As we all know, galvanized steel tubes generally do not exhibit visible spangles. This is because the surface of steel tubes is rough and uneven. The pure zinc layer is cooled in hot water before it fully solidifies. Additionally, the wall of steel tubes is typically thicker than sheet metal, leading to a longer immersion time in zinc and a higher zinc liquid temperature. This results in a thicker iron-zinc alloy layer, which disrupts the crystallization process of the pure zinc layer and thus affects the growth of crystals and the formation of spangles.
In the galvanizing process of steel tubes, if metallic elements such as tin and antimony are not added to the zinc liquid, the conditions for forming spangles are not sufficient. Although adding aluminum can lead to coarse and aligned crystallization, making the grain extremely fine, it shortens the time the pure zinc layer remains in a liquid state on the surface of steel tubes and inhibits the growth of crystals. Therefore, patterns cannot be formed. Furthermore, galvanized steel tubes are cooled in hot water before the pure zinc layer solidifies, resulting in the formation of a glossy and uniform surface layer on the surface.
The production of galvanized sheet metal fully meets the conditions for generating spangles. The smooth and even surface of sheet metal, combined with the addition of metallic elements such as tin and antimony that promote spangle formation, its thinness, and low heat capacity, allow for shorter immersion times and lower zinc liquid temperatures. This produces a thinner iron-zinc alloy layer, reducing interference during the formation of spangles. By using methods such as water spray and steel mesh to artificially create crystallization nuclei, the desired spangles can be generated.
