Galvanized steel sheets are primarily classified by production process and surface treatment/zinc coating characteristics, with additional common classification dimensions. The core categories and key distinctions are as follows:
I. By Production Process (Core Criterion)
1. Hot-dip Galvanized Steel Sheet (GI): The steel sheet is immersed in molten zinc to form a zinc coating. Featuring a thick coating with strong adhesion and excellent corrosion resistance, it is widely used in industrial and construction fields.
2. Electrogalvanized Steel Sheet (EG/SECC): The zinc coating is formed by electrolytic deposition. With a thin, uniform coating and a smooth surface, it is suitable for home appliances and precision sheet metal fabrication.
II. By Surface Zinc Coating Characteristics/Treatment
– Alloyed Hot-dip Galvanized Steel Sheet (GA/Zn-Fe): Undergoes high-temperature alloying after hot-dip galvanizing, achieving tight zinc-iron bonding and excellent spot weldability; it is the mainstream choice for the automotive industry.
– Hot-dip Galvalume Steel Sheet (GL): Aluminum is added to the molten zinc bath, delivering far superior corrosion and high-temperature resistance compared to conventional GI; ideal for outdoor high-temperature applications.
– Prepainted Galvanized/Aluzinc Steel Sheet (PPGI/PPGL): A colored paint coating is applied to the GI/GL base sheet, combining corrosion protection with decorative effects; commonly used for building envelope systems.
– Passivated/Oiled Galvanized Steel Sheet: The GI/EG base sheet is treated with passivation (chromated/non-chromated) and oiling to enhance white rust resistance, facilitating warehousing and transportation.
III. Additional Common Classifications
1. By Zinc Coating Weight: Light coating (≤80g/㎡), medium coating (80-275g/㎡), heavy coating (≥275g/㎡), corresponding to different corrosion protection requirements.
2. By Surface Condition: Regular spangle, minimized spangle, spangle-free, skin-passed surface; the surface condition affects aesthetic appeal and adaptability for subsequent processing.
3. By Base Sheet Material: Galvanized cold-rolled base sheet, galvanized hot-rolled base sheet. The latter has a lower cost and is suitable for structural components with low surface finish requirements.