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Galvalume metal (GL metal) is a very commonly used building material in our life. Due to its excellent corrosion resistance, it is widely used in many applications. When it comes to GL steel, you may think about galvanized steel. So what are they and what are the differences between them? Keep reading and you will have a better understanding of galvalume metal.
Galvalume steel is a kind of metal obtained through the hot-dipping process at a high temperature of 600 ° C. It is with a cold-rolled steel sheet as the substrate and then be applied a layer of Al-Zn coating on the surface. The coating consists of 55% aluminum, 43.4% zinc, 1.6% silicon, and a few trace elements. This unique Al-Zn alloy combines the protection and high durability of aluminum with the electrochemical protection of zinc. So GL steel features superior corrosion resistance. In addition, the surface is smooth, bright, silver-gray color, and with regular spangles, which can also meet the aesthetic purposes.
In the 1970s, Bethlehem Steel, a U.S. shipbuilding company, attempted to add metals to molten zinc and begin to experiment with creating a mixture that could yield greater protection. Finally, the company settled on an ideal mixture, which is then called galvalume. Soon afterward, many manufacturers adopted it.
The corrosion resistance of galvalume coating is 3 times that of pure zinc coating due to the double protection of zinc and aluminum. When the zinc is worn away, the aluminum will form a dense layer of aluminum oxide, preventing further corroding of the base metal. So its service life is longer than that of galvanized steel. Here is a table showing the coating loss (um/y) per year in different use environments.
|Use Environment||Harsh marine area||Marine area||Industrial area||Rural area|
|Galvalume Steel (A)||9.8||1.3||1.4||0.38|
|Galvanized Steel (B)||16||4||4.2||1.3|
|Difference Ratio (B/A)||1.6||3.1||3.0||4.6|
Galvalume steel is silver-white in color. And it has a gorgeous finish and smooth surface. Compared to galvanized steel sheets, its spangles are more uniform. That’s why it is highly preferred as a building material or decorative panel.
This aluminum-zinc coating has good heat resistance. It can be used in high-temperature environments up to 315 degrees for a long time without discoloration. Besides, its heat reflectivity is almost twice that of galvanized steel, which is greater than 0.70. So it is an ideal choice for a roofing solution.
Due to its good adhesion, GL steel can be painted directly without any pretreatment and weathering. It is widely used as the base metal of color coated steel. Besides, it has good workability, which means it can be processed easily, such as bending, stamping, etc.
1. Galvalume coating contains aluminum, which is prone to chemical reactions if contacted with wet concrete directly. Therefore, it is not very suitable for floor decking.
2. Due to the reduction of zinc content and the zinc material being wrapped by aluminum and not easily electrolyzed, the anodic protection is greatly reduced. Therefore, once the GL sheet is cut, the edge will rust quickly. During use, the GL sheet should be cut as little as possible and the cut edge should be protected by anti-rust paint or zinc-rich paint.
3. The price of galvalume metal is more expensive than that of galvanized metal.
4. Once a certain point of the GL sheet is corroded, the rust will become larger and larger, and finally even spread over the entire surface. While if the galvanized sheet corrodes at a certain point, it will not spread.
Due to its beautiful appearance, galvalume steel can be used directly. It also has great adhesion so it is also an ideal choice for color coated steel. It is widely used in home appliances, building structures, etc.
1. Construction uses, such as roofing panels, cladding, partition walls, ceiling, garage doors, door panels, fence panels, chimneys, shutters of civil and industrial buildings, etc.;
2. Home appliances: back panels of refrigerators, air conditioners, ovens, solar water heater (0.32mm), power distribution cabinet (thickness is 1.2-2mm), and so on;
3. Automobile industry: mufflers, exhaust pipes, car body panels, road signs, fuel tanks, containers, and more;
4. Industrial uses: electric control cabinets, industrial freezers, vending machines, etc.
Galvalume steel proves to be a good roofing material. It has many advantageous features, such as high strength, excellent corrosion resistance, light in weight, beautiful appearance, long service life, and less maintenance. At Wanzhi Steel, we also offer a wide range of GL roofing sheets available in different sizes and designs. Welcome to contact us for more details.
There are different methods of surface treatment. You can choose according to your needs.
|Chromate Passivation||C||Through passivating, a chromate film is further applied to the surface to reduce white rust under humid conditions.|
|Oiling||O||The aim of oiling is to prevent GL sheets from getting wet and causing white rust.|
|Chromate & Oiling||CO||To effectively prevent the product from white rust during the use period.|
|Anti-fingerprint Treatment||UF||A thin anti-fingerprint protective film is coated on the surface of GL products to prevent fingerprints and also improve its corrosion resistance. It is especially suitable for GL metal for home appliances.|
The main difference between galvalume and galvanized steel is the coating composition. The galvanized coating is pure zinc coating; while the galvalume coating is Al-Zn alloy, which consists of 43.4% zinc, 55% aluminum, and 1.6% silicone. The combination of aluminum and zinc offers a better protection effect than pure zinc coating. Let’s have a brief review.
|Item||Galvanized Steel||Galvalume Steel|
|Coating||Zinc coating||Aluminum+Zinc Alloy (43.4% zinc, 55% aluminum, and 1.6% silicone)|
|Features||Strong corrosion resistance; good weldability||Superior corrosion & heat resistance; high heat reflectivity; Easier to paint|
|Service life||20+ years||50+ years|
|Surface||Shiny with big/small or zero spangles||Not shiny, but smooth, with uniform spangles|
|Not recommended||Coastal or severely corrosive environments||Alkaline environments; Livestock facilities|
|Applications||Agricultural and residential projects; light industry and more||Commercial and residential buildings; automobiles, home appliances, etc.|
After learning about their difference, you might be wondering if galvalume metal is more expensive than galvanized metal. The answer is yes, but not much expensive. Actually, there are many influencing factors on the price of galvalume and galvanized steel, such as the coating thickness. Generally, the thicker the zinc or Al-Zn coating, the higher the price. Moreover, for the GL and GI sheet with the same coating thickness, GL is more expensive but it can last longer. All in all, galvalume metal is an affordable product to choose from.
Which Is the Right Choice?
Actually, it depends. Whether you’re using galvalume or galvanized metal, you need to take the following factors into consideration, such as the use environment, your budget, etc. For example, both galvalume and galvanized steel are not suitable for severely coastal areas. In this case, you’d better use stainless steel sheets. If you are not sure, please talk to an expert to get a suitable solution.
Yes, it is. Galvalume coating is an Al-Zn Alloy, with 43.4% zinc, 55% aluminum, 1.6% silicone, and a few trace elements.
Galvalume metal looks silver-white in color with a matte-like appearance. It is not as shiny as a galvanized sheet but it is with even spangles. Due to its smooth finish and beautiful appearance, it is widely used in many applications directly without painting. While for aesthetic purposes, you can paint it with different colors due to its good adhesion.
Galvalume metal is a popular material that is ideal for many applications, such as roofing and wall panels, home appliances, automobiles, etc. At Wanzhi Steel, we have a hot dipping galvalume line with an annual output of 200,000 tons. Except for our own strict quality control system, third-party quality inspection is acceptable. If you are looking for galvalume steel products, welcome to contact us for details!