Alu-Zinc Coated Steel Coil (GL) for Roofing, Appliances & Industrial Use

Alu-Zinc Coated Steel Coil (GL) goes by a second name too. That name is Galvalume. A cold-rolled steel base gets hot-dip coated in an alloy. The mix is 55% aluminum, 43.4% zinc, and 1.6% silicon. That layer resists corrosion 2 to 6 times longer than plain galvanized steel. Tianjin Youcheng Technology has kept busy with steel distribution and export for 12 years. Our stock today sits at about 200 tons. We meet both GB/T 14978 and ASTM A792. Our shipments go to over 13 countries.

What Is Alu-Zinc Coated Steel Coil (GL)?

GL coil production begins with a low-carbon steel base. From there it moves through a continuous hot-dip coating line. A 55% Al-Zn alloy gets applied there. Every element in the coating has its own job. Aluminum forms a dense physical wall. That wall keeps air and moisture off the steel. If the wall gets cut or scratched, zinc gives itself up to shield the exposed edge. Silicon acts as the bonding agent. It links the alloy layer to the steel base. Because of that, adhesion gets better. The coating also stays even.

This yields a material that survives acidic industrial settings. High heat gives it no trouble. Damp coastal air is no problem either. Large cladding and roofing jobs get it too. It costs less than stainless steel. So when performance and budget both count, it's a practical pick.

Product Specifications

Key Performance Advantages

Corrosion resistance tops the list of reasons buyers pick GL instead of standard galvanized coil. In salt spray testing, the 55% aluminum barrier holds up 2 to 6 times longer than pure zinc coatings. Coastal zones are one clear case. Industrial sites with SO₂ in the air are another, because galvanized steel breaks down faster there.

Heat resistance is what decides how wide a coil's working temperature range can be. Up to 315°C of constant heat leaves the colors and the structure intact. Short jumps to 370°C do no damage either. HVAC ductwork, appliance heat shields, and roofing in hot climates all put it to work.

Thermal reflectivity above 0.70 means a roofing panel soaks up less heat. In warm-weather buildings the cooling load drops. Steel that is only galvanized never gets near that reflectivity level.

There is one more practical plus: surface versatility. You can leave the silver metallic spangle finish bare, or paint over it. Pre-painted Galvalume (PPGL) uses GL as its standard substrate. Paint sticks to its surface better than it does to GI. Where clean handling matters during transit and installation, an anti-fingerprint (AFP) treatment is an option.

Application Scenarios

Roofing and wall panels take up the biggest share of demand. Warehouses buy them. So do industrial plants and prefab builders. GL fights rust and pushes heat back. That counts most in coastal areas and in places where the air stays damp.

For home appliances, a base metal has to resist heat and moisture across a long product life. Refrigerator back panels, air conditioning units, and microwave interiors all fit that picture. GL coil covers both. At normal running temperatures, its surface holds up.

Agricultural silos and livestock buildings are hard on steel. Ammonia is always in the air, and damp never goes away. Condensation adds to it. GL Alu-Zinc Coated Steel Coil (GL) keeps working in those conditions, so the sector picks it a lot.

HVAC systems rely on GL for ductwork where both thermal stability and corrosion control are required. The heat resistance up to 315°C continuous covers the operating range of most commercial HVAC installations.

Quality Control Process

Coating weight verification comes down to two methods: the Triple Spot Test and X-ray fluorescence. What we look for is the AZ designation matching the contracted specification.

Adhesion and ductility get checked with the T-Bend Test (0T to 3T). The alloy layer must not crack or flake, and that is what this test proves. Why does it matter? The steel still has to survive roll-forming and profiling.

Corrosion resistance is measured with Neutral Salt Spray Testing, run to ISO 9227. Years of aging get squeezed into a short window. Before the coil leaves the plant, that test shows how the coating holds up.

Surface integrity checks look for black spot defects. Inspectors also review how evenly the passivation sits on the steel. AFP coating consistency gets checked across the full coil width as well. Every coil ships with a Mill Test Certificate (MTC) that lists what the inspection turned up.

Customization and Supply Options for Alu-Zinc Coated Steel Coil (GL)

GL coil comes in two standard widths, 1000 mm and 1250 mm. Custom slitting is something a buyer can ask for too. That lets a coil fit the exact needs of a given production line. Thickness ranges from 0.18 mm to 2.0 mm. Light-gauge appliance components fit inside that spread. Heavier structural panels do as well.

Leveling happens in house. So do slitting and cut-to-length. When a project needs set dimensions, OEM and ODM work is available. The same goes for Alu-Zinc Coated Steel Coil (GL) surface treatments. Documents built around local standards can be changed as well. Every order that ships goes out in export seaworthy packing. Freight support is already set up.

FAQ

Q: What is the difference between GL and galvanized (GI) steel?

A: GL uses a 55% Al-Zn alloy coating, which provides 2 to 6 times the corrosion resistance of a pure zinc GI coating. GL also has significantly higher thermal reflectivity, making it more suitable for roofing and heat-exposed applications.

Q: Can GL coil be used in coastal environments?

A: Yes. Pick a heavier coating weight for coastal jobs, AZ150 for example. Lead and copper should also stay out of direct contact. Galvanic corrosion then will not start at the joints.

Q: Why do GL coils sometimes develop black spots?

A: Black spots usually come from moisture caught between the coil laps in storage. That is what the trade calls storage stain. You can head it off by asking for chromated passivation, or by ordering oiling up front.

Q: Is GL coil suitable for painting?

A: Yes. The surface of GL is smooth and even. Paint holds onto it better than it does on GI. Pre-painted Galvalume steel (PPGL) normally uses this base.

Q: How hot can GL coil get while in service?

A: For continuous use, run GL coil at 315°C or lower and it will not discolor. Short bursts can reach 370°C. Almost every HVAC job and industrial heat shield requirement fits inside that range.

Q: Which options can I customize?

A: You pick the width and the thickness. Surface treatment is up to you as well, either regular spangle or anti-fingerprint. Cut-to-length sizes can be set to any measure you need. OEM and ODM work is offered too. This way, your national standards or project specs get covered.

Contact Us

Send your specs to sales@youchengkjsteel.com. You can also just tell us how many you need. A quote for your Alu-Zinc Coated Steel Coil (GL) order reaches you within 24 hours.