Galvalume Steel (GL) vs. Galvanized Steel (GI)

In the field of metal corrosion protection, hot-dip galvanized steel (GI) and galvalume (GL) play an important role as metal raw materials for roofing/wall/partition processing, home appliance manufacturing, industrial production, etc., because of their excellent corrosion resistance and long service life in general indoor, marine, and chemical environments. So when should you choose galvanized products and when should you choose aluminized zinc products? Today we will look at the differences and similarities between galvanized and aluminized products from the point of view of performance, application and so on.

Galvanized Galvalume Steel Specification

Material	SGCC,S350GD+Z,S550GD+Z,DX51D,DX52D,DX53D, etc
Thickness	0.12mm-6mm
Width	The conventional width below 0.5mm is 1000mm, 1200mm, and above is 1000, 1250mm
coil weight	8-10 tons /customized
Tolerance	"+/-0.02 mm
Substrate Type	Hot rolled coil, Cold rolled coil
Surface structure	Zero spangles, Small spangles, Regular spangles, Big spangles
Zinc layer thickness	30g/㎡-275g/㎡ (Z275/G90)
Standard	AISI, ASTM, BS, GB, JIS
Implementation standards	GB/T2518 GB/T25052, EN10346, JIS G3302, ASTMA653
Certificates	SGS, ISO 9001,CE

Galvanized Galvalume Steel Parameter Comparison

Parameter	GL Galvalume Steel	GI Hot-Dip Galvanized Steel
Coating Composition	55% Al – 43.4% Zn – 1.6% Si	≥99% Pure Zinc
Coating Density	3.75 g/cm³	7.14 g/cm³
Standard Coating Amount	AZ100/AZ120/AZ150 (g/m²)	Z60/Z100/Z150/Z275 (g/m²)
Coating Characteristics	Aluminum barrier + Zinc cathodic protection dual mechanism	Single zinc phase, sacrificial anode protection
Thickness Tolerance	±0.03mm	±0.05mm

Galvanized Galvalume Steel International Standard

GL (Galvalume)	GI (Galvanized)
ASTM A792 (US)	ASTM A653 (US)
EN 10346 (EU)	EN 10346 (EU)
JIS G 3321 (JP)	JIS G 3302 (JP)
GB/T 14978 (CN)	GB/T 2518 (CN)

Galvanized Galvalume Steel Performances

Performance Indicator	GL350	GI S350GD
Salt Spray Corrosion Resistance (h)	1000-1500	480-720
Heat Resistance Limit (°C)	315 (continuous use)	200
Reflectivity (%)	75-85	40-50
Thermal Conductivity (W/m·K)	65	50
Cut Edge Corrosion Rate	0.3mm/year (C4 environment)	1.2mm/year

Galvanized Galvalume Steel Anti-corrosion Performance

Scenario	GL	GI
Salt Spray Test	1500h (red rust ≤ 5%)	720h (red rust ≤ 5%)
Cut Edge Corrosion	0.3mm/year (C4 environment)	Corrosion rate 1.2mm/year (C4 environment)
Industrial Atmosphere	Lifetime 25+ years (SO₂ environment)	Lifetime 10-15 years (SO₂ environment)
Cathodic Protection	Weak (aluminum barrier inhibits electrochemical action)	Strong (zinc continuously sacrifices)

Galvanized Galvalume Steel Processing and Manufacturing

Manufacturing process

Process	GI Process	GL Process
Bath Composition	Pure Zinc Bath (Zn ≥ 99%)	Aluminum-Zinc-Silicon Alloy Bath (55% Al-43.4% Zn-1.6% Si)
Bath Temperature	460 ± 10°C	600 ± 10°C (higher temperature)
Surface Treatment	Chromic Acid Passivation (requires environmental treatment)	Chrome-free Passivation + Anti-fingerprint Coating (environmentally friendly)
Thickness Control	Air Knife Control ± 0.05mm	Air Knife Control ± 0.03mm (higher precision)

Molding Process

Process	GL	GI
Bending	Minimum radius = 0.8t (requires pre-cutting to prevent cracking)	Radius ≥ 1t
Stamping	Burr height 25-40μm	Burr height 50-80μm
Welding	Laser welding power +20%	Standard parameters

Welding Process

Welding Method	GL Parameter Adjustment	Reason
Resistance Spot Welding	Current +10% / Pressure +15%	High coating resistance (15μΩ·cm)
MIG Welding	Use Al-Zn alloy welding wire (ER4043)	Prevent zinc vapor porosity
Laser Welding	Power density ≥ 6×10⁶ W/cm²	High reflectivity of aluminum

Galvanized Galvalume Steel – Areas of Application

Application Scenario	Zinc-Coated Steel (GI)	Aluminum-Zinc-Coated Steel (GL)	Reason
Industrial Factory Roofs	–	√	GL steel has high reflectivity and long lifespan
Coastal Building Enclosures	–	√	GL steel resists salt spray for 1500h, with better corrosion resistance than GI steel
High-Temperature Chimneys/Baking Equipment	×	√	GL withstands 315°C, superior to GI’s 200°C tolerance
Agricultural Greenhouse Frames	√	–	GI is 30% cheaper, and high reflectivity affects crop growth
Underground Tunnel Supports	√	×	GI steel is more effective for cut edges/water-immersed areas
Photovoltaic Racks	–	√	GL has better weather resistance and high reflectivity
Car Fuel Tank Shells	√	–	GI has better deep drawing performance
Temporary Building Fences	√	–	GI is more cost-effective

Selection Advice

Compared to GI hot-dip galvanized steel, GL aluzinc steel has a higher initial cost but a lower long-term cost of ownership.

Aluminum zinc coated steels are recommended for high temperatures, in high temperature, highly reflective, industrial acid environments such as C3/C4 corrosive environments, in chemical zones; hot dipped galvanized steels are recommended for exposed cuts/submerged environments, for deep-drawn and complex components, or for short-term projects.

Galvanized steel and Aluminum zinc plated steel are not either/or, but can be combined in many applications to reduce project costs and maximize the benefits of different metal coatings. If you are looking for a galvanized steel solution, please leave a message and let us know, Wanzhi Group can provide OEM ODM service for you.