Effect of zinc temperature on hot dip galvanizing performance

Below 480 ° C, the zinc solution slowly dissolves on the matrix iron. When the temperature of the zinc solution is 430-480 ° C, the iron loss changes parabolically with time. Within this temperature range, the resulting alloy is dense and continuous. Therefore, the temperature of hot-dip galvanizing is generally controlled at about 450 ° C, and 495 ° C is the malignant dissolution temperature of zinc to iron. At this time, the coating is loose and is a forbidden area of hot-dip galvanizing. When the zinc solution temperature is 490-530 ° C, the iron loss has a linear relationship with time. When the temperature of the zinc solution is higher than 530 ° C (up to 580 ° C), the reaction returns to a parabolic law. At about 540 ° C, zinc solution has a strong dissolving power to iron and can be used for gray cast iron parts. However, the higher the temperature, the stronger the binding capacity of zinc and iron, the faster the alloy reaction, and the fluidity of the zinc solution increases. Therefore, the coating at this time is composed of a thick alloy layer and a thin pure zinc layer. Due to the rough appearance of the thick alloy layer, the appearance of the coating is rough. Around 620 ℃, the iron-zinc bonding layer is formed quickly; above 660 ℃, the iron dissolves quickly, and the workpiece surface does not have zinc. This is the temperature that should be avoided.