.6mm (26-24 gauge) for optimal balance of strength and weight
- Appliance Back Panels: 0.3mm to 0.5mm (30-26 gauge) for lightweight durability
- Industrial Equipment: 1.0mm to 2.0mm (20-14 gauge) for structural components
Note: Total weight = steel base weight + zinc coating weight. For corrugated sheets, width calculations use "developed width" which accounts for the corrugation profile.
GI Sheet Weight Calculator
Types of GI Sheet — Hot-Dip vs Electro-Galvanized
Hot-Dip Galvanized (HDG)
Steel is immersed in molten zinc (typically 450°C) to form a thick, durable coating with excellent corrosion resistance. The zinc-iron alloy layers provide superior protection, especially in harsh environments.
- Coating: 40-275 g/m² (Z40-Z275)
- Lifespan: 20-50+ years depending on environment
- Cost: Higher initial cost but lower lifetime cost
Electro-Galvanized (EG)
Zinc is electroplated onto steel in a thinner, more uniform coating. Provides good corrosion resistance for indoor applications and serves as an excellent base for painting (PPGI).
- Coating: 10-50 g/m² (E10-E50)
- Lifespan: 5-15 years in mild environments
- Cost: Lower initial cost but may require maintenance
| Feature | Hot-Dip Galvanized | Electro-Galvanized |
|---|---|---|
| Appearance | Spangled surface (visible zinc crystals) | Smooth, uniform matte finish |
| Typical Coating | Z40-Z275 g/m² (thicker) | E10-E50 g/m² (thinner) |
| Corrosion Resistance | Excellent (outdoor/harsh environments) | Good (indoor/mild environments) |
| Cost | Higher initial cost | Lower initial cost |
| Common Uses | Roofing, construction, infrastructure | Appliances, automotive, painted products |
Plain GI Sheets
- Flat sheets without corrugations
- Thickness: 0.2mm to 4.0mm
- Width: 600mm to 1500mm (standard)
- Length: Custom cut lengths available
- Ideal for fabrication, appliances, and painted applications
Corrugated GI Sheets
- Sheets with regular wave patterns for added strength
- Thickness: 0.3mm to 1.2mm (most common)
- Cover Width: 600mm to 1200mm
- Length: Typically 1.8m to 12m
- Common profiles: Trapezoidal, Sinusoidal, Tile, Custom
Applications of GI Sheets
Building & Construction
Roofing, wall cladding, rainwater systems, and roller doors benefit from GI's durability and weather resistance.
Automotive & Transport
Used in vehicle bodies, trailers, and components where corrosion resistance is critical.
Home Appliances
Back panels, housings, and internal components for washing machines, refrigerators, and more.
Furniture & Fabrication
Office furniture, shelving, cabinets, and general metal fabrication projects.
Advantages of GI Sheets
Corrosion Resistance
Zinc coating provides sacrificial protection, significantly extending the lifespan of steel components.
Cost Efficiency
More affordable than stainless steel or GL (Galvalume) while offering excellent protection.
Paintability
Excellent base for painted products (PPGI) with proper surface preparation and primers.
Wide Availability
Readily available in various thicknesses, sizes, and coating weights worldwide.
Manufacturing Process
Pretreatment
Steel is cleaned through alkaline degreasing, acid pickling (HCl or H₂SO₄), and rinsing to remove oils, rust, and mill scale.
Drying
After rinsing, the steel is dried to prevent steam explosions when entering the zinc bath.
Galvanizing
For HDG: Immersed in molten zinc at ~450°C. For EG: Electroplated in zinc electrolyte solution.
Cooling
Controlled cooling to room temperature to stabilize the zinc-iron alloy layers.
Leveling
Skin passing or tension leveling to improve flatness and surface quality.
Inspection
Quality checks for coating thickness, adhesion, surface defects, and dimensional accuracy.
Slitting/Cut-to-Length
Coils are slit to required widths or cut into sheets of specified lengths.
Packaging
Protected with VCI paper, edge protectors, and strapped to wooden pallets for safe transport.
Specifications & Standards
| Grades | Standards | Coating | Surface | Passivation/Oiling | Size Range | Tolerances |
|---|---|---|---|---|---|---|
| DX51D+Z DX52D+Z DX53D+Z |
EN 10346 ASTM A653 JIS G3302 |
Z40-Z275 g/m² (HDG) E10-E50 g/m² (EG) |
Regular spangle Minimized spangle Zero spangle |
Chromate Chromate-free Oiled/Non-oiled |
Thickness: 0.2-4.0mm Width: 600-1500mm Length: Custom |
±0.03mm (thickness) ±2mm (width) ±5mm (length) |
| SGCC SGCH |
JIS G3302 GB/T 2518 |
Z12-Z275 g/m² (HDG) |
Regular spangle Zero spangle |
Chromate Oiled/Non-oiled |
Thickness: 0.3-2.0mm Width: 600-1250mm |
±0.04mm (thickness) ±3mm (width) |
Pricing & Minimum Order Quantity
GI sheet pricing depends on multiple factors including market conditions, order specifications, and logistics. Below are the key variables that affect your quote:
- Base Metal: Steel grade and quality (commercial vs structural)
- Coating Weight: Higher zinc coating (Z275) costs more than standard (Z120)
- Dimensions: Thinner gauges and custom widths may have price premiums
- Surface Treatment: Special spangle control or passivation adds cost
- Order Quantity: Larger volumes typically qualify for better pricing
- Logistics: Delivery location and shipping method affect final cost
Frequently Asked Questions
Ready to Start Your GI Sheet Project?
Whether you need standard galvanized sheets or custom specifications, our team is ready to assist. Download our gauge chart for quick reference, request free samples to evaluate quality, or contact our sales team for personalized advice.