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HaiGang Yunyi
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Tianjin Haigang Steel Coil
Service first, quality assured. More dedicated and focused on crafting even better boards.
27
2020
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After the hot-dip galvanizing process, what methods can be used to protect the hot-dip galvanized coating?
After the hot-dip galvanizing process, what methods can be used to protect the hot-dip galvanized coating?
The pre-processed, clean strip steel needs to be immersed in a hot-dip galvanizing bath for hot-dip galvanizing. Before the strip steel is immersed into the hot-dip galvanizing bath, the surface of the bath must be free of zinc dross, zinc chips, and other impurities; otherwise, the quality of the hot-dip galvanized coating will be affected.
When immersing the strip steel into the hot-dip galvanizing bath, it must be tilted smoothly and without any obstruction.
As mentioned above, hot-dip galvanizing of strip steel can be carried out using various methods, such as the wet process, the dry process, the lead-zinc process, and the redox process. In actual production, regardless of which hot-dip galvanizing method is employed, the key parameters that determine the quality of the hot-dip galvanizing process itself remain the temperature of the zinc bath, the immersion time of the strip steel in the zinc bath, and the speed at which the strip steel is withdrawn from the hot-dip galvanizing bath.
After the hot-dip galvanizing process, what methods do we typically use to protect the hot-dip galvanized coating or enhance its corrosion resistance? Below are two approaches that have been compiled:
First, the workpiece is cooled after hot-dip galvanizing.
To promptly inhibit the growth of the iron-zinc alloy layer on the surface of the strip steel, improve the winding performance of the hot-dip galvanized coating, and enhance surface smoothness, the surface of the hot-dip galvanized workpiece should be rapidly cooled. There are two main cooling methods: one is direct water cooling, in which a spray device is installed about 300–500 mm above the surface of the hot-dip galvanizing bath immediately after the strip steel or other workpieces exit the bath, and water is sprayed directly onto the strip steel surface. This cooling method is particularly suitable for the vertical draw-out process. The other method is air cooling, in which air is blown onto the surface of the strip steel to rapidly reduce its temperature; this method is usually used in conjunction with water cooling.
Second, after hot-dip galvanizing, passivation is performed (trivalent chromium passivation and chromium-free passivation).
After hot-dip galvanizing, the chromate passivation method is typically employed. During online passivation, the concentrations are as follows: trivalent chromium at 5 g/L, hexavalent chromium at 1 g/L, sulfuric acid at 0.4 g/L, and nitric acid at 0.21 g/L. The passivation time usually ranges from 3 to 5 seconds. Alternatively, environmentally friendly chromium-free passivators can also be used for passivation treatment. Compared to trivalent chromium passivation, chromium-free passivation is more environmentally friendly, making it easier to meet national emission standards and significantly reducing the need for associated emission-control equipment.
Galvanized strip steel, galvanized strip steel manufacturers, Tianjin galvanized strip steel, galvanized strip steel passivation, galvanized strip steel processing
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We primarily produce various products including galvanized strip steel, pickled strip steel, and cold-rolled strip steel. These products are widely used in industries such as construction, mechanical manufacturing, automotive, and household appliances.
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Shuangtang High-end Hardware Products Industrial Park, Jinghai District, Tianjin City
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