1.What is the melting point of pure zinc?
419.5°C is the exact melting point of metallic zinc. When the temperature reaches this point, solid zinc begins to melt into liquid form.
2.What is the particularity of hot-dip galvanizing?
When we refer to galvanized coil, we mostly mean "hot-dip galvanizing" or "hot-dip galvanizing." In this process, the steel strip is immersed in a bath of liquid zinc at approximately 450°C to 465°C. During galvanizing, a metallurgical reaction occurs, forming a series of iron-zinc alloy layers between the steel substrate and the pure zinc layer.
Thus, a typical hot-dip galvanized layer structure, from the inside out, is:
Steel substrate -> Iron-zinc alloy layer -> Pure zinc layer
The melting point of these iron-zinc alloy layers is much higher than that of pure zinc, typically between 530°C and 670°C, depending on the ratio of iron to zinc.
3.What is the practical significance for galvanized coils?
Processing Temperature Warning: Although the outermost pure zinc layer melts at 419.5°C, this does not mean you can perform any processing (such as baking or welding) on galvanized steel near this temperature. This is because:
Exposed Alloy Layer: If the outer pure zinc layer melts and erodes, the underlying gray, rough iron-zinc alloy layer will be exposed. While this does not affect corrosion resistance, it will severely degrade the product's appearance.
Deterioration of the Overall Structure: Continuous operation at high temperatures accelerates the diffusion of iron and zinc, making the entire coating brittle and reducing adhesion.
4.Any recommended usage temperature?
Long-Term Operating Temperature: The recommended continuous operating temperature for galvanized parts should not exceed 200°C to 230°C. At this temperature, zinc oxidation and growth are slow, maintaining long-term stability.
Short-Term Peak Temperature: Higher temperatures can be tolerated for short periods (e.g., a few minutes), but temperatures exceeding 300°C should be avoided. Otherwise, the zinc layer will rapidly oxidize and turn gray or blue (producing a tempered color), or even begin to soften.
Temperatures to Avoid: Never exceed 419.5°C, as this will cause the coating to melt and lose, leading to complete failure.
5.What temperature should be cautious?
> 300 °C; the zinc layer will oxidize quickly, discolor, and degrade in performance.