Comparison of Three Coated Steel Sheets

Comparison of three coated steel sheets of pure zinc (+Z), aluminum zinc (+AZ), zinc aluminum magnesium (+AZM/AM)

Hot-dip galvanized metal-coated steel sheets or strips are often used in our trade or processing, such as galvanized, aluminum-zinc, zinc-aluminum-magnesium and other coatings. According to some foreign publicity materials, about half of the world's zinc production is used for surface anticorrosion treatment of steel and steel products (including various zinc series coatings and a large number of whole steel parts for immersion anticorrosion).

Pure zinc coating

The zinc content of the bath in the hot-dip galvanized zinc pot is not less than 99%, which is the most economical anti-corrosion coating type at present. Pure zinc-coated steel sheets are divided into two types: spangle-free and spangle-free, and their corrosion resistance is almost the same. If spraying or painting is required later, the product without spangles will be more beautiful; while the products with thick zinc layer are usually spangled, for example, the weight of the zinc layer is 275g/m2 on both sides.

Aluminum Zinc Coating

The plating solution contains about 55% aluminum, about 1.6% silicon, and the rest is zinc. The corrosion resistance of the aluminum-zinc coating is higher than that of the pure zinc coating in most environments, and the aluminum-zinc coating steel coils have spangles. Excellent steel mills can produce uniform and beautiful spangles, which can be directly used for home appliances, but the aluminum-zinc coating also has some shortcomings.

The weldability of aluminum-zinc-coated steel sheets is not as good as that of pure zinc, especially when using resistance welding, the molten coating metal will stick to the electrode tip. Because the hardness of the bonded metal after melting is relatively high, the removal efficiency of the ordinary grinding tool is very low, which will lead to the scrapping of the electrode tip, so the welding process should be minimized during use.

In addition, the protection of the aluminum-zinc coating on the cut of the steel plate is far inferior to that of the pure zinc coating, and it is far inferior to the zinc-aluminum-magnesium coating. It is necessary to do a good job of anti-corrosion work on the cut, such as painting and sealing.

Zinc-aluminum-magnesium coating

This is a coating product with excellent comprehensive performance. It was successfully developed and mass-produced by Japan's Nisshin Steel Works in the early 21st century, and registered a patent and trademark ZAM. The corrosion resistance of the zinc-aluminum-magnesium coating is much higher than that of galvanized and galvalume-coated coatings, and it has excellent protection for cuts and good welding performance.

The coating of zinc-aluminum-magnesium-coated steel sheet is composed of three metals: zinc, magnesium and aluminum. This coating has comprehensive performance far exceeding that of traditional zinc coating.

Features of zinc-aluminum-magnesium-coated steel sheets

The zinc-aluminum-magnesium-coated steel plate was originally developed to replace some stainless steel use scenarios. Although stainless steel has good corrosion resistance, the cost is too high; and other galvanized steel plates are not as corrosion-resistant as stainless steel, but more importantly, for Poor protection of fractured surfaces or damaged coatings.

The zinc-aluminum-magnesium coating has excellent red rust resistance and self-healing corrosion resistance of the shear section, and it also has welding performance far superior to that of the galvanized steel plate.

Zinc-aluminum-magnesium-coated steel sheet perfectly solves the shortcomings of ordinary coated steel sheets that cannot effectively protect shear fractures, missing coating points, and coating damage. It can be said to be one of the coated steel sheets closest to stainless steel in terms of comprehensive performance.

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