What causes zinc leakage in galvanizing equipment?
Author: Marisa
What causes zinc leakage in galvanizing equipment?
Foreign objects that have not been cleaned adhere to the surface of the substrate: This kind of zinc leakage defect may be distributed on the lower or upper surface of the strip, generally showing irregular block marks.
Reason: The emulsion on the surface of the substrate is uneven, or there is residual rolling oil on the surface of the substrate. Solid pollutants such as iron powder generated by deformation and wear of the substrate will contaminate the surface of the substrate. If these impurities are not removed cleanly during the cleaning process of the galvanizing line, the local area with pollutants cannot be infiltrated by the zinc liquid during the galvanizing process of the strip, which is prone to zinc leakage.
The oxide layer is not effectively reduced before entering the zinc pot: This zinc leakage defect will be distributed on the lower or upper surface of the galvanized sheet. If a horizontal furnace is used, the zinc leakage defect generated on the lower surface may be more serious than that generated on the upper surface, and it also presents an irregular distribution, and the defect morphology is generally a sheet of pinhole black spots.
Reason: In the process flow, the annealing section mainly plays the role of eliminating work hardening, ensuring that the substrate recovers recrystallization and the temperature of entering the zinc pot, and reducing the surface of the strip at the same time. Nitrogen and hydrogen protective gases are introduced into the reduction furnace to make the atmosphere in the furnace a reducing atmosphere. If the oxide layer cannot be effectively reduced before entering the zinc pot, the wettability of the zinc liquid to the substrate is reduced, and the zinc leakage of the galvanizing equipment is very likely to occur.
When designing a local exhaust hood, the form and installation method of the exhaust hood should be reasonably determined according to the characteristics and emission rules of harmful gases, the structure of the process equipment and its operating characteristics. Without affecting the production operation, a closed exhaust hood should be set as much as possible to ensure a certain wind speed at the exhaust port, so as to eliminate the emitted harmful gases with the smallest air volume and the largest extent.
For the same type of troughs, the exhaust should be merged into the same exhaust system as much as possible, but in a complete exhaust system, there should not be too many exhaust points, otherwise the exhaust effect of each exhaust point will not be easy to balance.
To improve the exhaust effect of the trough edge and reduce the emission, the exhaust hood should be as close to the trough edge as possible, and the height of the exhaust hood from the liquid level should be reduced as much as possible. If conditions permit, a closed movable cover can be set on the trough surface. When the groove surface cannot be covered, the inhibitor and other galvanizing agents can be added to the liquid surface to reduce the volatilization of harmful gases on the liquid surface.
The principle of the iron removal equipment of the galvanizing equipment is revealed
The surface of the substrate is adhered to foreign objects that have not been cleaned: this kind of leakage plating defect may be distributed on the lower or upper surface of the strip, generally showing irregular block marks.
The emulsion on the surface of the substrate is uneven, or there is residual rolling oil on the surface of the substrate. Solid pollutants such as iron powder generated by deformation and wear of the substrate will pollute the surface of the substrate. If these impurities are not removed cleanly during the cleaning process of the galvanizing line, it will cause the part with pollutants to be unable to be infiltrated by the zinc liquid during the galvanizing process of the strip, and leakage plating is prone to occur.