How to improve corrosion resistance in hot dip galvanizing line
1. In order to avoid white rust in the process of storage and transportation of hot-dip galvanized products, the hot-dip galvanized sheet should be chromic acid passivation and oiled.2. Increase of coating weight can also improve the corrosion resistance of products by:
(1) improving the roughness of the original galvanized sheet can effectively increase the plating thickness.
(2) reduce the content of AL in the zinc liquid, increase the galvanizing temperature, and select the original plate chemical composition that promotes the growth of alloy layer, such as Si sedation steel
(3) adding a certain amount of Mg or Cu into the zinc solution can improve the corrosion resistance, but the excessive amount will lead to deterioration of adhesion. This method is not widely used at present.
How to improve the coating performance (for surface coating and plastic coating)
1. The typical method to improve the coating performance is to phosphatize the galvanized sheet before coating, because the phosphoric acid film formed on the surface is a good base for painting and plastic coating.
2. Zinc layer alloying is carried out on the galvanized sheet of the outgoing zinc pot.
3. Spray or other mechanical methods are adopted to control the size of zinc flowers, and then the roll of the appliance with a certain roughness is polished with less than 1% pressure drop, so as to obtain zinc-free flower surface with a certain roughness on the surface of zinc-coated plate, which has a good coating performance.