Skip to content Galvalume steel is currently dominating the modern metal roofing and wall sector, with over a 90% shift from galvanized steel over the past few decades. Its aluminum-zinc coating usually performs significantly better than pure zinc coatings, offering around 2-4 times higher corrosion resistance than galvanized steel. It has now become an industry favorite across many coated-steel applications due to its excellent 40 to 60+ year lifespan.
However, even among regular users, only a few fully understand “What is Galvalume steel?” and the science behind its performance. If you want to move beyond the surface and get the most out of this material, it’s important to understand how it works. This guide will explain the Galvalume composition, its dual-action corrosion protection mechanism, common coating grades, and the applications where it delivers the most value.
What Is Galvalume Steel?
Galvalume steel belongs to the broader category of coated steels, alongside materials like galvanized steel, aluminized steel, etc. It is widely used in roofing, cladding, and construction, where durability and corrosion resistance are essential.
Definition of Galvalume
Galvalume steel is an aluminum-zinc-coated steel product, which is usually supplied as Galvalume coils or Galvalume sheets. Here, a carbon steel is coated with an aluminum-zinc alloy using a continuous hot-dip coating process. In simple terms, Galvalume’s structure has two main layers:
- Base material/substrate – cold-rolled carbon steel
- Metallic coating – aluminum + zinc + silicon alloy (aluzinc coating)
This combination creates a highly durable coated steel with excellent corrosion resistance and long-term performance.
How Galvalume Differs From Standard Galvanized Steel
The difference between Galvalume vs. galvanized steel is mainly in their protective coating composition:
- Galvanized steel has a pure zinc coating applied through hot-dip galvanizing.
- Galvalume is coated with an aluminum-zinc-silicon alloy coating.
Due to the advanced protection of the Galvalume steel coating composition, Galvalume generally outperforms traditional galvanized steel. It performs extremely well in outdoor conditions where you need long-term corrosion resistance.
What is Galvalume Steel Made of?
To understand how this aluminum-zinc coated steel collectively improves performance, we must get to know the specific ratios of the Galvalume steel coating composition.
Galvalume Steel Coating Composition
So, what is Galvalume made of in simple terms? The standard, globally recognized Galvalume coating composition consists of aluminum and zinc, with a small addition of silicon. This coating is also known as the Galvalume steel coating or 55% Al-Zn (aluzinc) alloy coating.
Table 1: Galvalume Steel Coating Composition
Element | Percentage |
Aluminum (Al) | 55% |
Zinc (Zn) | 43.4% |
Silicon (Si) | 1.6% |
This is the optimized Galvalume composition where both barrier and sacrificial protection are maximum.
Role of Aluminum
In the Galvalume alloy, aluminum’s role includes two main functions:
- Providing barrier protection against corrosion – aluminum naturally forms a dense layer of aluminum oxide on the surface. This oxide layer is nearly impenetrable to water and oxygen, effectively “sealing” the steel.
- Improving heat reflectivity – aluminum’s natural bright finish gives Galvalume its high heat reflectivity. This allows it to reflect solar radiation away rather than absorbing it into the building.
This is why Galvalume metal roofing performs better in high-temperature environments and is highly durable compared to many coated metals.
Role of Zinc
While aluminum provides the passive barrier, zinc provides the active defense by corroding before the steel. Since zinc is more chemically active than steel, it provides sacrificial protection to steel. It can protect even the slightly exposed areas like edges and scratches, preventing the rust from developing under the coating.
Zinc’s role in Galvalume is similar to hot-dip galvanized steel, but here it works together with aluminum for better performance, extending the life of Galvalume sheets and panels.
Role of Silicon
Silicon is present in small amounts but its role is extremely important in stabilizing the coating and improving the coating adhesion.
During the hot-dip process, molten aluminum and zinc can react too aggressively with the steel. This leads to a brittle layer that may crack during bending or forming. Silicon helps control this reaction, allowing the coating to bond properly to the steel.
How Galvalume Coating Protects Steel
The combined action of zinc and aluminum is the reason behind Galvalume’s strong corrosion resistance, which is even higher than galvanized steel.
Barrier Protection From Aluminum
When the aluzinc coating cools after the coating process, aluminum and zinc separate into slightly rich zones. The aluminum-rich zones form passive oxides and act as physical walls between the steel and the environment. This aluminum wall remains stable for a long time, even if zinc starts to deplete over decades, providing long-term corrosion resistance.
Sacrificial Protection From Zinc
In the gaps between the aluminum barrier, zinc is present. If the aluminum layer is damaged and the steel becomes exposed, zinc starts to react first. This provides sacrificial protection to steel, preventing red rust formation.
Combined Performance Advantage
In this dual-phase microstructure of Galvalume,
- Aluminum provides long-term stability
- Zinc provides the active mechanism for corrosion protection.
In simple terms, zinc is the backup protection system if the primary aluminum barrier is damaged. Together, they create a strong protective coating that outperforms many traditional coated metals, including galvanized steel.
Why the Composition Matters: Advantages of Galvalume
The specific chemistry of Galvalume coating translates directly into mechanical advantages, significantly reducing the repair and maintenance costs of Galvalume.
Better Corrosion Resistance Than Conventional Zinc Coatings
In standardized salt spray and atmospheric tests, Galvalume consistently outperforms G60 and G90 galvanized steels. Since the aluminum barrier does not wash away like a pure zinc coating, Galvalume lasts 2 to 4 times longer in most rural, urban, and industrial environments. This durability is why many manufacturers offer warranties of 40 to 60 years on Galvalume products.
Improved Heat Reflectivity
Galvalume’s high aluminum content provides excellent heat reflectivity, keeping the roofing cool. Galvanized steel is more heat-absorptive, and this effect increases over time as the zinc coating weathers. Galvalume can maintain much of its reflectivity over time, keeping building interiors significantly cooler during peak summer months.
Good Long-Term Roofing Performance
Roofing is the most demanding application for both galvanized and galvanized steel. Therefore, they experience constant UV exposure, thermal expansion, and standing water. The Galvalume composition is well-suited for these conditions even under extreme temperature swings.
Strong Value for Harsh Service Environments
Although the initial cost of Galvalume may be slightly higher than that of galvanized steel, its lifecycle value is very high. It does not need frequent repainting and replacements, making it the most economical choice for permanent structures.
Common Galvalume Coating Designations
Galvalume grades are specified using AZ codes such as AZ50, AZ70, AZ150, etc. These grades indicate the total aluminum-zinc coating weight in oz/ft². Higher AZ values mean thicker coatings and improved corrosion resistance.
AZ50
AZ50 has a lighter coating weight equivalent to 150 g/m² (both sides). It is commonly used as a PPGL (prepainted Galvalume) since the paint layer can add additional protection. You can choose this grade for applications requiring good formability, controlled cost, and moderate corrosion resistance.
AZ70
AZ70 Galvalume has approximately 210 g/m² coating weight. It provides a good balance between corrosion resistance and cost. AZ70 grade is suitable for general roofing sheets, wall cladding, and panels in normal outdoor environments.
AZ100
AZ100 features a thicker aluminum-zinc coating of nearly 300 g/m² in weight. It offers higher durability and improved protection in humid or moderately industrial conditions, where longer service life is required.
AZ150
AZ150 has a heavy coating weight of 450 g/m². It is designed for high-exposure and harsh environments, providing maximum corrosion resistance and long-term performance with minimal maintenance.
What Is Prepainted Galvalume Steel (PPGL)?
Under extremely harsh conditions, the metallic coating alone cannot provide sufficient long-term protection. To address this, manufacturers apply an additional non-metallic paint layer over the metallic coating. These are known as prepainted steels, such as PPGI and PPGL, which offer improved corrosion protection, durability, and surface finish.
Definition of PPGL
PPGL stands for Pre-Painted Galvalume Steel. That means it has a Galvalume base with a multi-layer paint system on top. This paint system consists of a primer and a highly durable topcoat like PE, PVDF, or SMP.
Why Paint + Galvalume Is a Strong Combination
When you paint Galvalume, you are adding a third layer of defense. The paint protects the Galvalume coating from the environment, and the Galvalume coating protects the steel from any moisture that might pass through the paint. This synergy results in a material that can last for generations with minimum maintenance.
Typical Applications of PPGL
You can use PPGL when both corrosion protection and decorative appearance are important. It is ideal for:
- Color-coated roofing sheets
- Architectural wall cladding
- Prefabricated building panels, ceiling panels, shutter doors, and partition systems
- Visible exterior components.
PPGL is also widely used in industrial and commercial buildings since it provides long-term weather resistance, a cleaner appearance, and color durability.
Galvalume vs. Galvanized Steel Differences Explained
When deciding between Galvalume and galvanized steel, the right choice depends mainly on the environmental exposure and expected service life. Both are widely used coated steels, but their performance differs due to the coating composition.
Galvanized vs. Galvalume Composition Difference
The main difference between Galvalume and galvanized steel is in the coating. Galvanized steel uses a 100% zinc coating, while Galvalume uses an aluminum-zinc alloy coating. This gives Galvalume a more stable and protective surface, making it more suitable for long-term exterior applications with high UV exposure.
Galvanized vs. Galvalume Corrosion Resistance
Galvalume generally offers higher corrosion resistance than galvanized steel, particularly in outdoor environments exposed to moisture and temperature changes. Its aluzinc coating provides a strong dual-protection mechanism, while zinc provides only the sacrificial protection.
However, in highly alkaline environments (such as animal barns with ammonia), aluminum can be reactive and unstable. Therefore, galvanized steel performs better than Galvalume due to zinc’s chemical stability.
Galvanized vs. Galvalume Cost Difference
Galvalume has a slightly higher initial cost compared to galvanized steel. However, if you consider the lifecycle cost, Galvalume stands ahead in many cases. Galvalume has minimal maintenance requirements, making it more cost-effective over time. For projects focused on lifecycle value rather than upfront savings, Galvalume is usually the better investment.
Typical Application Difference
Galvanized steel is commonly used in general construction, fabrication, and indoor or less demanding environments. Galvalume is preferred for roofing, wall cladding, and exposed structural applications where corrosion resistance and durability are critical over long periods.
Galvalume vs. Galvanized Steel: A Direct Comparison
Table 1: Comparison of Galvanized vs. Galvalume Steel Differences
Feature | Galvalume Steel | Galvanized Steel |
Base Metal | Carbon Steel | Carbon Steel |
Metallic Coating | Aluminum-zinc alloy coating | 100% zinc coating |
Protection Mechanism | Barrier + sacrificial protection | Sacrificial protection |
Corrosion Protection Level | Excellent (2-4x longer) | Good |
Heat Reflectivity | High | Moderate |
Applications | Roofing, cladding, panels | General construction, fabrication |
Common Applications of Galvalume Steel
Galvalume steel is widely used across construction and manufacturing due to its strong corrosion resistance, durability, and ease of fabrication.
Roofing Sheets and Panels
The most common use of Galvalume steel is in roofing. Galvalume roofing sheets and standing seam panels are widely used due to their durability, corrosion resistance, and heat reflectivity, making them ideal for long-term outdoor exposure.
Wall Cladding
Galvalume is widely used for wall cladding in industrial and commercial buildings, including facades and warehouse walls. It provides strong weather resistance while maintaining a clean metallic appearance over time.
Industrial and Agricultural Buildings
Galvalume performs well in environments with humidity and temperature variation. It is commonly used in factories, storage facilities, and agricultural structures where durability and low maintenance are required.
Prefabricated Structures
Due to its formability and strength, Galvalume is used in prefabricated and modular structures such as site offices and temporary buildings, where ease of fabrication and durability are important.
Appliances and Other Formed Components
Beyond construction, it is commonly found in HVAC systems, electrical enclosures, and equipment housings where corrosion resistance, lightweight structure, and ease of fabrication are required.
When Buyers Should Choose Galvalume
You should choose Galvalume steel when long-term performance matters more than the initial cost. Here’s a quick guide on how to strategically make your decisions for long-term value:
Choose Galvalume steel if:
- You need long-term corrosion resistance (2-4× better than galvanized steel)
- The project is outdoors or exposed to the weather
- Heat reflectivity is important (roofing applications)
- You value lifecycle cost, not just initial price
Choose galvanized steel if:
- The environment is alkaline or ammonia-rich (e.g., animal enclosures)
- The project is indoor or low exposure
- You need a lower initial cost
Choose PPGL (Prepainted Galvalume) if:
- You need both corrosion protection and color finish
- The application is visible (roofing, facades, panels)
- You want long-term aesthetics with added surface protection
Not sure whether to choose Galvalume, galvanized, or PPGL? Share your project details and get a practical recommendation with the right coating grade and cost.
FAQ
Is Galvalume better than galvanized steel?
In many environments, yes. Due to its aluminum-zinc-coated steel composition, Galvalume offers better corrosion resistance and a longer lifespan.
What is Galvalume Coating Composition?
Galvalume is made of a steel substrate coated with an alloy of aluminum (55%), zinc (43.4%), and silicon (1.6%). This is also known as aluzinc coating.
Can Galvalume rust?
Even though Galvalume provides excellent corrosion protection, it can eventually corrode, forming both white rust and red rust. However, it has a much slower rate of corrosion than regular steel or galvanized steel due to its dual protection system.
Is Galvalume magnetic?
Yes. Since the base steel of Galvalume is carbon steel, Galvalume is ferromagnetic.
Is PPGL made from Galvalume steel?
Yes. PPGL means prepainted Galvalume steel. It uses Galvalume as the base material and a non-metallic paint coating like PE, SMP, or PVDF.
Conclusion
To summarize, Galvalume steel is a steel substrate coated with an aluminum-zinc-silicon alloy coating. Compared to traditional coated metals like galvanized steel, Galvalume offers a more advanced protection system by combining barrier and sacrificial mechanisms. It delivers superior corrosion resistance and durability for roofing and cladding applications. If you need both performance and aesthetics, you can go for PPGL, which offers a range of colors, a good finish, and improved surface protection.
