Zinc ash is a compound of zinc oxide formed through the oxidation of zinc liquid when its surface 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 the surface of new liquid zinc to the air, resulting in the continuous generation of zinc ash.
The growth rate of zinc ash is determined by the following factors:
(1) Temperature of zinc liquid
The higher the temperature of the zinc liquid, the faster the oxidation rate and the greater the amount of zinc ash produced.
(2) Surface condition of zinc liquid
The larger the surface area of the zinc liquid in contact with the 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 collection devices and cooling fans, the faster the air on the surface of the zinc liquid is replaced. This accelerates the rate of air exchange in the workshop, increasing the opportunity for oxygen to react with the zinc liquid, thereby increasing the amount of zinc ash produced.
(4) Chemical composition of zinc liquid
The purer the zinc, the faster the oxidation rate and the more zinc ash is produced. When magnesium content in zinc reaches 0.1 to 1%, the oxidation rate is several times faster than that of zinc without magnesium. To obtain a patterned galvanized layer (especially in sheet production), antimony is added to the zinc liquid, which slightly increases the amount of zinc ash. The addition of aluminum forms a thin layer of alumina on the surface of the zinc liquid, isolating the air from the zinc liquid and reducing the amount of zinc ash.
(5) Degree of drying
If steel pipes are not sufficiently dried, when moisture-containing pipes come into contact with the aluminum film and zinc liquid on the surface of the zinc liquid, the oxidation rate accelerates, leading to an increase in zinc ash.
