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How Galvalume Steel Coils Are Manufacturing

Galvalume steel coils (also known as Aluzinc coils) are manufactured through the hot-dip Al-Zn coating line, in which steel substrates are coated with a specialized aluminum-zinc-silicon alloy. The typical composition is 55% Al / 43.5% Zn / 1.5% Si, designed to combine the oxidation resistance of aluminum with the sacrificial corrosion protection of zinc.

Compared with traditional galvanized steel, Galvalume coils demonstrate superior corrosion resistance, longer service life, and enhanced heat reflectivity. These advantages make them an excellent choice for roofing, wall panels, air-conditioning housings, and industrial applications.

At Hengze Steel, we specialize in producing high-quality Galvalume steel coils using advanced hot-dip Al-Zn production technology, ensuring consistent coating thickness, superior adhesion, and competitive pricing for global customers.

1. Key Features and Applications of Galvalume Steel Coils
1. Key Features and Applications of Galvalume Steel Coils

2. Raw Materials and Alloy Composition
2. Raw Materials and Alloy Composition

3. Pre-treatment: Cleaning, Pickling, and Degreasing
3. Pre-treatment: Cleaning, Pickling, and Degreasing

4. Hot-Dip Al-Zn Coating Process
4. Hot-Dip Al-Zn Coating Process

5. Cooling, Solidification, and Alloying
5. Cooling, Solidification, and Alloying

6. Post-treatment, Quality Control, and Packaging
6. Post-treatment, Quality Control, and Packaging

7. Production Line Layout and Key Equipment
7. Production Line Layout and Key Equipment

8. Factors Affecting Coating Quality and Optimization Strategies
8. Factors Affecting Coating Quality and Optimization Strategies

9. Conclusion and Future Outlook
9. Conclusion and Future Outlook

1. Key Features and Applications of Galvalume Steel Coils

Surface Cleaning and Chemical Pretreatment

Outstanding Corrosion Resistance – Dense aluminum oxide layers prevent oxygen and moisture penetration.
Sacrificial Protection – Zinc continues to protect cut edges and scratches.
High-Temperature Resistance – More stable than galvanized steel in hot environments.
Excellent Reflectivity – Reduces roof temperature, ideal for tropical and high-heat climates.
Superior Formability – Suitable for cutting, bending, and roll-forming.

Surface Cleaning and Chemical Pretreatment

Roofing sheets and panels
Exterior wall cladding
HVAC ducts and air-conditioner casings
Industrial equipment housing
Interior decorative steel products

At Hengze Steel, our Galvalume coils are engineered to meet international standards for both construction and industrial sectors.

2. Raw Materials and Alloy Composition

The quality of Galvalume coils begins with carefully selected raw materials:

Base Steel Coil: Cold-rolled or hot-rolled low-carbon steel, with controlled C content (0.05–0.15%).
Al-Zn-Si Alloy Bath Composition: 55% Al / 43.5% Zn / 1.5% Si, proven to provide the best balance of corrosion resistance, adhesion, and cost efficiency.
High-Purity Metals: Impurities such as Fe, Mg must be minimized to prevent coating defects.
Optional Additives: Small additions of Mg or rare earth elements may be used to further enhance corrosion resistance.

Hengze Steel sources only premium-grade steel and alloying materials to guarantee consistent performance and durability.

3. Pre-treatment: Cleaning, Pickling, and Degreasing

Before dipping, the steel strip must be thoroughly cleaned to ensure proper coating adhesion:

Degreasing: Alkaline cleaning removes rolling oils and lubricants.
Pickling: Mild acids remove oxides, scale, and rust from the surface.
Activation / Phosphating (optional): Enhances wettability and adhesion.
Drying & Preheating: Removes residual moisture to avoid defects during dipping.

Hengze Steel employs state-of-the-art pre-treatment systems to eliminate contaminants and guarantee a flawless substrate surface.

4. Hot-Dip Al-Zn Coating Process

4.1 Bath Composition and Temperature Control

Typical alloy ratio: 55% Al / 43.5% Zn / 1.5% Si.
Operating temperature: 450–480 °C, controlled precisely.
Bath stability ensured with alloy replenishment, agitation, and temperature feedback systems.

4.2 Immersion and Coating Formation

The steel strip passes through the molten bath, forming a metallurgical bond.
Fe-Al and Fe-Zn intermetallic compounds ensure strong adhesion.

4.3 Air Knife Control and Coating Thickness Adjustment

High-pressure air knives control coating thickness and uniformity.
Parameters such as strip speed, nozzle gap, and air pressure are finely tuned to achieve consistent results.

At Hengze Steel, advanced air knife technology ensures uniform coatings, improving both appearance and long-term durability.

5. Cooling, Solidification, and Alloying

After exiting the bath, the coated steel undergoes controlled cooling:

Rapid Cooling: Air or water mist cooling prevents excessive grain growth.
Alloying & Solidification: Controlled diffusion stabilizes the coating structure and improves adhesion.

6. Post-treatment, Quality Control, and Packaging

6.1 Coating Thickness Measurement

Non-destructive XRF (X-ray fluorescence) ensures accurate coating thickness.

6.2 Adhesion and Corrosion Resistance Tests

Cross-cut tests, peel-off tests, and salt spray tests simulate real-world conditions.

6.3 Surface Inspection and Defect Control

Visual and automated inspections detect bubbles, cracks, and inclusions.

6.4 Anti-rust Oil and Packaging

Anti-rust oil and moisture-proof film ensure safe long-distance transportation.
Coils are edge-trimmed, slit, and securely packed with identification labels.

Every coil from Hengze Steel undergoes rigorous inspection to meet international quality standards.

7. Production Line Layout and Key Equipment

A modern Galvalume coil production line typically includes:

Degreasing and pickling units
Molten Al-Zn bath with alloy replenishment system
High-precision air knives
Cooling sections with mist spray or air cooling
Online inspection devices (XRF, defect scanners)
Automatic coilers and slitting machines
PLC / DCS automation and real-time monitoring systems

Hengze Steel integrates advanced automation and quality monitoring to ensure stable and efficient production.

8. Factors Affecting Coating Quality and Optimization Strategies

Factor	Risk	Optimization
Bath temperature fluctuation	Poor alloy bonding or instability	Advanced thermal control & feedback systems
Coating composition drift	Reduced corrosion resistance	Regular analysis & automated replenishment
Air knife pressure	Too thick/thin coating	Adjustable nozzles & real-time monitoring
Strip speed	Uneven thickness	Precision tension control
Cooling rate	Weak adhesion or internal stress	Multi-zone controlled cooling
Surface cleanliness	Poor adhesion	Strict degreasing & pickling
Coiling tension	Edge defects	Automated tension control
Environmental dust	Surface contamination	Cleanroom design & air filtration

9. Conclusion and Future Outlook

The Galvalume steel coil manufacturing process involves multiple steps – from raw material selection, pre-treatment, and hot-dip Al-Zn coating, to cooling, post-treatment, and strict quality control. Each stage is critical to achieving superior corrosion resistance, uniform coating thickness, and long-term durability.

Compared with galvanized steel, the differences between Galvalume vs galvanized steel lie in their significantly enhanced corrosion resistance, heat reflectivity, and longer lifespan. With optimized coating thickness measurement methods and advanced quality control techniques, Galvalume coils are now widely used in roofing and industrial applications worldwide.

At Hengze Steel, we are committed to providing premium-quality Galvalume coils with consistent specifications, reliable performance, and competitive costs. Looking ahead, innovations such as magnesium-enhanced coatings, AI-powered process monitoring, and eco-friendly production lines will further expand the applications of Galvalume steel coils in global construction and industrial markets.