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    The galvanized steel coil (GI) consists of at least 97% Zinc, with less than 0.3% Aluminum and solidified at 460℃ high temperature. One main feature of galvanized steel is its excellent corrosion resistance from sacrificial protection of the zinc. When the zinc layer on the surface isolates the steel sheet from atmosphere, it is able to prevent corrosion and keep long lasting life on the substrate.

    Furthermore, the features of this products are economic, various, and fulfill different requirements and applications, providing high added-value. Lately, the galvanized steel sheets are commonly used in many fields such as architectures, 3C products, home electronic appliances, color coating and living goods, etc.

    Al-Zn alloy-coated steel sheet has high corrosion resistance. It is also named Galvalume. The surface is formed with diamond look spangles. 55% Al-Zn alloy-coated steel coils (GL) consists of 55% Aluminum, 43.4% Zinc, and 1.6% silicon, solidified at high temperature of 602℃. Its structure is compound by Al-Fe- Si-Zn, and become a protection layer to prevent corrosive penetration.

    Galvalume steel sheets are commonly used in different fields, applications, corrosion resistance, and pre-painted products as well. In the following table, it shows the classifications and features of Galvalume steel surface treatment.

【Surface treatment and Classifications】

Corrosion Resistance:
    The GI corrosion resistance is derived from Zinc sacrificial protection. Then, the GL corrosion resistance is from the Aluminum barrier protection, and Zinc sacrificial protection.
    Through outdoor exposure tests in various atmospheric environment for 55% Al-Zn alloy-coated steel coils, the result proved its protection is better than the galvanized steel sheet.

Heat Resistance / Heat Transmission and Reflectivity:
    Aluminum has excellent heat reflectivity properties, and is commonly used in architectures materials. It can be used to reduce the heat energy, regulate the room temperature. It is a energy-saving, environmentally friendly material. 55% Al-Zn alloy -coated steel products have better resistance to high temperature than galvanized products with regarding to its oxidation features. Therefore, 55% Al-Zn alloy- coated steel products can be used in a temperature up to 300℃.

Weight-saving:
    The Aluminum specific gravity is about 3.69g/cm3, and the Zinc is about 7.13g/cm3 . To make a comparison between Galvalume and galvanized steel coils based on the same subtracts and coating weight terms, the length of 55% Al-Zn alloy-coated steel coils is longer 1~3% than Galvanized coil. (Minor differences is acceptable)

Comparison Table of GL / GI: