GI Steel Coil - Galvanized Iron Coil for Construction
GI (Galvanized Iron) steel coil — the most widely traded zinc-coated steel product globally. Hot-dip galvanized with Z40-Z275 coating for reliable corrosion protection. Versatile material for corrugated roofing, roll-formed purlins, HVAC ductwork, appliance panels, automotive parts, furniture frames and general sheet metal fabrication. Competitive FOB/CIF/CFR pricing with flexible container loading.
| Product | Galvanized Steel Coil / GI Coil |
| Zinc Coating | Z40 – Z275 (40-275 g/m²) |
| Thickness | 0.12 – 4.0 mm |
| Width | 600 – 1500 mm |
| Spangle | Regular / Mini / Zero Spangle |
| Standard | ASTM A653, EN 10346, JIS G3302, GB/T 2518 |
| Surface | Chromate / Oiled / Chromate-free / Dry |
| Steel Grade | DX51D+Z, DX52D+Z, SGCC, S250GD+Z, S350GD+Z |
| Coil ID | 508 mm / 610 mm |
| Coil Weight | 3 – 12 MT (customizable) |
Galvanized Iron — The Most Versatile Zinc-Coated Steel for Every Application
What Is GI Steel Coil?
GI steel coil (Galvanized Iron coil) is the industry term for hot-dip galvanized steel coil used across construction, manufacturing and fabrication industries worldwide. The term "GI" is universally recognized in international steel trade and is the most commonly searched product name by steel buyers globally.
GI coil combines the structural strength of cold rolled steel with the corrosion protection of hot-dip zinc coating, creating a material that is durable, cost-effective and easy to process. It can be corrugated for roofing, roll-formed into purlins and channels, stamped into appliance panels, or fabricated into ductwork and enclosures.
As one of the highest-volume coated steel products in global trade, GI coil benefits from mature production technology, competitive pricing and broad specification availability.
Technical Specifications
Available in various thicknesses, widths and coating options. Common standards include ASTM, JIS, EN and GB/T. Different industries may choose different specifications depending on service life, corrosion requirements and fabrication method.
| Product | Galvanized Steel Coil / GI Coil |
|---|---|
| Zinc Coating | Z40 – Z275 (40-275 g/m²) |
| Thickness | 0.12 – 4.0 mm |
| Width | 600 – 1500 mm |
| Spangle | Regular / Mini / Zero Spangle |
| Standard | ASTM A653, EN 10346, JIS G3302, GB/T 2518 |
| Surface | Chromate / Oiled / Chromate-free / Dry |
| Steel Grade | DX51D+Z, DX52D+Z, SGCC, S250GD+Z, S350GD+Z |
| Coil ID | 508 mm / 610 mm |
| Coil Weight | 3 – 12 MT (customizable) |
Contact our technical team for specific grade and coating recommendations based on your application environment and processing requirements.
Applications
Thanks to its corrosion resistance, processing flexibility and cost-performance ratio, this product is widely used across construction, manufacturing and industrial sectors.
🏗️ Construction & Roofing
Roofing sheets, wall cladding, purlins, structural decking, and light gauge framing for residential and commercial buildings.
🏠 Home Appliance
Air conditioner housings, water heater shells, washing machine panels. Requires smooth surface finish with controlled zinc coating.
🔧 General Fabrication
Ductwork, cable trays, guard rails, storage racks, shelving, signage, enclosures, and general sheet metal fabrication.
🚗 Automotive & Transport
Floor pans, wheel housings, chassis components, fuel tanks, trailer bodies, and container panels.
Galvanized (GI) vs Galvalume (GL)
Many buyers compare GI and GL before purchasing. Both are coated steel but their coating composition, performance and best applications differ significantly.
Galvanized Steel Coil (GI)
Known for excellent cut-edge protection, superior formability and cost-effectiveness across a wide range of applications.
Galvalume Steel Coil (GL)
Offers better flat-panel atmospheric corrosion resistance and heat reflectivity, preferred for premium roofing.
| Comparison Item | Galvanized Steel Coil (GI) | Galvalume Steel Coil (GL) |
|---|---|---|
| Coating | Pure zinc (Z40-Z600) | 55% Al + 43.4% Zn + 1.6% Si (AZ) |
| Corrosion | Good; zinc sacrificial protection | Better flat-panel atmospheric resistance |
| Cut-Edge Protection | Excellent — zinc migrates to cut edges | Lower — aluminum does not migrate easily |
| Heat Resistance | Up to 230°C | Up to 315°C |
| Formability | Excellent for bending, drawing, welding | Good for roofing/cladding; less for deep drawing |
| Surface | Traditional zinc spangle | Bright metallic silver |
| Cost | More economical | 5-15% higher |
| Best For | Construction, ducts, fabrication, tubes | Roofing, solar, heat-exposed, PPGL substrate |
Main Advantages
This product combines durability, processing flexibility and cost-effectiveness for a wide range of applications.
- Excellent sacrificial protection — Zinc migrates to protect cut edges and scratches — self-healing corrosion protection
- Superior formability — Excellent for bending, stamping, deep drawing and welding — more versatile than GL
- Cost-effective — Lower cost per ton than Galvalume while providing reliable outdoor corrosion protection
- Wide coating range — Z40 to Z600 g/m² — from light indoor use to extreme marine environments
- Global standard — ASTM A653, EN 10346, JIS G3302 — accepted worldwide with broad market availability
- Versatile applications — Roofing, appliances, automotive, ductwork, furniture, pipes — the most widely used coated steel
Why Choose SunSea Steel?
Choosing the right supplier means more than buying steel. It also means stable quality, export experience, efficient communication and reliable delivery support.
Stable Product Quality
Uniform coating mass, reliable base steel quality and stable surface condition help ensure consistent performance in export orders.
Custom Specification Support
Thickness, width, coating mass, steel grade, surface treatment and packing can be customized according to project requirements.
Professional Export Service
Support for packing, loading, shipping documents and delivery coordination helps customers manage international orders more efficiently.
Fast Response and Quotation
Buyers can quickly get specification confirmation, technical support and quotation feedback for distribution, project procurement and manufacturing use.
Factory Strength and Production Capability
Our production system focuses on coating uniformity, thickness control, clean surface quality and export-standard packing. From raw material selection to final inspection and shipment preparation, every stage is managed to improve product consistency and reduce customer risk.
For buyers, factory capability means more than output volume. It also means communication efficiency, documentation support, shipment coordination and the ability to provide stable product supply over time.
- Stable production planning for export orders
- Support for customized sizes and coating requirements
- Professional handling of packing and shipment preparation
- Inspection and tolerance control before delivery
Quality Control and Inspection
Product quality is one of the key concerns for overseas buyers. Quality should be controlled not only by final visual inspection, but also by process stability, specification verification and export packing inspection.
Surface and Dimension Inspection
Surface condition, width, edge quality and dimensional tolerance are checked before delivery.
Pre-Shipment Quality Control
Packing condition, identification, quantity confirmation and shipment readiness are reviewed before export.
Thickness and Width Verification
Thickness tolerance, width and coil dimensions are checked to ensure the material is suitable for roll forming, profiling and project processing needs.
Coating and Surface Checking
Coating weight requirements and surface appearance are reviewed before packing and shipment.
Packing Inspection
Export packing is examined to ensure moisture-proof protection, steel straps and edge protectors are correctly applied.
Shipment Preparation
Quantity, identification, loading readiness and related documentation are confirmed before export delivery.
Standard Export Seaworthy Packaging
For steel export, correct packaging is extremely important. Even high-quality product can suffer surface damage, moisture exposure or edge deformation if packing is not suitable for sea shipment.
- Inner Moisture Protection: Waterproof kraft paper and plastic film help reduce moisture contact.
- Outer Steel Cover: Additional outer steel sheet gives stronger protection during handling.
- Edge Protection: Edge protectors reduce impact damage during lifting and stacking.
- Steel Strapping: Radial and circumferential straps help keep the coil stable.
- Pallet Support: Wooden or steel pallets can be used according to shipping requirements.
Shipping, Loading and Delivery Solutions
Shipping method depends on order quantity, coil size and destination requirements. Container shipment and break bulk vessel are the most common methods for steel coil export.
Container Shipment
Suitable for regular export orders. Coils packed on pallets and loaded into containers for safe sea transport. FOB/CIF/CFR available.
Break Bulk Vessel Shipment
For large volume orders or oversized coils. Professional lifting, lashing and port handling for bulk steel procurement.
Small to medium orders: container shipment is preferred. Large-scale or project orders: break bulk vessel may be more efficient.
Frequently Asked Questions
What is galvanized steel coil?
Galvanized steel coil (GI) is cold-rolled or hot-rolled steel coated with a zinc layer through the hot-dip galvanizing process. The zinc coating protects the base steel from corrosion through both barrier protection and galvanic (sacrificial) protection.
What is the difference between GI coil and GI strip?
GI coil is the full-width product (600-1500mm) from the galvanizing line. GI strip is slit from GI coil to narrower widths (30-600mm) for specific applications like pipe making and roll-formed profiles.
How long does galvanized steel last?
Service life depends on coating weight and environment: Z80 (urban) 15-20 years, Z180 (industrial) 20-30 years, Z275 (marine/severe) 30-50 years.
What does Z275 mean?
Z275 means 275 g/m² total zinc coating on both sides (approximately 137.5 g/m² per side, about 20μm per side). This is a heavy coating suitable for outdoor and corrosive environments.
Can you provide customized specifications?
Yes. Thickness, width, coating weight, steel grade, coil weight, surface treatment and export packaging can all be customized.
What is the MOQ?
25 MT per specification for full containers (20GP). Mixed containers: 5 MT/spec minimum with 25 MT total.
How do you ensure export quality?
We focus on thickness control, coating verification, surface inspection, packing inspection and shipment preparation to help ensure product quality before export.
Looking for a Reliable Galvanized Steel Coil Supplier?
Contact us for the latest GI coil pricing, specifications, coating options, export packing and shipping solutions. Factory direct supply for construction, appliance and industrial applications worldwide.
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