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Brief analysis of common iron removal technology for hot-dip galvanizing flux
Release time:2020-08-07 15:27:06      The number of clicks:534

In the hot-dip galvanizing industry, the application of the plating aid is a very important process in the pretreatment process, which not only directly affects the appearance quality of the coating, but also affects the corrosion resistance of the coating. Plays the role of cleaning and activating the surface of the steel substrate. Therefore, the flux must have good properties, such as stable composition. It is generally believed that the function of the plating aid is to peel off (dissolve) the residual iron oxide film on the steel base to improve the surface activity; reduce the surface tension of the alloy solution, improve the wettability of the alloy solution to the steel base, and prevent the degreasing and rust removal The surface of the clean steel base is oxidized again

The main components of the traditional plating aid are the double salt aqueous solution of zinc chloride (ZnCl2) and ammonium chloride (NH4Cl). After the workpiece is pickled, the water is not thoroughly cleaned, so the iron salt is brought to the zinc pot. 1 kg of iron can The production of 20-50 kg of zinc dross will not only increase zinc consumption and increase the cost of galvanizing, but also increase oxides and other impurities in the zinc solution, which will cause the zinc solution to age and reduce the quality of hot-dip galvanizing. Therefore, the plating flux must be treated to remove iron

The iron removal of the plating flux is mainly to remove the divalent iron ions in the plating flux. The divalent iron ions are oxidized to trivalent iron ions, and the trivalent iron ions are hydrolyzed to produce iron hydroxide. Iron hydroxide is insoluble in water and is separated in the plating flux by precipitation. There are many ways to remove iron. It can be oxidized with compressed air, oxidized with ozone, and oxidized with chemical oxidants. After long-term on-site operation practice, it is more reasonable to select the chemical oxidation iron removal process. The technological basis is: adjusting the pH value-removing iron from oxidation-filtering (separation).

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