Q:What are the various coating types for hot-dip galvanizing?

Hot-dip pure zinc (Z)
In the hot-dip pure zinc process, the zinc content in the molten pool must be no less than 99%. Pure zinc coatings can produce spangles of varying sizes. While these spangles affect the surface appearance, they do not affect corrosion resistance.

Hot-dip galvanized aluminum (ZA)
The molten metal in the molten pool contains approximately 5% aluminum (Al) and a small amount of rare earth elements, with the remainder being zinc. Zn-Al coatings have a brighter surface and offer greater corrosion resistance than pure zinc coatings, but are less commonly used in China.

Hot-dip aluminum silicon (AS)
The molten metal in the molten pool contains approximately 8% to 11% silicon (Si), with the remainder being aluminum. Al-Si coatings form a distinct aluminum-iron-silicon alloy layer on the steel surface. They offer excellent high-temperature resistance, making them suitable for high-temperature processing and operating environments. Hot-dip Al-Si coated steel sheets and strip are a type of "aluminum-coated sheet" referred to in the trade.

Hot-dip galvanized magnesium (ZM) coatings, also known as zinc-aluminum-magnesium (ZAM), consist of a molten metal pool composed of aluminum and magnesium, typically 1.5-8% combined (at least 0.2% magnesium is required), with the remainder being zinc. This coating offers exceptionally good overall corrosion resistance, particularly for shear fracture protection.

Time：01/09/2025 13:44:00