1.What types of galvanized coils are there according to the production process?
Hot-dip galvanized steel coil: After cleaning and annealing, the cold-rolled steel coil is immersed in molten zinc at approximately 460°C, depositing a zinc layer on the steel strip.
Electrogalvanized steel coil: Using electrochemical principles, zinc ions are deposited on the steel strip surface in an electrolytic cell. The coating is relatively thin and uniform.
2.What types of galvanized coils are there based on the chemical composition of the coating?
Pure zinc coating: The coating composition is mainly zinc and may contain a small amount of aluminum
Zinc-iron alloy coating: After hot-dip galvanizing, alloying treatment is immediately performed (such as heating to above 500°C) to convert the pure zinc layer on the surface into a zinc-iron alloy layer with a dark gray appearance.
Aluminum-zinc alloy coating: The coating composition is approximately 55% aluminum, 43.4% zinc and 1.6% silicon.
High aluminum coating: The coating is pure aluminum or aluminum-silicon alloy containing 5-11% silicon.
3.What types of galvanized coils are there according to post-processing methods?
Passivation Treatment: Chromic Acid Passivation: Available in chromium-containing and chromium-free color passivation, it significantly improves white rust resistance.
Chromium-free Passivation: An environmentally friendly treatment that complies with RoHS and other environmental directives.
Oil Treatment: A layer of rust-inhibiting oil is applied to the surface to prevent white rust during transportation and storage.
Phosphating: Provides a good base for subsequent painting and enhances paint film adhesion.
Compound Coating:
Galvanizing + Printing (Printed Coil): Wood grain, stone grain, and other patterns are printed on the surface of the galvanized coil, providing both corrosion protection and decorative properties.
Glazed Coil: A transparent organic coating is applied to the surface to enhance gloss and fingerprint resistance.
4.What are the different characteristics of different types of galvanized coils?
Hot-dip galvanizing: thick coating, good corrosion resistance, zinc flowers, low cost
Electrogalvanizing: smooth surface, good formability, thin and uniform coating
Zinc-iron alloy: excellent painting and welding properties, gray surface
Aluminum-zinc alloy: extremely corrosion-resistant and heat-resistant
5.How to choose?
Consider corrosion resistance: For outdoor applications requiring high corrosion resistance, choose thick-coated GI or GL.
Consider subsequent processing: For complex stamping and forming, choose EG or GA; for welding, choose GA.
Consider surface requirements: For direct exposure and aesthetically pleasing surfaces, choose small-speck GI, EG, or GA as the pre-coated substrate.
Consider environmental requirements: Choose a chromium-free passivated product.