Why are there generally no zinc flowers on galvanized steel pipes, but they are common on galvanized sheet metal?
As we all know, galvanized steel pipes generally do not have visible zinc flowers. This is because the surface of steel pipes is rough and uneven. The pure zinc layer is cooled in hot water before it completely solidifies. Additionally, the wall of steel pipes is generally thicker than sheet metal, leading to a longer immersion time in molten zinc and a higher molten zinc temperature. The thick iron-zinc alloy layer disrupts the crystallization process of the pure zinc layer, thereby affecting the growth of crystals and the formation of zinc flowers.
In the galvanizing process of steel pipes, if metals such as tin and antimony are not added to the molten zinc, the conditions for the formation of zinc flowers are not sufficient. Although adding aluminum can lead to coarse crystallization and crosswise crystallization, making the grain extremely fine, it shortens the time the pure zinc layer remains in a liquid state on the surface of the steel pipe, hindering the growth of crystals. Therefore, patterns cannot be formed. Furthermore, galvanized steel pipes are cooled in hot water before the pure zinc layer solidifies during production. As a result, only a glossy and uniform surface layer is formed on the surface.
The production of galvanized sheet metal fully meets the conditions for the formation of zinc flowers. Since the surface of sheet metal is smooth and flat, and metals such as tin and antimony, which promote the formation of flowers, are added, the sheet metal itself is thin and has a low heat capacity. This allows for a shorter immersion time in molten zinc and a lower molten zinc temperature, resulting in a thinner iron-zinc alloy layer. This reduces the interference during the formation of zinc flowers. By artificially creating crystallization nuclei using methods such as water spray and steel mesh, the desired zinc flowers can be generated.
