77. Why are galvanized steel pipes typically free of zinc flowers, whereas galvanized thin sheets usually exhibit them?

As is well known, galvanized steel pipes typically lack visible zinc flowers. This occurs because the pipe surface is inherently rough and uneven. When the pure zinc layer is immersed in hot water for cooling before complete solidification, combined with the thicker walls of steel pipes compared to plates, prolonged zinc immersion, high molten zinc temperatures, and the thick iron-zinc alloy layer, these factors interfere with the crystallization process of the pure zinc layer. Consequently, this disrupts crystal growth and hinders the formation of zinc flowers.
In the galvanizing process of steel pipes, the absence of metallic elements like tin or antimony in the molten zinc creates insufficient conditions for zinc flower formation. While adding aluminum promotes coarse and transverse crystallization, resulting in extremely fine grains, it also shortens the liquid state duration of the pure zinc layer on the pipe surface, thereby inhibiting crystal growth and preventing the formation of decorative patterns. Furthermore, if the galvanized steel pipe is immersed in hot water for cooling before the pure zinc layer solidifies during production, only a glossy, uniform surface layer will form.
The production of galvanized sheet metal inherently provides ideal conditions for zinc flower formation. With its smooth surface and incorporation of decorative elements like tin and antimony, combined with the material's thin profile and low thermal capacity, the process requires shorter zinc immersion durations and lower molten zinc temperatures to form a thin iron-zinc alloy layer, effectively minimizing interference during zinc flower generation. The water mist spraying method and wire mesh technique are then employed to artificially create crystallization nuclei, enabling the formation of the desired zinc flowers.