Zinc ash is the compound zinc oxide formed through the oxidation process when the surface of molten zinc comes into contact with air. Once this layer of zinc ash forms, it separates the underlying liquid zinc from the air, reducing or preventing the continued formation of zinc ash. However, in practical production, this cannot be fully achieved because scraping off the ash exposes new surfaces of liquid zinc to the air, leading to the continuous generation of zinc ash.
The growth rate of zinc ash is determined by the following factors:
(1) Temperature of Molten Zinc
The higher the temperature of molten zinc, the faster the oxidation rate and the greater the amount of zinc ash produced.
(2) Surface Condition of Molten Zinc
The larger the surface area of molten zinc in contact with air, i.e., the larger the opening of the galvanizing pot, the more zinc ash is generated.
(3) Indoor Airflow Conditions
The greater the airflow from dust extraction devices and cooling fans, the faster the air exchange on the surface of molten zinc. This accelerates the replacement of air in the workshop, increasing the opportunities for oxygen to oxidize the molten zinc, and consequently, increasing the production of zinc ash.
(4) Chemical Composition of Molten Zinc
The purer the zinc, the faster the oxidation rate and the greater the amount of zinc ash produced. When magnesium content in zinc reaches 0.1 to 1%, the oxidation rate is several times faster than that of pure zinc. To obtain galvanized patterns (especially in sheet production), antimony is added to the molten zinc, which slightly increases the production of zinc ash. The addition of aluminum forms a thin layer of alumina on the surface of molten zinc, isolating the air from the molten zinc and reducing the production of zinc ash.
(5) Drying Degree
If steel pipes are not sufficiently dried, contact between moisture-laden pipes and the alumina film or molten zinc on the surface of the molten zinc accelerates the oxidation rate, increasing the production of zinc ash.
